See Sharp and Rowell (2007) for collection and cytological methods.
Results
The various autosomal rings described in this chapter will be referred to as
“karyotypes” rather than “karyomorphs”, as karyomorph is used elsewhere to describe
chromosomal confi gurations which are fi xed in populations. Six new karyotypes were identifi ed which include rings of autosomes. These are: a ring of four chromosomes (RIV); ring of twelve (RXII); ring of fourteen (RXIV); ring of sixteen (RXVI); two rings of four (RIV+RIV) and a ring of six with a ring of four (RVI+RIV) (Figure 1 A F). All autosomes not involved in rings are in metacentric bivalents, and two X chromosomes are present, one a metacentric fusion product, and the other telocentric. This X fusion confi guration matches that of the mII karyomorph (Figure 2 C in Sharp & Rowell 2007), amongst which these rings are found. These ring carrying forms have
been found in two small disjunct locations near the edge of the distribution of the mII karyomorph, the Ovens Valley in the Victorian highlands, and near Tumbarumba in NSW (Figure 2 A). The various ring forms are found intermingled with one another and mII carrying individuals at sites and in colonies (Table 1 & Figure 3 A). Results pertaining to each locality are discussed in turn below.
Table 1 Collection site details and sample sizes.
Site GPS Tree. Colony No. males & karyotype
B(39) S36 45 44 E147 01 26
3 5 RXVI
6 2 mII & 1 RXVI
7 1 RIV 8.1 1 RXIV 8.2 1 mII 9 1 RXVI G(100) S36 48 30 E147 03 13 1 2 mII 2 1 mII 4 2 mII 7 2 mII 8 9 mII 9 2 mII
11 1 mII & 1 RXII
13 1 RIV
17 1 mII & 2 RXIV
19 1 mII
21 1 mII & 2 RXIV
P(146) S36 45 03 E147 01 15
1.1 2 mII, 3 RIV, 1 RIV+RIV & 1 RVI+RIV
1.2 1 mII
2 3 mII, 5 RIV & 1 RXII 3 1 mII, 2 RIV & 1 RIV+RIV 4 1 RIV & 1 RVI+RIV
5 1 mII
6 1 RIV+RIV
7 1 mII & 1 RIV
8 1 RIV+RIV
9 1 RIV+RIV
10.2 1 RIV & 4 RIV+RIV
10.3 2 mII
S(147) S36 46 07 E147 02 38
3 1 RIV
4 2 mII, 1 RIV & 1 RIV+RIV
5 1 RIV
F(148) S36 47 26 E147 02 28
3 1 mII
4 1 RXII
5 1 RXII
mII = metacentric bivalents; RIV = ring of four chromosomes; RXII = ring of twelve; RXIV = ring of fourteen; RXVI = ring of sixteen; RIV+RIV = two rings of four; RVI+RIV = ring of six and ring of four. Tree. colony column breaks the fi ndings down into individual colonies / retreat sites. Numbers in right hand column indicate the number of individuals with the given karyotype; lists of karyotypes in this column indicate karyotypes found cohabitating. All sites are in or near the Ovens Valley except T(153), which is near Tumbarumba in NSW. Note that mII individuals are found at all sites, and that a high proportion of colonies contain a mixture of karyotypes.
K(151) S36 42 51 E147 08 26
1 9 mII
3 5 mII & 4 RIV 4 2 mII & 1 RIV
5 2 mII
S(160) S36 45 31 E147 02 05 1 1 mII, 5 RIV & 1 RIV+RIV
2 6 RIV & 4 RIV+RIV
T(153) S35 49 52 E148 04 13 1 5 mII & 3 RIV
E(97) S36 37 04 E146 48 31 1 1 mII 2 1 mII 3 1 mII 4.1 3 mII 4.2 1 mII P(98) S36 40 54 E146 53 33 1 2 mII 2 5 mII B(99) S36 44 29 E147 00 41 3 1 mII 6 1 mII 9 2 mII 10 1 mII 12 5 mII 13.2 5 mII W(101) S36 46 19 E146 58 54 1 1 mII 2 1 mII 3 1 mII 4 1 mII 5 1 mII B(102) S36 45 39 E146 51 46 1.1 7 mII 2 1 mII 3.1 4 mII 3.2 2 mII MB(103) S36 44 28 E147 10 40 1.2 6 mII 2 1 mII 3 1 mII 5 1 mII 6 1 mII CP(149) S36 46 31 E147 01 53 1 1 mII 2.2 1 mII 3 8 mII 4 1 mII 5 2 mII S(159) S36 50 09 E147 04 22 3 3 mII
(a) (b)
(c) (d)
(e) (f)
Fig. 1 Photographs of meiotic spreads showing the various karyotypes observed: (a) RIV; (b) RIV+RIV; (c) RVI+RIV; (d) RXII; (e) RXIV; (f) RXVI. Metacentric X’s are marked with X, telocentric X’s marked with x.
