Presentation Detail

SSB Symposium: Ernst Mayr Symposium

Dorsey, Brian [1], Berry, Paul [2].

Integrating Phylogeny, Climatic Niche, and Biogeographic History to Explain Growth Form Evolution in the Spine-shield Euphorbias (E. sect. Euphorbia, Euphorbiaceae).

Explaining the evolution of morphological differences among species and the biogeographic history of clades are two main goals in evolutionary biology. Adaptive morphological evolution is expected to be related at least partly to changes in habitat, which is intimately tied to historical biogeography. We integrate estimates of ancestral ranges, climatic niche tolerances, and ancestral growth forms to investigate the role of habitat in growth form evolution in a morphologically diverse clade of stem-succulents (Euphorbia sect. Euphorbia). Specifically, we test the hypothesis that variation in climatic parameters encountered by species during the historical spread of the clade has selected for the evolution of three distinct growth forms. We construct a phylogeny for E. sect. Euphorbia and use it to infer ancestral growth forms and ancestral ranges. We then combine these with hypothesized selection regimes, defined by estimates of climatic niches, to compare models of neutral and adaptive morphological evolution. Contrary to previous biogeographic hypotheses concerning this clade, our results show that the ancestor of E. sect. Euphorbia was a tree that was widespread across Africa and southern Asia, and that the ranges of extant species are the result of a combination of vicariance events at the periphery of, and diversification within, the ancestral range . Our analyses also show that the evolution of different growth forms within E. sect. Euphorbia has been an adaptive response to variation in climatic parameters, and we attribute this partly to the heterogeneous paleoclimate in Africa during the diversification of this clade.

1 - The Huntington Botanical Gardens, 1151 Oxford Road, San Marino, CA, 91108, USA
2 - University Of Michigan, Department Of Ecology And Evolutionary Biology, 3600 Varsity Drive, Ann Arbor, MI, 48108, USA

Keywords:
ancestral states
Ornstein-Uhlenbeck
Natural selection
biogeography
OUCH package
Plant Form
Morphological Evolution.

Presentation Type: Symposium Presentation
Session: 210
Location: Ballroom 2/Cliff Lodge
Date: Sunday, June 23rd, 2013
Time: 8:30 AM
Number: 210001
Abstract ID:115
Candidate for Awards:Ernst Mayr Award