Genetica 83: 207-222,199l.
0 1991 Kluwer Academic Publishers. Printed in the Netherlands.
207
Chromosomesof Australian lygosomine &inks (Lacertilia: Scincidae)
I. The Egernia group: C-banding, silver staining, Hoechst 33258 condensation analysis
S. C. Donnellan
School of Biological Sciences,Macquarie University, New South Wales2113, Australia
Presentaddress:Evolutionary Biology Unit, South Australian Museum,Adelaide, South Australia 5000, Australia
Received
2X June 1990
Accepted
in revised
Form I1 December
1990
Abstract
The karyotypes of 25 speciesfrom the scincid generaEgernia, Corucia and Tiliqua have been investigated using
C-banding, silver staining of nucleolar organiser regions (NORs) and Hoechst 33258 induced condensation
inhibition. At least one member from each of the speciesgroups of Egernia recognisedby Storr et al. (1981) was
studied. The three generahave very similar conventionally stained karyotypes of 32 chromosomes.Some species
showdepartures from this basickaryotype but theseare due to additions of C-band positive material. Silver stained
NOR patterns are variable but most specieshave a silver staining site on a pair of larger microchromosomes.All
specimensstudied except one have a proximal C-band on the acrocentric ninth pair, which shows failure to
condensefollowing treatment with the fluorochrome Hoechst 33258. Heterogamety was not observed in any
species.Mabuya multifasciata, proposed asa relative of the Egernia group, while having 32 chromosomesdoesnot
sharethe C-band marker on pair nine, unique to the Egernia group. Tribolonotusgracilis, sometimesallied with the
Egernia group, has 32 chromosomes and a similiar karyotype, but prominent procentric C-bands on all
chromosomepairs obscurethe detection of the proximal C-band marker on pair nine.
Introduction to the series
The Scincidae is the largest and most diverse of the
lizard families, containing more than 1200speciesin
85 genera(Cogger et al., 1983).The family is found in
all tropical and temperateregions,with the Australian
zoogeographic region being a centre of diversity. All
skinks in this region have beenplaced in the subfamily
Lygosominae (Greer, 1970; 1979; 1986). The systematics of lygosomine skinks has received considerable attention in the past 20 years. Phylogenetic
hypotheseshave beenformulated for this group from
studies of external morphology, osteology and immunological comparisions(Greer, 1979; Hutchinson,
1980).These hypothesescan now be tested with data
from other character sets. Karyotypes are one such
character set.
There is a remarkable paucity of karyotypic in-
formation available for the Scincidae.The karyotypes
of fewer than 30 of the 1200or so speciesare recorded
(Gorman, 1973:King, 1973a,b; Kupriyanova, 1973;
Wright, 1973;Hardy, 1979;De Smet, 1981;Bhatnagar
& Yoniss, 1977; Cano et al., 1985; Colus & Ferrari,
1988; Ota et al., 1988). Chromosome data are too
sparseto provide data to meaningfully test the various
systematicschemesproposedfor the family. However,
King’s (1973a,b) data from 10 speciesin six generaof
lygosomine skinks show, that while some variation
existsbetweenspecies,the karyotypes are conservative
enough that they may be useful for higher order
phylogenetic analysis in this group. Clearly, there is a
need for a more comprehensive survey of skink
karyotypes. In this and following papersin the series,
karyotypes of Australian lygosomine skinks are reported and their utility for phylogenetic analysis is
assessed.
208
Further interest in the karyotypes of skinks involves
the occurrence and evolution of heteromorphic sex
chromosomes (HSC). A survey of skinks is prompted
by the reports of HSC from three diverse genera
(Becak et al., 1972; Wright, 1973; Hardy, 1979). The
phylogeny of skinks is sufficiently well investigated so
that the evolutionary and genetic basis of HSC could
be established. Additionally, chromosome banding
techniques could be used to determine the genetic
changes involved in the differentiation of sex chromosomes and as the male is the heterogametic sex, the
behaviour of the sex chromosomes during meiosis
could be investigated easily.
tionships of the species comprising Tiliqua have been
subject to continuous debate since Boulenger’s (1887)
revision of this genus. Authors’ opinions differ on the
generic ranking of T. rugosa and the T. casuarinae
species group. While Storr et al. (1981) and Cogger
(1983) place T. rugosa in the monotypic Trachydosaurus, Hutchinson (1980) and Greer (1979) retain this
species in Tiliqua. Starr (1976) removed the T. casuarinae group to the genus Omolepida, a view subsequently not supported by Hutchinson (1980).
In this paper, the karyotypes, with chromosome
banding, of 27 species from the Egernia group and
their proposed relatives Tribolonotus gracilis and
Mabuya multifasciata are presented.
Introduction to the Egernia group
Materials and methods
Based on studies of their external morphology and
osteology, Greer (1979) subdivided the Australian
members of the subfamily Lygosominae into three
informal groups: the Egernia, Eugongylus and Sphenomorphus groups. Hutchinson’s (1980) data, from
comparative immunoelectrophoresis
of serum proteins, support Greer’s scheme.
