Applying population genetics to define the units for conservation management in the European Tree Frog, Hyla arborea

Population genetic analyses are a powerful tool for obtaining information about cryptic genetic lineages, population structure, and the distribution of intra- and interpopulation genetic diversity across the landscape. This knowledge is crucial for establishing units for the conservation management of endangered species. Species with limited dispersal capacities, such as amphibians, are particularly affected by habitat fragmentation and reductions in gene flow among isolated populations. The European Tree Frog, Hyla arborea, has suffered from dramatic population declines in the last decades and is categorized as Vulnerable to Critically Endangered in its north-western distribution range. In Lower Saxony (Germany), the current
distribution of the tree frog is fragmented. In this study, we aimed to assess the population structure, genetic diversity, gene flow, and migration rates in order to define the units for conservation management. Across a distribution area of 250 km2, frogs were sampled at 14 localities and genotyped at seven microsatellite
loci, and the mtDNA cytochrome b gene was sequenced for a subsample. Whereas microsatellite pairwise Dest and FST values showed genetic differentiation among nearly all sampled populations, Bayesian analyses assigned the 14 localities to two distinct genetic clusters including seven subclusters. Together with a
slight correlation between geographic and genetic distance, the population structure indicates ongoing fragmentation. The cytochrome b haplotype distribution does not indicate divergence into mtlineages, but highlights the former connection of populations along the river Elbe. The results of this study suggest that the
intense anthropogenic pressures in this area over the last decades have had negative genetic consequences for this species. The fragmented population structure calls for reconnection of the isolated occurrences by the implementation of conservation measures.