Pollination in an invaded Hawaiian ecosystem

Background/Question/Methods:

Oceanic islands are well known for their high endemism and unique biological diversity, which make them particularly susceptible to disturbances such as non-native species invasions. Such invasions can disrupt pollination services and result in negative impacts on native plant reproduction and genetic diversity. Non-native invasive predators (NIPs) consume animal pollinators and, by doing so, reduce pollinator populations and possibly eliminate entire pollinator guilds. Loss of pollination services due to NIPs likely is an important, although poorly understood, factor in both native plant conservation and management of long-term sustainability of native island ecosystems. Our project is examining the impacts of NIPs on pollination and native plant reproduction in a tropical dryland ecosystem in Hawaii. We combine field observation, experimental manipulation, and laboratory analysis to examine interactions between native plants, pollinators (native and non-native), and NIPs.

Results/Conclusions:

We have conducted flower visitation observations, pollination experiments, and surveys of pollinators and predators to assess existing pollination of eight native plant species. Plant species were selected based on their distribution, generation times, and pollination by insects. We are investigating 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. The majority of flower visits to all plant species are by the non-native honeybee (Apis mellifera). Native solitary bees (Hylaeus spp.) also visit the plant species. Non-native predators (NIPs) are abundant in the dryland ecosystem field site and include rodents (house mouse, Mus musculus; black rat, Rattus rattus), ants (Argentine ant, Linepithema humile; ghost ant, Tapinoma melanocephalum), and yellowjacket (Vespula pensylvanica). In the next phase of our project, we will experimentally control these NIPs to determine their impacts on pollination and native plant reproduction. This will provide a more comprehensive understanding of current pollination services in landscapes invaded by non-native predators.