The Egernia group comprises three genera: Egernia
(26 species), Tiliqua (11 species) and the monotypic
Corucia. Skinks of two other genera, Tribolonotus (8
species) from New Guinea and the Solomon Islands,
and Mabuya multifasciata from Indonesia, have at one
time or another been considered possible relatives of
the Egernia group (Horton, 1974; Greer, 1979). However, the morphological data in support of a close
relationship for Tribolonotus and A4. multifasciata with
the Egernia group are equivocal (Hutchinson,
1980).
Further, the immunological data of Hutchinson (1980)
do not support this relationship.
The generic affinities of some species from the
genera Egernia and Tiliqua have been an issue of
contention. Horton (1972) in the first formal subdivision of Egernia, recognised six species groups. This
scheme has been subsequently modified by the revision of Western Australian species, addition of new
species and the incorporation of nomenclatural changes (Storr, 1978; Storr et al., 1981; Cogger, 1975).
Hutchinson (1980) questioned the validity of these
groups as a phylogenetic arrangement as they are not
defined by synapomorphies. The intragenetic rela-
Species examined and banding techniques applied to
each are listed in Table 1. Collection localities and
museum registration numbers of individual specimens
are presented in Appendix 1. The sex of specimens was
determined by examination of the gonads after dissection.
Chromosome
preparations were obtained from
either short term lymphocyte cultures or from libroblasts cultured from heart or lung tissue. For lymphocyte cultures, blood was collected from the heart by
cardiac puncture or from the caudal vein into a sterile
heparinised syringe. Three drops of whole blood along
with O.l8mg/ml of phytohaemagglutinin were added
to lml of culture medium (Hams FlO medium,
supplemented with 20% foetal calf serum, 0. Ipg/ml
penicillin, 0. lmg/ml steptomycin, lmg/ml glutamine,
2.8% sodium bicarbonate and buffered with Hepes
buffer (47mg/ml) to pH7.5) and cultured for 72h at
30°C. Near completion of the incubation period
colchicine (OSpg/ml final cont.) was added for the
final hour. Cells were treated with hypotonic solution
(0.53% KCl) for 25 min. Cells were fixed with
methanol/acetic acid (3: 1 v/v) and air dried chromosome spreads prepared on alcohol cleaned slides.
Fibroblasts from heart or lung tissue explanted
onto coverslips in Leighton tubes, were cultured at
30°C in medium as described above. Cells were
harvested in situ as they grew around the explanted
tissue pieces. A minimum of three replicate cultures
209
were initiated for each specimen. Cell harvesting was
as above except that colchicine was added for the final
three hours of incubation.
Standard karyotypes were stained with Giemsa
(Gurr R66) stain (10% in pH6.8 Sorensons buffer).
Measurements of relative chromosome lengths were
made with vernier callipers from five karyotypes per
species. C-banding was performed with either the
technique of Sumner (1972) or Drets and Shaw (1971).
The silver staining method of Bloom and Goodpasture (1976) was used to locate presumptive nucleolar organiser regions (NOR). To test for in vitro
sensitivity to the fluorochrome Hoechst 33258, cells in
culture were treated with the fluorochrome (80pg/ml
final cont.) for a minimum of six hours prior to
harvest. Colchicine was added for the last hour of this
period. Cells were harvested as above. Chromosome
preparations were stained with 10% Giemsa stain for
five minutes.
Results
All species studies have a diploid complement of 32
chromosomes. There was no evidence of sex chromosome heteromorphism in any of the specimens
studied.
centromere on pair nine corresponding to the site of
the secondary constriction of this pair (Fig. lc).
Procentric C-bands were not apparent.
Egernia
The karyotypes of all species but two (E. whitii and E.
depressa), are very similar and are typified by the
karyotype of E. frerei (Fig. 1b). The karyotypes of E.
whitii and E. depressa differ from the usual karyotype
format of Egernia by the addition of C-band blocks,
which are described below. The usual karyotype
format of Egernia only differs from that of Corucia in
that pair three is more metacentric presumably by
virtue of a pericentric rearrangement. C-banding
patterns are also similarly conserved. Two particular
C-bands are apparent in all species. On pair nine there
is a proximal C-band similiar to that in C. zebrata. On
the end of the long arm of pair two there is a less
intensively stained C-block. This block is apparent
after barium hydroxide induced C-banding (Sumner,
1972) but is not observed after the sodium hydroxide
procedure of Drets and Shaw (1971). In contrast, the
C-band of pair nine is produced by both treatments.
C-bands, additional to the proximal band on pair
nine and the distal long arm band on pair two, are seen
in some species, a description of these is given for each
species group (Storr et al., 1981).
