Miocene marine transgression and climate variation drove diversification of subtropical Proceratophrys frogs in the Araucaria Forest

Abstract

The Proceratophrys bigibbosa species group has a disjunct distribution in South America, with four out of five species inhabiting the Araucaria Forest. In this study, we investigated whether cycles of expansions/retractions of the Araucaria Forest or marine transgressions leading to the formation of the Paranean Sea may have contributed to the divergence of these frogs. It was inferred through DNA sequences from three mitochondrial and three nuclear genes across 82 individuals. Genetic divergence was assessed with haplotype networks, while demographic trends were explored using extended Bayesian skyline plots (EBSP). An environmental principal component analysis (ePCA) was also implemented to evaluate the degree of similarity of climatic spaces occupied by each species. Our phylogenetic analyses positioned P. palustris as the sister-species to P. brauni, forming a sister-clade to P. bigibbosa and an undescribed species (Proceratophrys sp.). In addition, we propose P. kaingang as a junior synonym of P. palustris. Our coalescent species tree showed divergence-time estimates ranging between 7.67 and 3.51 Mya, indicating that a marine transgression played a key role in this group diversification. Our findings highlight the combined role of Miocene marine transgressions and climatic variation as drivers of diversification in the Proceratophrys bigibbosa group.