Latitude, temperature, and habitat complexity predict predation pressure in eelgrass beds across the Northern Hemisphere

Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass (Zostera marina) at 48 sites across its Northern Hemisphere range, encompassing over 37 degrees of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas insitu water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simply increased metabolic activity at the time of predation. This large-scale biogeographic pattern was modified by local habitat characteristics; predation declined with higher shoot density both among and within sites. Predation rates on gastropods, by contrast, were uniformly low and varied little among sites. The high replication and geographic extent of our study not only provides additional evidence to support biogeographic variation in predation intensity, but also insight into the mechanisms that relate temperature and biogeographic gradients in species interactions.


biogeography, latitude, mesograzer, predation, seagrass, species interactions, temperature, Zostera

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Reynolds Pamela L., Stachowicz John J., Hovel Kevin, Bostrom Christoffer, Boyer Katharyn, Cusson Mathieu, Eklof Johan S., Engel Friederike G., Engelen Aschwin H., Eriksson Britas Klemens, Fodrie F. Joel, Griffin John N., Hereu Clara M., Hori Masakazu, Hanley Torrance C., Ivanov Mikhail, Jorgensen Pablo, Kruschel Claudia, Lee Kun-Seop, McGlathery Karen, Moksnes Per-Olav, Nakaoka Masahiro, O'connor Mary I., O'connor Nessa E., Orth Robert J., Rossi Francesca, Ruesink Jennifer, Sotka Erik E., Thormar Jonas, Tomas Fiona, Unsworth Richard K. F., Whalen Matthew A., Duffy J. Emmett (2018). Latitude, temperature, and habitat complexity predict predation pressure in eelgrass beds across the Northern Hemisphere. Ecology. 99 (1). 29-35.,

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