Phylogeography of the Australian Common Froglet, Crinia Signifera

摘要

Australia is an ancient continent with equally antiquated fauna. Crinia signifera, the Australian common froglet, is one of Australia's oldest species and has a geographic range covering much of the southeastern coast of Australia and much of Tasmania. Such broad dispersal makes C. signifera susceptible to genetic variation due to changes in the landscape. While many have studied the morphology of C. signifera, few have studied its phylogeographic history. In this study I compared mitochondrial DNA clades to nuclear DNA clades to analyze the role geography plays on genetic variation. I hypothesized that (i) sympatric nuclear clades and subclades would share more unique alleles than allopatric nuclear clades; (ii) nuclear genetic differences would be greater between subpopulations where dispersal and gene flow are limited; and (iii) nDNA clades would have similar distribution to mitochondrial DNA clades. DNA samples were amplified using PCR. Following sequencing and analysis summary statistics were generated and analyzed to determine genetic relationships among clades. First, shared nuclear haplotypes were found across all mtDNA clades on the mainland, regardless of sympatry or allopatry. Second, samples from Tasmania were shown to have more novel nuclear haplotypes than any other subclade. Third, nuclear haplotype distribution, Mantel tests and construction of a phylogenetic tree showed no support for distinct nDNA clades. This data suggests that (i) mainland populations are not affected by geographic features, (ii) the Bass Strait is an effective barrier to gene flow between Tasmania and mainland Australia, (iii) differential dispersal patterns between males and females individuals have a greater effect on genetic diversity on the mainland than isolation by distance or geographic features.