Diversification of deermice (Rodentia: genus Peromyscus) at their north‐western range limit: genetic consequences of refugial and island isolation

Abstract

Aim We surveyed the genetic variability of deermice (genus Peromyscus) at the north‐western edge of their range to test for occupancy in multiple, hypothesized ice‐free regions during the late Pleistocene and explore post‐glacial dynamics. Location North‐western North America. Methods We used sequences from four independent nuclear and mitochondrial loci from 341 specimens of Peromyscus maniculatus, Peromyscus keeni and Peromyscus sp. (Yukon) to assess species limits, population structure, and demographical change as a result of historical climate change, using a Bayesian approach. Species distribution models were built in MaxEnt to explore the niche overlap amongst genetically distinct species. Results Divergence amongst three lineages began before the last interglacial, and each shows signs of post‐glacial expansion. Multilocus species trees strongly support P. keeni and Peromyscus sp. (Yukon) as independent from P. maniculatus. Substantial substructure was observed for P. keeni across the fragmented Alexander Archipelago. Northern lineages or clades (Peromyscus sp. and P. keeni) differed in potential ecological distributions. Main conclusions At the extreme north‐western range of deermice in North America, three distinct lineages persist reflecting divergence in at least three ice‐free regions [Beringia, Coastal (near Southeast Alaska) and Southern Continental] throughout the latest Pleistocene glacial cycles. Although spatially proximate in Yukon, no locations were identified where these lineages are in contact. Further, west along the Pacific Coast, P. keeni is widespread across the complex landscape of Southeast Alaska, yet there is limited contemporary gene flow amongst island populations, a finding consistent with the barriers produced by rising sea levels at the end of the Last Glacial Maximum.

High genomic diversity in the bank vole at the northern apex of a range expansion: The role of multiple colonizations and end‐glacial refugia

“…We have shown that contact and mixing of lineages colonizing from the Carpathian and Eastern LGM refugia has contributed to the high genetic diversity observed at the regional level in populations of the bank vole in Fennoscandia. This supports the role of admixture between genomes originating from different refugia as a process reducing the influence of repeated founder events otherwise expected to result in low genetic diversity outside the refugial areas (Gömöry, Paule, Krajmerová, Romšáková, & Longauer, 2012; Havrdová et al., 2015; Neophytou & Michiels, 2013; Pedreschi et al., 2019; Rowe, Heske, Brown, & Paige, 2004; Sawyer, Flamme, Jung, MacDonald, & Cook, 2017; Tollefsrud et al., 2008; Widmer & Lexer, 2001). However, our results show that it is not only the admixture of long‐isolated populations originating from different refugia that can enhance genetic diversity in a colonized area, but increased diversity can also represent admixture from multiple colonizations originating from the same refugium.…”

Living on the edge: Exploring the role of coastal refugia in the Alexander Archipelago of Alaska

“…The range of the Island clade of M. longicaudus is limited to the AA and nearby mainland, a distribution consistent with their paleoendemism in the region (Figure ). The distributions in both P. keeni and the Island clade of S. monticola (south to Washington) extend beyond SE Alaska, but divergence dates, net genetic distance, genetic diversity, and expansion statistics, as well as models of refugial migration for P. keeni (Sawyer, Flamme, Jung, MacDonald, & Cook, ), suggest these species persisted along the coast during the LGM. The finding of an island paleoendemic clade for all three species is consistent with the phylogeographic pattern uncovered for ermine ( Mustela erminea ) in the region (Colella et al, ), but differs somewhat from two other carnivores, Pacific Coast marten ( Martes caurina ) and black bear ( Ursus americanus ), where the distribution of the island lineages now extend far beyond the boundaries SE AK (Dawson et al, ; Fleming & Cook, ; Peacock et al, ; Small, Stone, & Cook, ).…”

“…. The distributions in both P. keeni and the Island clade of S. monticola (south to Washington) extend beyond SE Alaska, but divergence dates, net genetic distance, genetic diversity, and expansion statistics, as well as models of refugial migration for P. keeni(Sawyer, Flamme, Jung, MacDonald, & Cook, 2017), suggest these species persisted along the coast during the LGM. The finding of an island paleoendemic clade for all three species is consistent with the phylogeographic pattern uncovered for ermine (Mustela erminea) in the region(Colella et al, 2018), but differs somewhat from two other carnivores, PacificCoast marten (Martes caurina) and black bear (Ursus americanus),…”

Relative efficiency of two models of snap traps for sampling boreal small mammals

“…are cryptic, with up to 3 species occurring in some regions (Sawyer et al 2017). However, based on detailed genetic analyses by Sawyer et al (2017), deer mice in our study areas were likely all P. maniculatus. Captured small mammals were sexed by external examination, and mass was obtained with a digital scale (±0.1 g).…”

“…In the Yukon, species of deer mice ( Peromyscus spp.) are cryptic, with up to 3 species occurring in some regions (Sawyer et al 2017). However, based on detailed genetic analyses by Sawyer et al (2017), deer mice in our study areas were likely all P .…”