Drainage Basin Formation as a Key Driver of Diversification in Neotropical Aquatic Frogs

Abstract

The Neotropics are one of the most biodiverse regions in the world, yet the processes driving this diversity remain poorly understood.This study explored the spatio-temporaldiversification of Pseudis paradoxa and Pseudis platensis, two closely relatedaquatic frog species associated with rivers and floodplains throughout South America. We addressed two questions: (1) How werethe hypothetical ancestors of the P. paradoxa + P. platensis clade distributed? and, (2) What biogeographic processes influencedthe diversification and current geographic distribution of the clade? Using two mitochondrial and three nuclear markers, weconducted lineage delimitation, divergence time estimation, and historical biogeography with BIOGEOBEARS. Results showedthat both species consist of multiple lineages. The initial divergence was estimated at around 4.8 million years ago (2.8–7.2 Mya),at the Miocene–Pliocene transition. Ancestral range estimation recovered the origin of the P. paradoxa/P. platensis clade in apaleo-regionspanning the Amazon and La Plata basins. Vicariance processes split this ancestral range, leading to allopatric populationsin each basin. The establishment of the modern Amazon Basin, shaped by river capture events approximately 4.9–5.6Mya, was likely the key factor promoting the diversification of the P. paradoxa/P. platensis clade.