Urban development decreases bee abundance and diversity within coastal dune systems

Abstract Globally, coastal human population density is approximately three times than that of inland areas. Such development threatens the integrity of coastal ecosystems. Coastal dune systems contain unique sets of terrestrial invertebrates and native plants, and represent some of the last remaining areas of semi-natural habitats along the coasts. In our study, we monitored bee and flowering plant abundance and diversity within coastal dune systems located within protected lands and developed sites throughout South and Central Florida. Our aim was to assess the potential impacts dune degradation and development could have on these economically and ecologically important insects. A total of 5,419 bees from 5 families and 56 taxa were captured using bowl traps. Halictidae accounted for 70% of all bees collected, followed by Apidae (28%), Megachilidae (2%), Andrenidae (0.1%) and Colletidae (0.07%). Both species richness and Shannon-Wiener diversity indices were higher in protected lands when compared with developed sites. A majority of the commonly collected bee species showed higher abundances in protected lands compared with developed sites. Protected lands also supported higher abundances of ground, wood, and tunnel-nesting bees when compared with developed sites. Bee species richness and Shannon-Wiener indices were lower in sites with greater percentages of development occurring within close proximity to the dune systems, and higher in sites with greater availability of dune coverage. We observed higher abundance and flowering plant species richness within protected lands when compared with developed sites; protected lands also supported more federally endangered/threatened or state protected plant species compared with developed sites. Overall, coastal dune systems are ecologically important bee sanctuaries and should be conserved to help sustain native bee communities and the flowering plants that occur within them.