Living on the edge: Exploring the role of coastal refugia in the Alexander Archipelago of Alaska - PubMed (original) (raw)

. 2019 Feb 1;9(4):1777-1797.

doi: 10.1002/ece3.4861. eCollection 2019 Feb.

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

Yadéeh E Sawyer et al. Ecol Evol. 2019.

Abstract

Although islands are of long-standing interest to biologists, only a handful of studies have investigated the role of climatic history in shaping evolutionary diversification in high-latitude archipelagos. In this study of the Alexander Archipelago (AA) of Southeast Alaska, we address the impact of glacial cycles on geographic genetic structure for three mammals co-distributed along the North Pacific Coast. We examined variation in mitochondrial and nuclear loci for long-tailed voles (Microtus longicaudus), northwestern deermice (Peromyscus keeni), and dusky shrews (Sorex monticola), and then tested hypotheses derived from Species Distribution Models, reconstructions of paleoshorelines, and island area and isolation. In all three species, we identified paleoendemic clades that likely originated in coastal refugia, a finding consistent with other paleoendemic lineages identified in the region such as ermine. Although there is spatial concordance at the regional level for endemism, finer scale spatial and temporal patterns are less clearly defined. Demographic expansion across the region for these distinctive clades is also evident and highlights the dynamic history of Late Quaternary contraction and expansion that characterizes high-latitude species.

Keywords: Coastal Refugia Hypothesis; comparative phylogeography; endemism; islands; small mammals.

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Conflict of interest statement

None declared.

Figures

Figure 1

Figure 1

Sampling scheme, range maps, and North American LGM glacial cover. Sampling localities are shown by major cyt_b_ lineage. The thick black lines are the current range for each species, with the addition of P. maniculatus (white line) on the Peromyscus map. The light blue in the bottom right image is LGM glacial ice cover. COP: Colorado Plateau; LGM: Last Glacial Maximum; NPC: North Pacific Coast. Color schemes for species and lineages are held constant across figures

Figure 2

Figure 2

Species distribution models (climate suitability at each time period) for Microtus longicaudus, Peromyscus keeni and Sorex monticola from the Last Inter‐Glacial (LIG), Last Glacial Maximum (LGM; solid blue = glacial ice coverage), Mid‐Holocene (Mid‐Hol.), Current, and Future (approximately the year 2080), including the change in habitat suitability between current and future models

Figure 3

Figure 3

Islands and nearby coastal mainland locations in Alaska, including paleoshorelines (kya = thousands of years ago) and hypothesized island groups (also see Table 2). Red arrows indicate potential colonization across the Alexander Archipelago as a result of change in sea level and glacial cover

Figure 4

Figure 4

Multilocus Bayesian Species Tree. Posterior probabilities of ≥0.95 are represented with open circles on branches of the consensus tree. A priori groupings were designated based on cyt b Bayesian supported (≥0.95 posterior probability) clades. Blue = Island/Peromyscus keeni, bright green = Northern/Peromyscus sp. nov. (Yukon), dark green = North Pacific Coast, light yellow‐green = Colorado Plateau/P. maniculatus Southwest, golden = Central/P. maniculatus West, orange = Southern/P. maniculatus East, black = outgroups. Horizontal gray bars represent divergence date estimates and vertical bars indicate approximate time for the LIG and LGM. LGM: Last Glacial Maximum; LIG: Last Inter‐Glacial

Figure 5

Figure 5

Cyt b Bayesian skyline plots (cyt_b_ data only) for the major cyt_b_ lineage populations: (a) Microtus longicaudus Island, (b) Peromyscus keeni, and (c) Sorex monticola Island. The _x_‐axis right‐to‐left from past (TMRCA) to present and is scaled in millions of years and the _y_‐axis is the log effective population size scaled by generation time. Vertical gray bars indicate the LIG (when applicable, right) and LGM (left) for reference. LGM: Last Glacial Maximum; LIG: Last Inter‐Glacial

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