| Abstrakt: |
Abstract It is generally accepted that native communities provide resistance against invaders through biotic interactions. However, much remains uncertain about the types of ecological processes and community attributes that contribute to biotic resistance. We used experimental mesocosms to examine how zooplankton community structure, invertebrate predation, and nutrient supply jointly affected the establishment of the exoticDaphnia lumholtzi. We predicted that establishment would increase with declining biomass and diversity of native zooplankton communities and that an invertebrate predator (IP) would indirectly facilitate the establishment ofD. lumholtzidue to its relatively long predator-deterring spines. Furthermore, we hypothesized that elevated nutrient supply would increase algal food availability and facilitate establishment. Only when the biomass and diversity of native zooplankton were significantly reduced, wasD.␣lumholtziable to successfully invade mesocosms. Although invertebrate predation and resource supply modified attributes of native zooplankton communities, they did not influence the establishment ofD. lumholtzi. Overall, our␣results are consistent with observed population dynamics in invaded reservoirs whereD.␣lumholtzitends to be present only during the late summer, coinciding with historic mid-summer declines in native zooplankton populations. Lakes and reservoirs may be more susceptible to invasion not only byD. lumholtzi, but also by other planktonic species, in the late summer when native communities exhibit characteristics associated with lower levels of biotic resistance. [ABSTRACT FROM AUTHOR] |
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