Patterns of genetic diversity of the Hawaiin spinner dolphin (Stenella longirostris)

Abstract

We used population genetic analyses to investigate the genetic structure of the Hawaiian spinner dolphin (Stenella longirostris). Genetic samples were collected from spinner dolphins at locations across the Hawaiian Archipelago: Kure Atoll (n=34), Midway Atoll (n=57), Pearl & Hermes Reef (n=21), French Frigate Shoals (n=15), Ni'ihau (n=39), O'ahu (n=47), Maui/Lana'i (n=60), and the Big Island of Hawai'i (n=77). A 429-base-pair region of the mitochondrial DNA control region was used to evaluate genetic diversity and population structure. Peaks in genetic diversity were found at the Big Island of Hawai'i (π=0.0082) and French Frigate Shoals (π=0.0072), and genetic diversity was reduced at the three most northwestern Hawaiian atolls (Kure Atoll π=0.0025, Midway Atoll π=0.0019, and Pearl & Hermes Reef π=0.0017). Analysis of Molecular Variance (AMOVA) and exact tests of population subdivision indicated significant genetic structure for the spinner dolphin within Hawai'i. With few exceptions, dolphins at every island were found to be significantly genetically differentiated from dolphins at every other island for one or more tests of population subdivision (FST or ΦST ≥ 0.02, p < 0.05). Exceptions included dolphins at Kure Atoll, Midway Atoll, and Pearl & Hermes Reef, which together seemed to form one interbreeding group, distinct from the rest of the Archipelago. Dolphins at O'ahu were also an exception in that they were not differentiated significantly from dolphins at Kure Atoll, Midway Atoll, or Pearl & Hermes Reef.