| Summary: | Marmots ( Marmota spp.) comprise a lineage of large-bodied ground squirrels that diversified rapidly in the Pleistocene, when the planet quickly transitioned to a drier, colder, and highly seasonal climate—particularly at high latitudes. Fossil evidence indicates the genus spread from North America, across Beringia, and into the European Alps over the course of only a few million years, beginning in the late Pliocene. Marmots are highly adapted to survive long and severely cold winters, and this likely favored their expansion and diversification over this time period. Previous phylogenetic studies have identified two major subgenera of marmots, but the timing of important speciation events and some species relationships have been difficult to resolve. Here we use ultraconserved elements and mitogenomes, with samples from all 15 extant species, to more precisely retrace how and when marmots came to inhabit a vast Holarctic range. Our results indicate marmots arose in North America in the mid Miocene (~16.3 Mya) and dispersed across the Bering Land Bridge in the late Pliocene (~3-4 Mya); in addition, our fossil-calibrated timeline is suggestive of the rise and spread of open grasslands as being particularly important to marmot diversification. The woodchuck ( M. monax ) and the Alaska marmot ( M. broweri ) are found to be more closely related to the Eurasian species than to the other North American species. Paraphyly is evident in the bobak marmot ( M. bobak ) and the hoary marmot ( M. caligata ), and in the case of the latter the data are highly suggestive of a second, cryptic species in the Cascade Mountains of Washington. Funding provided by: Alaska Department of Fish and Game Crossref Funder Registry ID: http://dx.doi.org/10.13039/100008144 Award Number: Funding provided by: University of Alaska Fairbanks Crossref Funder Registry ID: http://dx.doi.org/10.13039/100012574 Award Number: Funding provided by: Society of Systematic Biologists Crossref Funder Registry ID: http://dx.doi.org/10.13039/100006069 Award ...
|
|---|