Name: Guedes P

Biodeserts supervisors: Carvalho S; Velo-Antón G

Co-supervisors: Ana Veríssimo (CIBIO/UP); Carlos Fernandes (FCUL)

Title: Spatial patterns of genetic diversity in Hyla molleri

Institution: University of Lisbon, Portugal

Status: Completed



Global decline of amphibian population has become a major concern for the scientific and conservation communities. With 41% of amphibian species currently classified has threatened with extinction, amphibians are one of the most threatened group in the planet.
From a genetic point of view, amphibian populations generally have low effective size, which translates into a small amount of active breeders. Small populations are more prone to have low genetic diversity due to arbitrary genetic drift. Thus, being more likely to be affected by genetic drift and genetic diversity reduction. Habitat characteristics, such as elevation or geographical distance, can also impact amphibian genetic diversity by acting as a barrier to gene dispersal given the energy required to move between places. Landscape genetics encompass a sampling design focused in landscape characteristics and using a range of genetic and statistical tools to find patterns of genetic diversity that can be explained by one or several landscape/environmental characteristics
Hyla molleri is an Iberian endemism, belonging to the Hylidae family whose origin and diversity is located in the neotropics. It was only in 2008 that Stock et al. showed that the Iberian population was distinct from the rest of the European populations. Before this official separation from H. arborea, Rosa & Oliveira (1994) studied the genetic differentiation between Hyla meridionalis and “H. arborea molleri”, and found very low values of genetic diversity, even suggesting that the samples could be perceived as the result of a single population with random mating, regardless of their distance.
Since the official separation of H. molleri from H. arborea, few studies have been conducted on the species’ population structure and none of these studies has comprehensively studied the genetic population structure of the species across its entire range, or has had a sampling design that allowed for more robust conclusions. There is also a knowledge gap in environmental and geographical distance influence on genetic distances in this species. Therefore, this study aimed to: 1) Infer the spatial genetic population structure, across the whole range of H. molleri; 2) Analyse the influence of geographic and environmental distances on the distribution of the genetic diversity of H. molleri.
Our results point to a genetic differentiation gradient between individuals from northern and southern populations of the Iberian Peninsula, as well as a between individuals in the center and peripheral areas of the species distribution. This pattern is further corroborated by the uncover of four ancestral populations. Greater genetic diversity was found in southern populations. Genetic distance was positively correlated with both geographical and environmental distances. This suggests that H. molleri took refuge in the southern part of the Iberian Peninsula and has expanded its range from there, with the northern range being the last to be occupied. However, in a recent study by Sánchez-Montes et. al (2018, unpublished) using microsatellites, higher genetic diversity was found in northern populations, suggesting that H. molleri glacial refugia were in fact located in the north part of Iberia. Sample size and genetic marker choice are the main suspects for these contradictory results.
We suggest more sampling (both more individuals and localities) and adding other explanatory variables (e.g. topography, land cover, hydrologic map, road traffic, etc.), which have been found to affect similar amphibians’ distribution, in future works for a more complete analysis.