Abstract
Much of the immense present day biological diversity of Neotropical rainforests originated from the Miocene onwards, a period of geological and ecological upheaval in South America. We assess the impact of the Andean orogeny, drainage of Lake Pebas and closure of the Panama isthmus on two clades of tropical trees (Cremastosperma, ca 31 spp.; and Mosannona, ca 14 spp.; both Annonaceae). Phylogenetic inference revealed similar patterns of geographically restricted clades and molecular dating showed diversifications in the different areas occurred in parallel, with timing consistent with Andean vicariance and Central American geodispersal. Ecological niche modelling approaches show phylogenetically conserved niche differentiation, particularly within Cremastosperma. Niche similarity and recent common ancestry of Amazon and Guianan Mosannona species contrast with dissimilar niches and more distant ancestry of Amazon, Venezuelan and Guianan species of Cremastosperma, suggesting that this element of the similar patterns of disjunct distributions in the two genera is instead a biogeographic parallelism, with differing origins. The results provide further independent evidence for the importance of the Andean orogeny, the drainage of Lake Pebas, and the formation of links between South and Central America in the evolutionary history of Neotropical lowland rainforest trees.
Highlights
The immense biological diversity of the Neotropics is the net result of diversification histories of numerous individual lineages [1,2,3]
Understanding the importance of different factors in driving the origins of biological diversity requires approaches that directly compare biologically equivalent species radiations within the same geographical areas and evolutionary time scales with the ecological conditions that prevailed in those times and places [8,9,10]
The results of parsimony analyses were consistent with those obtained under maximum likelihood (ML) and Bayesian inference, but analyses of the matrices with more missing data resulted in a greater number of nodes subject to posterior probability (PP) ≥ 0.95 than those subject to bootstrap support (BS) ≥ 70
Summary
The immense biological diversity of the Neotropics is the net result of diversification histories of numerous individual lineages [1,2,3]. Comparing across Neotropical rainforests, tree alphadiversity peaks in the wetter, less seasonal part of Western Amazonia [6,11]. Correlation of this diversity with particular current conditions, such as climate and soils, may suggest a causal link in sustaining, and perhaps even driving, diversity [12,13]. Both species diversity and ecological conditions have changed dramatically in the Neotropics since the Oligocene [2,11]. Hoorn et al [11] concluded that the establishment of terrestrial conditions in Western Amazonia was a possible prerequisite for the (rapid) diversification of the regional biota
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