Pollination and plant reproductive success in restored urban landscapes dominated by a pervasive exotic pollinator

Although insect pollination is fundamental to the persistence of plants in restored habitats, it is rarely taken in to account in evaluations of restoration success. We evaluated a recovery of interactions between the insect-pollinated shrub Dillwynia sieberi and its pollinator assemblage dominated by exotic honeybee Apis mellifera in 5-year-old revegetated pastures and remnants of endangered Cumberland Plain Woodland (the aim of revegetation) in Sydney, Australia. We examined plant size, plant flower density, flower visitation rates by insects, counts of pollen per stigma and presence/absence of germinated pollen, fruit and seed set ratios and rates of pre-dispersal seed predation. Flower densities on plants in restored areas were significantly higher than in forest remnants. Bees were the most common flower visitors. Plants in revegetated areas attracted significantly more flower visitors with visitor assemblages usually dominated by A. mellifera. Plants in revegetated areas had similar numbers of flowers per inflorescence, while fruit and seed set per inflorescence was significantly higher in forest remnants. There was no significant difference in the rates of pre-dispersal seed predation. Plants in revegetated areas and forest remnants had similar seed output with no apparent negative effect of A. mellifera on seed production. Restoration of native vegetation in an urban context is a challenging long-term process. However, introduction of dominant plant species can foster a rapid return of their pollinators. The interactions between the plants and their native pollinators were resilient to pervasive exotic A. mellifera, and plants in restored ecosystems had an adequate reproductive output.