Ogburn, Matthew , Edwards, Erika .
Correlated morphological and ecological transitions in the clade Montiaceae.
The clade Montiaceae comprises the bulk of taxa previously circumscribed in the traditional Portulacaceae. They are distributed in a range of habitats primarily along the western American cordillera, with additional representatives in Australia and eastern North America. Montiaceae appear to represent an example of disparification in response to ecological opportunity, with multiple dissimilar forms and ecological niches co-occurring among closely related subclades. We undertook a biogeographic and morphological analysis to better understand the relationships between growth form and ecology in the group. Analysis of climate data indicates that Montiaceae are distinguished within the larger clade Portulacineae by their expansion into colder and more seasonally variable habitats. There is a significant relationship between elevation and growth form across all Montiaceae, with a general turnover from perennials to annuals as a function of decreasing elevation and/or latitude. We reconstructed 6-7 likely shifts from the perennial to the annual habit, with 2-3 subsequent reversals to perennials. Montiaceae also show substantial variability in succulent tissues, and we found a significant negative relationship between leaf succulence and elevation. We infer that Montiaceae are ancestrally perennial and initially diversified in response to ecological opportunity created by the uplift of the Andes, followed by subsequent evolution of annual forms with the opening of novel lowland habitats caused by Miocene aridification in the western Americas. While the high-elevation perennials across Montiaceae are consistently dwarf rosette chamaephytes, often with substantially thickened storage roots, there is more extensive variation in morphology and ecology of lowland annuals, including desert taxa with highly succulent leaves (Cistanthe, Philippiamra), ruderals (Calandrinia), and plants of more mesic habitats (Montia and Claytonia). Some of these taxa, in particular Cistanthe and Montiopsis, show extremely low sequence divergence across the markers analyzed relative to their morphological disparity, most likely indicating very recent radiation. This diversification within the group fits into a broader scenario of ecological opportunity created by the Andean uplift and aridification during the recent Tertiary.
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1 - Brown University, Ecology & Evolutionary Biology, 80 Waterman St., Box G-W, Providence, RI, 02912, USA
2 - Brown University, Box G-W, 80 Waterman St, Providence, RI, 02912, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Franklin A/Hyatt
Date: Tuesday, July 10th, 2012
Time: 10:15 AM