Dalhousie Springs hydrobiids ú 
"у Des == Т 5 T Ir z 
1 | 
s harrisi 7 
e at globosa 
D A 
E 
Ф е: | 
3 de 
I 
Og. | 
o 
2 Е 
2L | | 
D24 
) : 1 1 íi. 1 zi 1 L be 
= 06 07 08 09 10 05 06 07 08 09 10 
А Shell width/length B Shell width/length 
Figure 22. A. Plot of shell length and the ratio of shell width/length for sympatric populations of Dalhousia globosa 
(circles) and D. harrisi (diamonds). B. Plot of shell length and the ratio of shell IIR s Gu 
measured populations of Dalhousia globosa (except station D24), Cala (station D24) and D. E е 
ellipses in both figures contain 7596 of the variance. The individual data points have not been plotted in B. 
allocate to one of these genetic species on the basis of their allelic constitution for these loci. In 
пр Ca8 and Cd2, snails were allocated to D. globosa if they were homozygous for Lap 2, to D. 
arisi if they were homozygous for Lap 3, and to a “hybrid” category if they were 2/3 heterozygotes: 
ar number of other allozymes have distributions correlated with the genetic species (Tables 7,8). Two 
d “stricted to. D, globosa and 12 to D. harrisi. No individual in any spring was identified as a 
eal Е, hybrid so that the genetic isolation between the species is nearly SE When 
со 'Viduals are allocated to genetic species and samples pooled within spring groups there 1s a 
mplete Separation of D. globosa and D. harrisi in phenetic trees (Figs 23, 24). 
1 апе of genetic variation within samples are given in Tables 4-6, which detail Шы 
dies er of individuals scored per locus, the percentage of loci with more than one allele an 
ie and expected heterozygosity. These summaries show a notable level of genetic variation in 
m ousia, with most samples having multiple alleles at more than 20% of loci. The D. 8100000 
Wi Ple from the Cal pool (topotypic population) has multiple alleles at 53% of ect E es 
signi low variability are intriguing. Ca8 is one of the two springs where there is evidence o 
Scant hybridization between D. globosa and D. harrisi. Yet it has the lowest percentage of 
ac. aO phic loci among the populations of D. globosa and one of the lowest seen in E 
othe Pánied by a low value in the "hybrids" class. Polymorphic loci are quite frequent in , the 
Т Spring where hybridization is occurring. | j ry ; 
WIE: genetic isolation between D. globosa апа D. harrisi is emphasised by their Ke sympa y 
ine a tite springs. This criterion is not available for decisions regarding the specific status 0 
ot ages within the two nominate genetic species. Of particular interest here, is the population in a 
phe Spring near Cal, Cala (stn D24). This is an outlier to the other samples of D. globosa in 
E grams (Figs 23, 24), principally because of a very high frequency of ALKP 3, LGG-2 2, SDH-1 
Simi] SDH2 1 allozymes and the fixation of an unique GAL allozyme (3). Тһе SDH рпепозуре 15 
ог] аг to D. harrisi. The three other characteristic allozymes of this hot spring population are absent 
Іп Very low frequencies in D. harrisi, contradicting a hybrid origin. It appears more likely that the 
