Herbivore and predator diversity interactively affect ecosystem properties in an experimental marine community

Abstract

Interacting changes in predator and prey diversity likely influence ecosystem properties but have rarely been experimentally tested. We manipulated the species richness of herbivores and predators in an experimental benthic marine community and measured their effects on predator, herbivore and primary producer performance. Predator composition and richness strongly affected several community and population responses, mostly via sampling effects. However, some predators survived better in polycultures than in monocultures, suggesting complementarity due to stronger intra- than interspecific interactions. Predator effects also differed between additive and substitutive designs, emphasizing that the relationship between diversity and abundance in an assemblage can strongly influence whether and how diversity effects are realized. Changing herbivore richness and predator richness interacted to influence both total herbivore abundance and predatory crab growth, but these interactive diversity effects were weak. Overall, the presence and richness of predators dominated biotic effects on community and ecosystem properties.

Diversity of protists and bacteria determines predation performance and stability

“…Our results differ from other biodiversity-ecosystem functioning studies, suggesting that predator richness effects were driven by SEs only (that is, DE and TDC; for example, see Bruno and O'Connor (2005) and Douglass et al (2008)). Furthermore, the potential increase in complementarity appears to contradict many previously established paradigms that inter-predator competition, negative interactions and/or intra-guild predation are common and pre-dominant features of predator communities (Polis and Holt, 1992;Arim and Marquet, 2004).…”

“…Transferring conclusions drawn from miniaturized controlled laboratory experiments to open field situations might be challenging (Douglass et al, 2008;O'Connor and Bruno, 2009). Prey recovery time might be shorter in enclosed, self-contained habitat patches (such as our microcosms) than in open ecosystem, thus leading to an overrating of the importance of protist predators (Ellner et al, 2001;Cardinale et al, 2006).…”

“…All prey bacterial species used in our experiments were edible for the predators. Therefore, we speculate that the decrease in the predator performance with increasing bacterial prey diversity might be potentially due to the expression of positive interactions in diverse prey communities (Saleem et al, 2012) or increasing predator defense strategies (for example, biofilm formation; Matz and Kjelleberg, 2005;Pernthaler, 2005;Douglass et al, 2008;Edwards et al, 2010).…”

Strong effects of herbivorous amphipods on epiphyte biomass in a temperate seagrass meadow

“…Poore et al (2009) described a method of effectively excluding amphipods without cages using the insecticide carbaryl in a slow-release plaster matrix. Previously, insecticides have been used to remove amphipods from mesocosms and aquaculture facilities (Shacklock & Croft 1981, Duffy & Hay 2000, Douglass et al 2008, but attempts to manipulate densities in field conditions (Carpenter 1986, Brawley & Fei 1987, Bruno et al 2005 were hampered by its rapid breakdown in seawater and light, combined with the rapid re-colonisation of amphipods. Incorporating the insecticide into a slow-release matrix overcomes the need for frequent reapplications, and allows for high levels of replication with interspersed treatments (Poore et al 2009).…”

Density-dependent biodiversity effects on physical habitat modification by freshwater bivalves

“…Following other BEF experiments (Douglass et al 2008, Griffin et al 2008, we conducted 16 a priori planned linear contrasts to test for nonadditive biodiversity effects. The first set of contrasts (n ¼ 8) tested the null hypothesis that the observed polyculture mean is the same as the expected mean based on additive monoculture performances (i.e., a two-species polyculture treatment was given a contrast coefficient of 1, while the two monoculture treatments of the species present in that polyculture were given contrast coefficients of À0.5; testing the null hypothesis that the mean of the polyculture was equal to the weighted means of its monocultures).…”