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.
The importance of climate, habitat structure, and higher trophic levels on microbial diversity is only beginning to be understood. Here, we examined the influence of climate variables, plant morphology, and the abundance of aquatic invertebrates on the microbial biodiversity of the northern pitcher plant Sarracenia purpurea. The plant's cup-shaped leaves fill with rainwater and support a miniature, yet full-fledged ecosystem with a diverse microbiome that decomposes captured prey and a small network of shredding and filter-feeding aquatic invertebrates that feed on microbes. We characterized pitcher microbiomes of 108 plants sampled at 36 sites from Florida to Quebec. Structural equation models revealed that annual precipitation and temperature, plant size, and midge abundance had direct effects on microbiome taxonomic and phylogenetic diversity. Climate variables also exerted indirect effects through plant size and midge abundance. Further, spatial structure and climate influenced taxonomic composition, but not phylogenetic composition. Our results suggest that direct effects of midge abundance and climate and indirect effects of climate through its effect on plant-associated factors lead to greater richness of microbial phylotypes in warmer, wetter sites.
Aim Raptors, a highly threatened but ecologically important group of birds, have been recognized as a good proxy for overall biodiversity in conservation planning. However, previous work on raptor diversity focused predominantly on taxonomic diversity. Here, we assess the global patterns of raptor taxonomic, phylogenetic and functional diversity and their association with current and historical environmental factors. Location Global. Time period Present day. Major taxa studied Raptors. Methods We compiled information from distribution maps, global trait datasets and avian phylogenies for all extant raptors. We used generalized least squares (GLS) to assess the relationship between historical and contemporary environmental predictors and species richness, phylogenetic diversity [Faith's phylogenetic diversity index (Faith's PD), mean pairwise distance (MPD) and mean nearest taxon distance (MNTD)] and functional diversity of traits related to raptor morphology, lifestyles, diet, foraging and vagility, while controlling for spatial autocorrelation. Results Raptor taxonomic diversity peaked in tropical regions and nearby mountain ranges. After controlling for species richness, species‐poor assemblages in high latitudes and deserts were more phylogenetically and functionally diverse than expected by chance. In species‐rich assemblages, diet and foraging traits had greater variation, whereas morphological traits had less variation than expected, suggesting that species packing promoted adaptive radiation in these assemblages. Historical climate influenced phylogenetic diversity and functional diversity of morphological, foraging and diet traits, leaving a signal of evolutionary history on modern assemblages. Human footprint was also an important driver of MPD and of niche and vagility trait functional diversity, with higher phylogenetic diversity in disturbed areas and with higher functional diversity in regions with intermediate levels of disturbance. Main conclusions Both palaeoclimate and contemporary environmental conditions are important drivers of raptor phylogenetic and functional diversity. We found large mismatches among taxonomic, functional and phylogenetic diversity, demonstrating how different processes filter lineages and species traits shaping raptor assemblages. Our results highlight the need to consider multiple dimensions of diversity to inform conservation planning better when using raptors as umbrella species.
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