Syst. Biol. 45(4):415-450, 1996
A PHYLOGENETIC ANALYSIS OF GEESE AND SWANS
(ANSERIFORMES: ANSERINAE), INCLUDING
SELECTED FOSSIL SPECIES
BRADLEY C. LIVEZEY
Section of Birds, Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh,
Pennsylvania 15213-4080, USA; E-mail: [email protected]
Abstract.—A phylogenetic analysis of modern and selected fossil geese and swans was performed
using 165 characters of the skeleton, trachea, and natal and definitive integument. Five shortest
trees were found (length = 318; consistency index for informative characters = 0.634), which
differed only in details of relationships among three species of Branta. The trees supported (1)
iCnemiornis as sister group to other taxa analyzed; (2) a sister group relationship between the
moa-nalos of Hawaii and other geese and swans; (3) Cereopsis as sister group of Anser, Branta,
Coscoroba, and Cygnus (contra Livezey, 1986, Auk 103:737-754); (4) monophyly of Anser, Branta,
and iGeochen and confirmation of generic monophyly of each; and (5) Coscoroba as sister group to
Cygnus. Selective exclusion of fossil taxa from the analysis variably affected inferred relationships
and had substantial impacts on computational efficiency. Some nodes were not robust to bootstrapping: (1) nodes relating species groups within Anser, Cygnus, and iThambetochen and (2) the
node uniting Anser, Branta, Coscoroba, and Cygnus relative to Cereopsis. Bremer (decay) indices
indicated similar differences in relative support for nodes. Skeletal characters were comparatively
important in establishing higher order relationships, whereas integumentary characters were critical for lower order inferences. Constrained analyses revealed that other proposed phylogenetic
hypotheses entailed variable penalities in parsimony. The shortest tree(s) was considered with
respect to selected ecomorphological attributes (e.g., body mass, sexual size dimorphism, clutch
size) and biogeography, and a revised phylogenetic classification of the geese and swans is proposed. [Anseriformes; Anserinae; cladistics; comparative analysis; fossils; geese; morphology;
swans; waterfowl.]
The geese and swans (Anatidae: Anserinae; sensu Livezey, 1986) are among the
most conspicuous and familiar of waterfowl, in part because of a long and economically important history of domestication (Delacour, 1954, 1964b; Schudnagis,
1975) and widespread exploitation for
sport and subsistence hunting (Weller,
1964e; Dawnay, 1972). The group is largely
limited to the Northern Hemisphere (Weller, 1964b, 1964d) and has, at least by avian
standards, a substantial fossil record
(Lambrecht, 1933; Brodkorb, 1964; Howard, 1964; Olson and James, 1991). Geese
feed primarily by terrestrial grazing, and
swans feed by submergence of the head
and neck to reach aquatic plants; species
in neither group routinely dive for food
(Delacour, 1954; Weller, 1964a, 1964c;
Johnsgard, 1978). The subfamily includes
the most massive members of the Anseriformes (Scott, 1972), and most flighted
species breed at high latitudes, are migratory (Ogilvie, 1972), and have elongate
skeletal wing elements and moderate wing
loadings relative to body mass (Poole,
1938; Meunier, 1959; Hoerschelmann,
1971). Members of the group retain the
primitive anseriform characters of sexual
monochromatism and the absence of metallic plumage coloration (Delacour, 1954;
Boyd, 1972; Johnsgard, 1978).
Early classifications recognized the relationship between the geese and swans
and other waterfowl, although there was
considerable disagreement concerning taxonomic ranks and details of composition
(Willughby and Ray, 1676; Linnaeus, 1758;
Brisson, 1760; Eyton, 1838; Gray, 1871;
Sclater, 1880; Salvadori, 1895; Peters, 1931).
With few exceptions (e.g., Verheyen, 1953),
modern classifications differ principally in
the taxonomic ranks given to the geese and
swans or the inclusion of the Cape Barren
Goose {Cereopsis nuvaehollandiae) among the
"true" geese (Boetticher, 1942, 1952; Delacour and Mayr, 1945; Delacour, 1954,
415
416
VOL. 45
SYSTEMATIC BIOLOGY
1964a; Johnsgard, 1961a, 1965, 1978, 1979;
Woolfenden, 1961).
Classificatory schemes for the geese and
swans based on explicit attempts to reconstruct phylogeny generally have confirmed
this early consensus, whether based primarily on behavioral (Johnsgard, 1961a,
1974; Kear and Murton, 1973), morphological (Tyler, 1964; Livezey, 1986, 1989), or
molecular (Jacob and Glaser, 1975; Brush,
1976; Morgan et al., 1977; Jacob, 1982; Bottjer, 1983; Numachi et al., 1983; Patton and
Avise, 1985; Scherer and Sontag, 1986;
Shields and Wilson, 1987a; Jacob and Hoerschelmann, 1993) comparisons. However,
most of these studies, as well as the wellpublicized studies based on DNA hybridization (Sibley et al., 1988; Sibley and
Ahlquist, 1990; Sibley and Monroe, 1990),
are phenetic and include comparatively
few anseriform taxa; the DNA hybridization work has been the subject of diverse
criticism (Cracraft, 1987,1992; Sarich et al.,
1989; Lanyon, 1992; Mindell, 1992). Despite broad areas of agreement among
phylogenetic studies of waterfowl based
on diverse methods (Bledsoe and Raikow,
1990; Omland, 1994), debate persists regarding the membership of Cereopsis and
the position of Coscoroba within the Anserinae (e.g., Johnsgard, 1961a, 1965; Kear and
Murton, 1973; Livezey, 1986; Zimmer et al.,
1994), and only very limited study has
been undertaken to establish interspecific
relationships among geese.
In this paper, I present a phylogenetic
analysis of geese and swans, one of a series
of species-level analyses of groups of waterfowl (Livezey, 1991,1995a, 1995b, 1995c,
1996a, 1996b, 1997) prompted by an earlier
phylogenetic analysis of genera of Anseriformes (Livezey, 1986). The role of fossils
in phylogenetic inference has received increasing attention in recent years (Patterson, 1981; Novacek and Norell, 1982; Gauthier et al., 1988; Donoghue et al., 1989;
Huelsenbeck, 1991b; Smith, 1994; Springer,
1995); accordingly, several adequately represented fossil taxa were included in the
analyses. This paper includes a phylogenetic analysis of 31 taxa using 165 morphological characters, an assessment of
support and the analytical impacts of fossil species, maps of selected ecomorphological attributes on the resultant trees, and
a classification of modern and included
fossil species of geese and swans.
METHODS
Delimitation of Taxa
Conceptual frameworks and criteria
used in the delimitation of species are a
perennial source of debate (Cracraft,
1988b; McKitrick and Zink, 1988; Frost and
Hillis, 1990; Frost and Kluge, 1994). In this
analysis, all taxa diagnosably distinct using the qualitative characters included in
the analysis were treated as species, thus
delimiting species in rough accordance
with the "phylogenetic" species concept.
Of the modern geese and swans (Cereopsis,
Branta, Anser, Coscoroba, and Cygnus sensu
lato), 12 species are considered monotypic
under currently accepted classifications
(e.g., Delacour and Mayr, 1945; Delacour,
1954; Johnsgard, 1978, 1979): Cereopsis novaehollandiae, Anser cygnoides, A. rossii, A.
indicus, A. canagicus, Branta sandvicensis, B.
leucopsis, B. ruficollis, Coscoroba coscoroba,
Cygnus melanocoryphus, C. atratus, and C.
olor.
The Bean Goose (Anser fabalis) comprises five variable continental subspecies
(Alpheraky, 1905; Delacour, 1951, 1954;
Burgers et al., 1991) grading from orangebilled, taiga-breeding forms (fabalis, johanseni, middendorffii) to largely black-billed,
tundra-breeding forms (serrirostris,
rossicus); the continental forms were
treated as a single taxon for analysis. The
Pink-footed Goose (A. brachyrhynchus) of
Greenland and Iceland, although considered conspecific with the Bean Goose by
some taxonomists (Delacour, 1954; Johnsgard, 1978), is diagnosably distinct and
was analyzed separately here (Owen, 1980;
Madge and Burn, 1988). The two recognized forms of Greylag Goose (A. [a.] anser,
A. [a.] rubrirostris) differ in at least one of
the characters analyzed and were treated
separately. The Greater White-fronted
Goose (A. albifrons) and Lesser Whitefronted Goose (A. erythropus) were ana-
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
417
lyzed separately. The four subspecies of A. Swan (C. bucdnator) and qualitative differalbifrons, comprising weakly differentiated ences between the Whistling (C. columbicontinental (albifrons, frontalis, gambeli) and anus) and Bewick's (C. bewicki, including
Greenland (flavirostris) forms, were com- jankowskii) swans necessitated treating the
bined into a single taxon coded as poly- four taxa separately.
morphic for bill color because of substanIncluded genera known only from fossil
tial variation in this character (Fox and or subfossil remains (henceforth preceded
Stroud, 1981; Kaufman, 1994). The two col- by daggers) were iCnemiornis, a large
or morphs of the Snow Goose (A caerules- flightless "goose" of New Zealand comcens) were treated as a single polymorphic prising two allospecies (larger southern
species showing dynamic, geographically tC. calcitrans, smaller northern tC. gracilis)
variable frequencies of the two morphs and analyzed as a single taxon (Howard,
and substantial intergradation (Cooch, 1964; Livezey, 1989); subfossil Branta hylo1961, 1963; Cooke et al., 1975, 1988; Rock- badistes of Maui, Hawaiian Islands (Olson
well and Cooke, 1977; Quinn, 1992).
and James, 1982, 1991); iGeochen rhuax, a
Species limits within the Branta bernida large goose from the island of Hawaii
complex remain problematic (Delacour (Wetmore, 1943), largely characterized usand Mayr, 1945; Delacour, 1954; Johnsgard, ing newly collected, tentatively referred
1965, 1978, 1979); in this analysis the At- material of the "very large Hawaii goose"
lantic pale-bellied form (hrota) and the (Olson and James, 1991:48); and four spethree Pacific black-bellied forms (bernida, cies of flightless "moa-nalos" (\Thambetoorientalis, nigricans) were treated as two
separate species. Most current classifications list 12 subspecies of the Canada
Goose (B. canadensis), each variably distinct
and having largely allopatric breeding
ranges, among which there are indications
of localized reproductive isolation (Sutton,
1932), genetic differentiation (Baker and
Hanson, 1966; Van Wagner and Baker,
1986, 1990; Shields and Wilson, 1987b),
and graded differences in voice, body
mass (1.5-5.2 kg), darkness of plumage,
shape of bill, and presence of a narrow
white collar (Brooks, 1926; Aldrich, 1946;
Hanson and Smith, 1950; Todd, 1951; Delacour, 1954; Hatch and Hatch, 1983).
Widespread intergradation and an absence
of critically identified skeletons, tracheae,
and downy young of many populations
made separate coding of these taxa impractical; therefore B. canadensis was treated as a single taxon showing limited polymorphism.
The northern swans, Olor sensu Livezey
(1986), have been subjected to diverse classifications (Delacour and Mayr, 1945; Delacour, 1954; Johnsgard, 1965, 1974, 1979;
Mayr and Short, 1970; American Ornithologists' Union, 1983). However, the diagnosibility of the Whooper Swan (Cygnus
cygnus) as compared with the Trumpeter
chen chauliodous, fT. xanion, fPtaiochen pau,
fChelychelynechen quassus) from the Hawai-
ian islands of Kauai, Oahu, Molokai, and
Maui, respectively (Olson and Wetmore,
1976; Olson and James, 1982, 1991). The
possible, unique loss of the furcula in the
Molokai population of iThambetochen chauliodous is indicated as a polymorphism for
this species.
