Influence of Introgression and Geological Processes on Phylogenetic Relationships of Western North American Mountain Suckers (Pantosteus, Catostomidae)

Abstract

Intense geological activity caused major topographic changes in Western North America over the past 15 million years. Major rivers here are composites of different ancient rivers, resulting in isolation and mixing episodes between river basins over time. This history influenced the diversification of most of the aquatic fauna. The genus Pantosteus is one of several clades centered in this tectonically active region. The eight recognized Pantosteus species are widespread and common across southwestern Canada, western USA and into northern Mexico. They are typically found in medium gradient, middle-elevation reaches of rivers over rocky substrates. This study (1) compares molecular data with morphological and paleontological data for proposed species of Pantosteus, (2) tests hypotheses of their monophyly, (3) uses these data for phylogenetic inferences of sister-group relationships, and (4) estimates timing of divergence events of identified lineages. Using 8055 base pairs from mitochondrial DNA protein coding genes, Pantosteus and Catostomus are reciprocally monophyletic, in contrast with morphological data. The only exception to a monophyletic Pantosteus is P. columbianus whose mtDNA is closely aligned with C. tahoensis because of introgression. Within Pantosteus, several species have deep genetic divergences among allopatric sister lineages, several of which are diagnosed and elevated to species, bringing the total diversity in the group to 11 species. Conflicting molecular and morphological data may be resolved when patterns of divergence are shown to be correlated with sympatry and evidence of introgression.

Robust molecular phylogeny and palaeodistribution modelling resolve a complex evolutionary history: glacial cycling drove recurrent mtDNA introgression among Pelophylax frogs in East Asia

“…Climatic oscillations associated with glacial cycling have had substantial impacts on the demography of organisms, and the distributions of numerous species appear to have shifted repeatedly in association with glacial cycling (Melo-Ferreira et al, 2012;Sakaguchi et al, 2012). Many historical introgression events are thought to have occurred when two related species co-occurred in refugia or in areas where the species met after post-glacial range expansion (St€ ock et al, 2012;Miura et al, 2014;Unmack et al, 2014). Few studies, however, have investigated shifts in the distributional ranges of species and how these distributional shifts contributed to historical mtDNA introgression events.…”

Loss of dendritic connectivity in southern California's urban riverscape facilitates decline of an endemic freshwater fish

“…Catostomids are notorious for hybridization despite deep divergence between the species involved (Bangs, 2016;McDonald et al, 2008;Smith, Stewart, & Carpenter, 2013;Unmack et al, 2014), and those studied here are no exception ( Figure S3). Even though hybrids and non-native C. fumeiventris are restricted to stream reaches west of the Piru Gap, the predominant genotypes and mtDNA haplotypes belong to C. santaanae.…”

“…We used two fossil calibrations from Unmack et al. () to date the tree, with the goal of assessing whether the divergence time between these two hybridizing species was on the order of tens of thousands, hundreds of thousands or many millions of years. Further details on these analyses are presented in the Supplemental File.…”

“…To assess the phylogenetic distance and timing of divergence between C. santaanae and C. fumeiventris, we performed additional analyses in BEAST v2.4.6 (Bouckaert et al, 2014) using published ND2 data for other sucker species and a subset of C. santaanae and C. fumeiventris from this study. We used two fossil calibrations from Unmack et al (2014) to date the tree, with the goal of assessing whether the divergence time between these two hybridizing species was on the order of tens of thousands, hundreds of thousands or many millions of years. Further details on these analyses are presented in the Supplemental File.…”

“…Genetic data have never been used to verify the native or non-native status of these populations and only the latter is protected under the listed entity (USFWS 2017), a concern given how little-preferred habitat remains in the Los Angeles Basin. Previous population genetic studies on C. santaanae have been limited to allozymes and mtDNA haplotype frequency data (Buth & Crabtree, 1982;Buth, Sim, & Swift, 2008;Chabot et al, 2009;Crabtree & Buth, 1981), with more recent phylogenetic analyses including one or a few samples of C. santaanae to estimate species-level relationships within the catostomids (e.g., Bangs, 2016;Chen & Mayden, 2012;Doosey, Bart, Saitoh, & Miya, 2010;Unmack et al, 2014).…”