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Invasive plants harbor hungry detritivores that alter ecosystem function.
MAYER, PAUL1, TUNNEL, SUSAN2, ENGLE, DAVID2, 1 2
ABSTRACT- Ecosystems are expected to function more efficiently in response to a diverse community of inhabitants. However, biological invasions may change expected relationships between ecosystem function and diversity. We observed increased decomposition, a measure of ecosystem function, in response to decreased plant diversity in old fields due to invasion by introduced grasses. As introduced grasses increased, total species richness decreased. Manipulation of detritivores suggested that the displacement of native species by unpalatable introduced grasses caused shifts in detrivore feeding patterns, thereby altering decomposition rates. Therefore, macro-detritivores consumed less litter in mesh bags located in diverse plant communities (R2 = 0.427, P = 0.006). However, macro-detritivores consumed more litter in mesh bags located in less diverse plant communities containing proportionally more cover of introduced C3 grasses (R2 = 0.718, P < 0.001). Litter in bags that excluded macro-detritivores showed no such decomposition-diversity relationships. Cover of introduced C3 grasses, ranging from 0 to 9% of the total cover, was comprised mostly of tall fescue (Festuca arundinacea), an aggressive invader possessing a fungal endophyte toxic to detritivores. These results suggest that low intensity invasions can elicit significant changes in ecosystem function by influencing detritivores.
KEY WORDS: diversity, decomposition, function, invasion