E. cunninghami group
Conventionally stained and C-banded karyotypes
Corucia zebrata
Two specimens of unknown sex were examined. The
first two chromosome pairs are submetacentric with
relative lengths (% of total haploid genome length) of
17 and 16% (Fig. la). The third and fourth pairs are
submetacentric and metacentric respectively with relative lengths of 13%. The fifth pair is submetacentric
with a relative length of 7%. Pair six is submetacentric,
pairs seven and eight are metacentrics and pair nine
an acrocentric, with relative lengths ranging from 5 to
3%. A small secondary constriction is sometimes
apparent proximally on pair nine. Pairs ten to sixteen
are microchromosomes of which at least two pairs are
acrocentric, the remainder being metacentric (Fig. la).
The total relative length of the microchromosomes is
15%. There is an interstitial C-band proximal to the
Additional C-bands are found in E. cunninghami (Fig.
Id), E. depressa (Fig. If) and E. stokesii (Fig. le).
Variant interstitial C-bands are found in pairs five and
six in E. cunninghami; this variation will be described
elsewhere (Sadlier and Donnellan, unpublished). Of
the two E. stokesii C-banded, one individual was
heterozygous for the presence/absence of a small Cband at the proximal tip of pair nine (Fig. le), this
band was absent in the second individual. A silver
stained site was found terminally on the short arm of
pair nine (Fig. le). In E. depressa pair nine was
approximately the same size as pair six. The increase in
size of pair nine is due to the addition of a distal
C-band block. This pair could be identified as the
ninth pair by the possession of the conservative
proximal C-band (Fig. If). A silver stained site was
found terminally on the long arm of pair nine (Fig, If).
210
Fi,g, 1. Standard and C-band karyotypes of Coruciu zebrafa and some speciesof Egernia. (a) standard and (c) partial C-band karyotype of C.
Z&UIU from the Solomon islands; - (b) standard karyotype of E. frerei from Vrilya Point, Qld; - (d-f) partial C-band karyotypes of E,
~~~~j~~~rff~ri from near Collector, N.S.W., E. srokesjifrom near Oraparinna Station, S.A. and E. ~epressu from Menzies, W.A. respectively.
Boxes in (e) and (f) show silver stained pairs 9. Bar indicates 10pm.
Fi~q. 2 C-band karyotypes
ofeight species ofEpwziu.
(a)E. kingiifrom
near Warroona,
W.A.; - (b)E. coventryi
from near Tooradin,
Vie., c-h
partial C-band karyotypes
of(c)E.fvereifrom
Vrilya Point, Qld: - (d)E. majorfrom
near Port Macquarie,
N.S.W.; -(e)E. sfriolutofrom
near
Cobar, N.S.W.;-(f)E.
mcpheeifrom
Liston. N.S.W.:-(g)E
modesrufrom
near Bendemeer,N.S.W.and(h)E.
mu/tiscutatafrom
israeliteBay
area. W.A. Bar indicates IOflm.
212
E. kingii group
An additional C-band on a single pair of microchromosomes was found in one specimen from the
monotypic E. kingii group (Fig. 2a).
E. luctuosa group
The centromere of the largest pair of metacentric
microchromosomes had a prominent C-band in E.
coventryi (Fig. 2b).
when compared to other Egernia and to each other. In
E. whitii from Jenolan Caves, N. S. W. examined by
King (1973b), pairs ten and eleven were larger than
those in the standard karyotype format of the Egernia
group. King (1973b) also observed additional heterochromatin in orcein stained interphase nuclei of these
individuals which is perhaps the C-positive material
found in this species in the present study.
E. major group
The specimen of E. frerei was heterozygous both for a
proximal C-band on pair six and for a prominent
procentric C-band on one pair of acrocentric microchromosomes (Fig. 2~). In E. major, two pairs of
microchromosomes had C-band positive short arms
and as these were seen in association at metaphase
they are presumably the NOR sites in this species (Fig.
2d).
E. striolata group
In three species E. mcpheei (Fig. 29, E. saxatilis and E.
striolata (Fig. 2e) there was a prominent C-band on a
single pair of large metacentric microchromosomes.
E. whitii group
Three pairs of microchromosomes have prominent
procentric C-bands in E. modesta (Fig. 2g). In E.
multiscutata at least two pairs of microchromosomes
have obvious procentric C-bands (Fig. 2h). In E. whitii
pair nine is longer in all specimens examined and in
addition the two largest pairs of microchromosomes
are longer in some specimens. One specimen was
heterozygous for the length of the long arm of pair
seven (Fig. 3a). In all individuals the differences in the
length of chromosomes from the standard format of
the genus were due to the addition of C-band material
either in interstitial or, more commonly, in terminal
positions (Fig. 3b-e). All five specimens C-banded
showed a unique pattern of heterochromatin distribution and in four animals at least one pair of chromosomes was heterozygous for the size or presence/absence of C-band blocks. Chromosome pairs 9 to 11
not only show an increase in the amount of C-positive
heterochromatin which can be attributed to addition,
but they also show a loss of euchromatic material
Fig. 3. C-band karyotypes
ofEgernia whirii. (a) full C-banded cell of
a male from 13.8 km S. Cooma, N.S.W.; - (b-e) C-banded pairs 6,
7,9, 10 and I1 of(b) female from 13.8 km S. of Cooma, N.S.W.; (c)male from 15 km N. ofBombala,
N.S.W.;-(d)
male from 13 km
W. Gungal, N.S.W. and(e) male from 5 km E. of Evandale, Tas.
Bar indicates 10,um.
