Comparative landscape genetics of two endemic torrent salamander species, Rhyacotriton kezeri and R. variegatus: implications for forest management and species conservation

Abstract

Comparative landscape genetic studies provide insights into whether relationships between landscape features and patterns of spatial genetic structure differ among populations, species, habitat types, and regions. For species with fragmented distributions, especially when management practices contribute to fragmentation, tests of the factors structuring population connectivity are particularly important for understanding continued risks. We determined levels of genetic diversity and tested the relationships of landscape-scale vegetative, geographic, and climate variables with genetic distance in two congeneric, endemic salamander species with status of concern. Using microsatellite data for 326 Rhyacotriton kezeri and 557 Rhyacotriton variegatus individuals collected from 17 to 29 localities, respectively, we implemented a model of landscape resistance based on circuit theory. The northernmost portions of each species' range is more fragmented than areas to the south, leading to the prediction that these areas would have relatively lower genetic diversity in response. Due to reliance of both species upon cold-water habitats, we predicted that landscape variables maintaining cool, moist microhabitats would be correlated with gene flow. Genetic structure was high overall and trended toward increasing with the proportion of the forested landscape. Based on maximum likelihood population effects models across genetic clusters and species, land cover and roads were the best predictors of genetic distance, even though the degree of fragmentation differed across each species' geographic range. Our results suggest that forest cover is essential for dispersal in these salamanders, indicating negative effects of fragmentation resulting from timber harvest and other forest disturbances.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Urbanization reduces gene flow but not genetic diversity of stream salamander populations in the New York City metropolitan area

“…Richardson (2012) and McCartney-Melstad, Vu, and Shaffer (2018) found both distance and roads shape the genetic structure of wood frogs (Lithobates sylvatius) and Eastern tiger salamanders (Ambystoma tigrinum), which are often sympatric with E. bislineata in northeastern North America. Generally, our results are congruent with other studies that show urbanization affects spatial and population dynamics, as well as genetic structure for a broad range of amphibians (Jean-Marc et al, 2018;Emel, Olson, Knowles, & Storfer, 2019;Marsh et al, 2008;Munshi-South et al, 2013;Scheffers & Paszkowski, 2011;Vanek, King, & Glowacki, 2019;Villasenor, Driscoll, Gibbons, Calhoun, & Lindenmayer, 2017) and other animal taxa (DeCandia et al, 2019;Jaffé et al, 2019). Mechanisms underlying the effects of urbanization on amphibian gene flow include physical barriers to dispersal, lack of free-standing water or moist microhabitats, and the presence of extensive light and noise pollution (Eigenbrod, Hecnar, & Fahrig, 2009;Hale et al, 2013 (Holgerson, Lambert, Freidenburg, & Skelly, 2018), and leaves patches of unsuitable terrestrial habitat interspersed among undeveloped, seminatural areas (Hitchings & Beebee, 1997).…”

Physical and ecological isolation contribute to maintain genetic differentiation between fire salamander subspecies

“…Landcover-based models, on the other hand, always behaved similarly between regions, improving, although slightly, genetic differentiation predictions from IBD models in the ICS and MTR (Table S5). If we consider this together with the fact that forest cover had the highest weight in landcover ENMs (Table S6), our results add to the cumulative evidence that forested areas play a key role in genetic connectivity in salamander populations (Cushman 2006;Antunes et al 2018;Emel et al 2019;Lourenço et al 2019;Arntzen and van Belkom 2020).…”

Landscape Genetics of the Yellow-Bellied Toad (Bombina variegata) in the Northern Weser Hills of Germany

“…Implementing resistance models into the analysis can broadly improve the understanding of genetic connectivity in a landscape, and how certain elements can influence connectivity which was also the case for our study. Using the MLPE method a study on two salamander species, Rhyacotriton kezeri and Rhyacotriton variegatus, showed that forest coverage is essential for the dispersal of these species, while fragmentation and deforestation have an overall negative impact on the genetic connectivity [58]. Interestingly, in this study the calculations were separated via clusters and IBD was selected as the most fit model for the northern population clusters.…”