Citizen science reveals sharp decline of the Mediterranean tree frog Hyla meridionalis over 40 years in southeastern Iberia: potential causes and proposed solutions to prevent regional extinction

Citizen science reveals sharp decline of the Mediterranean tree frog Hyla meridionalis over 40 years in southeastern Iberia: potential causes and proposed solutions to prevent regional extinction. Several previous studies have suggested that the Mediterranean tree frog Hyla meridionalis, a species highly sensitive to habitat alterations, is currently threatened in this region. Here, we provide an update on the distribution and conservation status of the hylid in this area, based on monitoring through nocturnal acoustic surveys and visual prospections in sites with favorable characteristics for the species during 2016-2019. Some of these points had historical occurrence data (1980s-1990s), allowing us to analyze temporal variations in the species’ presence. Furthermore, we examined how habitat transformation and levels of protection were related to changes in the local presence of the anuran in the Adra basin, an area where human-induced environmental modifications and frog persistence have been documented over the past 40 years. The Mediterranean tree frog was found at low numbers in only 17 of the 144 sampled points, mostly isolated, during 2016-2019, and had disappeared from 27 of the 43 points where it was previously present 40 years ago. We found that the loss of favorable habitat and the absence of legally protected areas were directly linked to the decline in sites inhabited by the species. Based on the changes observed and IUCN criteria, we classified the Mediterranean tree frog as ‘endangered’ in southeastern Iberia. Conservation measures are proposed to support the recovery of the hylid in the study area. Key words: Agricultural impact, Conservation, Distribution, Greenhouses, Hyla meridionalis, Temporal evolution