Theoretical Models of Obligate Mutualism to Link Micro- with Macro-Coevolutionary Dynamics

Abstract

There is a need to link micro- and macro-coevolution to bridge mechanistic theory and observations of micro-coevolutionary change with observations of macro-coevolutionary patterns. This need is particularly conspicuous in theoretical models of obligate mutualism, where phylogenetic matching is the predicted outcome. However, these theoretical models of obligate mutualism create a mismatch with empirical studies of obligate mutualism, which experience extensive phylogenetic discordance. Although environmental variation on geographic scales is often invoked, there are other, non-mutually exclusive mechanisms that can possibly explain genetic diversity and co-phylogenetic patterns in mutualistic communities. In this study, we use a genetic-explicit mathematical model of obligate mutualism that explain host-switching outcomes and, consequently, discordance in cophylogenies. We then explore the role of temporal variation in maintenance of genetic variation (i.e., phenology), which can further account for phylogenetic discordance. These insights are possible due to the focus on initial conditions and short-term behavior of model results. This work ultimately supports the continued importance of theoretical work which expands its analysis of outcomes beyond asymptotic behavior.