CHROMOSOMES OF FIVE NORTH AMERICAN BUTEONINE HAWKS

j Raptor Res. 27(4):196-202
¸ 1993 The Raptor ResearchFoundation, Inc.
CHROMOSOMES
OF FIVE
BUTEONINE
NORTH
HAWKS
AMERICAN
SHEILAM. SCHMUTZ,JANE S. MOKER AND TRACEYD. THUE
Departmentof Animal and PoultryScience,Universityof Saskatchewan,
Saskatoon,SK, Canada S7N OWO
ABSTRACT.--Five
species
of buteoninehawkswere karyotypedfor the first time, includingthe Swainson's
Hawk (Buteoswainsoni),Gray Hawk (B. nitidus),FerruginousHawk (B. regalis),Harris' Hawk (Parabuteo unicinctus),and Broad-winged Hawk (B. platypterus).All five specieshave 68 chromosomes.The
karyotypesof the first four speciesappear to be very similar to eachother and to other buteosreported
previouslyin the literature, differing in the shapeof only one chromosome.The Broad-wingedHawk
karyotypediffers in the morphologyof severalchromosomes.
Cromosomas
de cincoespecies
norteamericanas
de halconesdel g•nero Buteo
RESUMEN.--Porprimera vez han sido examinadosy caracterizadoslos cariotiposde cincohalconesdel
g6neroButeo(Aguililla Migratoria Mayor Buteoswainsoni,
Aguililla Gris B. nitidus,Aguililla Real B.
regalis,Aguililla Rojinegra Parabuteounicinctus,y Aguililla Migratoria Menor B. platypterus).Todas las
cinco especiestienen 68 cromosomas.Parece ser que los cariotipos de halconesde las cuatro primeras
especies(B. swainsoni,
B. nitidus,B. regalis,y Parabuteounicinctus)sonmuy similaresentre ellos,asl como
lo sonconlosdeotroshalcones
deesteg6nero
ya referidos
en literaturaanterior.l•stossediferencian
s61opor la forma de s61oun cromosoma,mientrasque el Aguililla Migratoria Menor difiere por la
morfologlade varioscromosomas.
[Traducci6n de Eudoxio Paredes-Ruiz]
Chromosome
analysishasbeenusedto studyphy- pus; Bulatova1977), the RoadsideHawk (B. maglogeneticrelationshipsin severalspecies,such as nirostris;de Lucca 1983), and the White-tailed Hawk
falcons (Schmutz and Oliphant 1987) and owls (B. albicaudatus;de Lucca 1985).
(Schmutz and Moker 1991). In our view, cytogeneticsis well suitedto cladisticanalysisbecausethe MATERIALS AND METHODS
phylogenies
are basedon centricfusions(RobertThe blood sample from the Ferruginous Hawk was
sonian translocations)and inversions(White 1973,
Hsu 1979), bothof whichalsoimpair fertility (Therman 1980, Diedrichet al. 1983,Lippman-Hand and
collectedin Alberta, Canada. Bloodsamplesfrom the Harris' and four Gray Hawks were collectedin Arizona. The
bloodsamplesfrom the Swainson'sHawk and the Broadwinged Hawk were collectedfrom birds in captivityfor
Vekemans1983), part of the classicaldefinitionof rehabilitationat the Western Collegeof Veterinary Medspeciesseparation.
icine after injury near Saskatoon,Saskatchewan,Canada.
Lymphocytecultureswere establishedfrom 0.5 ml of
In an ongoingattemptto collectcytogenetic
data
on raptorsfor this purpose,we havekaryotypedfive whole blood and chromosomesprepared as describedby
Schmutzand Oliphant (1987). Karyotypeswere basedon
species
of buteonine
hawksnot previously
reported. the
bestmetaphase(s)obtainedon completecells.Several
The five species
of hawksare the Swainson's
Hawk cellswere photographedand the chromosomesarranged
(Buteoswainsoni),
Gray Hawk (B. nitidus),Ferru- Comparativestudiesof karyotypesnot donein our own
ginousHawk (B. regalis),Harris' Hawk (Parabuteo lab are baseduponfiguresin the originalpublishedpapers
unicinctus),and Broad-wingedHawk (B. platyp- when availableor photocopiesthrough interlibrary loan.
terus).
