A meta-analysis of Neotropical butterflies reveals long-term signature of the Pebas wetland on Neotropical biogeography

A recent meta-analysis of Neotropical butterflies has unveiled the lasting influence of the Pebas wetland on the biogeography of the region. Traditionally, the Andes or Amazonia have been considered primary drivers of biodiversity in the Neotropics, but the Pebas wetland system spanning western Amazonia during the Miocene has garnered attention as a potential dispersal barrier.

This wetland might have contributed to the observed imbalance in biodiversity between the Andes and Amazonia, known as the Gentry pattern. Most supporting evidence for this hypothesis is drawn from isolated case studies and fossils. In this study, researchers analyzed the distribution of 1,361 species of Neotropical butterflies to assess the impact of the Pebas wetland on dispersal and diversification dynamics.

The findings reveal that Andean and Amazonian clades exhibit complementary yet temporarily distinct biogeographic patterns. The high diversity observed in Andean clades is attributed to an Andean origin, with early occupancy and diversification occurring within the Andes, followed by post-Pebas dispersal into Amazonia. Conversely, Amazonian clades exhibit an Amazonian origin, with early diversification in Amazonia and subsequent colonization of the Andes post-Pebas.

While several clades display minimal evidence of Pebas influence, the meta-analysis suggests that the Pebas wetland did not uniformly suppress diversification but rather selectively limited dispersal between the Andes and Amazonia. This selective constraint prevented simultaneous diversification in both regions, resulting in the modern diversity imbalance that characterizes the Neotropical region.