213
Fig, 4. Standard and C-band karyotypes
of some species of Tiliqua. Standard karyotypes
of (a) Tiliqua gigas from Port Moresby.
P.N.G. and
(b) T. gwur&from
Mt. Nebo, Qld; -(c-h) partial C-band karyotypes
of(c) T. branchialis
from Port Pirie, S-A.; -(d) T. gerravdiifrom
Mount
Warning,N.S.W.;(e) T. nigmhtea from Bondi State Forest, N.S. W .; - (f) T. occipitahs from near Nullarbor
Station. S.A.; - (g) T. rugosa from
Fowler’s
Gap Station, N.S.W. and (h) T. scincoidcs from Epping, N.S.W. Bar indicates
IOpm.
214
Tiliqua
The karyotypes of Tiliqua species, as typified by T.
gigas (Fig. 4a), with the exception of T. gerrardii, are
very similar to those of Egernia. Pair five of Tiliqua is
metacentric whereas in Egernia and Corucia it is more
submetacentric. The largest pair of microchromosomes of T. gerrardiiis metacentric and larger than the
corresponding pair in other speciesof Tiliqua (Fig. 4b).
C-banding of this pair revealed a totally heterochromatic short arm and prominent procentric Cbands accounting for the increase in size. This same
pair, in another specimen, was heterozygous for the
presence/absence of a constriction, which stained
positively with the silver staining technique. The
standard karyotypes of Tiliqua nigrolutea and T.
rugosa reported by King (1973a, b) and T. scincoides
reported by de Smet (198 1) are indistinguishable from
those presented here.
All specimens of Tiliqua that were C-banded,
possess a proximal C-band on pair nine in a position
corresponding to a small secondary constriction frequently apparent in conventionally stained preparations. A less intensively stained C-block is found
distally on the long arm of the second pair in most
specimens. This band is absent in preparations from T.
nigrolutea and T. scincoides C-banded by the tech-
5. Standard and C-band karyotypes of Mabuya mulrifasciata and Tribolonorusgraciiis.
(afstandard and(b) C-band karyotype of female M.
from Indonesia. Insert shows silver staining of pair one; -(c) standard and (d) C-band karyotype of male 7: graci/is from Karkar
Island. P.N.G. Bar indicates 1Opm.
Fig
mulrifosciu/a
215
nique of Drets and Shaw (1971). However, as King
(1980) noted, the appearance of these less intensively
stained bands is dependent on the severity of the
banding pre-treatment. A variety of C-bands, in
addition to those on pairs two and nine, are found in
most species. In T. gerrardii, T. nigrolutea, T. rugosa
and T. scincoides prominent C-bands are found on
some of the larger microchromosomes (Fig. 4d, e, g,
h). C-banded preparations of T. branchialis were not
of sufficient quality to detect C-bands other than those
on pair nine.
Fig. 6. Hoechst 33258 treated chromosomes
of Corucia. Egernia, Tiliqua and Mabuya. (a-d)complete
karyotypes
of Hoechst 33258 treated cells
of (a)E. cunninghami;
- (b) 7: gerrardii;
-(c) T. occipi/a/is; - (d)M. mu/tifascia/a;
-(e-n) C-banded (c)or Hoechst 33258 treated (h) chromosome
pair nine from (e) C.2ebrata;
- (f) E. covenrryi;
- (g) E. depressa; -(i) E. saxutilis; -(j) E. sfriolata; (k) T. gigas; - (I) T nigrolutea;
- (m) T. rugosa
and (n) T. seineaides. Bar indicates IOpm.
216
Mabuya multifasciata
Mabuya multifasciata has 32 chromosomes (Fig. 5a),
but a number of features distinguish its karyotype
from that of the Egernia group. There is a secondary
constriction on the short arm of the largest pair of
chromosomes which stains with the silver staining
procedure (Fig. 5b). Pairs six and seven are metacentric and approximately of equal size, pair eight is
sub-metacentric and pair nine is metacentric (Table 2).
The C-banding pattern does not show any similarity
to that of any member of the Egernia group (Fig. 5b).
Procentric C-bands are minimal. There are small
procentric C-bands on the first two pairs which fail to
condense when treated with Hoechst 33258 (Fig. 6d).
stained blocks and three (13%) were heteromorphic
for a tandem duplication in one of the two homologous NORs.
Hoechst 33258 induced uncondensed sites
In this study, chromosomes of 13 species from the
Egernia group were examined for Hoechst 33258
sensitivity (Table 1 and Fig. 6). The chromosomes of
Egernia multiscutata did not show any evidence of
specific sites of sensitivity to Hoechst 33258. An
uncondensed region was not observed on pair nine in
Table
applied
Tribolonotus gracilis
has 32 chromosomes ( Fig. 5c) and
a karyotype that is very similar to that of the Egernia
group. Prominent procentric C-bands are observed on
most pairs including pair nine (Fig. 5d). It was not
possible to determine the presence of a proximal Cband on pair nine because of the prominent procentric
C-bands in this species. Cultured cells were not
available for testing with Hoechst 33258.
