Evidence that climate sets the lower elevation range limit in a high‐elevation endemic salamander

Abstract

A frequent assumption in ecology is that biotic interactions are more important than abiotic factors in determining lower elevational range limits (i.e., the “warm edge” of a species distribution). However, for species with narrow environmental tolerances, theory suggests the presence of a strong environmental gradient can lead to persistence, even in the presence of competition. The relative importance of biotic and abiotic factors is rarely considered together, although understanding when one exerts a dominant influence on controlling range limits may be crucial to predicting extinction risk under future climate conditions. We sampled multiple transects spanning the elevational range limit of Plethodon shenandoah and site and climate covariates were recorded. A two‐species conditional occupancy model, accommodating heterogeneity in detection probability, was used to relate variation in occupancy with environmental and habitat conditions. Regional climate data were combined with datalogger observations to estimate the cloud base heights and to project future climate change impacts on cloud elevations across the survey area. By simultaneously accounting for species’ interactions and habitat variables, we find that elevation, not competition, is strongly correlated with the lower elevation range boundary, which had been presumed to be restricted mainly as a result of competitive interactions with a congener. Because the lower elevational range limit is sensitive to climate variables, projected climate change across its high‐elevation habitats will directly affect the species’ distribution. Testing assumptions of factors that set species range limits should use models which accommodate detection biases.

Heat Waves, the New Normal: Summertime Temperature Extremes Will Impact Animals, Ecosystems, and Human Communities

“…warming (e.g., upwelling, water circulation in bays). In another example, high-altitude organisms may move higher up the slopes of mountains as the climate warms to seek cooler habitat at higher altitude to maintain the thermocline they prefer (46,122). However, other environmental factors are unlikely to shift up the mountain with temperature (e.g., soil moisture, plant forage, oxygen), and so those alpine taxa may not find suitable habitat in their preferred temperature range at higher elevation (133).…”

A demographic approach to understanding the effects of climate on population growth

“…Lower elevation range limits 248 amphibian ranges are limited by climate(Gifford and Kozak 2012; Cunningham et al 2016; 250 Lyons et al 2016;Grant et al, 2018;Caruso et al, 2019). While we did not formally test this 251 hypothesis, our results support these studies.…”

Genetic variation in Plethodon cinereus and Plethodon hubrichti from in and around a contact zone

“…The distributions of the five P. cinereus group mountaintop endemics are all nested within the range of P. cinereus (Figure 1). However, little is known about potential shifts in zones of parapatry between P. cinereus and closely related mountaintop endemics or increased hybridization resulting from any such shifts (but see Grant, Brand, De Wekker, Lee, & Wofford, 2018; Mulder, Cortes‐Rodriguez, Grant, Brand, & Fleischer, 2019). In the Southern Appalachian mountains where these species occur, climates are shifting to become warmer and drier, and in some cases, cloud heights are rising in elevation (Ingram, Dow, Carter, Anderson, & Sommer, 2013; Laseter, Ford, Vose, & Swift, 2012; Richardson, Denny, Siccama, & Lee, 2003) Each of these aspects of climate change, alone or in combination, has the potential to substantially shift salamander distributions and the nature of their interspecific interactions (Grant et al., 2018; Milanovich et al., 2010; Walls, 2009).…”