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.
Highlights
A classic dichotomy in ecology is whether communities are deterministic co-occurring sets of species (Clements 1916) or collections of many species following an independent set of stochastic rules (Gleason 1926)
The stickleback parasite metacommunity studied here is structured by a wide variety of factors: lake geography, host mean traits, host allele frequencies, and individual traits
These effects are almost all scaledependent, which means that the mechanistic basis of infection and epidemiology cannot readily be generalized from individual animals to their populations, or vice versa
Summary
A classic dichotomy in ecology is whether communities are deterministic co-occurring sets of species (Clements 1916) or collections of many species following an independent set of stochastic rules (Gleason 1926). Metacommunity theory (Leibold et al 2004, Leibold and Chase 2017) bridges the gap between these competing visions by considering relative roles of determinism and stochasticity at various spatial scales on a fragmented landscape. When species have similar filters governing dispersal to new patches and persistence within patches, they will tend to co-occur and form a more deterministic community (the Clementsian model). A particular form of this deterministic community assembly arises from between-species interactions, for instance, if competing species exclude each other or Manuscript received 7 April 2020; revised 8 June 2020; accepted 28 June 2020.
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