Dissertation Research: Molecular Evolution, Adaptive Radiation, and Geographic Speciation in Banksia (Proteaceae)

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9801572 Givnish This study seeks to make an important contribution toward describing the patterns of evolution in a striking example of continental adaptive radiation. The genus Banksia (Proteaceae) includes 79 species of trees, shrubs, and prostrate woody mats that occur only in Australia and are established in a broad range of climates and soils. Some characters vary greatly among the species, such as the leaves, which may vary from entire to spinose, and these plants display the widest range in lifespan known among flowering plants. In addition several co-occuring pairs of species in Banksia and the related genus Dryandra are remarkably convergent in leaf and flower form. A phylogeetic tree will be developed for Banksia and relatived genera based on variation in chloroplast and nuclear DNA. Once resolved the tree will be used for the following purposes: 1) analysis of the agreement between our DNA data and a recent set of morphological data with the aim of obtaining a classification of Banksia based on both kinds of information; 2) evaluation of the history of species formation within and between different geographic areas; 3) relating evolutionary shifts in plant form and ecology to inferred historical shifts to different climates and/or substrates; and 4) determination of whether the strikingly similarity between coexisting pairs of Banksia and Dryandra species represents evolutionary convergence under similar ecological conditions or the sharing of recent common ancestors. The proposed study will shed light on the history, geographic distribution, and ecology of one of the most diverse and characteristic groups of Australia's vegetation.