Abstract
Little is known about the mechanisms behind positive effects of species richness on ecosystem functioning. In a previous study that showed a positive effect of aquatic detritivore species richness on leaf litter breakdown (process) rates, we proposed that facilitation and release from intra-specific interference were the two most likely mechanisms. To test the interference hypothesis, we performed an experiment using three densities of each of three detritivore species and found varying effects on leaf breakdown rates across species: one species showed no effect, one a positive, marginally insignificant, effect, and a third species showed a significant, positive effect of decreasing density. The density (interference) effect thus partly explained the results from our previous study. The facilitation hypothesis was tested by sequentially introducing and removing two species. We predicted that, if this hypothesis were true, facilitation would be expressed in higher process rates than when replacing with individuals of the same species. We found that process rate per unit biomass did increase when one species was introduced after the other species, while the opposite sequence did not show any increase. Hence, this result was also confirmative of our previous results. Therefore, we conclude that both intra-specific interference and inter-specific facilitation may explain the positive effect of species richness observed in our system. Since many species exhibit intra-specific interference that inhibits foraging efficiency, this may be a general mechanism generating effects of species richness per se. If facilitation is unidirectional, or if it involves few species, it is more likely to be species specific with species identities being more important than species richness per se. We conclude that species loss may be expected to have negative consequences on ecosystem functioning if any species is lost, with additional effects in the event of losing "facilitator" species.
Similar content being viewed by others
References
Bazzaz FA (1975) Plant species diversity in old-field successional ecosystems in southern Illinois. Ecology 56:485–488
Benfield EF (1996) Leaf breakdown in stream ecosystems. In: Hauer FR, Lamberti GA (eds) Methods in stream ecology. Academic, San Diego, pp 579–589
Cardinale BJ, Palmer MA, Collins SL (2002) Species diversity enhances ecosystem functioning through interspecific facilitation. Nature 415:426–429
Cummins KW (1973) Trophic relations of aquatic insects. Annu Rev Entomol 18:183–206
Dangles O, Jonsson M, Malmqvist B (2003) The importance of detritivore species richness for maintaining stream ecosystem functioning following the invasion of a riparian plant. Biol Invasions (in press)
Doube BM (1987) Spatial and temporal organization in communities associated with dung pads and carcasses. In: Gee JHR, Giller PS (eds) Organization of communities: past and present. Blackwell, Oxford, pp 255–280
Dudley TL, D'Antonio CM, Cooper SD (1990) Mechanisms and consequences of interspecific competition between two stream insects. J Anim Ecol 59:849–866
Grafius E, Anderson NH (1979) Population dynamics, bioenergetics, and role of Lepidostoma quercina Ross (Trichoptera: Lepidostomatidae) in an Oregon woodland stream. Ecology 60:433–441
Hassel MP, Varley GC (1969) New inductive population model for insect parasites and its bearing on biological control. Nature 223:1133–1136
Heard SB, Richardson JS (1995) Shredder-collector facilitation in stream detrital food webs—is there enough evidence? Oikos 72:359–366
Huston MA (1997) Hidden treatments in ecological experiments: re-evaluating the ecosystem function of biodiversity. Oecologia 110:449–460
Jonsson M, Malmqvist B (2000) Ecosystem process rate increases with animal species richness: evidence from leaf-eating, aquatic insects. Oikos 89:519–523
Jonsson M, Dangles O, Malmqvist B, Guérold F (2002) Simulating species loss following disturbance: assessing the effects on process rates. Proc R Soc Lond B 269:1047–1052
Loreau M (1998a) Separating sampling and other effects in biodiversity experiments. Oikos 82:600–602
Loreau M (1998b) Biodiversity and ecosystem functioning: a mechanistic model. Proc Natl Acad Sci USA 95:5632–5636
Loreau M (2000) Biodiversity and ecosystem functioning: recent theoretical advances. Oikos 91:3–17
Loreau M, Behera N (1999) Phenotypic diversity and stability of ecosystem processes. Theor Popul Biol 56:29–47
Loreau M, Hector A (2001) Partitioning selection and complementarity in biodiversity experiments. Nature 412:72–76
Loreau M, Naeem S, Inchausti P, Bengtsson J, Grime JP, Hector A, Hooper DU, Huston MA, Raffaelli D, Schmid B, Tilman D, Wardle DA (2001) Biodiversity and ecosystem functioning: current knowledge and future challenges. Science 294:804–808
Lotka AJ (1932) The growth of mixed populations: two species competing for a common food supply. J Wash Acad Sci 22:461–469
Mouquet N, Moore JL, Loreau M (2002) Plant species richness and community productivity: why the mechanism that promotes coexistence matters. Ecology Lett 5:56–65
Naeem S, Li S (1997) Biodiversity enhances ecosystem reliability. Nature 390:507–509
Nijs I, Impens I (2000) Underlying effects of resource use efficiency in diversity-productivity relationships. Oikos 91:204–208
Oberle D (1993) Interactions among stonefly larvae (Plecoptera) in a stream leaf pack community. Thesis, Julius-Maximilians University, Würzburg
Richardson JS (1991) Seasonal food limitation of detritivores in a montane stream: an experimental test. Ecology 72:873–887
Short RA, Maslin PE (1977) Processing of leaf litter by a stream detritivore: effect on nutrient availability to collectors. Ecology 58:935–938
Smith C, Good M, Murphy JF, Giller PS, O'Halloran J (2000) Life-history patterns and spatial and temporal overlap in an assemblage of lotic Plecoptera in the Araglin Catchment Study Area, Ireland. Arch Hydrobiol 150:117–132
Soluk DA (1993) Multiple predatory effects: predicting combined functional response of stream fish and invertebrate predators. Ecology 74:219–225
Soluk DA, Richardson JS (1997) The role of stoneflies in enhancing growth of trout: a test of the importance of predator-predator facilitation within a stream community. Oikos 80:214–219
Swift MJ (1987) Organization of assemblages of decomposer fungi in space and time. In: Gee JHR, Giller PS (eds) Organization of communities: past and present. Blackwell, Oxford, pp 229–254
Tilman D, Lehman CL, Thomson KT (1997) Plant diversity and ecosystem productivity: theoretical considerations. Proc Natl Acad Sci USA 94:1857–1861
Tilman D, Lehman CL, Bristow CE (1998) Notes and comments: diversity-stability relationships: statistical inevitability or ecological consequence? Am Nat 151:277–282
Volterra V (1926) Variations and fluctuations of the numbers of individuals in animal species living together. In: Chapman RN (ed) Animal ecology. McGraw Hill, New York
Yachi S, Loreau M (1999) Biodiversity and ecosystem productivity in a fluctuating environment: the insurance hypothesis. Proc Natl Acad Sci USA 96:1463–1468
Acknowledgements
We thank Michel Loreau, Brendan McKie, Shahid Naeem, Lennart Persson and an anonymous referee for helpful comments on earlier versions of the manuscript, and Kristina Ulvcrona, Magnus Lindberg and Jens Råberg for technical assistance. Financial support was provided by the Swedish Council for Forestry and Agricultural Research (SJFR).
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Jonsson, M., Malmqvist, B. Mechanisms behind positive diversity effects on ecosystem functioning: testing the facilitation and interference hypotheses. Oecologia 134, 554–559 (2003). https://doi.org/10.1007/s00442-002-1148-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00442-002-1148-5