BRS: CHITTY LECTURE Simon Hart "How diversity within species affects the maintenance of species diversity"

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Abstract: Although ~25 % of the trait diversity in ecological communities occurs within species, explanations for the maintenance of species diversity tend to ignore the effects of this variation on the dynamics and outcome of species interactions. I will show that ignoring this variation is unlikely to be justified. Using a combination of theory and experiments, I will show how trait diversity within species (i.e. intraspecific variation) affects species diversity maintenance via: 1) ecological pathways, 2) phenotypic plasticity, and 3) rapid evolution. In contrast to common expectations, the purely ecological effects of intraspecific variation tend to erode species diversity. Meanwhile, phenotypic plasticity and rapid evolution have opposing effects on species diversity maintenance that occur via a novel pathway not considered in current ecological models. Only by explicitly accounting for the various effects of diversity within species on the dynamics of species interactions can we hope to understand the mechanisms maintaining diversity in ecological communities.