Fig. 2a Map showing the two locations at which rings of chromosomes have been found; Tumbarumba and the Ovens Valley. Note the tII populations on the south-eastern side of the Great Dividing Range, suggesting that the ring localities are close to the edge of the mII distribution.
Fig. 2b Collection sites within the Ovens Valley, see Figure 3 A for the percentage of the karyotypes at each site, and Table 1 for details.
Fig. 3b The number of individuals with each karyotype found at polymorphic collection sites in and around the Ovens Valley.
The Ovens Valley
The Ovens Valley in the Victorian high country is a long, narrow almost fl at valley running in a south-east / north-west direction. The Ovens River drains Mt Hotham and Mt Feathertop in the south-east, and runs down out of the high country towards the plains of northern Victoria to the north-west. This is close to the edge of the mII distribution, which appears to be somewhere near Mt Hotham running north-east to south-west along the spine of the Great Dividing Range (GDR). D. cancerides habitat in this area is mostly limited to the valley fl oors, although small patches of habitat are apparent in the more protected gullies.
The area around the Ovens Valley has been relatively densely sampled; 16 collection sites were established, including seven at which ring forms were found. Most sites from which rings were observed are along a 9.5 km stretch of the Ovens Valley, or in adjoining valleys (Figure 2 B). These seven sites are surrounded by sites at which only mII individuals have been found, however given small sample sizes at several of these sites it is uncertain whether they are fi xed for the mII confi guration (Table 1). Across the seven ring sites, males were analysed for meiotic confi guration from 42 separate colonies, yielding 68 ring carrying individuals and 62 mII individuals (48%). This ratio of ring and mII individuals is not signifi cantly different to 50:50 (χ2= 0.277,
df = 1, p = 0.599). Figure 3 A shows the distribution of individuals carrying mII and each of the rings at the various sites in the Ovens Valley, and the relative frequency of
the karyotypes overall is shown in Figure 3 B. Given the linearity of the valley habitat, Figure 3 A approximates a transect running through the zone (if K(151) and MB(103) are ignored). The largest ring karyotypes (RXII, RXIV & RXVI) were only found at four sites from the middle of the zone, whereas the smaller ring karyotypes were found over a larger area.
The various ring karyotypes are generally found mixed with one another and mII individuals. All sites included mII individuals, and of the 25 colonies from which more than one male was analysed, only nine (36%) included one chromosomal confi guration, eight of which were mII colonies. Only one colony was found apparently monomorphic for a ring type, B(39) tree 3 contained fi ve males carrying RXVI. The remaining sixteen colonies (64%) contain both ring and mII males. This includes eight colonies with mII and one type of ring, four colonies with mII and two types of ring, one colony with mII and three types of ring, and three colonies with two different rings forms present. Given the limited sample sizes at sites and in colonies, this is almost certainly an underestimation of the actual variation present at this location.
Tumbarumba
The Tumbarumba site T(153) is around 150km north of the Ovens Valley, near the town of Tumbarumba in NSW. Like the Ovens Valley, this site is close to the edge of the mII distribution, and is situated in the mountainous area on the inland side of the GDR (Figure 2 A). This site is close to a tributary of the Tumbarumba Creek, which drains the Burra Ridge and Bago Range to the north-east out towards central Australia. The area surrounding this site provides very patchy habitat, being in the transition between the heavily forested mountains of the GDR to the east, and the rolling open woodlands inland of the GDR. Only one colony was found at this site, and eight males were analysed cytologically. These included fi ve individuals with the mII confi guration, and three with a ring of four chromosomes (Table 1).
As individual chromosomes cannot be distinguished in this species, it is not possible to determine whether or not the Tumbarumba RIV is the result of the same combination of fusions as the RIV form found in the Ovens Valley. Therefore, the Tumbarumba ring will be referred to as RIV2, to distinguish it from the RIV1 from the Ovens Valley for the purposes of this discussion, without making any assumptions about their actual similarity.