Functional connectivity of an endemic tree frog in a highly threatened tropical dry forest in Mexico

Recent habitat modification of a tropical dry forest hotspot drives population genetic divergence in the Mexican leaf frog: a landscape genetics approach

Tropical dry forests (TDF) are among the ecosystems with the highest deforestation and transformation rates. Because of habitat loss and fragmentation, modified landscapes can impose resistance to the movement of individuals, with important genetic consequences. One of the most affected taxa due to habitat alteration are amphibians, which currently face extreme population declines globally. Here, we used single nucleotide polymorphisms (SNPs) to evaluate genetic diversity, genetic structure, and the effect of landscape elements on genetic connectivity of the Mexican tree frog (Agalychnis dacnicolor) in a TDF biodiversity hotspot in Mexico. We collected samples of 96 individuals from 16 sites located within fragmented areas of TDF and within continuous forest in the Chamela-Cuixmala region. Sampling sites from the fragmented forest showed slightly lower genetic diversity and effective population size compared to those in the continuous forest. We detected three admixed genetic groups, in which most of the sites within the fragmented forest were differentiated from the sites within continuous forest. Although these analyses suggest historical gene flow, we did not detect significant recent migration among the three genetic groups. While original vegetation (TDF + tropical evergreen forest), and in some areas, agriculture facilitated genetic connectivity, open-areas (grasslands + human settlements + exposed soil), and agriculture in other areas limited genetic connectivity in A. dacnicolor. This study helps to understand the factors shaping contemporary population divergence in highly modified complex landscapes, and highlights the importance to maintain connectivity in a rapidly changing ecosystem.