TriboIontusgraciIis
1. Species of skinks
to each specimen.
and banding
techniques
SND- sex not determined,
S- standard
karyotype,
C- C-band
karyotype.
A- silver stain, H- Hoechst 33258 sensitivity
Species
Male
SCAHSCAH
Corucia
zebrata
1 (SND)
Egernia
coventryi
cunninghami
2
12 5
I
2
1
1
1
1
I
III
111
1 1
1
2 1
3 1
2 2
5 4
depressa
frerei
hosmeri
inornata
kingii
lurtuosa
major
mcpheei
Silver stained NOR patterns
In the 18 species of the Egernia group studied, there are
a variety of chromosomal locations for silver stained
NORs (Fig. 7). The most common site was on a large
pair of microchromosomes. Most NORs are terminal
except in T. gerrardii where there is an interstitial site
corresponding to a secondary constriction on the
largest microchromosome. In better, conventionally
stained preparations of species with sites on microchromosomes there is a faint satellite on a pair of
microchromosomes; presumably these are the pair
that silver stains as they are found often associated at
metaphase.
Of the 24 individuals which were silver stained,
seven (29%) had homologous silver-stained NORs of
unequal size. Of these, four (17%) individuals were
heteromorphic for the presence/absence of silver-
karyotyped
modesta
multiscutata
napoleonis
saxaiilis
striolata
s f okesii
whitii
Tiliqua
branchialis
casuarinae
gerrardii
gigas
multtfasciata
nigrolutea
occipitalis
rugosa
scincoides
Mabuya
Tribolonotus
S, C, H.
I
4
I
1
1
2
1
12
I
1
1
6
1
1
7
I
1
22
I
1
I
1
I
I
1
I
2
2
I
1
I
4
1
1
I
1
1
I
I
I
1
2
I
2 1 I
I
1
I
1 I
I 3
I
1
1
111
2
I
2 (SND) 2S, lC, IH.
2
1 1 (lSND,S,C)
2 1 I I I I I I
2 I
1 2
1
I
multifasciata
gracilis
Female
1
1
1
I
1
217
HAPLOID
Egernia
cunninghami
headed
5
6
10
7
OF NOR
9
8
ti
m
1
2
n
E. stokesi
1
H
1
1
E. coventryi
1
1
E. frerei
1
E. major
1
2
E. mcpheei
1
1
E. saxa tilis
2
1
E. striolata
1
1
E. modesta
2
E. multiscutata
1
Tiliqua
2
branchialis
H
x
H
K
2
1
H
2
n
1
T. casuarinae
2
T. gerrardii
1
2
I
1
T. scincoides
2
1
T. rugosa
2
1
T. m ultifascia
column
3/4
PAIR AND POSITION
E. depressa
E. kingii
Fig, 7. Distribution
v
n
SPECIES
CHROMOSOME
ta
n
of silverstained
NORs among 18 species of the Egernia
group.
m represent the number of pairs of microchromosomes
showing
this species, but this pair does have a small procentric
C-band (Fig. 2h). In the remaining 12 species, a variety
of sensitive sites and effects were observed. The
secondary constriction on pair nine always showed
some sensitivity to the compound. The effects on this
site range from lengthening of the achromatic gap to
chromatid or chromosome breaks. In two species,
Tiliqua occipitalis and T. rugosa,two achromatic gaps
separated by a fine darkly stained areas were observed
(Fig. 6c, m). In all 12 species the sensitive site appeared
n is the number ofspecimens
silver stained NORs.
examined,
numbers
under the
to correspond to the position of the proximal C-band
on the ninth pair (Fig. 6e, n). This site was the only
sensitive area in C. zebrata, E. coventryi, T. nigrolutea,
T. occipitalis (Fig. 6c) and T. rugosa. While the
proximal C-band of pair nine of E. depressawas
sensitive to Hoechst 33258 the distal C-block showed
no effect (Fig. 6g). In Figure 6g the chromatids of the
distal C-block show lack of chromatid apposition.
This behaviour is seen very frequently in standard
preparations and therefore is not due to the Hoechst
218
33258 treatment. In some species sensitive sites in
addition to that on pair nine were observed. These
were located on pairs six, seven, ten and a smaller
microchromosome pair in T. gerrurdii (Fig. 6b) and on
pair six in E. depressa. These were no C-bands detected
at the sensitive sites on pairs six and seven in both
species. Some species, E. kingii, T. scincoides, E.
cunninghami (Fig. 6a), E. striolata and E. saxatilis
possessed one or more microchromosomes with sensitive sites.
