Phylogeographic structure in long‐tailed voles (Rodentia: Arvicolinae) belies the complex Pleistocene history of isolation, divergence, and recolonization of Northwest North America's fauna

Abstract

Quaternary climate fluctuations restructured biodiversity across North American high latitudes through repeated episodes of range contraction, population isolation and divergence, and subsequent expansion. Identifying how species responded to changing environmental conditions not only allows us to explore the mode and tempo of evolution in northern taxa, but also provides a basis for forecasting future biotic response across the highly variable topography of western North America. Using a multilocus approach under a Bayesian coalescent framework, we investigated the phylogeography of a wide‐ranging mammal, the long‐tailed vole, Microtus longicaudus. We focused on populations along the North Pacific Coast to refine our understanding of diversification by exploring the potentially compounding roles of multiple glacial refugia and more recent fragmentation of an extensive coastal archipelago. Through a combination of genetic data and species distribution models (SDMs), we found that historical climate variability influenced contemporary genetic structure, with multiple isolated locations of persistence (refugia) producing multiple divergent lineages (Beringian or northern, southeast Alaska or coastal, and southern or continental) during glacial advances. These vole lineages all occur along the North Pacific Coast where the confluence of numerous independent lineages in other species has produced overlapping zones of secondary contact, collectively a suture zone. Finally, we detected high levels of neoendemism due to complex island geography that developed in the last 10,000 years with the rising sea levels of the Holocene.

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

“…Additionally, minimal intraclade variability and inter‐island diversification characterized the Island clade of S. monticola (Figure and Supporting Information Appendix ). Coalescent simulations suggest a more recent divergence of M. longicaudus , potentially reflecting geographic proximity and relatively recent segregation (20 kyr) between contemporary populations representing the Island and Northern cyt b clades, rather than post‐glacial expansion of mainland populations into the AA (Sawyer & Cook, ). Inconsistent estimates within each species partially stem from our inability to calibrate trees with fossils, and thus account for rate decay (Ho, Phillips, Cooper, & Drummond, ).…”

The Beringian Coevolution Project: holistic collections of mammals and associated parasites reveal novel perspectives on evolutionary and environmental change in the North

“…Some of these distinctive lineages of mammals and associated parasites represent paleoendemics, meaning that their DNA signatures reflect long-term persistence and divergence in glacial refugia along the North Pacific Coast (Koehler et al 2009a;Hoberg et al 2012b;Sawyer and Cook 2016), and these signatures are consistent with the Coastal Refugium Hypothesis. Phylogeographic studies along the North Pacific Coast, combined with insight from fossils recovered from the extensive karst systems (Heaton and Grady 2003), suggest that a suite of terrestrial species persisted nearby in coastal ice-free refugia during glacial advances.…”

“…5) that help interpret the impact of the boundaries of the Beringian refugium, such as the Upper Kolyma region of Siberia in the west (e.g., Galbreath and Cook 2004;Kohli et al 2015;Haukisalmi et al 2016) and near the YukonAlaska border in the east (Dawson et al 2014). In addition, the influence of smaller peripheral refugia in the Canadian Arctic (Fedorov and Stenseth 2002;Fedorov et al 2003;Cook et al 2016b), southeast Alaska Sawyer and Cook 2016), and in the periglacial zone south of the Laurentide and Cordilleran ice sheets ) is being explored. Early attempts to unravel the evolutionary history of arctic ground squirrels (Urocitellus parryii), one of the quintessential high-latitude mammals, relied on a view of Beringia as a vast steppe with few natural barriers to gene flow (e.g., Nadler and Hoffmann 1977).…”

“…1), depending on region being sampled and on particular collaborative projects with natural resource agencies and commercial trappers. Within most of the mammalian species examined using molecular genetic analyses, substantial phylogeographic structure and cryptic species have been identified (e.g., Dawson et al 2014;Sawyer and Cook 2016).…”

A review of phylogeography: biotic and abiotic factors

“…Quaternary climatic changes restructured biodiversity across North American high latitudes through repeated episodes of range contractions, population isolation and separation, and finally expansion. Using multilocus method under a Bayesian Coalescent framework, the phylogeography of a broad-ranged mammal, long-tailed vole, Microtus longicaudus were studied by Sawyer and Cook (2016). In this study, an expansioncontraction model was tested on the C. elaphus using modern as well as ancient mitochondrial DNA.…”