Historical demography of four gecko species specializing in boulder cave habitat – its implications in the evolutionary dead end hypothesis and conservation

Specialization in narrow ecological niches might not only help species to survive in competitive or unique environments but also contribute to their extermination over evolutionary time. Although the “evolutionary dead end” hypothesis has long been debated, empirical evidence from species with detailed information on niche specialization and evolutionary history is still rare. Here we used a group of four closely related Cnemaspis gecko species that highly depend on granite boulder caves in the Mekong Delta to illuminate the potential impact of ecological specialization on their evolution and population dynamics. Isolated by the unsuitable habitat of a flood plain, these boulder-dwelling geckos are among the most narrowly distributed Squamata species in the world. We applied several coalescence-based approaches combined with the RAD-seq technique to estimate their divergence times, gene flow and demographic fluctuations during the speciation and population differentiation processes. Our...