Ecological resistance surfaces predict fine‐scale genetic differentiation in a terrestrial woodland salamander

Abstract

Landscape genetics has seen tremendous advances since its introduction, but parameterization and optimization of resistance surfaces still poses significant challenges. Despite increased availability and resolution of spatial data, few studies have integrated empirical data to directly represent ecological processes as genetic resistance surfaces. In our study, we determine the landscape and ecological factors affecting gene flow in the western slimy salamander (Plethodon albagula). We used field data to derive resistance surfaces representing salamander abundance and rate of water loss through combinations of canopy cover, topographic wetness, topographic position, solar exposure and distance from ravine. These ecologically explicit composite surfaces directly represent an ecological process or physiological limitation of our organism. Using generalized linear mixed-effects models, we optimized resistance surfaces using a nonlinear optimization algorithm to minimize model AIC. We found clear support for the resistance surface representing the rate of water loss experienced by adult salamanders in the summer. Resistance was lowest at intermediate levels of water loss and higher when the rate of water loss was predicted to be low or high. This pattern may arise from the compensatory movement behaviour of salamanders through suboptimal habitat, but also reflects the physiological limitations of salamanders and their sensitivity to extreme environmental conditions. Our study demonstrates that composite representations of ecologically explicit processes can provide novel insight and can better explain genetic differentiation than ecologically implicit landscape resistance surfaces. Additionally, our study underscores the fact that spatial estimates of habitat suitability or abundance may not serve as adequate proxies for describing gene flow, as predicted abundance was a poor predictor of genetic differentiation.

Geographic variation of resistance to water loss within two species of lungless salamanders: implications for activity

“…However, we suspect that physiological differences along the elevational gradient are due to acclimatization because suitable habitats are continuous across the elevational range (but see Peterman et al 2014). However, the variation of R along elevational gradients has important implications for modeling activity.…”

Estimating effective landscape distances and movement corridors: comparison of habitat and genetic data

“…This suggests that there is not necessarily a correspondence between habitat use patterns and dispersal movements. Conditions providing suitable habitat for permanent establishment and local resource may often be different than the conditions facilitating dispersal movements (Cushman et al 2013a, Peterman et al 2014. Since suitability models are based on occurrence data that usually represent locations within home ranges, habitat suitability models may not adequately reflect how environments affect animals during movements outside of their usual home ranges, such as dispersal or mating excursions (Cushman et al 2013a).…”

Mapping landscape friction to locate isolated tsetse populations that are candidates for elimination

“…The novelty of our approach is to relax the need for expert opinion and to rely fully on the genetic distance for an evidence-based mapping of landscape connectivity and for the identification of the most likely dispersal paths. We subsequently combined the genetics-based analysis of friction with a tsetse distribution model built using a fully different dataset, thus considering that habitat suitability and connectivity might not be influenced by the same environmental factors (14). The end result is a reproducible methodology that enabled us to locate potentially isolated tsetse populations that might be considered as targets in eradication programs.…”

“…Landscape friction has been studied in a number of species, with insects only represented in fewer than 10% of the studies (13). For example, studying friction allowed researchers to demonstrate that the rate of water loss plays a key role in the movement of a terrestrial woodland salamander, but also that models of habitat suitability or abundance may not be adequate proxies for gene flow (14).…”