No distinct barrier effects of highways and a wide river on the genetic structure of the Alpine newt (Ichthyosaura alpestris) in densely settled landscapes
2018
Linear landscape elements such as roads, railways and rivers have been shown to act as barriers to dispersal and
gene flow, hence impeding functional connectivity and increasing genetic differentiation between individuals or populations on opposite sides of the barrier. Such putative barriers act through a confluence of mechanisms, including crossing mortality, barrier avoidance and modifications to organisms’ effective dispersal patterns. Small,
terrestrial animalssuch as amphibians are predicted to be vulnerable to the effects of such barriers given their limited locomotive performance and their dependence on spatially distinct breeding habitats. Here, we examined the effects of highways and a wide river on
Ichthyosaura alpestrisin three regions of northern Switzerland by measuring the genetic differentiation between local populations and describing the spatial
genetic structure. Moreover, we estimated
effective population sizesas an indicator for the susceptibility of populations to random
genetic drift. Based on genetic differentiation, we found evidence to suggest that the highways and river acted as barriers to
gene flowfor the newt in the study regions, but results were inconsistent when ignoring breeding ponds with low samples sizes. Admixture-based genetic clustering suggested the delineation of the genotypes to rough regional clusters, with only weak structure inferred within these clusters. Thus, results suggest that at present, highways and rivers do not substantially affect the
genetic structureof I. alpestris within northern Switzerland in a negative manner. Alternatively, the lack of a distinct
genetic structurein regional newt populations may be explained by, e.g., large
effective population sizes.
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