Discussion
Karyotype evolution
A number of studies indicate that analysis of chromosomal variation without the benefit of G-banding or
similar techniques grossly underestimates the extent of
rearrangements in the euchromatic portion of the
karyotype (Haiduk et al., 1981). Therefore the magnitude of variation revealed by this study should be
regarded as a preliminary result awaiting further
analysis with a differential staining technique such as
G-banding. Nevertheless the euchromatic component
of the karyotype of the 28 species from the Egernia
group appears to have undergone little apparent
change. The only rearrangements observed are small
pericentric rearrangements involving two chromosome pairs.
The heterochromatic component of the karyotype
of the Egernia group shows both conserved and
dynamic aspects. A notable feature is the possession of
the proximal C-band on pair nine in the three genera.
With the exception of one species this band shows
sensitivity to the fluorochrome Hoechst 33258 while
none of the other C-bands show sensitivity across such
a wide range of species. The conservation of Hoechst
33258 sensitive heterochromatin on the sex chromosomes in macropodid marsupials parallels this case
(Hayman & Sharp, 1981). Other C-bands show
species specific distributions or appear as variants
within individuals. These usually occupy terminal or
procentric positions, interstitial bands being uncommon. The loss of euchromatic material through
transformation into C-positive heterochromatin in
some of the chromosomes of E. whitii, appears
another example of the transformation of euchromatin into heterochromatin (King, 1980).
A ‘grey’ C-band, similiar to the band which occurs
distally on the second largest pair in the Egernia group,
is present on the largest pair in the karyotype of
Varanus (King et al., 1982) and Cnemidophorus (Bull,
1978) on one of the larger metacentric pairs in Anolis
(Blake, 1983), and Amphibolorus (Donellan, unpublished) and on the second pair in several species of the
Eugongylus and Sphenomorphus groups of lygosomine
skinks (Donnellan, unpublished). In the skinks, as
with Varunus, this block is G-band negative. A
combination of G-banding analysis to determine the
homology of the chromosome segment bearing this
band and fluorochrome analysis to determine the
composition of this band would be necessary before
the pattern of distribution of such a band amongst the
lizard families could be used to infer phylogenetic
relationships.
Silver staining patterns
It should be noted that the silver staining technique of
Bloom and Goodpasture (1976), used here to localize
NORs, is not specific for 18s and 28s ribosomal RNA
loci in some amphibians (Varley & Morgan, 1978) and
grasshoppers (White et al., 1982). It should be noted
also that the secondary constriction, which was frequently apparent proximally on pair nine in the
Egernia group karyotype, does not silver stain.
The chromosome pairs involved, the chromosomal
position, and number of silver stained NORs in each
species from the Egernia group are variable. However,
this variability is accompanied by remarkable overall
conservatism of the karyotype, which would be
unexpected if conventional types of karyotypic rearrangements were implicated in shifting the chromosomal location of the NORs. This phenomenon has
been observed in many groups of animals (Schmid,
1978a, b; Seuanez, 1979; King, 1980). A number of
alternative hypotheses have been proposed to explain
this phenomenon (Tantravahi et al., 1976; Nardi et al.,
1977; King, 1980), but to date none has recieved
empirical support.
Presence/absence heteromorphisms of NORs occur
only in species with NORs located at more than one
219
site. There is a higher incidence of this type of
heteromorphism in skinks compared with the Anura
where Schmid (1982) found that the incidence was
about one percent. Almost all the species studied by
Schmid (1982) had a single pair of NORs and in the
three specimens that showed a presence/absence
heteromorphism, the deletion of the NOR was confirmed by the absence of the NOR associated C-band
heterochromatin. However, in skink karyotypes none
of the chromosomes showing presence/absence heteromorphisms
have any NOR associated heterochromatin. It is certainly possible that such heteromorphisms are due to the inactivity of one homologue, as has been reported with the human NOR
bearing chromosomes (Miller et al., 1977). However,
Ferraro et al. (1981) conclude that, although silverstaining patterns are clonally inherited, all NORbearing chromosomes can be silver stained in a given
cell population. Examination of a sufficiently large
number of cells should detect all the NORs present in
an individual.
Systematic considerations
1. Relationship of Egernia group to other Iygosomine
skinks
The presence of the distinctive C-band, which is prone
to Hoechst 33258 undercondensation, on pair nine in
combination with the unique karyotype format of the
Egernia group are two characters that clearly distinguish the three genera involved from members of
the Eugongylus and Sphenomorphus groups which
have their own conserved and distinctive karyotype
formats (King, 1973b; Donnellan, unublished). However, whether the unique C-band marker on pair nine
and the karyotype format of the group represent
synapomorphic
characters uniting members of the
group of the exclusion of all other lygosomine skinks
remains to be determined. Similar analyses of appropriate outgroup taxa, i.e. non-Australian lygosomines,
are required. Taxa of importance here would be those
that are clearly outside of the subfamily Lygosominae.
Unfortunately appropriately analysed karyotypic data for such taxa are almost non-existent.
