First mainland records of an unusual island bee (Anthophora urbana clementina) highlight the value of community science for adventive species monitoring Michael C. Orr1+, Keng-Lou James Hung2,3+, Erin E. Wilson Rankin4, Patricia M. Simpson5, Douglas Yanega4, John S. Ascher6 +Authors contributed equally Authors for correspondence: michael.christopher.orr@gmail.com, kenglou.hung@gmail.com 1Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China 2Department of Ecology and Evolutionary Biology, University of Toronto, Ontario, Canada 3Current address: Oklahoma Biological Survey, University of Oklahoma, Norman, OK, USA 4Department of Entomology, University of California, Riverside, California, USA 5Independent researcher 6Department of Biological Sciences, National University of Singapore, Singapore Abstract Although islands are often invaded by mainland species, sometimes the reverse occurs. Here, we report multiple individuals of the distinctively orange-colored San Clemente Island-endemic Anthophora urbana clementina found by community scientists in mainland California, USA, and hypothesize that naval or other marine transport is the most probable route of invasion. Further, we discuss the overarching importance of community science for exotic species discovery and monitoring, relations of the mainland and island forms and faunas, and the implications of this finding and potential invasion dynamics for the other species of San Clemente Island and the California Channel Islands in general, informed by an updated checklist of bee species on San Clemente compiling literature, specimen, and community science records of species and morphospecies.