C. Gascon et al., GENETIC AND MORPHOLOGICAL VARIATION IN VANZOLINIUS-DISCODACTYLUS - A TEST OF THE RIVER HYPOTHESIS OF SPECIATION, Biotropica, 28(3), 1996, pp. 376-387
Allozyme and morphological variation among populations of an Amazonian
frog were analyzed to test for a riverine effect on population differ
entiation. High levels of genetic diversity within populations and gen
etic diversification among populations were Found. Although correlatio
ns between generic and geographic distances of population pairs were p
ositive, they were nor significant and indicated that sires that mere
dose geographically were nor genetically more similar. Only one of the
15 polymorphic loci showed any variation in allozyme frequency attrib
utable to the presence of the river, but none of the overall among-pop
ulation component of allozyme frequency variation (F-ST = 0.368) can b
e attributed to the river (F-RT = 0.000). Significant differences in m
orphology (corrected for sire differences) were Found among the 11 pop
ulations in canonical variate space. In univariate Nested ANOVAs, five
of the 12 morphological variables showed significant differences due
to the presence of the river. However, cluster analysis performed on a
ll morphological variables failed to detect obvious groups based on ri
ver bank locality. We could detect no congruence of pattern between mo
rphological and generic variation among populations. These results sug
gest that morphological characters may evolve at different rates than
detectable allozyme differentiation.