title: Diversification of sympatric broadcast-spawning limpets (Cellana spp.) within the Hawaiian archipelago.
abstract: Speciation remains a central enigma in biology, and nowhere is this more apparent than in shallow tropical seas where biodiversity rivals that of tropical rainforests. Obvious barriers to gene flow are few and most marine species have a highly dispersive larval stage, which should greatly decrease opportunities for speciation via geographic isolation. The disparity in the level of geographic isolation for terrestrial and marine species is exemplified in Hawai'i where opportunities for allopatric speciation abound in the terrestrial realm. In contrast, marine colonizers of Hawai'i are believed to produce only a single endemic species or population, due to the lack of isolating barriers. To test the assertion that marine species do not diversify within Hawai'i, we examine the evolutionary origin of three endemic limpets (Cellana exarata, C. sandwicensis and C. talcosa) that are vertically segregated across a steep ecocline on rocky shores. Analyses of three mtDNA loci (12S, 16S, COI; 1565bp) and two nDNA loci (ATPSβ, H3; 709bp) in 26 Indo-Pacific Cellana species (N=414) indicates that Hawai'i was colonized once ∼3.4-7.2Ma from the vicinity of Japan. Trait mapping demonstrates that high-shore residence is the ancestral character state, such that mid- and low-shore species are the product of subsequent diversification. The Hawaiian Cellana are the first broadcast-spawners demonstrated to have speciated within any archipelago. The habitat stratification, extensive sympatry, and evolutionary history of these limpets collectively indicate a strong ecological component to speciation and support the growing body of evidence for non-allopatric speciation in the ocean.
authors.affiliation: Hawai'i Institute of Marine Biology, School of Ocean and Earth Sciences, University of Hawai'i at Mānoa, PO Box 1346, Kāne'ohe, HI 96744, USA. cbird@hawaii.edu
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Bird
authors.forename: Brenden S
authors.initials: BS
authors.lastname: Holland
authors.forename: Brian W
authors.initials: BW
authors.lastname: Bowen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Toonen
mesh_terms: D000483:Alleles; D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics; D049851:Gastropoda / Q000145:classification / Q000235:genetics*; D051456:Gene Flow / Q000235:genetics; D049810:Genetic Speciation; D006239:Haplotypes / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny
chemical_list: D004272:DNA, Mitochondrial