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.

Over the past few decades, the population of cod in the Eastern Baltic has faced numerous challenges due to environmental changes, overfishing, and predation, as well as the effects of infection by third-stage larvae of the Anisakidae parasite in the liver. The aim of this study was to estimate the prevalence and infection level of Anisakidae nematodes in the Eastern Baltic cod stock over a five-year period and analyze the effect of infection on cod health condition. A total of 1946 samples of the Eastern Baltic cod (Gadus morhua) were collected and tested for the presence of Anisakidae nematode larvae. All nematodes found in livers were identified as Anisakidae with an overall prevalence of 30.9%, a mean infection density of 0.8 (median 0.4) nematodes per gram of liver tissue, and a range of 0.01–29.2 nematodes per gram. The prevalence of infection tended to increase with the age of the fish. In multivariate analysis, increasing infection intensity decreased the odds of cod having good Fulton’s and Clark’s condition scores and a hepatosomatic index (HSI) above the population average. While our study shows a clear Anisakidae effect on Fulton’s and Clark’s condition scores and the HSI, these indicators could also be influenced by other environmental, physiological, and pathological factors.