Worldwide biodiversity loss is coinciding with an increase in disease emergence events. It has been suggested that these trends are related through a mechanism in which biodiversity either increases (amplification) or decreases (dilution) disease prevalence among hosts. This disease-biodiversity relationship is still heavily debated. Amplification and dilution effects can occur simultaneously and may be either direct (contact with a competent host is replaced by sink host) or indirect (through regulation of host abundances). Whether a pathogen is diluted or amplified depends on the disease-competence of the hosts. In our multi-host SI model, we define this competence through hosts’ evolutionary history. In this model, we explore two scenarios: (1) The probability of transmission depends on the evolutionary distance between the transmitting and recipient hosts (no adaptation of the pathogen to transmitting host), and (2) Transmission depends on the distance from the receiving to the main reservoir host of the pathogen (pathogen is adapted to the reservoir host). Here, we simulate host communities with equal abundances and varying diversity in terms of species numbers and phylogenetic diversity, where the probability of successful transmission is inversely related to phylogenetic distance between hosts.
Results/Conclusions
Our model shows that communities composed of more distantly related species have lower pathogen prevalence than communities composed of more closely related hosts. However, these phylogenetic diversity measures can only explain about 80% of the overall outbreak potential. Additionally, we apply this model to our study system; the infection of the bacterium Mycobacterium bovis (causing bovine Tuberculosis) and its spillover and -back from the main reservoir, the African buffalo (Syncerus caffer), to other Savanna wildlife species. Our model shows a novel approach to investigating the relative contribution of species in a multi-host disease system and can help in identifying reservoir hosts of a pathogen, with which we can determine which hosts function as sinks or amplifiers. This research shows that the phylogenetic structure of the host community, and the place of the reservoir within the phylogeny, play a vital role in the disease transmission, and shed light on the disease-biodiversity relationship.
