title: Large-scale introduction of the Indo-Pacific damselfish Abudefduf vaigiensis into Hawai'i promotes genetic swamping of the endemic congener A. abdominalis.
abstract: Hybridization in the ocean was once considered rare, a process prohibited by the rapid evolution of intrinsic reproductive barriers in a high-dispersal medium. However, recent genetic surveys have prompted a reappraisal of marine hybridization as an important demographic and evolutionary process. The Hawaiian Archipelago offers an unusual case history in this arena, due to the recent arrival of the widely distributed Indo-Pacific sergeant (Abudefduf vaigiensis), which is hybridizing with the endemic congener, A. abdominalis. Surveys of mtDNA and three nuclear loci across Hawai'i (N = 396, Abudefduf abdominalis and N = 314, A. vaigiensis) reveal that hybridization is significantly higher in the human-perturbed southeast archipelago (19.8%), tapering off to 5.9% in the pristine northwest archipelago. While densities of the two species varied throughout Hawai'i, hybridization was highest in regions with similar species densities, contradicting the generalization that the rarity of one species promotes interspecific mating. Our finding of later generation hybrids throughout the archipelago invokes the possibility of genetic swamping of the endemic species. Exaptation, an adaptation with unintended consequences, may explain these findings: the endemic species has transient yellow coloration during reproduction, whereas the introduced species has yellow coloration continuously as adults, in effect a permanent signal of reproductive receptivity. Haplotype diversity is higher in Hawaiian A. vaigiensis than in our samples from the native range, indicating large-scale colonization almost certainly facilitated by the historically recent surge of marine debris. In this chain of events, marine debris promotes colonization, exaptation promotes hybridization, and introgression invokes the possible collapse of an endemic species.
authors.affiliation: Hawai'i Institute of Marine Biology, University of Hawai'i, P.O. Box 1346, Kaneohe, HI, 96744, USA; Department of Biology, University of Hawai'i, Mānoa, 2450 Campus Road, Dean Hall Room 2, Honolulu, HI, 96822, USA.
authors.forename: Richard R
authors.initials: RR
authors.lastname: Coleman
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Gaither
authors.forename: Bethany
authors.initials: B
authors.lastname: Kimokeo
authors.forename: Frank G
authors.initials: FG
authors.lastname: Stanton
authors.forename: Brian W
authors.initials: BW
authors.lastname: Bowen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Toonen
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D005828:Genetics, Population; D006254:Hawaii; D006824:Hybridization, Genetic; D058865:Introduced Species; D007438:Introns; D008969:Molecular Sequence Data; D010473:Perciformes / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: Papahānaumokuākea; hybridization; marine debris; newhybrids; population density; structure