Comparison of the Egernia group karyotype with
the karyotype of Mabuya multifasciata, which lacks
the distinctive C-band marker on pair nine and has a
different karyotype format, does not lend credence to
Horton’s view of a close relationship for A4. muftifasciata with the Egemia assemblage. Karyotypes of
11 forms of Mabuya have been reported (Becak et al.,
1972; Gorman, 1973; Desmet, 1981; Colus & Ferrari,
1988; Schmid & Guttenbach, 1988). Diploid numbers
vary from 26 to 32. However, specimen misidentification, inadequate taxonomy (Greer, pers. comm.) and
inferior cytological techniques require that some of
these data be critically reexamined.
The karyotype of Tribolonotus gracilis is very
similar to that of the Egernia group, but the presence
of the distinctive C-band marker on pair nine could
not be determined. Thus at this stage it is not possible
to determine from the karyotype data whether T.
gracilis has a close affinity to the Egernia group.
2. Relationships of species of the Egernia group to each
other
Chromosomal variants that occur as differences between species are usually restricted to single taxa and
are hence autapomorphic. Such variation is phylogenetically uninformative and thus the karyotypic
data fail to contribute further to an understanding of
the phylogenetic relationships between species of the
Egernia group.
Acknowledgements
I am grateful to the following for supplying animals:
W. Boles, E. Cameron, H. Cogger, H. Ehmann, F.
Geiser, A. Greer, A. Grice, M. Hutchinson,
G.
Mengden, C. Moritz, P. Robertson, R. Sadlier, G.
Shea, and J. Wombey. G. Mengden generously
provided suspensions of fixed cells of Corucia and
Tribolonotus. I am grateful to the fauna authorities of
all Australian states for their cooperation. G. Sharman and P. Johnston provided laboratory space and
equipment. C. Murtagh, B. McAllan and K. McGinnis provided technical assistance. The South Australian Museum provided support for the preparation
of this manuscript.
220
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Appendix 1
Specimens karyotyped.
Institution
codes follow Leviton c’t al. (1985). E and T prefixes
to the author’s laboratory
numbers.
refer
Corucia
C. zehrata
l?grmia
E. covenrryi
of Emuvale, Qld. 28”12’S, 152’24’E. AMS Rl12877 near Yetman,
N.S.W. 29”04’S, 150’44’E.
E. depressa
AMS Rl02676-7
Menzies, W.A. 29’3l’S.
121”02’E.
E.fierei
AMS R958 I2 Captain Billy Creek, Qld. I l”38’S. 142”50’E,
AMS RI00018 S. of Djawamba
Massif, N.T. 12”33’S, 132”56’E,
AMS RI06841 Vrilya Point, Qld. I l”l4’S,
142”07’E.
E hosmeri
AMS RI06841 30 km S. McArthur
R., N.T. 16”38’S,
136”OO’E.
E. inornata
AMS Rl02991-2 Round Hill, N.S.W. 33”03’S, 146”12E’.
E. kingii
ANWC
R3188 IOkm E. of Esperance,
W.A. 33”47’S.
121”58’E, AMS R102709, 110399 3.4km N. of Warroona,
W.A.
32”49’S. 155”55’E.
E luctuosa
AMS R98690S,ofJarrahdale,
W.A. 32”25’S, ll6”lO’E.
E. major
AMS R97861-2
Connondale
Range, Qld. 26”45’S,
152”37’E, captive specimen, l5km S. of Port Macquarie,
N.S.W.
31”32’S, 152’47.E.
E. modtwa
AMS R98692, 106894-5 12.9km W. of Bendemeer.
N.S.W. 30”5l’S. 15l”Ol’E.
E. tnultrscurata
AMS R96632 Israelite Bay, W.A. 33”17’S. I32”25’E.
E. napoleonis
AMS R96627 Boxer Is., W.A. 34”Ol’S, 121’4l’E.
AMS RI05602 Albany, W.A. 35”Ol’S, ll7”53’E.
E. sawarilis
AMS R93330 Mount Tomah, N.S.W. 33”33’S, 150”25’E,
AMS R96631 Grose Valley, N.S.W. 33”36’S, 150”20’E,
AMS
R92285 Brindabella
Range, N.S.W. 35”2O’S. 148”5O’E.
E. striolara
AMS Rl06936 90km E. of Cobar, N.S.W. 31”34’S,
146”4X’E, AMS R96628 near Uralla, N.S.W. 30”4l’S,
151”30’E,
AMS R96629 Girilambone,
N.S.W. 31”15’S, 146”54’E.
E. sroliesiiAMS
Rl06914,91527km
WSW. ofBroken
Hil1,N.S.W.
32”02’S, 141”08’E, AMS RI06836 5.3km N. of Oraparinna
Station.
S.A. 31”19’S, 138’42’E.
E. n$titii
AMS R92313 Micalong
State Forest, N.S.W. 35”15’S,
148”30’E.
AMS R94875. 876 Mount
Dowe, N.S.W.
30”17’S,
150”lO’E, AMS Rl06838-9
13.8km S. of Cooma, N.S.W. 36”2l’S,
149”12’E, AMS RI 12344 l5km N. of Bombala, N.S.W. 36”48’S,
149”16’E,
AMS R106897
1.3km of Gungal,
N.S.W.
