Neotropical forest expansion during the last glacial period challenges refuge hypothesis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 113; no. 4; pp. 1008 - 1013
• Main Authors: Leite, Yuri L. R., Costa, Leonora P., Loss, Ana Carolina, Rocha, Rita G., Batalha-Filho, Henrique, Bastos, Alex C., Quaresma, Valéria S., Fagundes, Valéria, Paresque, Roberta, Passamani, Marcelo, Pardini, Renata
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 26.01.2016; National Acad Sciences
• Subjects: Biodiversity; Biodiversity hot spots; Biogeography; Biological Sciences; Climate; Climatic conditions; Continental shelves; Ecosystem; Evolution, Molecular; Forest ecosystems; Forests; Genetic structure; Glaciers; Habitats; Hypothesis testing; Mathematical models; Phylogeography; Physical Sciences; Rainforests; Speciation; Tropical forests; South America; Atlantic Forest; ASW, South America; continental shelf; last glacial maximum; Atlantic Forest; Quaternary; sea level
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1513062113

The forest refuge hypothesis (FRH) has long been a paradigm for explaining the extreme biological diversity of tropical forests. According to this hypothesis, forest retraction and fragmentation during glacial periods would have promoted reproductive isolation and consequently speciation in forest patches (ecological refuges) surrounded by open habitats. The recent use of paleoclimatic models of species and habitat distributions revitalized the FRH, not by considering refuges as the main drivers of allopatric speciation, but instead by suggesting that high contemporary diversity is associated with historically stable forest areas. However, the role of the emerged continental shelf on the Atlantic Forest biodiversity hotspot of eastern South America during glacial periods has been ignored in the literature. Here, we combined results of species distribution models with coalescent simulations based on DNA sequences to explore the congruence between scenarios of forest dynamics through time and the genetic structure of mammal species cooccurring in the central region of the Atlantic Forest. Contrary to the FRH predictions, we found more fragmentation of suitable habitats during the last interglacial (LIG) and the present than in the last glacial maximum (LGM), probably due to topography. We also detected expansion of suitable climatic conditions onto the emerged continental shelf during the LGM, which would have allowed forests and forest-adapted species to expand. The interplay of sea level and land distribution must have been crucial in the biogeographic history of the Atlantic Forest, and forest refuges played only a minor role, if any, in this biodiversity hotspot during glacial periods.