Browsing by Author "Cusson, Mathieu"
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- Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approachPublication . Duffy, J. Emmett; Reynolds, Pamela L.; Bostroem, Christoffer; Coyer, James A.; Cusson, Mathieu; Donadi, Serena; Douglass, James G.; Ekloef, Johan S.; Engelen, Aschwin H.; Eriksson, Britas Klemens; Fredriksen, Stein; Gamfeldt, Lars; Gustafsson, Camilla; Hoarau, Galice; Hori, Masakazu; Hovel, Kevin; Iken, Katrin; Lefcheck, Jonathan S.; Moksnes, Per-Olav; Nakaoka, Masahiro; O'Connor, Mary I.; Olsen, Jeanine L.; Richardson, J. Paul; Ruesink, Jennifer L.; Sotka, Erik E.; Thormar, Jonas; Whalen, Matthew A.; Stachowicz, John J.Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors.
- Latitude, temperature, and habitat complexity predict predation pressure in eelgrass beds across the Northern HemispherePublication . 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; 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. EmmettLatitudinal 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.
- A Pleistocene legacy structures variation in modern seagrass ecosystemsPublication . Duffy, J. Emmett; Stachowicz, John J.; Reynolds, Pamela L.; Hovel, Kevin A.; Jahnke, Marlene; Sotka, Erik E.; Boström, Christoffer; Boyer, Katharyn E.; Cusson, Mathieu; Eklöf, Johan; Engelen, Aschwin; Eriksson, Britas Klemens; Fodrie, F. Joel; Griffin, John N.; Hereu, Clara M.; Hori, Masakazu; Hughes, A. Randall; Ivanov, Mikhail V.; Jorgensen, Pablo; Kruschel, Claudia; Lee, Kun-Seop; Lefcheck, Jonathan S.; Moksnes, Per-Olav; Nakaoka, Masahiro; O’Connor, Mary I.; O’Connor, Nessa E.; Orth, Robert J.; Peterson, Bradley J.; Reiss, Henning; Reiss, Katrin; Richardson, J. Paul; Rossi, Francesca; Ruesink, Jennifer L.; Schultz, Stewart T.; Thormar, Jonas; Tomas, Fiona; Unsworth, Richard; Voigt, Erin; Whalen, Matthew A.; Ziegler, Shelby L.; Olsen, Jeanine L.Distribution of Earth's biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate-trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth's environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (Zostera marina), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.
- The biogeography of community assembly: latitude and predation drive variation in community trait distribution in a guild of epifaunal crustaceansPublication . Gross, Collin P.; Duffy, J. Emmett; Hovel, Kevin A.; Kardish, Melissa R.; Reynolds, Pamela L.; Boström, Christoffer; Boyer, Katharyn E.; Cusson, Mathieu; Eklöf, Johan; Engelen, Aschwin; Eriksson, Britas Klemens; Fodrie, F. Joel; Griffin, John N.; Hereu, Clara M.; Hori, Masakazu; Hughes, A. Randall; Ivanov, Mikhail V.; Jorgensen, Pablo; Kruschel, Claudia; Lee, Kun-Seop; Lefcheck, Jonathan; McGlathery, Karen; Moksnes, Per-Olav; Nakaoka, Masahiro; O'Connor, Mary I.; O'Connor, Nessa E.; Olsen, Jeanine L.; Orth, Robert J.; Peterson, Bradley J.; Reiss, Henning; Rossi, Francesca; Ruesink, Jennifer; Sotka, Erik E.; Thormar, Jonas; Tomas, Fiona; Unsworth, Richard; Voigt, Erin P.; Whalen, Matthew A.; Ziegler, Shelby L.; Stachowicz, John J.While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass (Zostera marina) spanning 30 degrees of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how both latitudinal variation in species interactions and historical contingency shape these responses. Community trait distributions have implications for ecosystem stability and functioning, and integrating large-scale observations of environmental filters, species interactions and traits can help us predict how communities may respond to environmental change.