A presentation of Jarrett’s dissertation research on predator diversity an ecosystem function, for a general audience, in 7 minutes.

Overfishing, habitat degradation, climate change, pollution, and more can all led to declines in species diversity. In the oceans, predators tend to be the first species driven extinct.

Most marine extinctions at both the local and global scale are of predators. Within kelp forests of the Channel Islands, fewer predator species correlated with less kelp and more herbivores. Experimentally, I have shown that this may be due to different predator species each causing different herbivores to reduce consumption of kelp.

Within communities of marine fouling organisms, I have found similar patterns. There, predator diversity is negatively correlated with the amount of their sessile invertebrate prey. This appears to be due to some complementarity, but also a trade-off in interspecific and intraspecific interactions. Over time, communities with more species of predators have lower cover and biomass, and are able to filter less plankton from the water.

A panel from my fouling community predator diversity experiment. This little limpet had very little impact.

Future Directions: Integrating food web structure
Manipulations of predator diversity in different systems have had radically different impacts on ecosystem function. The results appear to hinge on food web structure. And yet, we have no solid framework for how food web structure alters the effects of predator extinctions. Nor does theory address many of the impacts of predator extinctions beyond trophic effects. There’s a lot of world still left to explore in the predator BEF world, and many different approaches to take.

Relevant References
Griffin, J. N., Byrnes, J. E. K., and Cardinale, B. J. 2013. Effects of predator richness on prey suppression: a meta-analysis. Ecology. 94:2180-2187. [doi]

Byrnes, J.E. and Stachowicz, J.J. 2009. The consequences of consumer diversity loss: different answers from different designs. Ecology. 90: 2879-2888. [doi] [pdf]

Byrnes, J.E., Reynolds, P.L., Stachowicz, J.J. 2007. Invasions and extinctions reshape coastal marine food webs. PLoS One. 2: e295. [doi] [pdf]

Byrnes, J.E., Stachowicz, J.J., Hultgren, K.M., Hughes, A.R., Olyarnik, S.V., Thornber, C. 2006. Predator Diversity Enhances Trophic Cascades in Kelp Forests by Modifying Herbivore Behavior. Ecology Letters. 9: 61-71. [doi] [pdf]