Experimental niche evolution alters the strength of the diversity–productivity relationship

Biodiversity in the ecosystem The positive relationship between biodiversity and ecosystem function is well established, but the specific shape of the relationship can vary. A study combining experimental evolution with a biodiversity–ecosystem functioning experiment helps to fill in the details. Twenty marine bacterial species were evolved so that they were adapted to few (specialists) or many (generalists) resources, and the biodiversity of communities constructed from these derived strains was manipulated. Assemblages of specialists proved more productive on average as they could exploit environmental heterogeneity, but specialists contribute more to the slope of the biodiversity–ecosystem function curve. This work provides the first experimental evidence that evolutionary history shapes the functional consequences of species extinctions, and is relevant to work on conservation strategies. The positive relationship between biodiversity and ecosystem function is well established, but the specific shape of the relationship can vary. Here, experimental evolution is used to show that the strength and slope depends on evolutionary history, with specialists and generalists that have evolved from the same ancestor giving rise to different diversity–function relationships. The relationship between biodiversity and ecosystem functioning (BEF) has become a cornerstone of community and ecosystem ecology 1 , 2 , 3 and an essential criterion for making decisions in conservation biology and policy planning 4 , 5 . It has recently been proposed that evolutionary history should influence the BEF relationship because it determines species traits and, thus, species’ ability to exploit resources 6 , 7 . Here we test this hypothesis by combining experimental evolution with a BEF experiment. We isolated 20 bacterial strains from a marine environment and evolved each to be generalists or specialists 8 . We then tested the effect of evolutionary history on the strength of the BEF relationship with assemblages of 1 to 20 species constructed from the specialists, generalists and ancestors 9 . Assemblages of generalists were more productive on average because of their superior ability to exploit the environmental heterogeneity 10 . The slope of the BEF relationship was, however, stronger for the specialist assemblages because of enhanced niche complementarity. These results show how the BEF relationship depends critically on the legacy of past evolutionary events.