Model general overview
We modeled the eco-evolutionary trajectories of parasites influenced by their host evolutionary history and host-switching events. Thus, we assumed that the evolutionary history of the host can represent a proxy for the resources for parasite species (Agosta et al. 2010; Imrie et al. 2021). We also assumed that the probability of host-switching decreases as the phylogenetic distance between the species of host involved in the event (original and new host species) increases. Finally, the model assumes that parasite evolution occurs at the same evolutionary time scale as the host, which increases possibilities for host-switching as host speciation occurs. Parasite individuals are explicitly modeled and characterized by their used host species and genetic identity, following the description of the model proposed by Higgs & Derrida (1991) and Manzo & Peliti (1994). This approach allows us to model parasite speciation. The host species are modeled as resources that impose a carrying capacity to parasite species, analogous to islands in the Manzo-Pelit model (Manzo & Peliti 1994), but in the present model, the islands (hosts species in our case) emerge (as a new host species that speciate) and the distance between them varies over time, according to a predetermined time host diversification (i.e. based on ultrametric empirical phylogenies). The model does not consider the selection pressure imposed by parasites on the evolution of the resource. Therefore, we are not modeling a process of reciprocal evolution, or co-evolution.