Pollination is a critical ecosystem service and the vast majority of flowering plants world-wide are pollinated by animals. Non-native invasive predators (NIPs) consume animal pollinators and can disrupt pollination services, resulting in negative impacts on native plant reproduction and genetic diversity. Oceanic islands are particularly susceptible to non-native species invasions, due to their high endemism and unique biological diversity, and long-term sustainability of native island ecosystems may be at risk due to these invasions. Our project is examining the impacts of NIPs (specifically rodents, ants, and wasps) on pollination and native plant reproduction in a tropical dry forest ecosystem in Hawai'i. We are combining field observation, experimental manipulation, and laboratory analyses to examine interactions between native plants, pollinators (native and non-native), and NIPs. We have conducted flower visitation observations, pollination experiments, predator diet analyses, and experimental removal of NIPs to assess pollination of eight native plant species. Plant species include four endangered plant species and four common plant species, which have a diversity of floral traits to maximize the potential diversity of pollinators that are attracted to our study plants overall.
Results/Conclusions:
Pollination treatments show that our focal plant species can self-fertilize and are not pollen-limited, however endangered species appear to be more pollen-limited than common species. The number of flower visitor species is low overall but endangered plant species receive fewer visitor species than common plant species. Visitation to all plant species is performed mainly by non-native insect species. Non-native invasive predators are widespread in our study area and diet analyses show that they consume flower visitor taxa for all focal plant species. Experimental treatments to control NIPs have variable success according to habitat type and season. By controlling NIPS, there may be a change in pollination dynamics. This may be in the insect visitor species (non-native vs native), the amount of visitation by insect species, or in plant fruit or seed set. Impacts on pollination services from NIPs might differ for endangered versus common plant species in this dry forest ecosystem.