The distribution and phylogeography of the Alaska marmot (Marmota broweri)

Thesis (M.S.) University of Alaska Fairbanks, 2007The taxonomic and distributional status of the Marmota broweri has been the subject of much debate and confusion since it was first described as a subspecies of the hoary marmot (M caligata). Through a review of all museum specimens, published accounts of this species, field surveys, and the identification of previously unidentified marmot specimens we have determined the current distribution of the Alaska marmot to include the Brooks Range, the Ray Mountains, and the Kokrines Hills of northern Alaska. The Yukon River forms the boundary between the peripatric distributions of M broweri and M caligata in Alaska. Since M broweri was a resident of Beringia during the Pleistocene, I expect the phylogeographic structure of Alaska marmots (M broweri) to exhibit the signature of persistence in Beringia and subsequent expansion into glaciated areas. My objective is to investigate the phylogeographic structure of Alaska marmot populations through phylogenetic tree construction, measures of genetic diversity, a mismatch distribution, and nested clade analysis of DNA sequence data from the mitochondrial cytochrome b gene. I found significant geographic structure across the range of M broweri. The results of my analyses suggest a recent population expansion from central Alaska (Beringia) into the formerly glaciated Brooks Range1. The distribution of the Alaska marmot (Marmota broweri) -- 2. The phylogeography of the Alaska marmot (Marmota broweri) based on DNA sequence variation in the mitochondrial gene cytochrome b -- General conclusion -- Appendix

Comparative Phylogeography Highlights the Double-Edged Sword of Climate Change Faced by Arctic- and Alpine-Adapted Mammals

Made available in DSpace on 2015-08-19T13:49:25Z (GMT). No. of bitstreams: 2 license.txt: 1914 bytes, checksum: 7d48279ffeed55da8dfe2f8e81f3b81f (MD5) marcelo_weksler_etal_IOC_2015.pdf: 2290876 bytes, checksum: 3d5639fcebbe32bfddc36064f4a170e6 (MD5) Previous issue date: 2015University of Alaska Fairbanks. University of Alaska Museum. Fairbanks, Alaska, USA / University of Wyoming at Casper. Department of Zoology & Physiology. Casper, Wyoming, USA.University of Alaska Fairbanks. University of Alaska Museum. Fairbanks, Alaska, USA.University of Alaska Fairbanks. University of Alaska Museum. Fairbanks, Alaska, USA / Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Ecoepidemiologia da Doença de Chagas. Rio de Janeiro, RJ, Brasil.University of Alaska Fairbanks. Institute of Arctic Biology. Fairbanks, Alaska, USA.University of Alaska Fairbanks. University of Alaska Museum. Fairbanks, Alaska, USA.Recent studies suggest that alpine and arctic organisms may have distinctly different phylogeographic histories from temperate or tropical taxa, with recent range contraction into interglacial refugia as opposed to post-glacial expansion out of refugia. We use a combination of phylogeographic inference, demographic reconstructions, and hierarchical Approximate Bayesian Computation to test for phylodemographic concordance among five species of alpine-adapted small mammals in eastern Beringia. These species (Collared Pikas, Hoary Marmots, Brown Lemmings, Arctic Ground Squirrels, and Singing Voles) vary in specificity to alpine and boreal-tundra habitat but share commonalities (e.g., cold tolerance and nunatak survival) that might result in concordant responses to Pleistocene glaciations. All five species contain a similar phylogeographic disjunction separating eastern and Beringian lineages, which we show to be the result of simultaneous divergence. Genetic diversity is similar within each haplogroup for each species, and there is no support for a post-Pleistocene population expansion in eastern lineages relative to those from Beringia. Bayesian skyline plots for four of the five species do not support Pleistocene population contraction. Brown Lemmings show evidence of late Quaternary demographic expansion without subsequent population decline. The Wrangell-St. Elias region of eastern Alaska appears to be an important zone of recent secondary contact for nearctic alpine mammals. Despite differences in natural history and ecology, similar phylogeographic histories are supported for all species, suggesting that these, and likely other, alpine- and arctic-adapted taxa are already experiencing population and/or range declines that are likely to synergistically accelerate in the face of rapid climate change. Climate change may therefore be acting as a doubleedged sword that erodes genetic diversity within populations but promotes divergence and the generation of biodiversity

Hypotheses.

<p>Expectations of relative genetic diversity, signal of range expansion, and the number of separate divergence times suggested for Beringian (B) and eastern (E) lineages under each historical model (corresponding to patterns in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118396#pone.0118396.g001" target="_blank">Fig. 1C</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118396#pone.0118396.g001" target="_blank">Fig. 1B</a>, and to a no common pattern model, respectively).</p><p>Hypotheses.</p

Past demographic shifts.

<p>Demographic change (in units of effective population size scaled by mutation rate) over time (in substitutions per site) for all five species shown using Bayesian skyline plots. Note the different x- and y- axes for Brown Lemmings (e), for which a longer population history and a larger scaled effective population size were suggested. The median population size is the center dashed line, the 95% highest posterior density (HPD) intervals are shown in surrounding grey, and the relative timing of the Wisconsin glaciation (based on taxon-specific mutation rates) is shown in blue. Because of the single locus and contemporaneous sampling utilized in this study, only recent demographic trends are evident.</p

Beringian phylogeographic patterns.

<p>Patterns of ancestral areas and colonization routes (arrows) inferred for alpine mammals of eastern Beringia, modeled after [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118396#pone.0118396.ref021" target="_blank">21</a>]. A–C) Panels above show the ice sheet extent (blue) at the last glacial maximum, the ice-free corridor (light blue) thought to have opened between the Laurentide and Cordilleran ice sheets around 14 kya [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118396#pone.0118396.ref022" target="_blank">22</a>], relative Pleistocene population locations under each scenario. Suggested diversification and post-glacial colonization routes (arrows) shown below under a history of: a) sub-Laurentide colonization, b) vicariance between Beringian and sub-Laurentide populations, and c) intra-Beringian diversification. d) Available Beringian habitat during the Pleistocene. d) Glacial margins and ice-free areas of the Bering Land Bridge and Easternmost Beringia [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118396#pone.0118396.ref023" target="_blank">23</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118396#pone.0118396.ref024" target="_blank">24</a>].</p

Scaled likelihood trees.

<p>Scaled likelihood trees for a) Collared Pikas, b) Hoary Marmots, c) Singing Voles, d) Arctic Ground Squirrels, and e) Brown Lemmings. Beringian (above, blue) and east (below, red) lineages are depicted for all species. The northern lineage of Arctic Ground Squirrels is sister to the east-Beringian phylogroups. Pairwise net divergences (<i>Da</i> calculated in DnaSP; [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118396#pone.0118396.ref061" target="_blank">61</a>]) are shown between phylogroups.</p

Divergence between clades within a species.

<p>Divergence (measured as Nei’s <i>D</i>) is generally correlated to within-clade diversity (<i>π</i>) for alpine mammals in this study. Hoary Marmots are the exception to this trend, demonstrating low within-clade diversity for the amount of between-clade divergence. Diversity levels in the eastern clade of Singing Voles are shown for reference but should be interpreted with caution as the clade is represented by only two samples.</p