Effect of host-switching on the ecological and evolutionary patterns of parasites.

Speciation via host-switching is a macroevolutionary process that emerges from a microevolutionary dynamic where individual parasites switch hosts, establish a new association, and reduce reproductive contact with the original parasite lineage. Phylogenetic distance and geographic distribution of the hosts have been shown to be determinants of the capacity and opportunity of the parasite to change hosts. Although speciation via host-switching has been reported in many host-parasite systems, its dynamic on the individual, population and community levels is poorly understood. Here we propose a theoretical model to simulate parasite evolution considering host-switching events on the microevolutionary scale, taking into account the macroevolutionary history of the hosts, to evaluate how host-switching can affect ecological and evolutionary patterns of parasites in empirical communities at regional and local scales. In the model, parasite individuals can switch hosts under variable intensity and have their evolution driven by mutation and genetic drift. Mating is sexual and only individuals that are sufficiently similar can produce offspring. We assumed that parasite evolution occurs at the same evolutionary time scale as their hosts, and that the intensity of host-switching decreases as the host species differentiate. Ecological and evolutionary patterns were characterised by the turnover of parasite species among host species, and parasite evolutionary tree imbalance respectively. We found a range of host-switching intensity that reproduces ecological and evolutionary patterns observed in empirical communities. Our results showed that turnover decreased as host-switching intensity increased, with low variation among the model replications. On the other hand, tree imbalance showed wide variation and non-monotonic tendency. We concluded that tree imbalance was sensitive to stochastic events, whereas turnover may be a good indicator of host-switching. We found that local communities corresponded to higher host-switching intensity when compared to regional communities, highlighting that spatial scale is a limitation for host-switching.