Patterns of gene flow and population genetic structure in the canyon treefrog, Hyla arenicolor (Cope)

Patterns of gene flow and genetic structuring were examined in the canyon t reefrog, Hyla arenicolor (Cope). Hierarchical analysis of genetic variation was performed on mitochondrial cytochrome b haplotypes from 323 individual s, representing 32 populations from previously described phylogeographic re gions. Results from AMOVA revealed that 60.4-78.9% of the recovered genetic variation was the result of differences in the apportionment of genetic va riation between subdivisions of the primary phylogeographic regions. In con trast, populations only contained between 13.9 and 30.1% of the observed ha plotypic variation. Gene flow estimates based on calculations of Phi(ST) re vealed moderate levels of gene flow within phylogeographic regions, but the re was no evidence of gene flow between these regions, suggesting that geog raphical boundaries were probably important in the formation of phylogeogra phic structure in H. arenicolor. Phylogeographic regions exhibited very dif ferent patterns of gene flow. One region showed evidence of recent coloniza tion. Another region exhibited very limited gene flow. Moderate to high est imates of gene flow were obtained for populations from two distinct phyloge ographic regions characterized by mesic and xeric environments. Isolation b y distance was observed in both regions suggesting that these regions are i n genetic equilibrium. Because gene flow is extremely unlikely between the populations in the xeric region, this result is interpreted as historical g ene flow. These results indicate that isolation-by-distance effects may sti ll be observed even when population genetic structure and gene flow are the result of historical association.