80  W.F. Ponder, D.J. Colgan, Т. Terzis, S.A. Clark, A.C. Miller 
E3 (D23) 
Ga6 (D15) 
Ga2 (D5) 
Gal (D13) 
F9 (D53) 
Cd11 (D70) 
E1 (D62) 
Figure 25. Phenogram showing relationships between populations of Fluvidona centralia based on an unweighted рай 
group (UPGMA) clustering of Nei's unbaised (Nei, 1978) genetic distances. 
which is usually absent from the C and D spring groups, the ADH 4 allozyme with a disjunct distri 
bution in groups A and H and the HK 3 allozyme concentrated in B and the adjacent Db groups. 
Sample sizes are small іп F. centralia, yet the apparent low levels of variation in this species 
(Table 6) probably reflect its biology, implying smaller founding populations and longer periods d 
isolation than іп Dalhousia. There are two principal lineages within the species (Fig. 25), these 
characterised by а fixed-difference іп Gpt-2. This may reflect a significant biological division 0 
geographic variation within the the taxon as we recognise it. There are no other allozymes with 
distributions concordant with the Gpr-2 pattern although there are some loci (such as Pgd) with 
allozymes found only in some populations of one of the two lineages. The shell morphologies (Fig: 
18; Table 3) of members of these two lineages do not differ greatly, there being no significant 
differences between any of the measurements for the pooled measured populations listed in each 
group. However, the ratios of shell width/shell length and aperture length/shell length were signifi 
cantly different (P<0.001; Fig. 21B) between the two groups for the subset of measured populations. 
Discussion 
Using the criterion of sympatry, we have recognised only two species-group taxa within Dalhousid: 
However, as outlined above, some of the lineages within both these species are genetically distinct, 
although allopatric, and both taxa show considerable intra and interpopulation variation in shell size 
and shape. Similarly within what we treat as a single species of Fluvidona there is considerable 
interpopulation variation in shell, opercular and radular morphology, as well as allopatric geneti? 
subdivision. 
The considerable variation seen in shell morphology in Dalhousia (Figs 2-5, 16, 17), briefly 
described above, will be analysed in more detail elsewhere. 
As noted above, it is very likely that Dalhousia and Fonscochlea, from the Lake Eyre Supergroup 
are sister taxa. The probable sister taxon to (Fonscochlea + Dalhousia) is Jardinella (Ponder an 
Clark, 1990), found in artesian springs in western Queensland, as well as in some coastal drainages 
in northern Queensland. Species of Jardinella, like most hydrobiids, have a normal bursa copulatrix 
and seminal receptacle. The presence of a single sperm sac (presumably the bursa copulatrix) 17 
Dalhousia might appear to suggest that it is more derived than Fonscochlea which has two. Howevel: 
the two sperm sacs of Fonscochlea are very similar histologically and may be the result of subdivision 
of an original single sperm sac (the bursa) (Ponder et al., 1989). If this is the case, in this respect 2! 
least, Dalhousia is the more plesiomorphic of the two genera and in this genus the oviduct functions 
as a sperm storage site. 
