“Persist or produce: a community trade-off tuned by species evenness”

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Rudolf P. Rohr, Serguei Saavedra, Guadalupe Peralta, Carol M. Frost, Louis-Félix Bersier, Jordi Bascompte, and Jason M. Tylianakis

Is biodiversity a good indicator of ecosystem health?

Native southern beech forest (Nothofagus spp.), Kites Valley, South Island, New Zealand.
(Credit: Guadalupe Peralta)

Biodiversity has been a central concern in conservation, in part due to its relationship with ecosystem processes such as biomass production. However, because it is expected that rare species face greater danger of extinction, species evenness—a measure of how similar abundances are across species—is seen as a key component of biodiversity and a potential indicator of environmental disturbance. This study demonstrates that declining species evenness can be used as a general indicator of the risk of further species extinctions under environmental perturbation. In contrast, species evenness cannot be used as a direct indicator of the level of biomass production. Indeed, depending on the species that dominates at low evenness, biomass production can increase or decrease with species evenness. For the first time, researchers provide a theoretical framework to capture simultaneously the relationship among species evenness, species survival, and biomass production. While previous studies have failed to find a consistent relationship between species evenness and biomass production, these results demonstrate that such mixed outcomes are not idiosyncratic artifacts of different studies, but rather represent equally plausible outcomes. This study shows that high species evenness and an intermediate level of biomass production is the configuration that maximizes the average species survival probability. Read the Article