Specimens Examined
Plumage patterns of adults of modern
species were compared using series of
study skins, most importantly those in the
National Museum of Natural History
(NMNH) and American Museum of Natural History (AMNH). Colors of the irides,
bill, tarsi, and feet of adults were confirmed using published descriptions (Delacour, 1954; Johnsgard, 1974, 1978; Todd,
1979; Kear and Berger, 1980; Brazil, 1981;
Scott, 1981; Madge and Burn, 1988; Marchant and Higgins, 1990; del Hoyo et al.,
1992) and photographs. Natal patterns
were characterized using study skins and
published descriptions (Delacour and
Mayr, 1945; Delacour, 1954; Nelson, 1976,
1993). Skeletal specimens of adults of
modern species, generally five or more
specimens of each species, were included
in osteological comparisons. Tracheal char-
418
SYSTEMATIC BIOLOGY
acters of modern species were confirmed
using ossified elements in skeletal specimens and intact tracheae removed from
fluid-preserved specimens (some previously mounted and dried). Fossil taxa were
represented by most major skeletal ele-
VOL. 45
the confident coding of basal states for
these groups, these were coded either as
polymorphic (where states included a subset of the states present within the Anserinae; 17 instances) or missing (where states
not present within the Anserinae were repments, and for fThambetochen, fPtaiochen, resented or where states encompassed all
and fGeochen at least one bulla syringealis those present within the Anserinae; 12 inor tympanum was examined. Osteological stances). In addition, five entries for geese
and tracheal characters were confirmed us- or swans were coded as polymorphic.
ing the anatomical literature (Shufeldt, Characters resolving the relationship be1888, 1913; Miller, 1937; Wetmore, 1951; tween Dendrocygna and Thalassornis were
Humphrey, 1958; Johnsgard, 1961b, 1962; taken from Livezey (1995a); for purposes
Woolfenden, 1961; Humphrey and Clark, of this analysis, only one (character 94) of
1964; Moller, 1969a, 1969b; McLelland, two natal characters (Livezey, 1995a: char1989). Descriptive nomenclature follows acters 19 and 23) amenable to mutually exKing (1989, 1993), Baumel and Witmer clusive synapomorphic interpretations in
(1993), and Clark (1993).
these two genera was included, and character changes unique to either of these two
genera were not included (see Livezey,
Definition of Characters
A total of 165 morphological characters 1995a). Characters that establish monophythat defined or varied among the Anseri- ly of the Tadorninae or Anatinae are connae and other included taxa were included sidered elsewhere (Livezey, 1996b). The rein the analysis: 76 skeletal characters (most sultant 39 X 165 data matrix (including a
after Livezey, 1986), 8 tracheal characters, hypothetical ancestor, discussed below) is
10 characters of the natal plumage, and 71 presented in Appendix 2.
characters of the definitive plumage and
Of the 35 characters having more than
soft parts (Appendix 1). Each character one derived state, 13 represented naturally
comprised a primitive (plesiomorphic) ordinal series (e.g., numbers of cervical
state and one or more derived (apomor- vertebrae or rectrices) or gradations in dephic) states. Where available specimens gree (e.g., relative sizes of contrasting loral
did not permit the determination of states, patches) and were analyzed as ordered;
missing-datum codes (?) were entered into the analytical impact of ordering was asthe matrix; these accounted for all charac- sessed through analyses in which all charters of the integument (567 entries), 129 os- acters were treated as unordered. Characteological character states, and 36 tracheal ters in which a derived state(s) was
character states for fossil species. Missing- possessed by a single species (autapomordatum codes also were entered 46 times phy) were included in the analysis to confor noncomparable states, i.e., where the firm monophyly of terminal taxa of geese
determination of states was impossible be- and swans and to permit estimates of total
cause of the absence or profound modifi- evolutionary divergence.
cation of the structure in question (e.g.,
Phylogenetic Analysis and Classification
general diminution of a wing element in a
Topological searches.—Trees were derived
flightless species or the obfuscation of certain characters of plumage pattern in the under the principle of global parsimony
(Wiley, 1981) using PAUP 3.1 (Swofford,
"all-white" swans).
States for several characters differed 1993) and MacClade 3.01 (Maddison and
within one or more of the subfamilial and Maddison, 1992) on a Macintosh Quadra
generic taxa; where resolution of phyloge- 800. Topological searches were undertaken
netic relationships (Livezey, 1991, 1995a, using heuristic techniques retaining 10
1995b, 1995c, 1996a, 1996b, 1997) or the trees at each step of the search; this algodistribution of character states precluded rithm was implemented using options for
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
both simple and random order of entry of
taxa and retention of multiple equally parsimonious trees throughout the search.
Also, three branch-swapping methods
(nearest-neighbor interchanges, tree-bisection-reconnection, subtree-pruning-regrafting) were used to avoid local optima
or "islands" of suboptimal topologies
(Maddison, 1991; Page, 1993). Summary
statistics used to describe the inferred trees
were total tree length; consistency index,
both including (CI) and excluding (CI*)
uninformative characters; homoplasy index, both including (HI) and excluding
(HI*) uninformative characters; retention
index (RI); and rescaled consistency index
(RC).
Where multiple equally parsimonious
trees were discovered using the same set
of analytical options, strict consensus trees
(showing only those nodes shared by all
equally parsimonious trees) and majorityrule consensus trees were employed to
summarize the supported regions in the
trees. Consensus trees are seldom interpretable in the same ways as the actual
trees from which they are compiled (Miyamoto, 1985; Swofford, 1991; Wiley et al.,
1991); therefore, consensus methods were
used simply to summarize areas of congruence among equally parsimonious
trees.
419
lengths (Hillis, 1991; Huelsenbeck, 1991a;
Hillis and Huelsenbeck, 1992; Kallersjo et
al., 1992); skewness statistics were estimated using a random sample of 106 trees (excluding the hypothetical ancestor). Stability of nodes in minimal-length trees was
assessed using bootstrapping with 100
replicates; this method remains controversial (Hillis and Bull, 1993). The characters
analyzed violate the assumption of statistical independence required for formal statistical inferences (Felsenstein, 1985; Sanderson, 1989) and resultant percentages
may be biased (Li and Zharkikh, 1995);
therefore, the procedure was employed
simply as an index to empirical support.
The support (decay) index of Bremer
(1988), the minimal increase in tree length
at which topologies not supporting a given
node are discovered, was estimated using
inverse topological constraints, random
taxon addition (10 replicates), and several
search algorithms to avoid local optima
(Swofford, 1993).
Quantitative comparisons with other hypoth-
eses.—Searches constrained to preserve
specific phylogenetic relationships were
used to quantify the sacrifices in parsimony required by previously proposed topologies or classifications using the present data set. Comparisons with the
Hypothetical ancestor.—Trees were rooted phylogenetic hypothesis proposed by Sibusing a set primitive states inferred ley and Ahlquist (1990) and Sibley and
through reference to the sister genera of Monroe (1990) necessitated the partitionthe analyzed taxa (Livezey, 1986), i.e., the ing of the Anatinae into the stiff-tailed
Magpie Goose (Anseranatidae: Anseranas ducks (Oxyurini) and the Anatinae exclusemipalmata) and the screamers (Anhimi- sive of the Oxyurini (designated as Anatidae: Anhima and Chauna). As in previous nae*); using the characters defined here,
phylogenetic analyses of the order (Livez- the Oxyurini differed from other Anatinae
ey, 1986,1989,1995a, 1995b, 1995c; Livezey in the absence of a bulla syringealis (charand Martin, 1988), this method facilitated acter 81) and the restriction of two charrootings of trees without digressions into acters polymorphic in other Anatinae to
relationships among outgroups. Basal po- single states (characters 86 and 110).
larities of one natal character and one charPhylogenetic classification.—The resultant
acter of the definitive integument were not phylogenetic tree(s) formed the basis for a
determinable; a missing-datum code was classification using the methods described
entered for these two states in the hypo- by Wiley (1981). Unconventional taxonomthetical ancestor.
ic ranks, e.g., subtribes, supergenera, and
Assessments of support.—One measure of subgenera, were based on senior taxa of
the phylogenetic signal is the skewness appropriate rank, in part based on the
statistic (ga) for the distribution of tree classifications of Boetticher (1942, 1952)
420
SYSTEMATIC BIOLOGY
and the synonymies of Brodkorb (1964)
and Wolters (1976).
VOL. 45
Wiley, 1988), the approach was employed
here to summarize patterns across genera
in the Anserinae. The presence of a fossil
Ecomorphological Attributes and Biogeography
swan (fCygnus sumnerensis) in New ZeaNine general ecological and functional land, inferred to be a member of the grade
attributes of evolutionary interest were of swans between Coscoroba and the monocoded for comparative analysis (Brooks phyletic "Olor" group (Livezey, 1989), was
and McLennan, 1991; Harvey and Pagel, incorporated in the codings for areas.
1991). A number of attributes showing
variation in other waterfowl were essenRESULTS
tially invariant in the Anserinae: perching
Higher Order Relationships
habit (not developed), diving habit (abFor
the
38-taxon matrix that included
sent), activity period (variably diurnal),
migratory habit (characteristic except in in- fossil species, five shortest trees were
sular endemics), and participation by male found, each having length = 318, CI =
in nest construction (absent, except in Cer- 0.733 (CI* = 0.634), HI = 0.336 (HI* =
eopsis) and incubation (absent). Several 0.396), RI = 0.866, and RC = 0.634. The
other attributes were too poorly docu- CI* for the trees exceeds the expected valmented for many species of Anserinae for ues for phylogenetic analyses of comparaanalysis: frequency of intraspecific and in- ble scale (Sanderson and Donoghue, 1989;
terspecific nest parasitism (Rohwer and Klassen et 6al., 1991). The skewness statistic
Freeman, 1989), formation of creches (Ea- (gj) for 10 randomly generated trees for
die et al., 1988), or parental carrying of this matrix (including ordered characters)
young (Johnsgard and Kear, 1968). Cod- was -0.674 (P <C 0.01; Hillis, 1991). The
ings were based on the literature (Johns- five trees differed only in the topology ingard, 1960a, 1962,1965, 1978; Schonwetter, ferred for Branta canadensis, B. sandvicensis,
1961; Frith, 1967; Wilmore, 1974; Bellrose, and B. hylobadistes, resulting in a polytomy
1976; Cramp and Simmons, 1977; Kear and in Branta in a strict consensus tree (Fig. 1).
Numbers of unambiguous synapomorBerger, 1980; Brown et al., 1982; Rohwer,
1988; Marchant and Higgins, 1990; del phies supporting each node (Fig. 2) varied
Hoyo et al., 1992; McNeil et al., 1992; Dun- from 10 for the entire group exclusive of
ning, 1993). Mean body masses of species the hypothetical ancestor, for the swans
were estimated by averaging the mean (Coscoroba and Cygnus), and for the genus
masses of the two sexes. Sexual size di- Cygnus, to 1 for a number of clades supmorphism was expressed as the ratio of ported by single unambiguous character
the mean body mass of males divided by changes (two subgroups of Anser, one subthat of females. Relative clutch mass was group of Branta, two subgroups of Cygnus,
defined by the product of mean clutch size two subgroups within the moa-nalos). The
and mean egg mass divided by the mean trees supported (1) a basal position of
body mass of the adult female. Maps of iCnemiornis, (2) the monophyly of the Denattributes were made using MacClade 3.01 drocygninae (Dendrocygna and Thalassornis), contra Livezey (1986) but in agree(Maddison and Maddison, 1992).
Area cladograms were constructed by ment with Livezey (1995a), (3) the sister
coding distributional information for ter- group relationship between Stictonetta
minal taxa and ancestral nodes by hierar- and the clade comprising the Tadorninae
chical summation using the inferred phy- and Anatinae (Livezey, 1996b), (4) a sister
logenetic tree (Wiley et al., 1991); area group relationship between the moa-nalos
cladograms were derived using the and the true geese and swans, (5) the
branch-and-bound algorithm. Although monophyly of the moa-nalos, within
primarily used to reveal geographical con- which fChelychelynechen is the sister group
gruences across distantly related taxonom- of "iPtaiochen and iThambetochen, (6) a sisic groups (Cracraft, 1988a; Kluge, 1988; ter group relationship between Cereopsis
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
421
Dendrocygna
Thalassornis
Ce. novaehollandiae
A. cygnoides
A. fabalis
A. brachyrhynchus
A. anser
A. rubrirostris
A. albifrons
A. erythropus
A. indicus
A. caerulescens
A. rossii
A. canagicus
G. rhuax
B. bernicla
B. hrota
B. leucopsis
B. ruficollis
B. canadensis
B. sandvicensis
B. hylobadistes
Co. coscoroba
Cy. melanocoryphus
Cy. atratus
Cy. olor
Cy. columbianus
Cy. bewickii
Cy. cygnus
Cy. buccinator
T. chauliodous
T. xanion
P.pau
Cn. quassus
Stictonetta
Tadorninae
Anatinae
Cnemiornis
Ancestor
FIGURE 1. Strict consensus tree of five shortest trees for modern and fossil Anserinae and related taxa. A.
