Biodiversity affects many ecosystem functions and services, including carbon cycling and retention. While it is known that the efficiency of carbon capture and biomass production by ecological communities increases with species diversity, the role of vertebrate animals in the carbon cycle remains undocumented. Here, we use an extensive dataset collected in a high-diversity Amazonian system to parse out the relationship between animal and plant species richness, feeding interactions, tree biomass and carbon concentrations in soil. Mammal and tree species richness is positively related to tree biomass and carbon concentration in soil-and the relationship is mediated by organic remains produced by vertebrate feeding events. Our research advances knowledge of the links between biodiversity and carbon cycling and storage, supporting the view that whole community complexity-including vertebrate richness and trophic interactions-drives ecosystem function in tropical systems. Securing animal and plant diversity while protecting landscape integrity will contribute to soil nutrient content and carbon retention in the biosphere.
Seed-dispersing birds can be expected to optimize their energy intake through fruit selection and hence exert a positive selection on fruit pulp content, that is to say, favoring big fruits with small seeds. On the other hand they may select both, average fruit size and its variation. We addressed this issue by analyzing the phenotypic selection exerted by the dispersers of Crataegus monogyna on the fruit and seed size of this species. Fruit and seed size were analyzed at two ontogenic plant stages: the initial size of seeds (and their fruits) as future individuals and the mean size of fruits and seeds produced by adult plants. Fruit diameter and its within-individual variation are the actual targets of selection for maternal fruit traits, negatively affecting relative fitness, although total selection acts only on mean fruit size. For individual seeds, size selection is positive and directed at fruit diameter and seed length, while the remaining traits are subject to indirect selection. Birds exerted a correlational selection favoring big fruits with small seeds. Nevertheless the evolutionary consequences of this selection are expected to be limited by several factors. For example, the positive correlation between fruit and seed sizes, the existence of counteracting selective pressures exerted by other mutualistic or antagonist interactions and temporal or spatial changes in the environmental conditions that may alter the selective forces and even the optimum phenotype in each situation.
Flower color variation among plant populations might reflect adaptation to local conditions such as the interacting animal community. In the northwest Iberian Peninsula, flower color of Gentiana lutea varies longitudinally among populations, ranging from orange to yellow. We explored whether flower color is locally adapted and the role of pollinators and seed predators as agents of selection by analyzing the influence of flower color on (i) pollinator visitation rate and (ii) escape from seed predation and (iii) by testing whether differences in pollinator communities correlate with flower color variation across populations. Finally, (iv) we investigated whether variation in selective pressures explains flower color variation among 12 G. lutea populations. Flower color influenced pollinator visits and differences in flower color among populations were related to variation in pollinator communities. Selective pressures on flower color vary among populations and explain part of flower color differences among populations of G. lutea. We conclude that flower color in G. lutea is locally adapted and that pollinators play a role in this adaptation.
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