Can human-made structures enhance the genetic diversity and population dynamics of midwife toads (Alytes dickhilleni)?

The Betic midwife toad ( Alytes dickhilleni ) is a threatened amphibian endemic to southeastern Spain. Its populations are threatened by current climate change, desertification, habitat fragmentation, and chytridiomycosis. This study evaluates the role of artificial water sources (e.g., livestock ponds and fire ponds) as permanent habitats that support higer genetic diversity and population connectivity than natural temporary ponds. We genotyped 539 individuals from 20 locations in Sierra de Cazorla, Segura y Las Villas Natural Park using 12 microsatellite markers. Genetic diversity (observed heterozygosity, allelic richness) and the inbreeding coefficient (FIS) were similar between artificial and natural ponds. However, we observed genetic structure along the main mountain system, with a Bayesian cluster analysis identifying two main genetic groups. Populations showed a strong pattern of isolation by distance, indicating that geographical distance is a key factor driving genetic differentiation. Migration analyses revealed limited but asymmetric gene flow, with certain populations acting as sources and sinks. Our results suggest that artificial ponds can maintain levels of genetic diversity as high as natural ponds, but not higher, and may play a crucial role in helping populations persist in fragmented landscapes. Pond size and distance to the nearest pond, more than being natural or artificial, are key factors to explain their genetic diversity. Small ponds suffer a rapid decline in genetic diversity with increasing isolation, whereas large ponds maintain stable diversity even when geographically isolated. Conservation strategies should focus on maintaining a network of interconnected ponds, both natural and artificial, to ensure genetic flow and the long-term viability of A. dickhilleni populations.