Assessing the role of partner choice exhibited by the widespread legume Medicago lupulina on natural rhizobia communities

Mutualisms are predicted to be evolutionary unstable given that they involve some fitness cost to maintain, and that natural selection should favour “cheating” (i.e., receive the benefit without paying the cost). Contrary to these theoretical predictions, however, mutualisms appear to be evolutionary robust. One hypothesis explaining mutualism stability, defined as “partner choice” (PC), involves the ability of a focal partner (i.e., the host) to discriminate and act favorably toward cooperative versus uncooperative partners, resulting in selection on the former relative to the latter. Some of the strongest empirical evidence in favor of PC comes from the legume-rhizobia symbiosis; however, the majority of these studies were conducted in laboratory and/or greenhouse settings, which may bias our ability to understand how variation in PC affects the evolution of rhizobia communities. By setting up a series of common gardens across the Koffler Scientific Reserve (KSR), we will quantify the degree to which hosts that vary in PC affect the genetic variation of natural rhizobia communities, and whether variation in PC is adaptive.

Principal Investigator: Megan Frederickson

Researcher: Rebecca Batstone


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