Genetic diversity of European tree frogs (Hyla arborea group): A systematic review

Amphibian populations are increasingly threatened by global change and the study of their genetic diversity is a major conservation priority. Western palearctic tree frog species of the  Hyla arborea  group are commonly distributed across Europe and the Middle East and many have declining populations. We performed a PRISMA systematic review to gain insight into the genetic diversity of  H. arborea  group. Sixteen published studies were included in the final qualitative analysis. While the genetic diversity of  H. arborea  group species was widely variable, it could often be explained by phylogeographic history. Populations in Western and Northern Europe had lower genetic diversity, with some populations also affected by habitat fragmentation. However, important regions of high genetic diversity were found in the Balkan peninsula for  H. arborea  sensu stricto and around the Black Sea for  H. orientalis . Genetic diversity of  H. molleri ,  H. savignyi ,  H. meridionalis ,  H. felixarabica, H. intermedia ,  H. sarda  has been investigated only across extensive phylogeographical studies, while data regarding their genetic diversity at the local level are missing. Through our review, we identify knowledge gaps about the genetic diversity of the  H. arborea  group that require further investigation, of and illustrate how filling these gaps might translate into future conservation efforts.