Species traits and environmental conditions govern the relationship between biodiversity effects across trophic levels
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Changing environments can have divergent effects on biodiversity–ecosystem function relationships at alternating trophic levels. Freshwater mussels fertilize stream foodwebs through nutrient excretion, and mussel species-specific excretion rates depend on environmental conditions. We asked how differences in mussel diversity in varying environments influence the dynamics between primary producers and consumers. We conducted field experiments manipulating mussel richness under summer (low flow, high temperature) and fall (moderate flow and temperature) conditions, measured nutrient limitation, algal biomass and grazing chironomid abundance, and analyzed the data with non-transgressive overyielding and tripartite biodiversity partitioning analyses. Algal biomass and chironomid abundance were best explained by trait-independent complementarity among mussel species, but the relationship between biodiversity effects across trophic levels (algae and grazers) depended on seasonal differences in mussel species’ trait expression (nutrient excretion and activity level). Both species identity and overall diversity effects were related to the magnitude of nutrient limitation. Our results demonstrate that biodiversity of a resource-provisioning (nutrients and habitat) group of species influences foodweb dynamics and that understanding species traits and environmental context are important for interpreting biodiversity experiments.
KeywordsBiodiversity partitioning Complementarity Ecosystem function Environmental context Freshwater Mollusk Nutrient limitation Species traits Trophic level
We thank T. Garrett for allowing access to the field site, R. Deaton, S. and B. Dengler, D. Fenolio, S. Frazier, P. Jeyasingh, M. Jones, S. Jones, F. March, K. Reagan, R. Remington, and E. Webber for field and/or laboratory assistance, and D. Allen for comments on the manuscript. This study was funded by the National Science Foundation (DEB-0211010) and is a contribution to the program of the Oklahoma Biological Survey.
- ASTM (1995) Standard methods for the examination of water and wastewater. American Public Health Association/American Water Works Association/Water Environment Federation, AlexandriaGoogle Scholar
- Cardinale BJ, Palmer MA, Collins SL (2002) Species diversity enhances ecosystem functioning through interspecific facilitation. Nature 414:427–429Google Scholar
- Hillebrand H, Shurin JB (2005) Biodiversity and aquatic food webs. In: Belgrano A, Scharler UM, Dunne J, Ulanowicz RE (eds) Aquatic food webs–an ecosystem approach. Oxford University Press, Oxford, pp 184–197Google Scholar
- Hillebrand H, Gruner DS, Borer ET, Bracken MES, Cleland EE, Elser JJ, Harpole WS, Ngai JT, Seabloom EW, Shurin JB, Smith JE (2007) Consumer versus resource control of producer diversity depends on ecosystem type and producer community structure. Proc Natl Acad Sci USA 104:10904–10909PubMedCrossRefGoogle Scholar
- Hunter MD, Price PW (1992) Playing chutes and ladders: heterogeneity and the relative roles of bottom–up and top–down forces in natural communities. Ecology 73:724–732Google Scholar
- Matthews WJ, Vaughn CC, Gido KB, Marsh-Matthews E (2005) Southern Plains Rivers. In: Benke AC, Cushing CE (eds) Rivers of North America. Elsevier, London, pp 283–325Google Scholar
- Pringle CM, Triska FJ (1996) Effects of nutrient enrichment on periphyton. In: Hauer FR, Lamberti GA (eds) Methods in stream ecology. Academic Press, San Diego, pp 607–623Google Scholar
- Schmid B, Hector A, Huston MA, Inchausti P, Nijs I, Leadley PW, Tilman D (2002) The design and analysis of biodiversity experiments. In: Loreau N, Naeem NS, Inchausti P (eds) Biodiversity and ecosystem functioning: synthesis and perspectives. Oxford University Press, Oxford, pp 61–75Google Scholar
- Spooner DE, Vaughn CC (2011) Species’ traits, dominance, and environmental gradients interact to govern primary production in freshwater mussel communities. Oikos (in press). doi: 10.1111/j.1600-0706.2011.19380.x