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Aggregation begets aggregation: spatial distribution of environmental parasites shapes parasite aggregation on host populations, but only at low-to-moderate parasite density
  • Chris Wojan,
  • Allison Shaw,
  • Meggan Craft
Chris Wojan
University of Minnesota Twin Cities

Corresponding Author:[email protected]

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Allison Shaw
University of Minnesota Twin Cities
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Meggan Craft
University of Minnesota Twin Cities
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Abstract

Spatial aggregation of environmental or trophically transmitted parasites has the potential to influence host-parasite interactions. The distribution of parasites on hosts is one result of those interactions, and the role of spatial aggregation relative to intrinsic host factors is unclear. We use a spatially explicit agent-based model to determine how spatial aggregation of parasites influences the distribution of parasite burdens across a range of parasite densities and host recovery rates. Our model simulates the random movement of hosts across landscapes with varying spatial configurations of areas infested by environmental parasites, allowing hosts to acquire parasites they encounter and subsequently recover from them. When parasites are more spatially aggregated in the environment, the aggregation of parasite burdens on hosts is higher (i.e., more hosts with few parasites, fewer hosts with many parasites), but the effect is less pronounced at high parasite density and fast host recovery rates. In addition, the correlation between individual hosts’ final parasite burdens and their cumulative parasite burdens (including lost parasites) is greater at higher levels of spatial parasite aggregation. Our work suggests that fine-scale spatial patterns of parasites can play a strong role in shaping how hosts are parasitized, particularly when parasite density is low-to-moderate and recovery rates are slow.