Sharp decline of the Mediterranean tree frog (Hyla meridionalis) over 40 years in the southeast of Iberia: causes, and possible solutions to an extinction

Abstract

Water-dependent amphibians often present marginal populations in arid and semi-arid regions of the world. This is the case of the Mediterranean tree frog (Hyla meridionalis) in the southeast of Iberia, where the species is currently threatened. Here we provide an update of the distribution of Mediterranean tree frog in the region by surveying in localities with appropriate characteristics for the species. In part of these localities, there is historical (1980s-1990s) occurrence data, which allows studying temporal changes in the presence of the species. Furthermore, for the Adra river basin, where human-induced environmental changes and frog persistence over the last 40 years are known, we study how habitat changes and level of protection relate to local frog extinction. The Mediterranean tree frog currently appears in low numbers in 17 sampled points, and has disappeared in 27 of the 43 sampled points where it was present 40 years ago. Sampled points with nowadays frog presence have almost three times surface of suitable and legally protected habitats than those without frog. In addition, sampled points where the frog have disappeared experienced a more pronounced reduction in suitable habitat, and have three times less protected area than those where the frog remained. In the current global change scenario, it is urgent to restore and protect areas that include masses of fresh or brackish water with shallow shores covered by thick marsh vegetation and to reinforce populations to prevent the probable extinction of the Mediterranean tree frog in the southeast of Iberia.