Abstract:The global distribution of primary production and consumption by humans (fisheries) is well-documented, but we have no map linking the central ecological process of consumption within food webs to temperature and other ecological drivers. Using standardized assays that span 105° of latitude on four continents, we show that rates of bait consumption by generalist predators in shallow marine ecosystems are tightly linked to both temperature and the composition of consumer assemblages. Unexpectedly, rates of cons… Show more
“…Our study provides a novel integration of large-scale experimental and observational approaches to explore interactions among communities of predators and prey. Our results expand the growing literature that shows stronger predation at lower latitudes in both marine and terrestrial systems (Schemske et al 2009, Roslin et al 2017, Reynolds et al 2018, Hargreaves et al 2019, Longo et al 2019, Freestone et al 2020, but contrast with studies that find consumption rates of standardized bait can peak at midlatitudes for some groups of marine predators (Musrri et al 2019, Roesti et al 2020, Whalen et al 2020. Subsets of predators may demonstrate different consumption patterns across latitude because of differences in abundance and composition of specific predator taxa or geographic variation in abiotic patterns along different coastlines.…”
Section: Discussionsupporting
confidence: 79%
“…To quantify predation intensity, studies that span biogeographic scales often assess predation rates (Jeanne 1979, Bertness et al 1981, Heck and Wilson 1987, Roslin et al 2017, Hargreaves et al 2019, Longo et al 2019, Roesti et al 2020, Whalen et al 2020, which have clear value in estimating top-down forcing in a community. Multiple dimensions of the predator community, however, contribute to predation intensity beyond predation rates and can vary among regions.…”
The hypothesis that biotic interactions strengthen toward lower latitudes provides a framework for linking community-scale processes with the macroecological scales that define our biosphere. Despite the importance of this hypothesis for understanding community assembly and ecosystem functioning, the extent to which interaction strength varies across latitude and the effects of this variation on natural communities remain unresolved. Predation in particular is central to ecological and evolutionary dynamics across the globe, yet very few studies explore both community-scale causes and outcomes of predation across latitude. Here we expand beyond prior studies to examine two important components of predation strength: intensity of predation (including multiple dimensions of the predator guild) and impact on prey community biomass and structure, providing one of the most comprehensive examinations of predator-prey interactions across latitude. Using standardized experiments, we tested the hypothesis that predation intensity and impact on prey communities were stronger at lower latitudes. We further assessed prey recruitment to evaluate the potential for this process to mediate predation effects. We used sessile marine invertebrate communities and their fish predators in nearshore environments as a model system, with experiments conducted at 12 sites in four regions spanning the tropics to the subarctic. Our results show clear support for an increase in both predation intensity and impact at lower relative to higher latitudes. The predator guild was more diverse at low latitudes, with higher predation rates, longer interaction durations, and larger predator body sizes, suggesting stronger predation intensity in the tropics. Predation also reduced prey biomass and altered prey composition at low latitudes, with no effects at high latitudes. Although recruitment rates were up to three orders of magnitude higher in the tropics than the subarctic, prey replacement through this process was insufficient to dampen completely the strong impacts of predators in the tropics. Our study provides a novel perspective on the biotic interaction hypothesis, suggesting that multiple components of the predator community likely contribute to predation intensity at low latitudes, with important consequences for the structure of prey communities.
