What parasite and host traits best explain the geographic range of mammal parasites and diseases?
A successful framework for understanding the factors that affect the distribution of free-living species has been to explore which traits and environmental characteristics make certain species more widespread. We apply this same framework to parasites to determine which attributes most influence their geographic spread. Such an analysis not only addresses basic questions about species distributions, but also can inform which parasites may be most sensitive to global environmental changes or most likely to emerge to spread to new spatial locations and hosts. Using the Global Mammal Parasite Database we compiled spatial occurrence data to calculate the geographic extent and the number of ecoregions occupied by parasite species of primates, ungulates, and carnivores. Using a variety of multivariate techniques, we analyzed how host and parasite traits affected parasite geographic range. For host traits we analyzed: diet breadth, home range, geographic range, longevity, body size, and group size. For parasite traits we analyzed the taxonomic group, and transmission attributes such as whether the parasite needs an intermediate host, close proximity for transmission, or a vector.
We compiled information for almost 2000 parasites; of these, 196 parasite species had sufficient numbers of georeferenced localities in our database to allow us to estimate geographic range area. Across the three groups of mammals analyzed, host traits seem more important to explain the geographic extent of parasites. Helminths and arthropods were the most represented parasites; bacteria were the group with more species shared between ungulates, carnivores and primates. We found that parasites are more widespread the greater the number and phylogenetic diversity of host species they utilize, the higher the trophic level of host species, and the larger the mean home range of host species. Our results suggest some important characteristics governing large range size; parasites that share these characteristics but are not widespread are possible candidates for emergence.