Award: OCE-1558852

When the Polynesians colonized Hawaii about 1200 years ago, they found a lush tropical paradise, but they could have found bare rock instead. The Hawaiian Archipelago has a volcanic origin, which means in their original form, these islands were lifeless rock rising out of the ocean. Every form of life in this biodiversity hotspot had to come from somewhere else. The overall goal of this project was to resolve the origins of Hawaiian reef fishes, using a combination of field efforts, archival information, and molecular genetic data. Intellectual Merit: We show that reef fishes colonized into the Hawaiian Archipelago through multiple pathways at multiple times. We have evidence of colonization from reefs south of Hawaii, including Johnston Atoll and Line Islands. We also have evidence of colonization from reefs west of Hawaii, especially the Japanese Archipelago. Most of this colonization was in the Pleistocene (last two million years), but a few colonization events are older, on the order of 10 million years. Broader Impact: The pathways of colonization into Hawai’i are important from a conservation perspective. In particular, Johnston Atoll, the closest shallow habitat south of the Hawaiian Archipelago, is a gateway into Hawai’i. Johnston was a nuclear test site in the 1960s, resulting in heavy plutonium contamination that was dumped (as topsoil) into the lagoon. Subsequently this atoll was used to test biological weapons, then was a storage facility for 25 000 barrels of the defoliant ‘agent orange’ (used in the Vietnam War from 1961 to 1971) and nerve gas, both of which leaked into the environment. In the years 1990–2001, it was a chemical weapons disposal site for the United States, to eliminate nerve gas that had been banned by international treaty. Chemical contamination is believed to be the cause of developmental abnormalities in resident reef fishes, and the cumulative effects are postulated to be the reason why marine mammals are rare at Johnston Atoll. In sum, Johnston Atoll was subject to severe environmental insults over the last century, and it turns out to be an essential gateway for biodiversity to colonize into Hawai’i. During each expedition we make it a priority to present our research to the community. In Kiritimati, a very rural and small community, much of our dissemination was through conversations at evening social events with the fishermen and other people we encountered. In Japan on the other hand, we were able to put together a well attended and advertised presentation that lasted about an hour and resulted in many questions. Additionally, we participated in three episodes of The Voice of the Sea, a TV production that is broadcast across the Pacific. These episodes explain in layman's terms why it matters where our Hawaiian biodiversity comes from. This project supported two graduate student dissertations and provides funding for two more graduate student projects. They have been trained in all aspects of field work and lab-based DNA data production. The senior graduate student on this project, Joshua Copus, perished in a diving accident in November 2019. Amazingly his partner is still on track to complete a Ph.D., despite being a single mother with two young children. This would not have been possible without NSF support. Last Modified: 05/11/2022 Submitted by: Brian W Bowen