species richness and trophic diversity increase decomposition in a co-evolved food web物种丰富度和营养多样性增加分解在一个食物网密切相关.pdf

Species Richness and Trophic Diversity Increase Decomposition in a Co-Evolved Food Web 1 2 1 Benjamin Baiser *, Roxanne S. Ardeshiri , Aaron M. Ellison 1 Harvard Forest, Harvard University, Petersham, Massachusetts, United States of America, 2 Environmental Science, Policy and Management, University of California, Berkeley, California, United States of America Abstract Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators — larvae of the pitcher- plant mosquito — indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs