Abstract:
There is accumulating evidence that the degree of vagility explains little of the extent of population subdivision found within elasmobranch species. Instead, patterns of gene flow in elasmobranchs appear more closely linked to the presence of dispersal barriers, either physical or biological. Here, we investigate the potential role of some of these isolating mechanisms in shaping the population structure of a member of the stingray family Dasyatidae (Dasyatis brevicaudata) at various scales (southern hemisphere vs. coastal New Zealand). Analyses of the mitochondrial DNA control region from 176 individuals revealed significant genetic structure between South Africa, Australia, and New Zealand populations (analysis of molecular variance [AMOVA], overall ФST = 0.67, P < 0.001), although New Zealand and Australia shared some haplotypes. Surprisingly, significant population differentiation was found among several coastal New Zealand locations (AMOVA, overall ФST = 0.05, P < 0.05). However, data did not support the genetic differentiation between individuals from an offshore breeding area and mainland individuals. Comparisons suggest that these stingrays exhibit similar levels of population differentiation as other coastal elasmobranchs, with high divergence across oceanic basins and lower differentiation along continuous coastal habitats. Differences in coastal population structuring in elasmobranch species studied to date may be attributed to species-specific preferences for coastal habitats, which may be linked to life history functions (e.g., feeding and pupping).
