Hawaiian hawksbills: a distinct and isolated nesting colony in the Central North Pacific Ocean revealed by mitochondrial DNA

Although the hawksbill turtle ( Eretmochelys imbricata ) nesting colony in Hawaiʻi may constitute one of the smallest hawksbill nesting populations in the world, it is also the largest in the U.S. Pacific Islands and the Central North Pacific Ocean. The isolated nature of the Hawaiian Archipelago has raised interest in the genetic characterization of the population, yet research remains lacking. In this study we use mitochondrial DNA (mtDNA) to provide the first genetic characterization of nesting (n = 108) and foraging (n = 29) hawksbills in the Hawaiian Islands. We combine our data with sequences previously published from the West and East Pacific to evaluate the genetic distinctiveness of the nesting assemblage in Hawaiʻi, and to gain insights into the origin of hawksbills found at foraging grounds around the archipelago. We found strong differentiation (F ST > 0.238, P-value < 0.001) between the Hawaiʻi hawksbill nesting colony and those in the West and East Pacific, indicating the Hawaiʻi nesting colony is demographically isolated and warrants recognition as a distinct management unit. We also found evidence that the Hawaiʻi nesting colony is likely the primary source of juvenile hawksbills occurring at foraging grounds around the archipelago, conforming to the natal foraging philopatry model and suggesting that hawksbills in Hawaiʻi generally constitute a closed population. Despite these findings, we also found evidence of potential dispersal of turtles from the Hawaiian nesting colony to foraging grounds in the West Pacific. This study lends insights into the life-history of hawksbills around Hawaiʻi that can facilitate effective management decision making.