Mchenry, Monique , Barrington, David .
Divergence history, elevation and geographic shifts in Andean Polystichum (Dryopteridaceae).
Uplift of the tropical Andes has had a significant effect on the diversification of organisms in South America as revealed by recent phylogenetic studies. Using a plastid phylogeny of Andean Polystichum, we investigated the provenance and the patterns of diversification. We reconstructed biogeographic patterns with Maximum Parsimony implemented in Mesquite and estimated divergence times with BEAST. We found that the exindusiate Andean Polystichum clade diverged from a lineage rich in species endemic to montane southern Mexico during the middle Miocene. The majority of Andean Polystichum diversification took place in the central Andes in the Pliocene and the Pleistocene. Radiations to the northern Andes as their uplift opened habitats and onto the more ancient Brazilian Highlands are more recent. Expansion into new habitats at different elevations is accompanied by morphological change. For example spore size increases and perispore folds become appressed with increased median elevation, suggesting that selection for these traits occurred at higher elevations.
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1 - University Of Vermont, Plant Biology, Marsh Life Science Building, Burlington, VT, 05405-0086, USA
2 - University Of Vermont, Jeffords Hall, 63 Carrigan Drive, Burlington, VT, 05405, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Union E/Hyatt
Date: Monday, July 9th, 2012
Time: 2:00 PM