Organismal responses to environmental change

Microbial phylogeography and dispersal

Will legume migration in response to environmental change be constrained by access to compatible rhizobia? We have established reciprocal transplant experiments to answer this question for Lupinus bicolor and Acmispon strigosus.

We are also asking if rhizobia interacting with invasive legumes have escaped natural enemies such as bacteriophage. Bacteriophage, or “phage” for short, are viruses that attack bacteria and commandeer the bacteria’s reproductive machinery to produce and package new phage particles. Many phages are highly specialized and so might be important regulators of bacterial populations in their native range. Ellen’s collaborator Jannick Van Cauwenberghe wonders if phages accompany their bacterial hosts when those bacteria are introduced into new areas, because if they do not, then this could be a mechanism by which introduced bacterial populations become invasive by escaping population regulation. We are testing this hypothesis by examining the phage within native and invasive rhizobium populations in California. Jannick and Ellen hypothesize that this mechanism might provide an important boost to co-invading leguminous plants, which depend on specialized rhizobia for access to atmospheric di-nitrogen.