Dissertation Research: Diversity, Specificity, and Dynamics of Rhizobia-legumes Associations in Canyons of the Sonoran Desert

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PROJECT SUMMARYRecently, there has been growing interest in legume-rhizobia associations asmodel systems for studying mutualisms, but a central obstacle is that little is known aboutthe genetic structure of native communities. We know that associations can be specificor promiscuous, but very few studies have described spatial or temporal variation innative rhizobia-legume communities. We intent to examine levels of spatial andtemporal variation in communities of rhizobia and legumes in natural environments. Wewill compare associations at various geographic scales, from within nodules to betweencanyons. We will measure how associations change over time, considering variationbetween months, seasons, and years. By considering specificity of associations and thegenetic structure of a native community, our goal is to better understand the potential forcoevolution to shape this mutualism. The proposed work uses sequences from 1329strains from 15 plant species to characterize the effect of plant taxa, microhabitatdifferences, and seasonal differences on rhizobial genetic variation and specificity ofassociations. We will contribute to the understanding of this imporant mutualism byseeking to describe natural systems in detail, characterizing rhizobial genetic diversity,and measuring the extent that specialization and generalization is achieved in naturallyevolving populations.