The invasion of Megachile policaris (Hymenoptera: Megachilidae) to Hawai‘i

Authors: Koch, Jonathan; TABOR, JESSE - Utah State University; MONTOYA-AIONA, KRISTINA - Us Geological Survey (USGS); EIBEN, JESSE - California University Of Pennsylvania

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2021
Publication Date: 9/14/2021
Citation: Koch, J., Tabor, J.A., Montoya-Aiona, K., Eiben, J. 2021. The invasion of Megachile policaris (Hymenoptera: Megachilidae) to Hawai‘i. Journal of Insect Science. 21(5):1-9. Article 4. https://doi.org/10.1093/jisesa/ieab065.
DOI: https://doi.org/10.1093/jisesa/ieab065

Interpretive Summary: Hawai‘i is home to exceptional biodiversity due to its insular nature, volcanism, and dynamic biogeographic history. In Hawai‘i, at least 21 non-native bees have been documented to date, joining the diversity of >9000 non-native and invasive species to the archipelago. The goal of this study is to describe the persistence, genetic diversity, and natural history of the most recently established bee to Hawai‘i, Megachile policaris (Hymenoptera: Megachilidae). We present evidence for the establishment of M. policaris across the Hawaiian archipelago and their capacity to use novel floral resources to supplement their diet. Furthermore, based on a fragment of cytochrome oxidase I, we have detected at least two distinct haplotypes of M. policaris present on Hawai‘i Island. Haplotype 1 has been detected multiple years, suggesting the species establishment in Hawai‘i. Finally, ensemble SDMs of M. policaris based on occurrence records and bioclimatic data from their historic range suggests that HS is greatest on the leeward side of the archipelago and across low elevation and high elevation habitats. However, it is also clear that our modelling approach may not capture the true flexibility of the species to invade novel bioclimatic niches outside of their natie range. The results of our study contribute to the knowledge of non-native bee ecology and persistence to Hawai‘i, and sets the groundwork for continued research on M. policaris across its native and non-native distribution.

Technical Abstract: Islands are insular environments that are negatively impacted by invasive species. In Hawai‘i, at least 21 non-native bees have been documented to date, joining the diversity of >9000 non-native and invasive species to the archipelago. The goal of this study is to describe the persistence, genetic diversity, and natural history of the most recently established bee to Hawai‘i, Megachile policaris (Hymenoptera: Megachilidae). Contemporary surveys identify that M. policaris is present on at least O‘ahu, Maui, and Hawai‘i Island, with the earliest detection of the species in 2017. Furthermore, repeated surveys and observations by community members support the hypothesis that M. policaris has been established on Hawai‘i Island from 2017 - 2020. DNA sequenced fragments of the cytochrome oxidase I locus (i.e., “barcoding gene”) identify two distinct haplotypes on Hawai‘i Island, suggesting that at least two genetic founders have colonized the island. In their native range, M. policaris is documented to forage on at least 21 different plant families, which are represented in Hawai‘i. However, the specific plant species M. policaris has been documented to forage upon in Hawai‘i increases the species richness of documented floral hosts. Finally, ensemble species distribution models (SDMs) constructed with four bioclimatic variables and occurrence data from the native range of M. policaris predicts high habitat suitability on the leeward side of islands throughout the archipelago and at high elevation habitats. While many of the observations fall within the predicted habitat suitability of M. policaris on Hawai‘i, we also detected the species on the windward side of Hawai‘i Island suggesting that the SDMs we constructed likely do not capture the bioclimatic niche flexibility of the species. In summary, our study demonstrates that M. policaris is an established bee species to Hawai‘i and will likely interact with other non-native and native bee and plant species.