Plant succession is regulated by a combination of abiotic and biotic factors. However, previous studies of biotic drivers have focused overwhelmingly on direct pairwise species interactions, ignoring the likely prevalent higher-order interactions (HOIs) in natural systems. Climate also plays a significant role in determining successional dynamics with both direct effects and indirect effects via altered biotic interactions. Here we explored the relative effects of direct species interactions, HOIs, climate, and their interactions on population dynamics of herbaceous plants during 50 years of post-agricultural secondary succession and tested whether the inclusion of HOIs and climate data improved forecasts of population dynamics. Direct intraspecific interactions were competitive and prevalent across the 90 herbaceous plants examined, while direct interspecific interactions only affected populations of 29% species. HOIs, mainly arose from intraspecific HOIs of conspecifics, were mostly positive and thus largely mitigated the competitive effects of direct intraspecific interactions. Species with lower peak cover experienced stronger intraspecific competition and positive intraspecific HOIs of conspecifics. Direct interspecific interactions had neutral or facilitative effects on species with lower peak cover, and tended to have competitive effects on species with higher peak cover. Climate simultaneously influenced population dynamics both directly and indirectly via altered species interactions. Forecast performance was significantly improved with the inclusion of HOIs or climate for about half and one-third of species, respectively. Our study emphasizes the importance of HOIs, which largely mitigated direct competitive effects on population dynamics of herbaceous plants during succession. Teasing apart HOIs from direct species interactions substantially refined our understanding of successional dynamics of herbaceous plants and improved the accuracy of forecasting population dynamics during succession in a changing world.
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Abstract Animals often change their behaviour in the presence of other species and the environmental context they experience, and these changes can substantially modify the course their populations follow. In the case of animals involved in mutualistic interactions, it is still unclear how to incorporate the effects of these behavioural changes into population dynamics. We propose a framework for using pollinator functional responses to examine the roles of pollinator–pollinator interactions and abiotic conditions in altering the times between floral visits of a focal pollinator. We then apply this framework to a unique foraging experiment with different models that allow resource availability and sublethal exposure to a neonicotinoid pesticide to modify how pollinators forage alone and with co‐foragers. We found that all co‐foragers interfere with the focal pollinator under at least one set of abiotic conditions; for most species, interference was strongest at higher levels of resource availability and with pesticide exposure. Overall our results highlight that density‐dependent responses are often context‐dependent themselves.
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Abstract Aim How do factors such as space, time, climate and other ecological drivers influence food web structure and dynamics? Collections of well‐studied food webs and replicate food webs from the same system that span biogeographical and ecological gradients now enable detailed, quantitative investigation of such questions and help integrate food web ecology and macroecology. Here, we integrate macroecology and food web ecology by focusing on how ecogeographical rules [the latitudinal diversity gradient (LDG), Bergmann's rule, the island rule and Rapoport's rule] are associated with the architecture of food webs.
Location Global.
Time period Current.
Major taxa studied All taxa.
Methods We discuss the implications of each ecogeographical rule for food webs, present predictions for how food web structure will vary with each rule, assess empirical support where available, and discuss how food webs may influence ecogeographical rules. Finally, we recommend systems and approaches for further advancing this research agenda.
Results We derived testable predictions for some ecogeographical rules (e.g. LDG, Rapoport's rule), while for others (e.g., Bergmann's and island rules) it is less clear how we would expect food webs to change over macroecological scales. Based on the LDG, we found weak support for both positive and negative relationships between food chain length and latitude and for increased generality and linkage density at higher latitudes. Based on Rapoport's rule, we found support for the prediction that species turnover in food webs is inversely related to latitude.
Main conclusions The macroecology of food webs goes beyond traditional approaches to biodiversity at macroecological scales by focusing on trophic interactions among species. The collection of food web data for different types of ecosystems across biogeographical gradients is key to advance this research agenda. Further, considering food web interactions as a selection pressure that drives or disrupts ecogeographical rules has the potential to address both mechanisms of and deviations from these macroecological relationships. For these reasons, further integration of macroecology and food webs will help ecologists better understand the assembly, maintenance and change of ecosystems across space and time.
