Abstract
Producer diversity is frequently assumed to be detrimental to herbivores, because less edible taxa are more likely to dominate diverse communities. Many producers are, however, complementary in their resource use, and primary production is often positively related to producer diversity. We performed an experiment with microalgae and a generalist herbivore to explore the hypothesis that such positive effects are transferred up the food chain and are functionally comparable to effects of enrichment with a limiting resource. In both absence and presence of grazers, primary production was positively affected by both light supply and producer diversity. Survival, reproduction, and biomass of herbivores were also positively affected by light supply and producer diversity, with both factors contributing equally to grazer performance. We conclude that producer diversity can indeed have similar positive effects on secondary production as enrichment with a limiting resource and discuss conditions under which such positive effects are likely to dominate over negative ones.
Highlights
Trophic transfer of primary production is a conceptual cornerstone of ecosystem ecology
We conclude that producer diversity can have similar positive effects on secondary production as enrichment with a limiting resource and discuss conditions under which such positive effects are likely to dominate over negative ones
This raises the question: Are resource supply and diversity of primary producers functionally equivalent in that their positive effects on primary production are transferred up the food chain? studies of biodiversity effects spanning more than one trophic level are receiving increasing attention (Duffy et al 2007; Srivastava et al 2009), this hypothesis has, to our knowledge, not yet been clearly formulated and addressed with experiments
Summary
Trophic transfer of primary production is a conceptual cornerstone of ecosystem ecology. Ecologists have focused on enrichment (increased supply with limiting resources) as the source of increased primary production, and a large body of ecological theory has been developed to describe the consequences of enrichment for ecological communities (Oksanen et al 1981; Holt et al 1994; Grover 1995; Wollrab et al 2012). Positive effects of diversity on primary production can be on the same order as effects of enrichment (Reich et al 2001; Fridley 2003; Hooper et al 2012). This raises the question: Are resource supply and diversity of primary producers functionally equivalent in that their positive effects on primary production are transferred up the food chain? This raises the question: Are resource supply and diversity of primary producers functionally equivalent in that their positive effects on primary production are transferred up the food chain? studies of biodiversity effects spanning more than one trophic level are receiving increasing attention (Duffy et al 2007; Srivastava et al 2009), this hypothesis has, to our knowledge, not yet been clearly formulated and addressed with experiments
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