Adaptive radiations of New World lupins revealed by transcriptome sequencing

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Studies of adaptive radiations - groups of closely related species adapted to very different conditions - have yielded important insights into our understanding of evolution ever since the pioneering works of Darwin and Wallace. Rapid recent radiations of species can be used as models allowing us to study general evolutionary processes that were at work during the major adaptive radiations in the history of our planet. The conditions under which adaptive radiations occur are not well understood and generally it is not clear why some groups of organisms are very species-rich, while others consist of only few species despite similar age. Adaptive radiations can form in a very short period of time, e.g. species-rich groups of African cichlids are only few thousand years old and speciation rates in such groups is very high, yet general reasons for such rapid ('explosive') speciation require further investigation. This project is devoted to the analysis of evolutionary genetic processes during multiple rapid radiations in a plant genus Lupinus (Leguminosae), which exhibits some of the highest known rates of net diversification in plants. Exceptional rates of species diversification have been documented for Andean lupins, where 85 species have evolved in the last 1.8 million years. An independent lineage of lupins is actively radiating in North America. Such replicate radiations provide powerful comparative systems to address questions about the evolutionary forces driving episodes of diversification. Detailed evolutionary genetic analysis of replicate rapid radiations has not been undertaken previously.Despite relatively low sequence divergence among recently diverged species of Western New World lupins, the range of life forms (from dwarf annuals and prostrate herbs to small trees), and habitats occupied is striking. This accelerated morphological and ecological diversification suggests that many genes may have been under strong adaptive selection. The aim of the project is to address currently unanswered questions about the types of genes involved in adaptation during adaptive radiations as well as the relative roles of selection at the amino acid level versus regulatory regions. This will involve the comparisons of the patterns of DNA sequence divergence and gene expression between closely related and recently diverged species with divergent life forms and adapted to a range of environments. Genome-wide DNA polymorphism/divergence as well as expression data will be obtained by Solexa/Illumina sequencing of cDNA. This will be done for actively radiating clades of species in the Andes and North America as well as for a set of species outside actively radiating clades for comparison.