Dr. Tia Harrison, Postdoctoral Fellow, Queen's University Patterns, consequences, and processes of mutualism evolution in the legume-rhizobium system Cooperation between species is widespread in nature yet the circumstances under which
mutualism evolves remain mysterious. My research uses the legume-rhizobium interaction to better understand patterns in mutualism evolution across geographic space, the ecological consequences of engaging in mutualism, and how mutualism evolves at a molecular level. Currently, our understanding of the legume-rhizobium interaction comes from a few well-studied temperate species. My research advances the field of legume-rhizobium research by sampling, sequencing, and analyzing non-model species from other parts of the globe, including the tropics. Legume-rhizobium interactions are greatly influenced by nutrient and partner availability in their habitat. I investigated changes in microbial community assembly on legumes across a large latitudinal gradient to understand how this interaction changes in temperate and tropical habitats. Although legumes hosted similar numbers of rhizobia partners across the range, tropical legumes associated with more non-rhizobia strains suggesting that tropical plants are less choosy of their symbiotic partners. There are many predicted benefits of being a less choosy host or generalist host to many symbiotic microbes. Using meta-analysis methods, I demonstrated that legume hosts that associate with many different rhizobial partners are more likely to find a compatible partner when introduced to a novel habitat. Generalist legumes establish in many new ranges and therefore experience greater ecological success compared to legume species that specialized on only a few rhizobia partners. It is unclear whether or how mutualism effects rates of molecular evolution. Most of the literature is focused on understanding how parasitic interactions are predicted to increase evolutionary rates in interacting species. I generated new sequence data from several non-model mutualistic species and found that mutualistic lineages in plants and rhizobia show elevated rates of molecular evolution. Therefore, mutualists may experience greater genetic change because they adapt to both a changing environment and symbiotic partners. Comments are closed.
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