32’16%
150”3O’E, AMS R106837 5km E. of Evandale, Tas.
41”34’S. 147”17’E, AMS R97806 Freycinet
Peninsula, Tas.
42”12’S, 148”19’E,AMSR76617GibralterRange.N.S.W.
29”35’S.
152”13’E.
E. mcpheei
AMS R76514
Liston.
N.S. W. X39’S,
152”05’E.
Tiliqua
two captive
specimens
collected
from Solomon
Islands.
ECOI Boneo, Vie. 38’25%. 144”53’E, AMS RI06920
Deep Ck, E. of Tooradin,
Vie. 38”13’S, 145”26’E.
E. cunninghami
AMS R93474 Fleurieu Peninsula, S.A. 35”4O’S,
138”09’E, EC22 Clarkefield,
Vie. 37”29’S, 144’45’E, EC23 You
Yangs, Vie. 37”56’S,
144”26’E,
AMS RI12343
l5km
N. of
Bomba1a.N.S.W.
36”48’S, 149”16’E,AMSRl02740-I
13.8kmS.of
Cooma. N.S.W. 36”21’S, 149”12’E, ECI-3 5km W. of Collector,
N.S.W. 34”56’S, 149”2l’E, AMS Rl04190-I
Kanangra Walls Area,
N.S.W. 33”59’S, 150”08’E, EC76 Boyd River, N.S.W. 33”58’S,
150”03’E. EC5, 6, 8, II l2.3km W. of Rylstone N.S.W. 32O48’S,
149”53’E, AMS R76523 Newnes, N.S.W. 33”lO’S, 150”75’E, AMS
RI 10622 Dobroyd
Point,N.S.W.
33”52’S, 151”16’E,AMS
R110623
Barrenjoey
Head, N.S.W.
33”35’S,
151”20’E,
AMS
RI02745
Watagan Mtns, N.S.W. 33”02’S. 151’27’E. AMS RI02979
IOkm
N.W. of Ashford,
N.S.W. 29”16’S, 151”02’E, AMS R95875 l4km
W. of Ashford. N.S.W. 29”2O’S. 150°57’E, QM 5400434 17.8km E.
T. branchialis
SAMA R22969 Port Pirie, S.A. 33”12’S, 138”0O’E,
AMS RI02665
near Lancelin.
W.A. 31”02’S, Il5”20’E.
AMS
Rl02715-6Tamala
Station, W.A. 26”4l’S, 113”42’E, AMSR106834
Arubiddy,
W.A. 31”48’S, 125”55’E.
T casuarinae
AMS R76516 Watagan
Mtns, N.S.W.
33”02’S,
151°17’E.TCI
2.6kmS.ofBronteLagoon.Tas.42”15’S,
156”30’E.
T gcrrardii
AMS RI11344
Mount
Warning,
N.S.W. 28”22’S,
153”17’E, AMS R76522.97892
Mt. Nebo, Qld. 27”23’S, 152”47’E,
AMS RI06901 Kirrama State Forest, Qld. l8ol6’S, 145’50’E.
T. gigas AMS Rll6664
Port Moresby,
P.N.G. 9”3O’xS, 47”07’.E
T mu/rifascia/a
AMS RI02739 350km NE. Kaoungie, W.A.
17”57’S, 124”47’E, AMS R98686 Coulomb
Point, W.A. 17”22’S,
122”09’E. AMS RI06904
near Bulloo Downs,
W.A. 24”OO’S.
Il9”44’E.
T. ni<grolutea
AMS RI06842 Bondi State Forest, N.S.W.
37’08’S, 149’09’E. captive specimen, Freycinet
Peninsula, Tas.
42’08’S, 148” l7’E.
T. occipitalis
AMS R102736 Tamala Station,
W.A. 26O4l’S,
I l3”42’E, AMS RI02680 45.6km W. of Madura.
W.A. 31”59’S.
222
126”36’E.
specimen
AMS RI02737 Albany, W.A. 35”02’S, 117”55’E,captive
20km E. of Nullarbor
Station, S.A. 31”4O’S, 131”06’E.
T. rugosa 2 specimens lost, Fowlers Gap Station, N.S.W.
31”OS’S. 141”42’E, AMS RI02978 Port Gregory,
W.A. 28”12’S,
I14”15’E,AMS
R102714TamalaStation,
W.A. 26’41’s. 113”42’E.
r \c~inc~oit/~.c AMS R92279 East Alligator
River, N.T. 12”28’S,
132”52’E. specimen lost, Budgewoi.
N.S.W. 33”14’S, 151”34’E,
AMS RI06900 Epping, N.S.W. 33”46’S, 151”05’E, AMS R97537
East Alligator
River, N.T. 12”46’S, 132”44’E.
Tribolontus
T. grucilis
AMS
RI21447
Karkar
Is., P.N.G.
4”42’S, 45’55.E.
Mabuya
M. mu&kwiuru
AMS
R73713 Indonesia,
exact locality
unknown