Aggregated parasite distributions on hosts in a homogeneous environment: examining the Poisson null model

Abstract

Parasites are typically aggregated on their hosts in nature. The null hypothesis is that parasites should follow a Poisson distribution if environment, parasites and hosts are homogeneous. From this starting point, models have shown that factors such as heterogeneity in host susceptibility and spatial aggregations of parasites may cause parasite aggregations on hosts. I used computer simulations to show that parasites typically become aggregated on their hosts even in a homogeneous environment where parasites do not differentially prefer any host, and hosts do not differ in susceptibility, provided that hosts are randomly distributed and spatial distance between host and parasite influences the likelihood of colonisation.