Historical Species Distribution Models Predict Species Limits in WesternPlethodonSalamanders

Abstract

Allopatry is commonly used to predict boundaries in species delimitation investigations under the assumption that currently allopatric distributions are indicative of reproductive isolation; however, species ranges are known to change over time. Incorporating a temporal perspective of geographic distributions should improve species delimitation; to explore this, we investigate three species of western Plethodon salamanders that have shifted their ranges since the end of the Pleistocene. We generate species distribution models (SDM) of the current range, hindcast these models onto a climatic model 21 Ka, and use three molecular approaches to delimit species in an integrated fashion. In contrast to expectations based on the current distribution, we detect no independent lineages in species with allopatric and patchy distributions (Plethodon vandykei and Plethodon larselli). The SDMs indicate that probable habitat is more expansive than their current range, especially during the last glacial maximum (LGM) (21 Ka). However, with a contiguous distribution, two independent lineages were detected in Plethodon idahoensis, possibly due to isolation in multiple glacial refugia. Results indicate that historical SDMs are a better predictor of species boundaries than current distributions, and strongly imply that researchers should incorporate SDM and hindcasting into their investigations and the development of species hypotheses.

Comparing range evolution in two western Plethodon salamanders: glacial refugia, competition, ecological niches, and spatial sorting

“…All populations were allowed to expand (c = 0-5) and theta (h = 4N e l) was set between 0.01 and 5. Priors were based on previous Plethodon studies (Pelletier & Carstens, 2014;Pelletier et al, 2015) and past climatic fluctuations (Webb & Bartlein, 1992). A total of 6,000,000 simulations were conducted using ms (Hudson, 2002), and the following five summary statistics were calculated: {p, ss, D, h H , H}.…”

“…The models were evaluated using area under the curve (AUC) and true skill statistic (TSS) scores. We also projected models for P. vandykei and P. larselli with data from Pelletier et al (2015) onto the Mid-Holocene bioclimatic data and compared the niches of P. dunni to the current and LGM models of these two species from Pelletier et al (2015).…”

“…During the Last Glacial Maximum (LGM; c. 21Ka), ice sheets covered much of Washington (WA) and extended into southern Oregon (OR) along the Cascade Mountains, shifting species habitat by the presence of ice, and associated changes in temperature and water availability. The LGM has been implicated as an important factor that influenced the phylogeographical history of many species from the PNW, including salamanders (Carstens et al, 2004;Kuchta & Tan, 2005;Wagner et al, 2005;Steele & Storfer, 2007;Pelletier et al, 2011Pelletier et al, , 2015. These investigations concluded that glacial refugia were available during the LGM south of the ice sheets, either in the foothills of the Cascades or in pockets along the coast, and demonstrated that range expansion occurred as the glaciers retreated (Brunsfeld et al, 2001;Shafer et al, 2010).…”

Union of phylogeography and landscape genetics

“…Later ecological studies in the same geographic region found that the contact zones between parapatrically separated lineages of an endemic Californian salamander and potential incipient species were inhospitable for migrants and thus barriers to gene flow (66). These kinds of phylogeographic and landscape genetics studies, which integrate geographic and ecological analyses, have spawned new methods in species delimitation that explicitly consider the extent of ecological divergence when diagnosing species (66,(107)(108)(109). Thus, understanding the role of ecological and evolutionary processes across a landscape can be illuminating to the study of both the processes and the resulting biogeographic patterns of speciation.…”

The roles of aridification and sea level changes in the diversification and persistence of freshwater fish lineages

“…Dramatic changes in climate, hydrology and topography have long been 46 recognised to have lasting impacts on the diversity, distribution and divergence of 47 species and populations (Pelletier et al 2015). Understanding the relationship 48 between the historical environment and the genealogy of species remains critical for 49…”