Dispersal acts as both bane and balm for invaded zooplankton communities

Abstract

Dispersal of native species from the regional pool can recover invaded communities to a pre-invaded state by supplementing declining populations or providing resistant species. However, dispersal may also exacerbate the negative effects of an invader. Introduced species can open or create new niche space, which could facilitate the establishment of competitors or predators that previously could not succeed in the uninvaded local community. To investigate the interaction between dispersal and invasion by a non-native consumer, we conducted a field mesocosm experiment that introduced zebra mussels into native zooplankton communities. Regional zooplankton were collected and added to both invaded and uninvaded communities. In uninvaded communities, zooplankton dispersal reduced cladoceran diversity by 40%, rotifer abundance by 65% and copepod nauplii abundance by 80%. In invaded communities, dispersal increased cladoceran diversity by 60%, but also further exacerbated the negative effects of zebra mussels on rotifer abundance. This experiment illustrates the potential for dispersal to both positively and negatively affect local communities, and how these effects may change with disturbance and the taxa or community metric of study.