Anser; B. = Branta; Ce. = Cereopsis; Ch. = fChelychelynechen; Co. = Coscoroba; Cy. = Cygnus; G. = iGeochen; P.
fPtaiochen; T. = iThambetochen.
and other geese (Anser and Branta) and the
swans, contra Livezey (1986), (7) a sister
group relationship between the monophyletic genera Anser and Branta, with the fossil iGeochen placed as the sister group of
Branta on the basis of a single synapomorphy, and (8) a sister group relationship between Coscoroba and other swans.
within the other swans, C. olor is the sister
group of the four species segregated as
Olor by Livezey (1986). Within Anser, there
is a primary dichotomy between a basal
four-species clade, which includes A. indicus, and a clade containing the other seven
species (Figs. 1, 2). Within Branta, B. bernicla and B. hrota compose the sister group
of B. ruficollis and B. leucopsis (Figs. 1, 2).
Subgeneric Relationships
Among the anserine taxa, aberrant CereopIn the typical swans (Cygnus), C. melano- sis novaehollandiae showed the greatest
coryphus + C. atratus is inferred to be the number of autapomorphies, with several
sister group of other swans (Figs. 1, 2); others (Branta ruficollis, Coscoroba coscoroba,
^
pomorphies supporting associated nodes. A. = Anser; B. = Branta; Ce. = Cereopsis; Ch. = iChelychelynechen; Co. = Coscoroba; Cy. = Cygnus; G. = iGeochen; P. =
iPtaiochen; T. = fThambetochen.
FIGURE 2. Detailed depiction of one of five shortest trees for modern and fossil Anserinae and related taxa. Boxes enclose number of unambiguous syna-
#
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
423
Anser canagicus, \Chelychelynechen) showingother taxa analyzed here (Figs. 1, 2), resignificant numbers as well (Figs. 2, 3). The sulted in two trees that were topologically
foiiowing modern taxa lacked an unam- identical for the remaining taxa with the
biguous autapomorphy, and therefore the exception that one placed Dendrocygna and
monophyly of each was not explicitly con- Thalassornis as paraphyletic with respect to
firmed: three swans (Cygnus columbianus, the other taxa (cf. Livezey, 1986). This outC. bewickii, C. cygnus), Anser rubrirostris, A. come occurred whether fCnemiornis was
albifrons, and A. caerulescens (Fig. 2).
excluded alone or in combination with othReanalysis of this matrix treating all er fossil taxa.
characters as unordered resulted in 1,890
Deletion of all four species of moa-nalos
trees of length 315 (CI* = 0.635, RI = (fThambetochen spp., fPtaiochen, iChelche0.860, RC = 0.636); g1 for 106 random trees lynechen), alone or in combination with the
was -0.611 (P <C 0.01). A majority-rule deletion of fCnemiornis, placed the Denconsensus tree differed from that for trees drocygninae (Dendrocygna and Thalassornis
including ordered characters in several as sister genera) as the sister group of Sticways: (1) Cereopsis, the typical geese (Anser, tonetta, Tadorninae, and Anatinae (the last
fGeochen, Branta), and the swans (Coscoro-two being sister groups); this departure
ba, Cygnus) form a trichotomy; (2) the from the other trees (Figs. 1-3) was one of
swans Cygnus melanocoryphus and C. atratusthree topological alternatives described by
form a trichotomy with other members of Livezey (1989). Deletion of only the most
the genus; (3) fGeochen is included in a tri- well-known member of the moa-nalos
chotomy with Anser and Branta; and (4) (iThambetochen chauliodous) had the same
Anser comprised a grade in which sub- effect on the shortest trees, except that the
groups (in order of increasingly close re- remaining moa-nalos were placed as more
lationship) were A. cygnoides, A. fabalis + closely related to the Anatinae and TadorA. brachyrhynchus, A. anser + A. rubrirostris,ninae than to Stictonetta. Conversely, deleA. albifrons + A. erythropus, A. indicus, A. tion of the moa-nalos exclusive of YT. chaucanagicus, and A. caerulescens + A. rossii. liodous resulted in a single tree that was
otherwise topologically identical to those
found in the all-taxon analysis (Figs. 1, 2).
Exclusion of Fossil Taxa
The impact of fossil taxa on phylogenetAssessments of Support
ic inferences was assessed by selective exclusion of taxa and reanalysis of the reFossil taxa, regardless of their topologimaining taxa. Deletion of fGeochen rhuax cal effects on inferred phylogenetic trees,
and \Branta hylobadistes, fossil taxa placed pose substantial computational problems
in comparatively terminal positions and because of the significant numbers of missincluding the single species responsible for ing data that necessarily characterize fosmultiple shortest trees (tB. hylobadistes) in sils in analyses including nonosteological
the all-taxon analysis, resulted in a single characters. For example, otherwise identimost-parsimonious tree: length = 314, CI cal heuristic searches of all taxa required
= 0.732 (CI* = 0.636), HI = 0.338 (HI* = approximately six times the computing
0.394), RI = 0.866, RC = 0.635, g1 (106 ran- time of those in which only \Geochen rhuax
dom trees) = -0.671 (P <C 0.01). The to- and \Branta hylobadistes were deleted. For
pology among remaining taxa in this tree example, an attempt to bootstrap the allwas identical to that of the consensus tree taxon matrix was terminated at replicate 10
for the all-taxon analysis, with an addi- after more than 24 hr, whereas exclusion
tional resolution within Branta (Fig. 3) per- of these two species permitted the compimitted through the exclusion of tB. hylo- lation of 100 bootstrapped replicates in 40
badistes and additional topologies hr; an analysis in which two modern taxa
were excluded at random (but the fossils
stemming from missing data.
Deletion of fCnemiornis from the analy- were retained) required more than 28 hr to
sis, inferred to be the sister group of all reach replicate 10. Fortunately, the minimal
FIGURE 3. Shortest phylogenetic tree for modern Anserinae and related taxa, but excluding fGeochen rhuax and iBranta hylobadistes. Boxes enclose number
of unambiguous synapomorphies supporting associated nodes. A. = Anser, B. = Branta; Ce. = Cereopsis; Ch. = fChelychelynechen; Co. = Coscoroba; Cy. = Cygnus;
P. = iPtaiochen; T. = iThambetochen.
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
Dendrocygna
Thalassornis
Ce. novaehollandiae
A. cygnoides
86
i — A. fabalis
A. brachyrhynchus
96
i
A. anser
A. rubrirostris
99
1
A. albifrons
79 |
A. erythropus
1
A. indicus
1001
A. caerulescens
97
ftft
1
61
A. rossii
A. canagicus
80 1
B. bernicla
83
B. hrota
1
83 1
B. leucopsis
94
B. ruficollis
90 1
B. canadensis
1
B. sandvicensis
Co. coscoroba
99
75
Cy. melanocoryphus
1
Cy. atratus
1
99
Cy. olor
96
Cy. columbianus
761
Cy. bewickii
176|
100
Cy. cygnus
Cy. buccinator
T. chauliodous
T. xanion
100
65
70
425
i
1
•
77
1r~ P.pau
73
81 1
1
Ch. quassus
Stictonetta
Tadorninae
Anatinae
Cnemiornis
Ancestor
FIGURE 4. Majority-rule consensus tree of 100 bootstrapped replicates of the shortest tree for modern Anserinae and related taxa. A. = Anser; B. = Branta; Ce. = Cereopsis; Ch. = fChelychelynechen; Co. = Coscoroba; Cy.
= Cygnus; G. = iGeochen; P. = fPtaiochen; T. = iThambetochen.
3, 4) the three nodes uniting species
groups within the seven-taxon subclade of
Anser, the node uniting Anser indicus with
its congeners in its four-taxon subclade, the
node defining Cereopsis as the sister group
of the swans (Coscoroba and Cygnus) and
the typical geese (Anser and Branta), the
nodes defining the nested relationships
cluding fGeochen rhuax and fBranta hylo- among the geese and swans, moa-nalos,
badistes (Fig. 4) indicated that most nodes and nonanserine clades exclusive of tCnein the shortest tree (Fig. 3) were well sup- miornis, and the node uniting the two speported. Nodes not conserved in a majority cies of fThambetochen within the moa-naof the 100 replicates were (contrasting Figs. los. Within the genus Anser, the branches
effects of the deletion of these two taxa on
relationships inferred among remaining
taxa rendered assessments of support for
the taxonomically reduced matrix almost
as useful as those for the complete set of
taxa.
A majority-rule consensus tree for 100
bootstrapped replicates of the matrix ex-
426
VOL. 45
SYSTEMATIC BIOLOGY
Dendrocygna
Thalassornis
Ce. novaehollandiae
A. cygnoides
A. fabalis
A. brachyrhynchus
A. anser
A. rubrirostris
A. albifrons
A. erythropus
A. indicus
A. caerulescens
A. rossii
A. canagicus
B. bernicla
B. hrota
B. leucopsis
B. ruficollis
B. canadensis
B. sandvicensis
Co. coscoroba
Cy. melanocoryphus
Cy. atratus
Cy. olor
Cy. columbianus
Cy. bewickii
Cy. cygnus
Cy. buccinator
T. chauliodous
T. xanion
P.pau
Ch. quassus
Stictonetta
Tadorninae
Anatinae
Cnemiornis
Ancestor
FIGURE 5. Bremer (decay) indices for nodes of the shortest phylogenetic tree for modern Anserinae and
related taxa. A. = Anser; B. = Branta; Ce. = Cereopsis; Ch. = iChelychelynechen; Co. = Coscoroba; Cy. = Cygnus;
G. = iGeochen; P. = iPtaiochen; T. = iThambetochen.
not robust to bootstrapping closely resembled those not conserved in a majority of
trees based on unordered data.
Of the nodes not robust to bootstrapping, seven had Bremer indices of 1 and
the other had an index of 2 (Fig. 5). However, six nodes robust to bootstrapping
also had Bremer indices of 1. Greatest support for internal nodes, as indicated by
Bremer indices (Fig. 5), was found for the
nodes uniting Coscoroba with Cygnus, species within Cygnus, Anser, and Branta, the
genera of moa-nalos, the sister species An-
ser caerulescens and A. rossii, and the "Olor"
subgroup of swans.
Patterns of Character Evolution
The four groups of characters used in
this analysis (skeletal, tracheal, natal integumentary, definitive integumentary) had
virtually identical mean consistency indices. Based on the all-taxon trees, consistency indices (x ± SD, n ) were computed for
each character group: skeletal (0.83 ± 0.24,
76), tracheal (0.84 ± 0.23, 8), natal integumentary (0.85 ± 0.24, 10), and definitive
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
427
cluded that this genus and the subsequently described moa-nalos are instead derivatives of the shelducks (Tadorninae) or
dabbling ducks (Anatinae), primarily on
the basis of the presence of asymmetrically
enlarged bullae syringeales attributed to
iThambetochen and iPtaiochen. As in the
foregoing analyses, the somewhat dissimilar bullae of the moa-nalos were coded as
homologous to those of most Tadorninae
and Anatinae (Appendices 1, 2). Under
this assumption and bearing in mind the
substantial numbers of missing data for
these species, the minimal penalty (two
additional steps) for requiring the monophyly of the moa-nalos, Tadorninae, and
Anatinae is not unexpected. Furthermore,
one of these additional steps for including
the moa-nalos with the Tadorninae and
Anatinae is negated if the questionable
state for number of cervical vertebrae
(character 16) of iT. chauliodous is treated
as missing (Appendices 1, 2).
Other explicit hypotheses of relationship
concern only modern taxa, and therefore
comparisons of these were made using
constrained analyses excluding all fossil
taxa (gj = -0.706 for 106 random trees, including ordered characters; P <C 0.01).
Also, to accommodate the hypothesis proposed by Sibley and Ahlquist (1990), comparisons were made with a matrix in
which the stiff-tailed ducks (Oxyurini)
were segregated from other Anatinae. The
Comparisons with Other Phylogenetic
shortest unconstrained tree for this modiHypotheses
fied matrix had a length of 271 steps, 1
iCnemiornis, here inferred to be the sis- step shorter than the tree constrained to
ter group to all other included taxa, has conform to the relationships among modbeen considered by others to occupy sev- ern taxa inferred in the all-taxon analysis
eral other phylogenetic positions (Livezey, (Figs. 1, 2), associated with the placement
1989). Increases in tree length entailed by of Dendrocygna and Thalassornis as the sisthese alternatives are (1) iCnemiornis as ter group of taxa exclusive of the geese and
sister group to the Tadorninae, 13 steps swans. Alternative hypotheses were comlonger (4% increase in total tree length); (2) pared with the shortest tree (length = 272)
iCnemiornis as sister group to Cereopsis, 8 for this suite of taxa that conformed to the
steps longer (3%); and (3) iCnemiornis as global solution (Fig. 2).
sister group of the true geese {Cereopsis, Johnsgard (1961a: fig. 2) depicted a speAnser, Branta), 10 steps longer (3%).
cies-level diagram of "evolutionary relaOlson and Wetmore (1976) and Olson tionships" for the geese and swans based
and James (1982) considered iThambeto- primarily on comparative behavior; this
chen chauliodous to be a true goose, but tree, the slightly revised relationships he
Olson and James (1991) subsequently con- proposed (Johnsgard, 1978:xviii), and the
integumentary (0.86 ± 0.23, 71). The distribution of changes in these character
groups throughout the all-taxon trees (not
including changes defining subfossil
groups, which were necessarily restricted
to skeletal characters) differed substantially, however, indicating different mean rates
of evolution in the groups. Nodes defining
families and subfamilies were supported
by 38 (72%) skeletal, 2 (4%) tracheal, 5 (9%)
natal integumentary, and 8 (15%) definitive integumentary character changes.
