Testing a biological mechanism of the insurancehypothesis in experimental aquatic communities - Data Deposit

1.The insurance hypothesis predicts a stabilizing effect of increasing species richness on commu-nity and ecosystem properties. Difference among species’ responses to environmental fluctuationsprovides a general mechanism for the hypothesis. Previous experimental investigations of theinsurance hypothesis have not examined this mechanism directly.

2.First, responses to temperature of four protist species were measured in laboratory microcosms.For each species, we measured the response of intrinsic rate of increase (r) and carrying capacity(K) to temperature.

3.Next, communities containing pairs of species were exposed to temperature fluctuations. Com-munity biomass varied less when correlation inKbetween species (but notr) was more negative,and this resulted from more negative covariances in population sizes, as predicted. Results werecontingent on species identity, with findings differing between analyses including or not includingcommunities containing one particular species.

4.These findings provide the clearest support to date for this mechanism of the insurance hypo-thesis. Biodiversity, in terms of differences in species’ responses to environmental fluctuations (i.e.functional response diversity) stabilizes community dynamics.