Modeling the Genetic Consequences of Mutualism on Communities

Three models of coevolutionary dynamics between mutualistically interacting species are developed. The first is a three loci, haploid model describing a general plant-pollinator system, such as Greya moth and its host plant. In this case, the system will always collapse to a single plant type and pollinator type. In a community with an mutant plant type, it is possible for a host-switch to occur, governed by the initial relative abundance plant type and the pollinator choosiness. In addition, genetic diversity can be maintained if the pollinator has no differential host preference, only adaptation to a host. Next, this model is extended to the case of the fig-fig wasp system, implementing a more complex life cycle of overlapping generations due to asynchronous flowering populations. In the fig system, extensive hybridization due to asynchronous flowering can maintain genetic diversity for thousands of generations, when pollinator choosiness is high. Therefore, mutualism can lead to low confidence trees in phylogenetic reconstructions affecting discordance among plant and pollinator phylogenetic trees. Lastly, the consequences of host-switching and other speciation events on coevolving phylogenies are explored through stochastic numerical simulations. The goal is to determine to what extent cophylogeny should be expected between mutualistic partners and what features of mutualistic webs can be explained by mutualistic coevolution alone.