Nodes delimiting tribes within the Anserinae incorporated 23 (52%) skeletal, 3 (7%)
tracheal, 2 (5%) natal integumentary, and
16 (36%) definitive integumentary character changes. Character changes supporting
genera within the Anserini and Cygnini
comprised 11 (30%) skeletal, 2 (5%) tracheal, 5 (14%) natal integumentary, and 19
(51%) definitive integumentary apomorphies. Character changes within Anser,
Branta, and Cygnus comprised 9 (8%) skeletal, 5 (5%) tracheal, 7 (6%) natal integumentary, and 88 (81%) definitive integumentary apomorphies. The opposite
trends in frequencies of skeletal and integumentary apomorphies when moving
from higher to lower taxonomic levels
strongly indicate that skeletal changes are
more conservative evolutionarily than are
characters of the integument in Anseriformes (Livezey, 1991, 1995c, 1996a).
428
rS- <&• ($><$>O® ^
VOL. 45
SYSTEMATIC BIOLOGY
V V ^
>• >• >• >• V" V ^- K <b- <b- <&• «>• <b- <&• 0 ° ' CP" 0^' 0^' 0^' 0^' 0^' CP'
U U
u u
(a)
/ / . / / / •
/ •
/ / /
(b)
FIGURE 6. Constraint trees summarizing proposed relationships among modern Anserinae and related taxa
(Anatinae* denotes subfamily exclusive of Oxyurini). (a) Johnsgard (1961a, 1978). (b) Sibley and Ahlquist (1990)
and Sibley and Monroe (1990). A. = Anser; B. = Branta; Ce. = Cereopsis; Co. = Coscoroba; Cy. = Cygnus.
accompanying narrative provided the basis for the Johnsgard constraint tree (Fig.
6a). This summary tree was constructed
under the assumption that the trees de-
picted by Johnsgard (1961a, 1978) are interpretable phylogenetically and that
where Johnsgard (1961a) merged two taxa
into a single species he considered them to
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
be sister groups. This global constraint tree
was 30 steps (11%) longer than the shortest
tree conforming with the global hypotheses in the present analysis (Figs. 1, 2).
Much of the increase in length for the
Johnsgard (1961a, 1978) tree derived from
the relationships for taxa other than geese
and swans, only vaguely indicated by
Johnsgard (1961a, 1978), and from the position of Cereopsis. Differences within Cygnus accounted for only six additional steps,
and relationships within the "Olor" subgroup of Cygnus required only one additional step.
The Sibley constraint tree was based on
that of Sibley and Ahlquist (1990: fig. 357),
with supplementary details inferred from
the associated classification (Sibley and
Monroe, 1990). This constraint tree includes several polytomies (Fig. 6b), which
correspond to ambiguities of relationships
among the geese, Tadorninae, and Anatinae implied by Sibley and Monroe (1990)
and the few taxa sampled by Sibley and
Ahlquist (1990). Despite these allowances,
the Sibley constraint tree required an increase of 21 steps (8%) in total length.
Zimmer et al. (1994) proposed, on the
basis of DNA sequence data, that Coscoroba
might be the sister group of the geese and
swans, as opposed to being the sister
group of the swans alone (cf. Johnsgard,
1978; Livezey, 1986). This single change required an increase of nine steps (3%) in
total tree length, regardless of the position
assumed in the constraint tree for Cereopsis
(not analyzed by Zimmer et al. [1994]).
429
group of other swans, (4) retention of the
monotypic genus fGeochen, for which
available evidence prompts the conservation of generic rank within the Anserini,
and (5) revision of the subgeneric classification of Cygnus (contra Livezey, 1986) to
avoid delimitation of a paraphyletic taxon
Cygnus at generic or subgeneric levels.
Ecomorphological Maps
Based on the inferred phylogenetic tree
(Fig. 3), mean body mass underwent several evolutionary changes among modern
Anserinae, including (Fig. 7a) (1) an initial
increase in the ancestor of the Anserinae
(not shown), (2) a decrease in the common
ancestor of Anser and Branta followed by
one or more increases in A. cygnoides and
A. anser + A. rubrirostris, and (3) two or
more increases in the swans, attaining
maxima in Cygnus olor and C. buccinator.
Sexual size dimorphism of Anserinae,
which in most members approximates that
shown by many Anseriformes (Livezey
and Humphrey, 1984), paralleled in part
trends in body mass (Fig. 7b): (1) a substantial increase in Cereopsis, (2) a decrease
in Anser and Branta followed by a reversal
in B. ruficollis, and (3) an increase in the
swans, with independent further increases
in Cygnus melanocoryphus and C. cygnus.
Evolutionary changes in clutch size (Fig.
7c) closely followed changes in body mass
within the Anserinae, showing (1) one or
two increases in A. cygnoides, A. anser, and
A. rubrirostris and (2) an increase in the
swans followed by independent further increases in Coscoroba and Cygnus olor and
Phylogenetic Classification
independent decreases in Cygnus melanoThe inferred phylogenetic trees (Figs. 1- coryphus and C. columbianus. Combined
3) and associated assessments of support changes in body mass (Fig. 7a), egg mass
(Figs. 4, 5), combined with a secondary (not shown), and clutch size (Fig. 7c) progoal of conserving existing taxonomy duced a divergent evolutionary pattern in
where possible, formed the basis for a re- relative clutch mass (Fig. 7d), including (1)
vised classification of the Anserinae (Ap- a basal increase in the ancestor of Anser,
pendix 3). Important aspects of the pro- Branta, Coscoroba, and Cygnus, (2) further
posed classification include (1) placement increases independently in B. ruficollis, B.
of Cereopsis in a monotypic tribe, contra sandvicensis, and some populations of polyLivezey (1986), (2) erection of a separate morphic B. canadensis, and (3) an increase
tribe for the moa-nalos, a group only pro- in Coscoroba and a decrease in Cygnus olor
visionally included within the Anserinae, and basal Olor followed by a reversal in
(3) placement of Coscoroba as the sister Cygnus bewickii and C. cygnus.
430
VOL. 45
SYSTEMATIC BIOLOGY
(a)
(b)
FIGURE 7. Mappings of evolutionary patterns in selected ordered ecomorphological attributes of modern
Anserinae. A. = Anser; B. = Branta; Ce. = Cereopsis; Co. = Coscoroba; Cy. - Cygnus. (a) Body mass. State a
(confined to other taxa) and polymorphism of B. canadensis are not shown. • = b; • = c; M = d; • = e; •
= equivocal, (b) Sexual size dimorphism. State a is confined to other groups and is not shown. • = b; • =
c; • = d; 3 = equivocal, (c) Clutch size. • = a; • = b; B = c; • = d; • = equivocal, (d) Relative clutch
mass. Polymorphism of B. canadensis is not shown. • = a; • = b; • = c; • = equivocal.
1996
431
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
Y
Y Y9y9y
*>• <?>• <$•<??• 0° 0^ 0^
(c)
^V
TJ
M
FIGURE 7.
Continued.
0° 0^ 0^ 0^'0^ 0^ 0^ 0^
432
VOL. 45
SYSTEMATIC BIOLOGY
Preferred nest site, in which the primitive state of ground nesting was retained
by the three genera of geese, was replaced
by overwater sites in the swans (including
Coscoroba); this shift was coincident with
an increase from 2 to ^ 3 years for age at
sexual maturity and a change from terrestrial grazing to aquatic feeding habit (Appendices 1, 2). Semicolonial nesting habits
appear to have evolved in three groups of
geese independently: (1) the ancestor of
Africa
India
Australia
Neotropics
New Zealand
E. Palearctic
C. Palearctic
Anser fabalis and A. brachyrhynchus, (2) the
ancestor of A. caerulescens and A. rossii, and
(3) the ancestor of Branta bernicla, B. hrota,
B. leucopsis, and B. ruficollis. Typical habitat
W. Palearctic
Greenland-Iceland
during nesting appears to have undergone
two independent shifts from inland to
coastal localities, one in Cereopsis and one
in the ancestor of the species pair Branta
E. Nearctic
C. Nearctic
bernicla and B. hrota.
W. Nearctic
Biogeographic Patterns
Ancestor
Although most basal anseriform taxa inFIGURE 8. Area cladogram for modern and fossil
clude Southern Hemisphere members, of Anserinae.
The Tadorninae and Anatinae were comthe Anserinae only Cereopsis (Australia), bined for analysis.
Coscoroba (South America), and three basal
Cygnus (C. atratus of Australia, C. melanocoryphus of South America, tC. sumnerensis
of New Zealand) have Southern Hemisphere distributions. This southern grade
appears to have given rise to two major
radiations throughout the Northern Hemisphere (Figs. 1-3): (1) Anser and Branta and
(2) Cygnus olor and the subgenus Otor.
These generalities were summarized by
four equally parsimonious area cladograms for continental regions (CI = 0.75,
RI = 0.85, RC = 0.63). A strict consensus
tree (Fig. 8) reveals that (1) regions of the
Southern Hemisphere compose a basal
"grade" of areas, two of which (Africa, India) are included only in the distributions
of nonanserine taxa; (2) this grade of
southern areas gives rise to a closely related group of Holarctic areas; (3) the seven
subregions of the Holarctic realm compose
two major continental subregions, equivalent to the Nearctic and Palearctic (the latter including Greenland and Iceland); and
(4) within the Nearctic and the Palearctic,
subregions are increasingly closely related
progressing from west to east.
DISCUSSION
Problematic Groups
Although the present analysis succeeded in producing a completely dichotomous
phylogenetic tree for modern taxa (Fig. 3),
several of the included nodes have only
moderate support (Figs. 4, 5). Constrained
analyses of several competing phylogenetic hypotheses for modern members, especially those involving Cereopsis and Coscoroba (Fig. 6), revealed that these
alternative proposals require modest to severe penalties in parsimony relative to the
shortest trees discovered for these data
(Fig. 3). Congruence among independent
analyses is a crucial adjunct to statistical
assessments of support (Bledsoe and Raikow, 1990; Hillis, 1995), but few phylogenetic studies of Anseriformes are available.
Where trees based on molecular data have
been presented, regardless of methodology, congruence with the present hypothesis for modern Anserinae is substantial, at
least to the extent that differing taxonomic
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
representations among studies permit
comparisons (Brush, 1976; Patton and Avise, 1985; Scherer and Sontag, 1986; Shields
and Wilson, 1987a; Madsen et al, 1988;
Quinn et al., 1991).
The subfamilial relationships of the
433
The fossils included in this analysis
spanned the range of inferential and analytical significance described by Novacek
(1992) for fossil eutherian mammals. The
logistic penalty for including fossils in
phylogenetic analyses is related to the immoa-nalos (iChelychelynechen, iPtaiochen, pact of missing data on computational
and fThambetochen), here tentatively in- times and the numbers of equally parsicluded as a separate tribe of the Anserinae, monious trees (Wiens and Reeder, 1995;
remains the greatest analytical challenge Wilkinson, 1995). In this study, the availamong the taxa analyzed here. The lack of ability of skeletal material and the early dicompelling evidence for this assignment vergence of iCnemiornis resulted in an imlargely results from the strictly osteologi- portant contribution to an understanding
cal material available for all three genera, of basal relationships in the order, with
and several available elements are so de- minimal increase in computational time
rived (principally related to giantism and and no increase in the number of miniSightlessness) as to render a number of os- mum-length trees (Figs. 1-3). Analytical
teological characters problematic (Olson inclusion of the moa-nalos did not affect
and James, 1991). Possible sources for ad- relationships within the geese and swans
ditional data include extraction and ampli- and had only a modest impact on the other
fication of adequate segments of DNA or groups; however, inferences were prothe recovery of mummified remains in foundly influenced by the taxa included in
which critical portions of the integument analyses (Figs. 1, 2, 4, 5). Inclusion of the
comparatively well known fGeochen rhuax
are intact (e.g., the acrotarsium).
and \Branta hylobadistes significantly increased computational times in this analAnalytical Influences and Challenges of
ysis without providing important insights
Fossils
Many fossil anserines are known from into relationships among extant taxa, and
comparatively few, fragmentary elements missing data permitted five equally parsi(Lambrecht, 1931; Tate and Martin, 1968; monious topologies among congeners (Fig.
