Data from: Species loss drives ecosystem function in experiments, but in nature the importance of species loss depends on dominance

Aim: Decades of experimental research have conclusively shown a positive
relationship between species richness and ecosystem function. However,
authoritative reviews find no consensus on how species loss affects
function in natural communities. We analyse experimental and observational
data in an identical way and test whether they produce similar results.
Location: North America and Europe (experimental communities); global
(natural communities). Time period: Experimental communities: 1998–2013;
natural communities: 1982–2018. Major taxa studied:  Experimental
communities: temperate grassland plants; natural communities: temperate
grassland plants, tropical forest trees, kelp forest producers and native
bees. Methods: We used an approach inspired by the Price equation to
analyse 129 datasets from experimental and natural communities worldwide.
We tested how the effects of species loss on ecosystem function varied
with dominance and the nonrandomness of species loss and, in turn, how
these two factors differed between experiments and observations. Results:
Studies carried out in experimental and natural communities reached
different conclusions regarding the effects of species loss. First,
species loss had greater effects on ecosystem function in experiments than
in nature. Second, the importance of species loss was negatively
correlated with dominance in nature because as dominance increased, lost
species were increasingly those contributing little to ecosystem function.
Although experimental and natural communities exhibited similar levels of
dominance, an analogous relationship was not possible in experiments
because the order of species loss was randomized by design. Main
conclusions: Species loss was sometimes, but not always, the major driver
of loss of function in nature. Variation in the importance of species loss
was not messy and context dependent; instead, it was predicted by
functional dominance. Although results from experimental and natural
communities were similar in several key ways, they differed in that
species loss was a consistent predictor of ecosystem function in
experiments and not in nature.