PHYLOGEOGRAPHY OF NORTHERN POPULATIONS OF THE PACIFIC

Phylogeography of northern populations of the Pacific treefrog, Pseudacris regilla, was investigated using mitochondrial cytochrome b sequence data (725 bp). Thirty-six haplo- types were detected among 59 samples collected from 20 populations. Two divergent coastal and inland clades were supported by several phylogenetic analyses including maximum par- simony, maximum likelihood, and Bayesian methods. Sequence differences among these clades ranged from 5.0 to 6.5%, suggesting they diverged during the Pliocene (approximately 3 MYA), coinciding with High Cascade orogeny and subsequent xerification of the Columbia Basin. Fur- ther, haplotype divergence within each clade was lower (0 to 1.8%), possibly as a consequence of population reduction during the Pleistocene. The overall pattern of divergence was not de- tected by previous morphological and protein analysis and is concordant with many other Northwest taxa. These results do not support previous intraspecific classification schemes, in- dicating the need for further examination of the taxonomic status of the coastal and inland clades.