1). Inclusion of any of the many poorly
Northcote, 1988, 1992). These limitations represented
fossil Anserinae, even limiting
can reduce the reliability of classification; the selections to those for which associae.g., Wetmore (1943) inferred that the frag- tion of elements is not a major concern
mentary type material of \Geochen sug- (e.g., Short, 1969; Martin and Mengel, 1980;
gested a closer relationship to the Austra- Northcote, 1988, 1992), would almost cerlian Cereopsis than to either Anser or Branta tainly render some analytical algorithms
(see Figs. 1, 2). The traditional referral of impractical (e.g., bootstrapping).
fossil anseriforms to the most similar modern genus (Livezey and Martin, 1988) and
Evolutionary Ecology and Biogeography
a preoccupation with identifying ancestral
Prominent morphological trends in the
lineages has led to important misinterpretations of the avian fossil record (Cracraft, Anserinae, including those for sexual size
1979, 1980b). However, inclusion of fossils dimorphism, egg mass, and clutch size, are
in phylogenetic analyses can provide im- correlated to a substantial degree with patportant evolutionary insights and impose terns in body mass (Fig. 7). Several other
critical constraints on the phylogenetic hy- evolutionary transitions characterize the
potheses generated, especially for ade- swans, including a preference for overwaquately known fossil taxa representing ter nest sites, a shift to aquatic "tipping
otherwise poorly documented regions of up" for foraging, and an increase in age at
trees (Novacek and Norell, 1982; Dono- sexual maturity. The phylogenetic position
ghue et al., 1989; Huelsenbeck, 1991b; of Coscoroba inferred here, as sister group
to Cygnus, suggests a simpler evolutionary
Smith, 1994).
434
VOL. 45
SYSTEMATIC BIOLOGY
scenario for the unique ecological attributes shared by the Cygnini than that proposed by Zimmer et al. (1994).
Behavioral patterns, with adequate information on homologies and polarities,
can be reliable indicators of phylogenetic
relationship (de Queiroz and Wimberger,
1993). However, with the exception of the
possession of a ritualized "triumph ceremony," performed by mated pairs after
territorial encounters, there are no evidently derived behaviors that unite the
Anserinae (Johnsgard, 1961a, 1962, 1965,
1968, 1978). The well-developed capacity
for vocalization in the Anserinae, especially geese, may represent an additional corroboration of subfamilial monophyly
(Johnsgard, 1965, 1971). Vocalizations are
involved in mate selection in the Anserinae
(Johnsgard, 1963), but the frequency of intrageneric and intergeneric hybridization
in the group (Johnsgard, 1960b; Scherer
and Hilsberg, 1982) argues against a highly evolved system of selectively refined
isolating mechanisms (Sibley, 1957; Johnsgard, 1963). Many behaviors shared by the
geese and swans, e.g., protracted monogamous pair bonds and paternal attendance
of broods, like sexual monochromatism of
plumage, are primitive in the Anseriformes (Johnsgard, 1965; Kear, 1970; Sigurjonsdottir, 1981; Scott and Clutton-Brock,
1989). Other specific displays, such as
threat postures, precopulatory "head dipping," sexually uniform postcopulatory
displays, and preflight movements (Johnsgard, 1965, 1978), remain inadequately understood for formal phylogenetic analysis.
The traditional view of a northern origin
for the Anseriformes evidently derives
from the probably artifactual higher diversity of Holarctic fossils (Brodkorb, 1964;
Howard, 1964) and the greater number of
modern Holarctic species (Howard, 1950;
Weller, 1964d). However, phylogenetic
analyses strongly indicate a Southern
Hemisphere origin for the order (Cracraft,
1980a; Livezey, 1986, 1989); the present
analysis indicates a southern origin for the
Anserinae as well, one somewhat obscured
by comparatively recent northern radiations in Anser, Branta, and Cygnus (Figs. 1-
3, 8). The west-to-east biogeographic patterns within the Palearctic and Nearctic
regions evident for the Anserinae (Fig. 8),
however, are difficult to explain. Coincident patterns of glaciation seem the most
plausible vicariant events (Rand, 1948;
Ploeger, 1968), but such interpretations of
present distributions may be overly simplistic (Avise et al., 1992). The biogeographic origins of the endemic waterfowl
of the Hawaiian Islands, not amenable to
analysis through area cladograms, must
await the construction of phylogenetic hypotheses for other avian groups showing
endemism, e.g., ibises (Plataleidae), rails
(Rallidae), crows (Corvidae), and finches
(Fringillidae), with ancillary analyses of
the most probable geographic sources for
ancestral colonists (James and Olson, 1991;
Olson and James, 1991).
ACKNOWLEDGMENTS
This research was supported by National Science
Foundation grants BSR-8515523, BSR-9129545, and
BSR-9396249 and by grants from the National Museum of Natural History and the American Museum of
Natural History. G. Mack and R. L. Zusi made possible several protracted visits to New York and Washington, D.C. I thank S. L. Olson and H. F. James (Division of Birds, National Museum of Natural History)
and C. Kishinami (Division of Vertebrate Zoology,
Bernice P. Bishop Museum) for access to recently collected subfossil elements. In addition to specimens in
the Carnegie Museum of Natural History, I examined
specimens from the following institutions: Division of
Birds, National Museum of Natural History, Washington, D.C. (USNM); Department of Ornithology, American Museum of Natural History, New York (AMNH);
Department of Ornithology, Peabody Museum of
Natural History, Yale University, New Haven, Connecticut; Division of Birds, Museum of Zoology, University of Michigan, Ann Arbor; Division of Birds,
Field Museum of Natural History, Chicago, Illinois
(FMNH); Sub-department of Ornithology, Natural
History Museum, Tring, Hertfordshire, England; Division of Vertebrate Zoology, Bernice P. Bishop Museum, Honolulu, HI (BPBM); Wildfowl and Wetlands
Trust, Slimbridge, Gloucester, England; and Division
of Ornithology, Natural History Museum, University
of Kansas, Lawrence. I thank P. S. Humphrey and two
anonymous referees for constructive criticisms of the
manuscript.
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440
SYSTEMATIC BIOLOGY
VOL. 4 5
ventral curvature: (a) present; (b) absent (Livezey, 1986: character 12, part). CI = 1.00.
QUINN. 1994. Phylogenetic analysis of the Coscoroba
coscoroba using mitochondrial srRNA gene sequenc- 11. Os premaxillare, crista tomialis, and os dentale,
margo dorsalis; blunt, bony projections ("pseues. Mol. Phylogenet. Evol. 3:85-91.
dodentes"): (a) absent; (b) present. CI = 1.00.
Received 25 June 1995; accepted 2 May 1996
12. Os premaxillare, crista tomialis, and os dentale,
Associate Editor: Kevin de Queiroz
margo dorsalis: (a) comparatively sharp; (b) flattened, chelonian. CI = 1.00.
APPENDIX 1
13. Maxilla (ossa premaxillare et maxillare): (a) not
extraordinarily deep, broad; (b) extraordinarily
CHARACTER DESCRIPTIONS
deep, broad. CI = 1.00.
Characters employed by Livezey (1986), often con14. Ossa maxillare et palatinum, elongate sulcus mesiderably revised or restricted, are so indicated. All
dialis: (a) indistinct or moderately deep; (b) exmultistate characters were analyzed as unordered, extremely deep, broad. CI = 1.00.
cept where indicated as ordered. Basal polarities are
15. Ossa maxillare et palatinum, paired, elongate
coded as state a unless another state is given in bold;
suld laterales: (a) lacking; (b) indistict; (c) deep.
characters for which polarity was undetermined are
CI = 1.00.
marked by an asterisk. Consistency index (CI) for each
character was based on the ordered analysis including Columna vertebralis
fossil species.
16. Vertebrae cervicales, modal number (ordered,
primitive in bold): (a) 16 (Anatinae); (b) 17; (c)
Skeleton
19 or 20; (d) 21; (e) 22-25 (Livezey, 1986: charSkull
acter 21, revised). CI = 1.00. Intraspedfically
variable; state for iThambetochen estimated based
1. Fades, arcus suborbitalis: (a) absent; (b) typical.
on holotype in which the series evidently was
CI = 1.00.
incomplete.
2. Fades, pila supranasalis, dorsal convexity: (a) ab17. Vertebrae thoradcae (et caudales), modal number
sent; (b) present, but not pronounced; (c) present,
synostotic in synsacrum (ordered): (a) 15 or 16;
pronounced (Livezey, 1986: character 19, re(b) 17-19; (c) 20-22. CI = 0.67.
vised). CI = 0.67. See character 99; some Anser
18. Vertebrae caudales, modal number of elements
show slight, variable convexity.
(not synostotic with synsacrum), including mod3. Fades, apertura nasalis: (a) large, distinctly craally conformed pygostyle as single unit (orniocaudally elongate; (b) reduced, weakly dordered): (a) 7; (b) 8; (c) 9 or 10, less frequently 8.
soventrally elongate. CI = 1.00.
CI = 0.50.
4. Mandibula, ventral curvature: (a) essentially
lacking; (b) pronounced. CI = 0.50.
5. Mandibula, regio coronoidei: (a) not markedly Sternum
deep (others); (b) markedly deep. CI = 1.00.
19. Corpus sterni, trabecula mediana; caudal, irregularly shaped, roughly drcular extension of thin
6. Os prefrontale, synostosis with os frontale: (a)
bone: (a) absent; (b) present (Livezey, 1986: charlacking; (b) present (Livezey, 1986: character 10,
acter 85). CI = 1.00.
part). CI = 1.00.
7. Os prefrontale, processus supraorbitalis: (a)
20. Corpus sterni, processus caudolateralis: (a) exsmall, variably laterally oriented; (b) large, flat,
tend significantly caudad to margo caudalis; (b)
medially appressed to dorsolateral margin of orcaudal extent subequal to margo caudalis (Livbit (Livezey, 1986: character 11, part). CI = 1.00.
ezey, 1986: character 81). CI = 0.50.
8. Ossa nasale et frontale, immediately caudal to
21. Corpus sterni, indsura medialis: (a) present; (b)
zona elastica craniofadalis; rounded, pneumatic,
obsolete. CI = 1.00.
dorsal swelling(s): (a) absent (includes uniquely
22. Corpus sterni, fades muscularis sterni, linea inornamented Anhimidae and Anseranas); (b) prestermuscularis: (a) extends caudally to margo cauent, variably prominent, espedally medially (Cerdalis; (b) angling medially to carina well craniad
eopsis, Anser cygnoides, and Cygnus olor extreme;
margo caudalis (Livezey, 1986: character 88, reBranta less pronounced) (Livezey, 1986: character
vised). CI = 0.33.
16, corrected, much revised). CI = 1.00. See M6123. Corpus sterni, pars cardiaca, pori pneumatid: (a)
ler (1969a, 1969b); intraspecifically variable,
widely scattered throughout; (b) essentially absometimes manifested only by bilateral swellings
sent; (c) limited to caudal margin of pila corawith shallow medial sulcus; particularly develcoideus (Livezey, 1986: character 89, revised). CI
oped in adult males, can be extreme in domestic
= 1.00.
varieties of Anser.
24. Corpus sterni, foramen pneumaticum: (a) present, largely occluded by medial lamina; (b) pres9. Os frontale, facies dorsalis, sulcus glandulae naent, open; (c) absent (Livezey, 1986: character 78,
salis: (a) absent; (b) present, typically lateral, not
revised). fCnemiornis noncomparable. CI = 0.50.
enclosed dorsally by osseus lamina (Branta sandvicensis and B. hylobadistes vestigial); (c) present, 25. Corpus sterni, margo costalis, processus costales,
enclosed dorsally by osseus lamina. CI = 0.33.
modal number per side (ordered, primitive in
bold): (a) 4; (b) 6; (c) 7; (d) 8. CI = 0.60.
10. Os premaxillare, anterior terminus, pronounced
ZIMMER, R., B. ERDTMANN, W. K. THOMAS, AND T. W.
