Scale‐dependent effects of host patch traits on species composition in a stickleback parasite metacommunity

Abstract

A core goal of ecology is to understand the abiotic and biotic variables that regulate species distributions and community composition. A major obstacle is that the rules governing species distributions can change with spatial scale. Here, we illustrate this point using data from a spatially nested metacommunity of parasites infecting a metapopulation of threespine stickleback fish from 34 lakes on Vancouver Island, British Columbia. Like most parasite metacommunities, the composition of stickleback parasites differs among host individuals within each host population, and differs between host populations. The distribution of each parasite taxon depends, to varying degrees, on individual host traits (e.g., mass, diet) and on host-population characteristics (e.g., lake size, mean host mass, mean diet). However, in most cases in this data set, a given parasite was regulated by different factors at the host-individual and host-population scales, leading to scale-dependent patterns of parasite-species co-occurrence.

What evolutionary processes maintain MHC IIꞵ diversity within and among populations of stickleback?

“…Despite spatial heterogeneity in the distribution of parasite species (Bolnick et al, 2020b), we did not detect parasite-mediated spatially fluctuating selection. The Mantel test between the distance matrix of parasite community and the distance matrix of MHC variants across all populations suggested that the two matrices were not correlated (r = .089, p = .22, Figure 5).…”

“…In total, 11.8% of the variation in parasite richness could be explained by habitat type, 4.9% could be explained by watershed (ANOVA, habitat term, p < 2e‐16), while 28.3% could be explained by sample site (ANOVA, watershed/site term, p < 2e‐16). Bolnick et al (2020) provide further analysis of ecological factors structuring the parasite metacommunity (diversity, composition, co‐occurrence) within and among lakes.…”

“…Details are provided in Bolnick and Ballare (2020). These samples were used to examine within‐ and between‐population variation in diet (Bolnick & Ballare, 2020), parasite community composition (Bolnick et al, 2020b), and parasite species richness (Bolnick et al, 2020a). The parasite infection data for this study are archived at the Dryad Digital Repository (Bolnick & Ballare, 2020).…”

“…Then we used a Mantel test to examine if the two distance matrices were correlated. A previous analysis (Bolnick et al, 2020b) found no significant effect of as‐the‐crow‐flies (i.e., Euclidean distance) or as‐the‐fish‐swims (i.e., the shortest in‐water path) geographical distance on parasite community structure, so we omit that as a covariate in this distance analysis.…”

“…The parasite communities of stickleback differ significantly among the different sites on Vancouver Island (Bolnick et al, 2020a;Stutz & Bolnick, 2017;Stutz et al, 2015 Then we used a Mantel test to examine if the two distance matrices were correlated. A previous analysis (Bolnick et al, 2020b) found no significant effect of as-the-crow-flies (i.e., Euclidean distance) or as-the-fish-swims (i.e., the shortest in-water path) geographical distance on parasite community structure, so we omit that as a covariate in this distance analysis.…”