Using host species traits to understand the consequences of resource provisioning for host-parasite interactions

Abstract

Supplemental food provided to wildlife by human activities can be more abundant and predictable than natural resources, and subsequent changes in wildlife ecology can have profound impacts on host-parasite interactions. Identifying traits of species associated with increases or decreases in infection outcomes with resource provisioning could improve assessments of wildlife most prone to disease risks in changing environments. We conducted a phylogenetic meta-analysis of 342 host-parasite interactions across 56 wildlife species and three broad taxonomic groups of parasites to identify host-level traits that influence whether provisioning is associated with increases or decreases in infection. We predicted dietary generalists that capitalize on novel food would show greater infection in provisioned habitats owing to population growth and food-borne exposure to contaminants and parasite infectious stages. Similarly, species with fast life histories could experience stronger demographic and immunological benefits from provisioning that affect parasite transmission. We also predicted that wide-ranging and migratory behaviours could increase infection risks with provisioning if concentrated and non-seasonal foods promote dense aggregations that increase exposure to parasites. We found that provisioning increased infection with bacteria, viruses, fungi and protozoa (i.e. microparasites) most for wide-ranging, dietary generalist host species. Effect sizes for ectoparasites were also highest for host species with large home ranges but were instead lowest for dietary generalists. In contrast, the type of provisioning was a stronger correlate of infection outcomes for helminths than host species traits. Our analysis highlights host traits related to movement and feeding behaviour as important determinants of whether species experience greater infection with supplemental feeding. These results could help prioritize monitoring wildlife with particular trait profiles in anthropogenic habitats to reduce infectious disease risks in provisioned populations.

Keywords: conservation; consumer-resource interactions; dietary breadth; home range; infectious disease; parasitism; phylogenetic meta-analysis; supplemental feeding; urbanization.

Figure 1

Distribution of trait covariates based on species feeding behaviour (a), movement ecology (b) and the first phylogenetic PC for pace of life covariates (c), representing an axis of slow to fast life histories. Galapagos finches were standardized as Geospiza fuliginosa

Figure 2

Phylogenetic visualization of infection outcomes of resource provisioning for microparasites (a), helminths (b) and ectoparasites (c). Boxplots show the median and first and third quartile of effect sizes (back‐transformed r), whiskers show the range of non‐outliers and open circles show potential outliers. Filled circles display the weighted mean effect sizes per host species. Legends display estimates of Pagel's λ and phylogenetic heritability (H ²) in effect sizes

Figure 3

Competitive mixed‐effects models (MEMs) correlating trait and supplemental feeding predictors to effect sizes (back‐transformed r) for microparasites, helminths and ectoparasites, with points scaled by the inverse sampling variance. Predicted means and 95% confidence intervals are shown with solid lines and bands. The dashed line shows where r = 0 (i.e. provisioning has no effect on infection)