“…Our study provides a novel integration of large-scale experimental and observational approaches to explore interactions among communities of predators and prey. Our results expand the growing literature that shows stronger predation at lower latitudes in both marine and terrestrial systems (Schemske et al 2009, Roslin et al 2017, Reynolds et al 2018, Hargreaves et al 2019, Longo et al 2019, Freestone et al 2020, but contrast with studies that find consumption rates of standardized bait can peak at midlatitudes for some groups of marine predators (Musrri et al 2019, Roesti et al 2020, Whalen et al 2020. Subsets of predators may demonstrate different consumption patterns across latitude because of differences in abundance and composition of specific predator taxa or geographic variation in abiotic patterns along different coastlines.…”
Section: Discussionsupporting
confidence: 79%
“…To quantify predation intensity, studies that span biogeographic scales often assess predation rates (Jeanne 1979, Bertness et al 1981, Heck and Wilson 1987, Roslin et al 2017, Hargreaves et al 2019, Longo et al 2019, Roesti et al 2020, Whalen et al 2020, which have clear value in estimating top-down forcing in a community. Multiple dimensions of the predator community, however, contribute to predation intensity beyond predation rates and can vary among regions.…”
The hypothesis that biotic interactions strengthen toward lower latitudes provides a framework for linking community-scale processes with the macroecological scales that define our biosphere. Despite the importance of this hypothesis for understanding community assembly and ecosystem functioning, the extent to which interaction strength varies across latitude and the effects of this variation on natural communities remain unresolved. Predation in particular is central to ecological and evolutionary dynamics across the globe, yet very few studies explore both community-scale causes and outcomes of predation across latitude. Here we expand beyond prior studies to examine two important components of predation strength: intensity of predation (including multiple dimensions of the predator guild) and impact on prey community biomass and structure, providing one of the most comprehensive examinations of predator-prey interactions across latitude. Using standardized experiments, we tested the hypothesis that predation intensity and impact on prey communities were stronger at lower latitudes. We further assessed prey recruitment to evaluate the potential for this process to mediate predation effects. We used sessile marine invertebrate communities and their fish predators in nearshore environments as a model system, with experiments conducted at 12 sites in four regions spanning the tropics to the subarctic. Our results show clear support for an increase in both predation intensity and impact at lower relative to higher latitudes. The predator guild was more diverse at low latitudes, with higher predation rates, longer interaction durations, and larger predator body sizes, suggesting stronger predation intensity in the tropics. Predation also reduced prey biomass and altered prey composition at low latitudes, with no effects at high latitudes. Although recruitment rates were up to three orders of magnitude higher in the tropics than the subarctic, prey replacement through this process was insufficient to dampen completely the strong impacts of predators in the tropics. Our study provides a novel perspective on the biotic interaction hypothesis, suggesting that multiple components of the predator community likely contribute to predation intensity at low latitudes, with important consequences for the structure of prey communities.
“…We predicted: (i) that trait dispersion would increase with decreasing latitude as species interactions become more intense, and (ii) that abiotic filters would be strongest and result in clustering at higher latitudes and where biotic interactions are weak. While marine systems often show nonlinear variation in species diversity and interaction strength with latitude (peaking at mid-latitudes; [ 20 , 31 ]), our predictions are reasonable within the range of latitudes occupied by eelgrass (approx. 30–70° N).…”
Section: Introductionsupporting
confidence: 63%
“…On the other hand, selection for tolerance of extreme heat conditions could also cause trait clustering at low latitudes. Finally, patterns in community structure along latitudinal gradients could be dominated by idiosyncratic and historically contingent effects of predators, prey, competitors, and mutualists that vary among biogeographic provinces [ 17 – 20 ]. Local abiotic factors, habitat complexity, assemblage composition and adaptation to these local factors could further obscure broader geographical patterns of community assembly [ 17 , 21 ], stressing the importance of assessing patterns across multiple independent species pools.…”
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° 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.
“…Understanding spatial and temporal variation in consumption is crucial for predicting how ecosystems will respond to global and local change, including warming climate and fishing impacts (Ling et al, 2009;Vergés et al, 2011). Although relative variation in primary production and producer biomass can be compared efficiently in both terrestrial and marine environments, the mobility, diet, and behavior of consumers (e.g., fishes) make their distribution and top-down impacts challenging to quantify, especially in marine habitats (Duffy et al, 2015;Fraser et al, 2020;Whalen et al, 2020). However, an increasing number of studies have demonstrated that top-down processes vary predictably across latitude within a handful of marine habitats (Freestone et al, 2011;Rodemann and Brandl, 2017;Musrri et al, 2019;Whalen et al, 2020;Lefcheck et al, 2021), which may give insight into fish presence and behaviors, and help with the interpretation of consumption processes (Ferreira et al, 2004;Navarrete et al, 2005).…”
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