First report of the introduced isopod Ligia exotica Roux, 1828 in rocky intertidal habitats of Midway Atoll, Papahānaumokuākea Marine National Monument as confirmed by morphological and molecular approaches.

The Papahānaumokuākea Marine National Monument (PMNM) is one of the world's largest marine protected areas and covers marine habitats as well as the islands and atolls of the Northwestern Hawaiian Islands. Despite its protected status, the biodiversity of the PMNM face several threats to its preservation, including the presence of introduced species. Given its history as a shipping and military outpost, Midway Atoll represents a potential entry point for introduced species to the PMNM. Thus, monitoring for new introduced species in Midway is of importance for the management and preservation of the PMNM. In this study, we use morphological and molecular approaches to confirm the presence of the coastal isopod Ligia exotica, a species of Asian origin that has been introduced to coastlines around the world, in Midway Atoll and thus the PMNM. The presence of L. exotica in Midway Atoll is of concern as islands of this marine monument harbor endemic species of Ligia isopods. [ABSTRACT FROM AUTHOR]