Phylogeography of the Tailed Frog (Ascaphus Truei): Implications for the Biogeography of the Pacific Northwest

Abstract

Abstract. Tailed frogs are distributed in high-gradient streams within the disjunct mesic forests of the Pacific Northwest and represent the basal lineage of the anurans. We sequenced 1530 nucleotides of the mitochondrial cytochrome b and NADH dehydrogenase subunit two genes from 23 populations and used parsimony, maximum-likelihood, and nested-clade analyses to estimate relationships among populations and infer evolutionary processes. We found two divergent haplotype clades corresponding with inland Rocky Mountain populations and coastal populations and separated by up to 0.133 substitutions per site. Within the coastal assemblage, haplotypes formed clades by mountain range with 0.010-0.024 substitutions per site divergence among populations. Inland haplotypes exhibited minimal genetic structure, with the exception of 0.021 substitutions per site distance between populations from the East Fork of the South Fork of the Salmon River and all other inland haplotypes. The magnitude of divergence between inland and coastal populations, as well as the paleobotanical record, suggest isolation of these lineages occurred during the late Miocene to early Pliocene, probably in response to the rise of the Cascade Mountains. Genetic structure within coastal and inland populations is consistent with isolation in refugia during the late Pliocene and early Pleistocene. Closely related inland haplotypes reflect range expansion following glaciation. The depth of divergence between inland and coastal populations supports the persistence of mesic forests within the inland Pacific Northwest throughout the Pleistocene and is congruent with patterns found in several other mesic forest species. Based on mitochondrial divergence and previous allozyme and morphological data, we recommend recognition of inland populations as a distinct species, Ascaphus montanus.

To name or not to name: Criteria to promote economy of change in Linnaean classification schemes

“…Monotypic taxa often indicate lineages in which much extinction has taken place and much of the original diversity has not yet been recovered from the fossil record. Over time, as more extant and fossil species are discovered and described, at least some monotypic taxa will lose their monotypic status (e.g., Erdmann et al 1998;Nielson et al 2001;Maciel 2009;Rohland et al 2010;Pombal et al 2012;Barata et al 2012;Castroviejo-Fisher et al 2012). On the other hand, clades that underwent successful and fast adaptive radiations, often with limited or homoplastic phenotypic divergence, are best reflected in classification by being considered as species-rich genera.…”

Investigating the effects of Pleistocene events on genetic divergence within Richardsonius balteatus, a widely distributed western North American minnow

“…In northwestern North America, refugia are postulated to have occurred in several areas, including Beringia [22-25], the Chehalis River Valley [4,26-28], the lower Columbia River drainage [29-31], the Upper Columbia River drainage [32-36], Haida Gwaii (a.k.a., Queen Charlotte Islands: an archipelago off the Pacific Coast of British Columbia) [37-39], and the Klamath-Siskiyou region [5,36,40-42] (Figure 1). Additionally, some taxa have retained genetic signatures of survival in northern and southern refugia along the Pacific Coast [27,43,44].…”

“…It is hypothesized that R. balteatus colonized the northernmost parts of its range (i.e., British Columbia) post-glacially from a refugium in the Upper Columbia River Basin based on current distributions above barrier falls and several known geomorphic connections [18,19]. The Upper Columbia River drainage (including the Clearwater and Salmon rivers) is a hypothesized refugial area for fishes, amphibians, and plants [18,27,32,33,35], and could have been for R. balteatus as well. However, the current distribution of R. balteatus includes many proposed refugia other than the Upper Columbia River drainage, including the Chehalis River Valley, the lower Columbia River, and areas along the Oregon Coast.…”

Frogs, Fish and Forestry: An Integrated Watershed Network Paradigm Conserves Biodiversity and Ecological Services

“…Tailed frogs ( Figure 5(b)) are ribbed frogs, the most ancient of extant frogs, a life form that predates the dinosaurs. They are also members of an endemic family (Ascaphidae), with a coastal species and another in the Rocky Mountains [50].…”