Pathway analysis of recently established alien terrestrial arthropods in Hawai‘i

Hawai‘i is at the Crossroads of the Pacific with material originating from a vast area of the world. Those involved in Hawai‘i, U.S. and world agriculture are keenly interested in learning which pest species are or are not already established in Hawai‘i.  To address this need, we compiled a list of terrestrial arthropods that have been discovered in Hawai‘i since publication of the 2002 Hawaiian Arthropod Checklist; and determined the likely pathways used by a subset of these recently established species. We document establishment of 330 species in Hawai‘i since 2002; i.e. about 28 species per year.  However, there are significant lag times between establishment, detection and publication.  The value of intensive biological surveys at ports and other high risk areas cannot be overestimated.  Sufficient information on biology, world distribution and interceptions at ports were found to allow identification of possible pathways for 225 species.  Nearly a quarter arrived in Hawai‘i from the Old World; 17% from the Americas; 29% from either East or West; and 29% unknown.  Each of the 225 analyzed species could have been transported by more than one pathway. We conservatively identified over 700 potential pathway opportunities available to the 225 species.  Plant material (including host plants, nursery imports, cut flowers and consumable produce) was the most important pathway, followed by stowaways.  Other pathways identified were household goods, soil and potting mixtures, agriculture, pet industry, aquarium trade, host animals, smuggling, and miscellaneous.  The risk of introduction and establishment includes the number of individuals introduced, their physiological condition, the degree to which their environmental requirements match the newly invaded area and disposition of the imported material.