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
441
26. Corpus sterni, margo caudalis: (a) entire; (b)
39. Collum scapulae, facies lateralis: (a) marked by
unossified medially. CI = 1.00.
one prominent tuberculum muscularis; (b)
marked by two prominent tuberculi musculares,
27. Corpus sterni, margo cranialis, sulcus articularis
cranially by tuberculum retinaculi and caudally
coracoideus, medial foramen pneumaticum: (a)
by tuberculum scapulare (Livezey, 1986: characabsent; (b) present (Livezey, 1986: character 90).
ter 112). CI = 1.00.
CI = 1.00.
40. Scapus scapulae, relative width: (a) essentially
28. Rostrum sterni, spina interna: (a) essentially a
uniform throughout; (b) margo dorsalis et margo
rounded notch with variably prominent lateral
ventralis divergent in middle, width maximal
eminences; (b) rectanguloid flange (Livezey,
cranial to extremitas caudalis scapulae (Livezey,
1986: character 82, revised). CI = 1.00.
1986: character 108). CI = 1.00.
29. Rostrum sterni, spina externa: (a) present, a thick
wedgelike prominence (Anseranas tending to b);
(b) lacking; (c) present, a peglike or spatulate Coracoideum
flange (Livezey, 1986: character 79, revised). CI
41. Extremitas omalis coracoidei, processus acrocor= 1.00. Stictonetta, Tadorninae, Anatinae variable
acoideus: (a) present; (b) obsolete. CI = 1.00.
or represented state not found among ingroup
42. Extremitas omalis coracoidei, processus acrocortaxa, coded as missing.
acoideus, facies articularis clavicularis, foramina
30. Carina sterni, margo cranialis, fenestra (ordered):
pneumatica under caudomedial margin: (a) lack(a) absent; (b) present, but not accomodating aning; (b) present but comparatively few; (c) pressae tracheales; (c) present, accomodating ansae
ent, interspersed within larger fossae pneumatitracheales (Livezey, 1986: character 87). CI =
ca (Livezey, 1986: character 95). CI = 0.67.
1.00.
43. Extremitas omalis coracoidei, processus procor31. Carina sterni, ventral prominence: (a) comparaacoideus, foramen pneumaticum (typically withtively great, lateral profile conspicuously convex
in dorsoventral fenestra in processus; somewhat
(e.g., Branta sandvicensis) or essentially straight
variable): (a) present; (b) absent (Livezey, 1986:
(e.g., Branta hylobadistes); (b) greatly reduced, vescharacter 92). CI = 1.00. Ligamentum ossificans
tige restricted to cranial portion of facies musoccurs uncommonly in Cereopsis (Livezey, 1989).
cularis sterni (cf. Livezey, 1986: character 80). CI
44. Corpus coracoidei, facies dorsalis, foramen pneu= 0.50.
maticum cranial to facies articularis sternalis: (a)
present; (b) absent (Livezey, 1986: character 93).
Furcula
CI = 1.00.
32. Claviculae: (a) well developed, not widely diver45. Corpus coracoidei, facies ventralis, impressio m.
gent dorsally; (b) relatively weakly developed,
supracoracoideus: (a) indistinct; (b) deep, distinct
widely divergent dorsally, craniocaudally com(Stictonetta extreme) (Livezey, 1986: character 96).
pressed; (c) lacking. CI = 0.67.
CI = 0.50.
33. Extremitas sternalis claviculae, apophysis furcu46. Extremitas sternalis coracoidei, processus laterlae (hypocleideum): (a) present; (b) obsolete (cf.
alis: (a) broad, rounded flange extending well laLivezey, 1986: character 102). CI = 0.50.
terad to facies articularis sternalis; (b) variably
shaped, approximating facies articularis sternalis
34. Extremitas sternalis claviculae: (a) forming a conin lateral extent (Livezey, 1986: character 99). CI
tinuous curve with scapus; (b) markedly bowed
= 0.50.
caudodorsally, accomodating derivations of cari47. Angulus scapulo-coracoidei: (a) acute; (b) obtuse.
na sterni and enclosed ansae tracheales (Livezey,
1986: character 106). CI = 1.00.
CI = 0.50.
48. Synostosis with scapula and/or sternum: (a) ab35. Scapus claviculae, facies lateralis: (a) lacking fosent; (b) frequent, if not typical. CI = 1.00.
ramina pneumatica; (b) perforated by several
small foramina pneumatica in shallow depresOssa alae
sions; (c) perforated by large foramina pneumatica within a prominent depression (Livezey,
49. Pneumaticity, especially of distal elements: (a)
1986: character 105). CI = 0.33.
present; (b) absent (cf. Livezey, 1986: character
36. Extremitas omalis claviculae, processus acrocor50, revised). CI = 1.00.
acoideus: (a) indistinct; (b) distinct (Livezey,
50. Humerus, extremitas proximalis humeri, tuber1986: character 101, revised). CI = 0.50.
culum ventrale: (a) distal to caput humeri; (b)
proximal to caput humeri. CI = 1.00.
Scapula
51. Humerus, margo caudalis, "eminentia caudalis"
("capital shaft ridge"): (a) prominent, directed
37. Extremitas cranialis scapulae, caput, foramen
toward caput; (b) prominent, directed toward tupneumaticum: (a) present but variably conberculum dorsale; (c) obsolete (Livezey, 1986:
formed; (b) absent (Livezey, 1986: character 111,
character 22, revised). CI = 1.00.
revised). CI = 0.50.
52. Ulna et radius, extremitas distalis, exostosis as38. Extremitas cranialis scapulae, acromion: (a) apsociated with elongation of carpometacarpus,
proximating tuberculum coracoideum in cranial
processus extensorius into prominent spur: (a)
extent; (b) extending significantly craniad to tuabsent; (b) present (VLG). CI = 1.00.
berculum coracoideum (Livezey, 1986: character
53. Ulna, extremitas proximalis, depressio m. bra109). CI = 0.50.
442
SYSTEMATIC BIOLOGY
VOL. 45
ly sloping (Livezey, 1986: character 114). CI =
chialis: (a) distinct but not deeply undercutting
0.50.
cotylae proximales; (b) very prominent, deeply
undercutting cotylae proximales. CI = 1.00.
66. Pubis, corpus pubis, margo dorsalis (lateral
view): (a) concave; (b) convex (Livezey, 1986:
54. Ulno-radial and /or carpometacarpo-digital syncharacter 115). CI = 1.00.
ostosis: (a) absent; (b) infrequent. CI = 1.00.
67. Pubis, apex pubis, shape: (a) of uniform width
55. Carpometacarpus, extremitas proximalis carpowith corpus or monotonically widened caudally;
metacarpi, trochlea carpalis, fades arcticularis
(b) widened into semidrcular flange, espedally
ulnocarpalis, margo dorsalis: (a) essentially conextensive cranioventrally (Livezey, 1986: charactinuous, entire; (b) prominently notched (Livezey,
ter 117). CI = 1.00.
1986: character 38). CI = 1.00.
56. Carpometacarpus, extremitas proximalis carpometacarpi, os metacarpale alulare, processus ex- Ossa membri pelvici
tensorius, enlargement into blunt "spur" (calcar
68. Femur, extremitas proximalis femoris, caput,
alae) having length greater than craniocaudal
proximal extent relative to trochanter: (a) apwidth of rest of element (especially conspicuous
proximately equal; (b) proximal. CI = 1.00.
in adult males): (a) absent; (b) present (Livezey,
69. Femur, extremitas proximalis femoris, caput, ori1986: character 42, revised). CI = 0.33.
entation relative to corpus femoris, fades later57. Carpometacarpus, corpus carpometacarpi, os
alis: (a) significantly caudal; (b) essentially permetacarpale majus, fades dorsalis, impressio m.
pendicular (Livezey, 1986: character 51). CI =
extensor metacarpi ulnaris ("flexor" of Woolfen1.00. Moa-nalos somewhat intermediate.
den, 1961): (a) completely proximal to synostosis
70. Tibiotarsus, extremitas proximalis tibiotarsi, crismetacarpalis proximalis; (b) opposite, at least
ta cnemialis cranialis, lateral deflection: (a) lackpartly, synostosis proximalis metacarpalis (Living; (b) present (Livezey, 1986: character 63). CI
ezey, 1986: character 43, revised). CI = 0.50.
= 1.00.
fCnemiornis, moa-nalos considered noncompar71. Tarsometatarsus, hypotarsus: (a) laterally situatable and coded as missing.
ed on corpus, fossa parahypotarsalis medialis
58. Carpometacarpus, corpus carpometacarpi, os
distinct (deep in Anseranas), only two prominent
metacarpale majus, fades dorsalis, proximal segcristae hypotarsi present; (b) centered on corpus,
ment: (a) flattened or angular; (b) rounded (Livlacking distinct fossa parahypotarsalis medialis,
ezey, 1986: character 39). CI = 1.00. Moa-nalos
three or four prominent cristae hypotarsi present
considered noncomparable and coded as miss(Livezey, 1986: character 72). CI = 1.00. Position
ing.
of hypotarsus intermediate in iThambetochen.
59. Carpometacarpus, corpus carpometacarpi, os
72. Tarsometatarsus, corpus tarsometatarsi, fossa
metacarpale minus, fades ventrocaudalis, proximetatarsi I: (a) deep; (b) obsolete (Livezey, 1986:
mal segment: (a) rounded; (b) concave, with eloncharacter 71). CI = 1.00.
gate sulcus (Livezey, 1986: character 44). CI =
0.50. tCnemiornis and moa-nalos considered non- 73. Tarsometatarsus, extremitas distalis tarsometatarsi, trochlea metatarsi TV, fades dorsalis, margo
comparable and coded as missing.
proximalis, deep sulcus: (a) absent; (b) present.
60. Carpometacarpus, corpus carpometacarpi, spaCI = 1.00.
tium intermetacarpale: (a) present; (b) occluded
74. Tarsometatarsus, extremitas distalis tarsometathrough synostosis of ossa metacarpale majus et
tarsi, foramen vasculare distale, orientation and
minus. CI = 1.00.
depth relative to corpus tarsometatarsi, fades
61. Carpometacarpus, extremitas distalis carpometaplantaris: (a) perpendicular to corpus, coplanar
carpi, fadei articulares digitorum, relative distal
with fades plantaris; (b) distoplantad to corpus,
extent: (a) fades articularis digitalis minor distad
distinctly recessed in sulcus between trochlea
to fades articularis digitalis major; (b) fadei armetatarsi III et IV (Livezey, 1986: character 77).
ticulares digitorum of approximately equal distal
CI = 1.00.
extent (Livezey, 1986: character 45). CI = 0.50.
75. Tarsometatarsus, extremitas distalis tarsometatarsi, trochlea metatarsi II, distal extent relative
Ossa cinguli membri pelvici
to trochlea metatarsi IV: (a) approximately equal;
62. Os coxae, foramen ilioischiadicum: (a) entire; (b)
(b) significantly proximal (Livezey, 1986: charfrequently (if not modally) open caudally. CI =
acter 68). CI = 1.00.
1.00.
76. Tarsometatarsus, extremitas distalis tarsometa63. Os coxae, fossa renalis, recessus iliacus: (a) prestarsi, trochlea metatarsi II, sulcus intertrochlearent; (b) absent (Livezey, 1986: character 120). CI
is: (a) obsolete; (b) distinct (Livezey, 1986: char= 1.00.
acter 74). CI = 0.50.
64. Ilium, ala postacetabularis ilii, margo lateralis,
crista iliaca dorsolateralis: (a) distinct to margo
Trachea and Syrinx
caudalis; (b) obsolete cranial to margo caudalis
77. Trachea, ansae tracheales, intrasternal (ordered):
(Livezey, 1986: character 118). CI = 1.00.
(a) absent; (b) rudimentary, a single short ventral,
65. Ischium, ala ischii, margo caudalis, caudal extent
furcular bend; (c) present, well developed (C.
relative to ala ilii, margo caudalis: (a) well caubuccinator uniquely extensive). CI = 1.00. Hodal; (b) subequal, margo caudalis pelvid oblique-
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
443
(a)
FIGURE Al. Tympani syringeales of selected Anserinae, caudal views (dorsal surfaces above), (a) Cereopsis
novaehollandiae (USNM 430244). (b) Anser cygnoides (USNM 19374). (c) Bmnta hrota (USNM 553108). (d) Cygnus
buccinator (USNM 430204). Caudal portion of first right cartilaginis bronchiosyringealis of C. buccinator is not
shown.
mologous with external ansae tracheales in Anseranas.
78. Trachea, fenestra et membrana tracheosyringealis dorsalis (females): (a) absent; (b) present. CI =
1.00.
79. Trachea, bulbus tracheosyringealis (most marked
in males): (a) absent, trachea cranial to syrinx of
essentially uniform diameter; (b) present, variably marked by constriction cranial to tympanum. CI = 0.50.
