Abstract
AbstractBiodiversity theories neglect individual-level variability in ecological interactions even though empirical work has revealed considerable genetic and phenotypic variation among individuals in natural populations. This impedes assessing the impact of individual-level variability on biodiversity in multi-trophic ecosystems. Here we use a density-dependent and individual-based food web model, tested against the largest individual-based food web to date, to show that non-random intraspecific variation in prey selection alters species diversity in food webs. Predators consuming many prey increase diversity by preferentially selecting common prey; predators consuming few prey inhibit diversity by preferentially selecting rare prey, putting them at risk of extinction. Thus species-level patterns cannot be explained by species-level averages, but instead must consider individual-level variation in prey selection. Individual-level variation occurs in many biological and social contexts, suggesting that analyses of individual-level interaction data will be relevant in a wide range of fields.
Highlights
The paradox of low diversity being predicted by food web theory but high diversity being observed in nature has been discussed intensively for more than a half-century [1,2,3,4,5]
Intraspecific variation in resource use can enable coexistence within an ecological community, but individual variation in prey selection across prey with different abundance can lead to species extinctions in food webs
We developed a suite of individual-based food web models 40, shown schematically in figure 1, to quantify the effect of intraspecific variation in predator populations on diversity in food webs
Summary
We have developed a framework for understanding the mechanisms driving intraspecific variability in the number of prey and the strength of prey selection in natural populations and its consequences for patterns of biodiversity in multi-trophic ecosystems Underlying this framework there are three simple birth-death models that include learning from previous feeding experience with negative, neutral and positive density-dependent prey selection. By examining these models under different parameter combinations and confronting them with data, we conclude that the factors driving prey selection in weakly and strongly connected individual predators at intraspecific level vary significantly, and population level means, classically used to develop food web theory, can fail to anticipate the mechanisms driving species extinction, coexistence and diversity in multi-trophic ecosystems
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