Landscape-genetic analysis of Natterjack toad (Epidalea calamita) populations in the Suhre valley (Switzerland)
Frei, M., 2014: Landscape-genetic analysis of Natterjack toad (Epidalea calamita) populations in the Suhre valley (Switzerland). Master thesis. 25 p.
Frei, M., 2014: Landscape-genetic analysis of Natterjack toad (Epidalea calamita) populations in the Suhre valley (Switzerland). Masterarbeit der ETH Zürich, D-USYS, geleitet von Janine Bolliger und Felix Gugerli, WSL Birmensdorf.
Understanding the influence of landscape elements on dispersal and connectivity of potentially isolated populations is essential for the successful conservation management, especially in agricultural landscapes. Here, we assessed the migration pattern and genetic structure of the endangered Natterjack toad (Epidalea calamita) in the Suhre valley (Switzerland), a homogeneous agriculture area with a comparatively large occurrence of this toad. We further analysed the population dynamics in the spatial and temporal dimension. We also studied the influence of land-use on population size and migration. Finally, we compared the performance of radio-tracking with genetic analyses to identify migration.
Our results showed that none of the distinguished populations were genetically isolated. Accordingly, we found that migration takes place regularly. Most of the uncovered migration events were found by genetic analyses and not by radio-tracking. The network analysis revealed that the largest populations were the most important for the population network, confirmed by the source?sink analysis. Among land-use elements, forests seemed to have a negative effect on gene flow as well as on population size.
We conclude that neither main roads nor the canalised Suhre are migration barriers for the Natterjack toad. It seems that this species can survive in agriculture landscapes, if enough breeding ponds exist. Nevertheless, conservation activities should focus on the large populations since they are sources and therefore essential for the continuance of a viable Natterjack toad population. We recommend using genetic analyses to detect migration if one is not interested in the exact migration route of individuals.