80. Syrinx, tympanum, lateromedial compression:
(a) present; (b) absent, tympanum essentially cylindrical. CI = 0.50. See Figure Al.
81. Syrinx, bulla syringealis (asymmetrical synostosis of relatively few, caudal-most ossa tracheales,
with weakly developed pessulus and interchamber septum): (a) absent; (b) present (presumably
only in males), single chamber; (c) present, large
and small chambers, blind chamber (cf. Livezey,
1986: character 6, much revised). CI = 0.75. See
Figure A2; homology of state b in moa-nalos is
questionable. This character was coded as poly-
(a)
FIGURE A2. Bullae syringeales of moa-nalos, presumptive males, ventral (a, c) and caudal (b, d) views, (a,
b) iThambetochen chauliodous (USNM uncataloged), cranial aspect of which was shown by Olson and James
(1991: fig. 8), missing portions shown in diagonal overlay, (c, d) iPtiaochen pau (BPBM 158937).
444
VOL. 4 5
SYSTEMATIC BIOLOGY
M. sternotracheaiis
M. tracheolateralis
Bulbus
Tympanum
tracheosyringealis
CM
Membrana tympaniformis
IateraI is
Cartilaginis
bronchiosyringealis
Foramen
interbronchiale
Membrana tympaniformis
medialis
Bulbus
bronchiosyringealis
Ligamentum
interbronchiale
FIGURE A3. Trachea (caudal portion), tympanum, and cartilagines bronchiosyringeales of male Whistling
Swan (Cygnus columbianus), ventral view (USNM 322875).
morphic for Anatinae, in which only Oxyurini
lacks bulla.
82. Syrinx, pessulus osseus (ordered): (a) complete,
firmly synostotic with midline of tympanum; (b)
incomplete, reduced to dorsal and ventral tubercula; (c) absent. CI = 1.00. Small hiatus in some
worn specimens of moa-nalos coded as state a.
83. Syrinx, membrana tympaniformis lateralis: (a)
absent or inconspicuous; (b) bilaterally enlarged,
associated with deeply concave, often craniolaterally recessed margo caudolateralis of tympanum. CI = 1.00.
84. Syrinx, bulbus bronchiosyringealis, cartilagines
bronchiales syringes, latticelike synostosis
among elements cranially: (a) absent; (b) present.
CI = 1.00. See Figure A3.
Natal Integument (Fig. A4)
85. Bill color: (a) gray; (b) flesh. CI = 1.00.
86. Foot color: (a) gray; (b) orange or yellow; (c)
pink. CI = 1.00.
87. Dorsum (crown, back, rump, wings): (a) darker
than venter (slight in A. rossii, C. atratus); (b) does
not contrast with pale venter ("all white"). CI =
1.00.
88. Dusky periorbital patch: (a) present but variably
extensive (vestigial in A. caerulescens, A. rossii);
(b) absent. CI = 1.00.
89. Darkish cap (separate from cheek patch by pale
supraorbital stripe, if present): (a) present; (b) absent. CI = 1.00.
90. Dark corona sharply contrasting with comparatively wide, pale frons: (a) absent; (b) present (B.
sandvicensis comparatively faint). CI = 0.50.
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
445
FIGURE A4. Diagrams of natal patterns of selected Anserinae, lateral views, (a) Cereopsis novaehollandiae
(AMNH 744127). (b) Anser erythropus (FMNH 14032). (c) Branta canadensis kucopareia (USNM 530208). (d) Coscoroba coscoroba (FMNH 16703). (e) Cygnus atratus (USNM 385928). (f) Cygnus buccinator (AMNH 744385).
102. Maxilla, tomium, marked ventral decurvature,
tending to expose lamellae laterally and associated with ventral prominence of maxillary integument near gape, most conspicuous in males (ordered): (a) absent; (b) present but moderate; (c)
present, marked. CI = 1.00. Evidently convergent, variably developed in some Tadorninae (Alopochen, Chloephaga).
103. Maxilla, rhamphotheca, dertrum, color: (a) black;
(b) pale. CI = 0.33.
104. Mandibula, rhamphotheca of rami: (a) colored
Definitive Integument
like rest of bill; (b) contrastingly blackish. CI =
1.00.
Rhamphotheca, ground color: (a) gray to black;
105. Maxilla, rhamphotheca, dorsal surface: (a) not
(b) flesh-colored or pink; (c) orange; (d) red. CI
marked with black; (b) variably marked with
= 0.63. Variably orange tones of rhamphotheca
black, contrasting with paler ground color. CI =
of Anser albifrons flavirostris of questionable reli1.00.
ability in comparison with Nearctic forms (Palmer, 1976; Kaufman, 1994) and not detectable us106. Maxilla, rhamphotheca, contrasting, bright yeling study skins, necessitated coding A. albifrons
low lateral patches (ordered): (a) absent; (b) presas polymorphic (b/c).
ent, restricted to loral strip; (c) present, comparatively extensive. CI = 1.00. Intraspecifically
Maxilla, basal "knob": (a) absent; (b) present, orvariable.
ange; (c) present, black. CI = 1.00.
107. Maxilla, rhamphotheca, caudal margin: (a) terMaxilla, rhamphotheca, small, grayish, basal caminates well anterior to orbit; (b) extends posruncles: (a) absent; (b) present. CI = 1.00.
teriorly to orbit as narrow strip (covered with
Cere, bright green color: (a) absent; (b) present.
down in very young cygnets). CI = 1.00. Not
CI = 1.00.
considered homologous with bare cere and orMaxilla, tomium, contrasting blackish color: (a)
bital region in Anhimidae and Anseranas.
absent; (b) present (least conspicuous in A. canagicus, most conspicuous in A. caerulescens). CI = 108. Maxilla, rhamphotheca, tomium, laterally prom1.00.
inent subterminal flaps with enlarged lamellae,
presenting subspatulate aspect: (a) absent; (b)
Maxilla, tomium, narrow reddish basal stripe:
present. CI = 1.00.
(a) absent; (b) present. CI = 1.00.
109. Mandibula, interramal region: (a) lacks feathers
Maxilla (ordered): (a) of typical proportion; (b)
anteriorly; (b) completely feathered. CI = 0.50.
intermediate in profile; (c) short, high-based,
subconical. CI = 1.00. Branta canadensis variable, 110. Foot color*: (a) orange; (b) pink; (c) black. CI =
apparently size related, and coded as polymor0.43. Problematic coding for Tadorninae, Anatiphic (b/c).
91. Ground color of down*: (a) white; (b) yellow. CI
= 0.50.
92. Distinct, pale scapular and rump spots: (a) present; (b) absent. CI = 0.50.
93. Pale scapular and rump spots (if present): (a)
separate; (b) confluent, forming bilateral dorsal
stripes. CI = 1.00.
94. Pale suborbital stripe (ordered): (a) terminating
at nape; (b) separated dorsally by narrow, dark
nuchal stripe; (c) meeting across nape. CI = 1.00.
95.
96.
97.
98.
99.
100.
101.
446
SYSTEMATIC BIOLOGY
111. Interdigital webbing of feet (exclusive of hallux):
(a) truly semipalmate; (b) palmate (includes variably incised webbing in Cereopsis, Bmnta sandvicensis) (Livezey, 1986: character 4, revised). CI =
1.00.
112. Tarsal integument, fades dorsalis: (a) reticulate;
(b) scutellate. CI = 1.00.
113. Molt of remiges: (a) sequential; (b) simultaneous
(Livezey, 1986: character 1). CI = 1.00.
114. Ground color of primary remiges, proximal portions of vanes: (a) medium brown; (b) silvery
gray (not evident in white morphs of Anser); (c)
blackish brown; (d) white. CI = 0.60.
115. Contrastingly black tips of distal primary remiges: (a) absent; (b) present. CI = 1.00.
116. Primary remiges, rachises, color of proximal segment: (a) white; (b) brownish. CI = 1.00.
117. Secondary remiges, ground color: (a) essentially
uniform in color with adjacent feathers; (b) distinctly darker than dorsal coverts or primary
remiges. CI = 1.00.
118. Ground color of dorsal median and greater primary and secondary coverts: (a) plain grayish
brown; (b) pale brownish gray; (c) bluish silvery
gray (not evident in white morphs of Anser); (d)
white. CI = 1.00.
119. Lesser (cranial-most) dorsal primary and secondary coverts: (a) not pale silvery gray; (b) contrastingly pale silvery gray. CI = 1.00.
120. Tips of greater secondary coverts: (a) without
contrastingly pale margins; (b) with narrow, contrastingly pale margins, forming a weak bar; (c)
with comparatively broad, contrasting white
margins. CI = 0.40. Cygnini considered noncomparable.
121. Tertials: (a) dark with pale margins, margins
generally broader on lateral vanes; (b) elongate,
three-toned, dark (blackish) medially, brownish
in middle of vanes, pale laterally (not evident in
white phases); (c) immaculately black, lacking
pale margins. CI = 1.00. Cygnini considered
noncomparable.
122. Wing linings: (a) dark, like remiges; (b) white;
(c) pale gray. CI = 1.00. Cygnini considered noncomparable.
123. Axillaries: (a) generally dark, comparable to color of adjacent feathers of side; (b) pale, silvery
gray; (c) white (essentially immaculate), contrasting with sides (not evident in white morphs
of Anser). CI = 0.50. Cygnini considered noncomparable.
124. Rectrices, modal number of pairs in birds not in
molt (ordered): (a) 6; (b) 7; (c) 8; (d) 9; (e) 10-12.
CI = 0.71. Subspecies of Bmnta canadensis polymorphic, coded b/c; intraspecific variation in
most species.
125. Rectrices, color: (a) essentially black; (b) grayish
black medially with pale lateral and terminal
edges (not evident in white morphs of Anser); (c)
white. CI = 0.67.
126. White (caudal) upper tail coverts producing
white band at base of rectrices: (a) present; (b)
absent. CI = 0.50.
VOL. 4 5
127. Contrastingly black "basal" upper tail coverts
producing black rump: (a) absent, rump similar
in color to back; (b) present. CI = 1.00.
128. Upper tail coverts, contrastingly pale gray color:
(a) absent; (b) present. CI = 1.00.
129. Plumage of head, neck, and (in some) entire
body exclusive of remiges uniform charcoal
black (ordered): (a) absent; (b) present, limited to
head and neck; (c) present, entire body exclusive
of remiges. CI = 1.00.
130. Dark (blue) and pale (white) color phases: (a) absent; (b) present but geographically variable frequencies (very rare in Anser caerulescens atlanticus, rare in A. rossii). CI = 1.00.
131. Mantle, ground color*: (a) medium brown; (b)
gray; (c) blackish; (d) white. CI = 0.50. States of
Tadorninae and Anatinae were problematic and
coded as missing.
132. Mantle, shape of feathers: (a) comparatively narrow to moderately broad, terminus rounded; (b)
distinctly broad with truncate tips. CI = 0.33.
133. Mantle and upper wing coverts, distinct whitish
terminal bars producing scalloped appearance:
(a) absent; (b) present. CI = 0.25.
134. Boldly barred dorsum, formed by sharply defined black subterminal bands and narrow white
terminal bands on otherwise gray dorsum: (a)
absent; (b) present (Branta leucopsis intermediate,
B. ruficollis comparatively dark and obscured). CI
= 0.50.
135. Large black central spots on dorsal contour
feathers: (a) absent; (b) present. CI = 1.00.
136. Rump, prominent barring of black and white on
gray: (a) absent; (b) present. CI = 1.00.
137. Rump, contrastingly white color: (a) absent; (b)
present. CI = 1.00.
138. Contrastingly black undertail coverts: (a) absent;
(b) present. CI = 1.00.
139. Sharply demarcated dark breast: (a) absent; (b)
present, black; (c) present, chestnut. CI = 1.00.
140. Fine white breast stripe, contrasting with black
ventrally: (a) absent; (b) present. CI = 1.00.
141. Coarse black spotting on lower breast, belly (ordered): (a) absent; (b) present (more conspicuous
in Anser albifrons [especially A. flavirostris] and A.
erythropus than in A. anser). CI = 0.50.
142. Coarse gray and black barring on belly and ventrum: (a) absent; (b) present. CI = 1.00.
143. Dark gray or black continuing ventrally from
black breast (if present): (a) absent; (b) present.
CI = 0.50.
144. Fine, caudally jagged, white side stripes, contrasting with black breast, belly: (a) absent; (b)
present. CI = 1.00.
