Host patch traits have scale‐dependent effects on diversity in a stickleback parasite metacommunity

Daniel I Bolnick,Kimberly Ballare,Yoel E Stuart,William E Stutz,Emlyn J Resetarits

doi:10.1111/ecog.04994

Abstract

Many metacommunities are distributed across habitat patches that are themselves aggregated into groups. Perhaps the clearest example of this nested metacommunity structure comes from multi‐species parasite assemblages, which occupy individual hosts that are aggregated into host populations. At both spatial scales, we expect parasite community diversity in a given patch (either individual host or population) to depend on patch characteristics that affect colonization rates and species sorting. But, are these patch effects consistent across spatial scales? Or, do different processes govern the distribution of parasite community diversity among individual hosts, versus among host patches? To answer these questions, we document the distribution of parasite richness among host individuals and among populations in a metapopulation of threespine stickleback Gasterosteus aculeatus. We find some host traits (host size, gape width) are associated with increased parasite richness at both spatial scales. Other patch characteristics affect parasite richness only among individuals (sex), or among populations (lake size, lake area, elevation and population mean heterozygosity). These results demonstrate that some rules governing parasite richness in this metacommunity are shared across scales, while others are scale‐specific.

Highlights

A long-standing question in ecology is, ‘why are some communities more diverse than others?’ To address this question, biologists have sought to identify and quantify the biotic and abiotic factors that affect community diversity, and which differ across a landscape
We focus on two parasite diversity statistics (Supplementary material Appendix 1 Fig. A2): 1) the number of uniquely identifiable parasite taxa for each fish, αij, i.e. parasite richness in individual host i from host population j; 2) the average per-individual parasite richness, aij, for all fish in population j
To evaluate possible phenotypic mechanisms of this dimorphism, we evaluated whether diet or ecomorphology dimorphism promotes sexually dimorphic infections

Summary

Introduction

Here we show that factors affecting parasite metacommunity diversity change depending on the spatial scale at which the communities are defined. We can view each discrete host population as a habitat patch for parasites, and a collection of host populations form the metacommunity. Parasites form a spatially nested metacommunity, whose diversity and composition varies among host individuals within host populations, and among host populations (Borer et al 2016). Most research on the ecological processes governing parasite diversity have emphasized one of these spatial scales (Poulin 1997, Vidal-Martínez and Poulin 2003, Poulin 2007). There is a need for more studies that bridge both spatial scales to ask whether the same processes regulate parasite diversity at both the host individual, and host population, scale?

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Discussion

Conclusion