Data from: Propagule pressure and native community connectivity interact to influence invasion success in metacommunities

Mechanistic insights from invasion biology indicate that propagule
pressure of exotic species and native community structure can
independently influence establishment success. The role of native
community connectivity via species dispersal and its potential interaction
with propagule pressure on invasion success in metacommunities, however,
remains unknown. Native community connectivity may increase biotic
resistance to invasion by enhancing species richness and evenness, but the
effects could depend upon the level of propagule pressure. In this study,
a mesocosm experiment was used to evaluate the independent and combined
effects of exotic propagule pressure and native community connectivity on
invasion success. The effects of three levels of exotic Daphnia lumholtzi
propagule pressure on establishment success, community structure, and
ecosystem attributes were evaluated in native zooplankton communities
connected by species dispersal versus unconnected communities, and
relative to a control without native species. Establishment of the exotic
species exhibited a propagule dose-dependent relationship with high levels
of propagule pressure resulting in the greatest establishment success.
Native community connectivity, however, effectively reduced establishment
at the low level of propagule pressure and further augmented native
species richness across propagule pressure treatments. Propagule pressure
largely determined the negative impacts of the exotic species on native
species richness, native biomass, and edible producer biomass. The results
highlight that native community connectivity can reduce invasion success
at a low propagule dose and decrease extinction risk of native
competitors, but high propagule pressure can overcome
connectivity-mediated biotic resistance to influence establishment and
impact of the exotic species. Together, the results emphasize the
importance of the interaction of propagule pressure and community
connectivity as a regulator of invasion success, and argue for the
maintenance of metacommunity connectivity to confer invasion resistance.