145. Flank: (a) not marked as follows (including superficially similar pattern of Branta ruficollis produced by unique white feathers with black edges); (b) barred with whitish on dusky-black
background (produced by dark feathers with
pale edges; includes taxa in which white phases
necessarily lack the pattern), darkening caudally,
most pronounced craniolateral to crural region.
CI = 1.00.
1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
146. Head: (a) not entirely black; (b) entirely black. CI
= 1.00.
147. Crown, sides of head, neck: (a) not as follows; (b)
white, in contrast with dark of mantle. CI = 1.00.
Anser indicus considered noncomparable and
coded as missing.
148. Black crown, anterior region of face (down-tilted
cap): (a) absent; (b) present. CI = 1.00. Branta
bernida, B. leucopsis, and B. ruficollis considered
noncomparable and coded as missing.
149. Medial black gular stripe, dividing pale cheeks
(if present) ventrally: (a) absent; (b) present. CI
= 1.00. All subspecies of B. canadensis polymorphic.
150. Contrasting black transverse nuchal bars formed
by dorsally serrate lateral neck stripes: (a) absent;
(b) present. CI = 1.00.
151. White cheek patches: (a) absent (tentatively includes A. canagicus in which white cheeks are not
bounded by black dorsally); (b) present (tentatively including Branta bernida having vestigial
patches on sides of neck and B. ruficollis in which
cheeks are chestnut centrally). CI = 1.00.
152. Deep chestnut cheek patches: (a) absent; (b) present. CI = 1.00.
153. Buffy color on cheeks, throat, foreneck: (a) absent; (b) present. CI = 1.00.
154. Sharply defined, contrasting white eye ring: (a)
absent; (b) present. CI = 1.00.
155. White transverse "visor" across anterior margin
of crown, defining black loral regions: (a) absent;
(b) present. CI = 1.00.
156. White tear-shaped orbital marks, contrasting
with black of face: (a) absent; (b) present. CI =
1.00.
157. Sharply delimited, blackish bordered white region at base of bill or frons (ordered): (a) absent
(includes infrequent narrow line around bill base
in A. fabalis and nominate A. anser); (b) present,
comparatively restricted, rounded dorsal terminus; (c) present, comparatively extensive and
acuminate dorsally. CI = 0.67.
158. Sides of neck: (a) not as follows: (b) with long,
narrow, basally dark, distally pale feathers forming conspicuous longitudinal streaks. CI = 0.67.
159. Narrow, blackish, caudally truncated dorsal neck
stripe: (a) absent (includes complete smooth
brown of A. cygnoides); (b) present (not evident
160.
161.
162.
163.
164.
165.
447
in white morphs of A. caerulescens and A. rossii).
CI = 0.50.
Complete brown dorsal nuchal stripe connecting
crown with mantle: (a) absent; (b) present. CI =
0.50.
Black neck "stocking," circumcomplete, at least
in pars intermedia: (a) absent; (b) present (cranially obscured by enlarged cheek patches in B.
sandvicensis, problematical in B. ruficollis). CI =
1.00.
Black neck stocking, pars caudalis, forming circumcomplete collar at base of neck and sharply
contrasting with adjacent breast: (a) absent; (b)
present (narrow in B. sandvicensis). CI = 1.00.
Broad, gray stripes on throat and nape separated
laterally by narrower white stripes: (a) absent; (b)
present. CI = 1.00.
Black chin and upper throat grading to grayish
barring ventrally: (a) absent; (b) present. CI =
1.00.
Semicircular white loral patches: (a) absent; (b)
present. CI = 1.00.
Ecomorphological Attributes
A. Mean body mass (ordered)*: (a) < 1,000 g; (b)
1,000-3,000 g; (c) 3,000-5,000 g; (d) 5,000-10,000 g;
(e) >10,000 g.
B. Sexual size dimorphism (ratio, mean mass for
males divided by mean mass for females; ordered)*: (a) <1.01; (b) 1.01-1.20; (c) 1.21-1.30; (d)
>1.30.
C. Mean clutch size (ordered)*: (a) 4 or 5; (b) 5 or 6;
(c) 6 or 7; (d) 7 or 8; (e) 8 or 9; (f) >9.
D. Mean egg mass (ordered)*: (a) <100 g; (b) 100 or
140 g; (c) 140 or 200 g; (d) >200 g.
E. Relative clutch mass (percentage of mean female
body mass; ordered)*: (a) <20%; (b) 20% or 30%;
(c) 30% or 40%; (d) >40%.
F. Preferred nest site (ordered): (a) over water; (b) terrestrial (includes Dendrocygna, which uses both terrestrial sites and cavities).
G. Age at sexual maturity (ordered): (a) 1 yr; (b) 2 yr;
(c) >3 yr.
H. Semicoloniality: (a) not characteristic; (b) characteristic.
I. Feeding habitat, diet: (a) surface aquatic; (b) diving; (c) terrestrial grazing.
J. Typical aquatic habitat during nesting: (a) freshwater; (b) salt water.
APPENDIX 2
CHARACTER-STATE MATRIX
Matrix of 165 morphological characters (Appendix 1) used in the phylogenetic analysis of 38 anserine and
related taxa and a hypothetical ancestor, followed by 10 mapped attributes (A-J). States are coded as lowercase
letters, and combinations of states in polymorphisms are shown as follows: g = a / b ; h = b / c ; i = a/b/c. ? =
missing data. A. = Anser; B. = Branta; Ce. = Cereopsis; Ch. = iChelychelynechen; Co. = Coscoroba; Cy. = Cygnus;
G. = iGeochen; P. = iPtaiochen; T. = fThambetochen.
448
SYSTEMATIC BIOLOGY
VOL. 45
111111111122222222223333333333444444444455555555556666666666777777777788888888889
Ancestor
Dendrocygna
Thalassornis
\Cnemiornis
Ce. nova.ehollan.diae
A. cygnoides
A. fabalis
A. bra.chyrhynch.us
A. anser
A. rubriroscris
A. albifrons
A. erythropus
A. indicus
A. caerulescens
A. rossii
A. canagicus
G. rhuax
B. bemicla
B. hrota
B. canadensis
B. sandvicensis
B. hylobadistes
B. leucopsis
B. ruficollis
T. chauliodous
T. xanion
P. pau
Ch. quassus
Co. coscoroba
Cy. mel anocoryphus
Cy. aCratus
Cy. olor
Cy. columhianus
Cy. bewickii
Cy. cygnus
Cy. buccinator
Stictonetta
Tadorninae
Anatinae
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1234567890123456789012345678901234567890123456789012345678901234567890123456789012345
Ancestor
Dendrocygna
Thalassornis
t Cnemiornis
Ce. novaehollandiae
A. cygnoides
A. fabalis
A. brachyrhynchus
A. anser
A. rubrirostris
A. albifrons
A. erythropus
A. indicus
A. caerulescens
A. rossii
A. canagicus
G. rhuax
B. bemicla
B. hrota
B. canadensis
B. sandvi censi s
B. hylobadistes
B. leucopsis
B. ruficollis
T. chauliodous
T. xanion
P. pau
Ch. quassus
Co. coscoroba
Cy. melanocoryphus
Cy. atratus
Cy. olor
Cy. columbianus
Cy. bewickii
Cy. cygnus
Cy. buccinator
Stictonetta
Tadorninae
Anatinae
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1996
LIVEZEY—PHYLOGENY OF GEESE AND SWANS
449
APPENDIX 3. Phylogenetic classification of the Anserinae and closely related outgroups. Only anserine taxa
are classified at subgenetic levels. Within higher taxa, three or more included taxa of equal rank are listed in
order of increasingly close relationship (i.e., terminal pair inferred to be sister species). Fossil taxa are preceded
by daggers. Sedis mutabilis indicates groups including three or more taxa of undetermined relationship and
provisionally accorded equal rank.
Order Anseriformes (Wagler, 1831)
Suborder Anseres Wagler, 1831
Family Anseranatidae Sclator, 1880
Genus Anseranas Lesson, 1828—Magpie Goose
tFamily Cnemiornithidae Stejneger, 1885
Genus Cnemiornis Owen, 1865—New Zealand geese
Family Anatidae Leach, 1820—true geese, swans, and ducks
Subfamily Dendrocygninae Reichenbach, "1850"—whistling-ducks and allies
Genus Dendrocygna Swainson, 1837—whistling-ducks
Genus Thalassornis Eyton, 1838—White-backed Duck
Subfamily Anserinae Vigors, 1825—geese and swans
Tribe Cereopsini (Vigors, 1825)
Genus Cereopsis Latham, 1801
Cereopsis novaehollandiae Latham, 1801—Cape Barren Goose
Tribe Anserini (Vigors, 1825)—true geese; sedis mutabilis
Genus Anser Brisson, 1760—pale-breasted geese
Subgenus Anser Brisson, 1760
Anser cygnoides (Linnaeus, 1758)—Swan Goose
Anser fabalis (Latham, 1787)—Bean Goose
Anser brachyrhynchus Baillon, 1833—Pink-footed Goose
Anser anser (Linnaeus, 1758)—greylag geese
Anser (a.) anser (Linnaeus, 1758)—Western Greylag Goose
Anser (a.) rubrirostris Swinhoe, 1871—Eastern Greylag Goose
Anser albrifrons (Scopoli, 1789)—Greater White-fronted Goose
Anser erythropus (Linnaeus, 1758)—Lesser White-fronted Goose
Subgenus Chen Boie, 1822
Anser indicus (Latham, 1790)—Bar-headed Goose
Anser canagicus (Sevastianov, 1802)—Emperor Goose
Anser caerulescens (Linnaeus, 1758)—Snow Goose
Anser rossii (Cassin, 1861)—Ross's Goose
tGenus Geochen Wetmore, 1943
Geochen rhuax Wetmore, 1943—Large Hawaiian Goose
Genus Branta Scopoli, 1769—Brent (dark-breasted) geese
Subgenus Leucoblepharon Baird, 1858; sedis mutabilis
Branta canadensis-gp. (Linnaeus, 1758)—Canada Goose
+Branta hylobadistes Olson and James, 1991—Greater Nene
Branta sandvicensis (Vigors, 1833)—Lesser Nene
Subgenus Branta Scopoli, 1769
Branta (b.) bernicla (Linnaeus, 1758)—Dark-bellied Brent
Branta (b.) hrota (Miiller, 1776)—Pale-bellied Brent
Subgenus Leucopareia Reichenbach, 1853
Branta leucopsis (Bechstein, 1803)—Barnacle Goose
Branta ruficollis (Pallas, 1769)—Red-breasted Goose
Tribe Cygnini (Vigors, 1825)—swans
Subtribe Coscorobina (Boetticher, 1936-1938), new rank
Genus Coscoroba Reichenbach, 1853
Coscoroba coscoroba (Molina, 1782)—Coscoroba Swan
Subtribe Cygnina (Vigors, 1825)
Genus Cygnus Bechstein, 1803
Subgenus Chenopis Wagler, 1823a
Cygnus atratus (Latham, 1790)—Black Swan
Cygnus melanocoryphus (Molina, 1782)—Black-necked Swan
Subgenus Cygnus Bechstein, 1803
Cygnus olor (Gmelin, 1789)—Mute Swan
Subgenus Olor Wagler, 1832—tundra swans
Olor buccinator (Richardson, 1831)—Trumpeter Swan
Olor columbianus (Ord, 1815)—Whistling Swan
450
SYSTEMATIC BIOLOGY
VOL. 4 5
APPENDIX 3. Continued.
Olor bewickii (Yarrell, 1830)—Bewick's Swan
Olor cygnus (Linnaeus, 1758)—Whooper Swan
tTribe Thambetochenini, new taxon—moa-nalosb
Genus Chetychelynechen Olson and James, 1991
Chelychelynechen quassus Olson and James, 1991—Turtle-billed Moa-nalo
Genus Ptaiochen Olson and James, 1991
Ptaiochen pau Olson and James, 1991—Short-billed Moa-nalo
Genus Thambetochen Olson and Wetmore, 1976
Thambetochen chauliodous Olson and Wetmore, 1976—Greater Moa-nalo
Thambetochen xanion Olson and James, 1991—Oahu Moa-nalo
Subfamily Stictonettinae (Boetticher, 1950)
Genus Stictonetta Reichenbach, 1853—Freckled Duck
Subfamily Tadorninae Reichenbach, "1850"—shelducks and allies
Subfamily Anatinae (Leach, 1820)—surface-feeding ducks and allies (including Oxyurini, stiff-tailed
ducks)
a
Recognition of subgenus based on weak support for sister group relationship between C. atratus and C.
melanocoryphus.
b
Subfamilial assignment of moa-nalos provisional; only slightly less parsimonious to consider them more
closely related to the Tadorninae and Anatinae.