Prior to our study,fiveotherspecies
of buteoshad
beenkaryotyped.Thesewerethe CommonBuzzard
RESULTS
Although most bird specieshave a large number
(B. buteo;RenzoniandVegni-Talluri 1966, De Boer of microchromosomesand few macrochromosomes,
1976), the Red-tailed Hawk (B. jamaicensis;Shoff- the hawksandeaglesare atypicalin that few of their
ner 1974, Pape and Ogasawara 1978, Stock and chromosomes could be called microchromosomes. The
Worthen 1980), the Rough-leggedHawk (B. lago- Swainson'sHawk (Fig. 1), Gray Hawk (Fig. 2),
196
DECEMBER
1993
BUTEO CHROMOSOMES
197
Figure 1. The karyotypeof a male Swainson'sHawk (Buteoswainsoni)with an arrow marking chromosome7, the
variable chromosomewhich is metacentricin this species.
FerruginousHawk (Fig. 3), and Harris' Hawk (Fig.
4) each had 68 chromosomesincluding one large
metacentricpair (the sex chromosomes),
five large
submetacentric
pairs, six medium-sizedmetacentric
pairs, eight small metacentricpairs, and 13 small
acrocentricpairs, and one pair which was variable
in morphology.This variable chromosomewas either a large submetacentricor large acrocentric.It
was the seventhlargest by size and therefore we
refer to it as chromosome7. Traditionally chromosomesare groupedby centromerepositionand
thensecondarily
by size.We havedecidedto arrange
the chromosomes
for easeof comparisonamongthe
species,in the traditional order for the $wainson's
The Broad-winged hawk differed from the other
four hawks we studied although the total number
remained 68 (Fig. 5). The largest pair was again
metacentricand we presume it to be the sex chromosomepair. However, therewere only 16 submetacentric or metacentricpairs in total as opposedto
20-21 pairs.
We subdivided
the buteonine
hawks into two ma-
jor groups basedon the different morphologiesof
chromosome
7 (Fig. 6) and placedB. platypterusin
a third separate group since chromosomes16-20
differed.Althoughthe karyotypeof the Gray Hawk
(Fig. 2) doesnot have an obviousacrocentricchromosome7, it is the clearest karyotype overall and
Hawk and Common Buzzard but with chromosome
thereforewe choseto publish it. Other karyotypes
7 out of its traditional place for the other species. we studied clearly indicate that chromosome7 is
Other authors, such as Stock and Worthen (1980)
acrocentricin this species.Less clear, is the morwho have publishedonly a singlespecieskaryotype, phologyof chromosome20 which also appearsacplace this chromosomewith the other acrocentrics rocentricin this photograph(Fig. 2).
so it would be number 21 in their karyotype.
We attemptedto include the other buteo species
198
SGHMUTZ ET AL.
VOL. 27, NO. 4
Figure 2. The karyotypeof a male Gray Hawk (Buteonitidus)with an arrow markingchromosome
7, the variable
chromosomewhich is acrocentricin this species.
Figure3. The karyotypeof a femaleFerruginousHawk (Buteoregalis)with an arrow markingchromosome
7, the
variable chromosomewhich is acrocentricin this species.
z
w
Figure 4. The karyotypeof a female Harris' Hawk (Parabuteounicinctus)with an arrow marking chromosome7,
the variable chromosome
which is acrocentricin this species.
z
z
Figure 5. The karyotypeof a femaleBroad-wingedHawk (B. platypterus).The karyotypeis arrangedto emphasize
that chromosomes
16-20 in the middle row are acrocentricin this speciesas opposedto metacentricin the other buteos.
200
SCHMUTZET AL.
I
2
3
4
5
VOL. 27, NO. 4
6
Buteo
Buteo
7
8
9
10
11
12
X
X
X
x
x
x
13
14
15
16
17
18
n
Buteo jamaicensis
Buteo iagopus
19
Buteo
n
nn
21
22
23
24
25
26
28
29
30
31
32
33
I
2
3
4
5
6
7
8
•
•0
n
X
X
X
x
•
•
x
13
14
15
16
17
18
19
21
22
23
24
25
26
27
29
30
31
32
33
2
$
4
Parabuteo
27
Buteo
1
X X Xx
7
8
9
10
&
x x
11
12 13; 14
n
n
n
n
16
17
18
19
20
22
25
24
25
26,
29
30
31
32
33
21
28
swainsoni
• •
z
x
tl
unicinctus
Buteo
buteo
•2
5
aibicaudatus
Buteo magnirostris
n
•
regalis
nitidus
Buteo platypterus
27
Figure
6. A cladogram
illustrating
therelationships
among
thebuteonine
hawks
studied
todate
andcomputer
drawn
idiograms
ofthethreekaryotypes
observed,
uponwhichthephylogeny
isbased.
