Since widespread urbanization contributes to the global decline of bees and other pollinators, it is important to study the response of bees to urbanization in areas representative of those experiencing urban growth. However, most urban bee research is conducted in temperate regions of North America and Europe, creating a geographical bias in our understanding of urban bee communities and their assembly. To address this geographic bias, we are conducting a study on bee communities in various habitats throughout San Juan, Puerto Rico. Our goal is to understand tropical urban bee community assembly, so we have identified (a) which species occur in San Juan and (b) their distribution throughout the city. Additionally, as bees are active year-round in the tropics, we assessed (c) how bee community composition changes over time.
Sampling was performed via netting and bowl traps at five different urban habitat types and at four peri-urban sites. Both urban and peri-urban sites were chosen to compare bee diversity between different levels of urbanization.
Results/Conclusions
During a summer 2021 pilot study, 12 different species (including Apis mellifera) were collected across several residential neighborhoods using only insect nets. Most specimens belonged to the genus Lasioglossum, and also included a number of specialists like Exomalopsis, Nomada, and Xylocopa.
In early winter 2022, we collected 229 bees (75 via netting; 154 via bowl traps), representing at least 14 species, with the addition of Melissodes and Hylaeus species. This represents 34% of known bee species in Puerto Rico. A 15th species is possible, as one specimen does not match any described species on the island and is being reviewed.
While these analyses are preliminary, L. enatum appears to be the most abundant species in San Juan, aside from A. mellifera. As expected, differences in abundance and species composition between sites are apparent, as well as temporal variation within sites. We observed differences between winter-time bee diversity in the peri-urban vs urban sites, with higher diversity in the city than peri-urban areas. Knowing which species reside in the city is the first step to identifying the drivers of bee community assembly in a tropical city, with the end goal of better protecting and promoting their populations.
