Population genomics of the Medicago lupulina and Ensifer mutualism in North America

Species interactions such as mutualisms are a key process affecting evolution. One agriculturally and ecologically important mutualism is the partnership between legume plants and rhizobia. Through characterizing and comparing the population genomic structure of the legume Medicago lupulina and rhizobia Ensifer, I explored whether coevolution is locally structured and differs between separate populations, or is broadly structured and is similar across large geographic scales. I found higher proportions of E. meliloti in southeast populations and higher proportions of E. medicae in northwest populations but no genetic differences between M. lupulina plants hosting different species of rhizobia. M. lupulina and Ensifer populations showed different spatial genetic structure. In particular, I detected very little genetic variation in both Ensifer species. My findings suggest there is little evidence of coevolution in the M. lupulina and Ensifer mutualism or coevolution is occurring on a large geographic scale.M.Sc.2017-11-26 00:00:0