studiedpreviously,althoughthe copiesof the kar-
tailed Hawk (B. albicaudatus;
de Lucca 1985) match
yotypesthat we usedmakeour interpretation
ten- the buteoswe did very closely.However,a minute
tative.The karyotypes
of theCommon
Buzzard( B. metacentricwas described(De Boer 1976, Stockand
buteo;De Boer 1976), the Red-tailedHawk (B.
maicensis;
Stockand Worthen 1980), and the White-
Worthen 1980) which we cannotverify or dispute
sincethe small chromosomesin our karyotypes are
DECEMBER 1993
BUTEO CHROMOSOMES
not elongatedenoughto determinethis.We worked
with poorphotocopies
of karyotypesof the RoughleggedHawk (B. lagopus;Bulatova1977) and the
RoadsideHawk (B. magnirostris;
de Lucca 1983)
andcanonlysaythat thetoptwo rows(Fig. 6) agree
in general with the karyotypesof the buteoswe
studied.
DISCUSSION
Four speciesof buteoninehawks studiedhere for
the first time have one of the sametwo karyotypes.
This similarity supportsthe closetaxonomicrelationshipBrownandAmadon(1968) suggested
among
thesespecies.
Further differentiationamongsubfamilies would needto be basedon other typesof data,
suchasDNA sequence
datawhichis currentlyunder
investigationby Bob Sheehy(pers.comm.).
The differencein morphologyof chromosome
number7 is likely due to an inversion,in this case
a pericentricinversion,one of the two cytogenetic
changesthat typicallyoccurduring evolution(Hsu
1979). We are unableto saywhichis the "ancestral"
shapeof chromosome
7 and thereforeour cladogram
is "unrooted"
and shows the two main branches as
201
mosomesto demonstratespecifictranslocationsand
inversionsin mammals (Ward et al. 1991). Avian
karyotypesare much more difficultto obtainthan
mammaliankaryotypes,primarily dueto the lower
numbersof dividing cells stimulatedby mitogens
(Prus and Schmutz1987). Low numbersof dividing
cells therefore make chromosomebanding difficult
sincemost techniqueswork well on only a small
proportion of these cells. Although chromosome
banding is necessaryto determinewith precision
which chromosomes are involved in translocations,
bandingis not necessary
to identifythe presenceor
absenceof translocations,which is the key to phylogeneticcomparisons.
In addition to a poor responseto mitogens,cytogeneticstudiesof birds have been further hamperedbecausefreshbloodsamplesor growingfeathers, capableof further cell divisionin culture, are
required for analysis.Many rare and endangered
birds exist in remote areas. Field collection of sam-
plesfrom wild caughtbirds is occasionally
possible
but the logisticsof air transportto an appropriate
lab within 24 hr is frequentlyimpossible.Despite
suchdifficulties,chromosomeanalysiscan providea
derivingat an equal point in time (Fig. 6).
useful tool in taxonomic studiesand we encourage
The Harris' Hawk is placedin the genus?ara- raptorbiologists
to collaborate
in suchstudies.
buteoas opposedto Buteo;however, its karyotype ACKNOWLEDGMENTS
would not distinguishit from mostof the other Buteo
We thank JosefK. Schmutz,Bob Sheehy,and Collette
species
studiedto date.This suggests
that the Harris' Wheler for collectingthe bloodsampleswhich madethis
Hawk
is indeed a close relative
of the buteos.
study possible.We acknowledgefunding from the Sas-
In contrastthe karyotypeof the Broad-winged katchewanAgriculturalDevelopmentFund and the NaHawk showsfive chromosomes,
numbers 16-20, that
differ in morphologyfromthe restof thebuteos(Fig.
5). This would suggestthat it is the most divergent
in the subfamily.It is more closelyrelated to the
Swainsoh's Hawk
and Common Buzzard
than the
tional Scienceand EngineeringResearchCouncil which
supportsour laboratory.
LITERATURE
CITED
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falcons of the world. McGraw Hill, New York, NY
other buteos,basedon the morphologyof chromoU.S.A.
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of falconsstudiedto dateexhibit
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karyoloõicalrelationships
of the order.Genetica
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sparverius
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(Longmire et
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and
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of the White-tailed
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Received25 April 1993; accepted30 August 1993

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