Convergent evolution to extreme altitude in tropical East Africa
Dr. Pádraic J. Flood
(Max Planck Institute for Plant Breeding Research, Cologne, Germany)
Altitudinal gradients are ideal for studying microgeographic adaptation across the landscape. Here we describe the adaptation of the model plant species Arabidopsis thaliana across 12 mountains in tropical east Africa. These populations are isolated from one another on so-called sky islands and thus acts as replicates to study the repeatability of evolution at both the phenotypic and molecular level. We have sampled across an altitudinal range of over 2600m ranging from savannah to tropical alpine ecosystems. The tropical alpine ecosystem is a very extreme one with large temperature fluctuations ranging from -5°C or less at night to above 20°C during the day. Across all sampled mountains we find remarkable morphological and life history convergence at high altitude (above 3800m) for a suite of phenotypes, most striking of which is a massive reduction in plant height (from 30cm+ at lower elevations to less than 1cm at higher elevations). To assay the molecular basis of this convergence we have sequenced accessions from across the altitudinal range and used a combination of quantitative and population genetic techniques. The morphological and life history convergence is polygenic with some large effect loci. We will present results showing the extent to which the molecular underpinnings of phenotypic convergence are themselves convergent.