Genetic differentiation between parapatric ‘nearshore’ and ‘offshore’ populations of the bottlenose dolphin

Abstract

The existence of nearshore and o¡shore populations of the bottlenose dolphin has been documented throughout its range. In several cases the two regional forms have been shown to be morphologically distinct, although there is considerable overlap for most characters. The populations o¡ the eastern coast of North America have been the subject of a long-term programme of research on their distribution and movements. In this study, we compare mitochondrial and nuclear genetic markers between dolphins classi¢ed as either nearshore or o¡shore type. These putative populations were found to be distinct at both nuclear and mitochondrial genetic markers. Further, the level of variation among the nearshore dolphins was reduced compared with the o¡shore population. A broader geographical comparison suggests a shared lineage between o¡shore dolphins from the western North Atlantic and both o¡shore and nearshore dolphins from the eastern Atlantic. These results are consistent with local di¡erentiation based on habitat or resource specialization in the western North Atlantic, and suggest di¡erences in the character of the nearshore/o¡shore distinction in di¡erent parts of the world.

Emergence of a novel prey life history promotes contemporary sympatric diversification in a top predator

“…Top predators can drive diversification of prey 20,21 and help maintain biodiversity 22 . It is typically assumed that apex predators display little phenotypic variation, but there is emerging evidence for rich phenotypic diversity and ecotype formation of predators at the top of multiple food webs 23,24 . Yet, the factors promoting this diversity are largely unknown, perhaps because studying large top predators is very difficult on any scale smaller than the whole ecosystem.…”

Phenotypic variation in dorsal fin morphology of coastal bottlenose dolphins (Tursiops truncatus) off Mexico

“…Also, the dorsal fin is the only appendage that is constantly exposed to 63 ambient air, and thus is subject to different thermoregulatory conditions from the rest of the body 64 Westgate et al, 2007;Barbieri et al, 2010). (Walker, 1981; 68 Vidal, 1993;Gao et al, 1995;Goodwin et al, 1996;Hoelzel et al, 1998; Turner and Worthy, 69 1998;. Polyphenisms in traits whose functions arose as adaptations to new life 70 conditions (e.g.…”

Molecular insight into the population structure of common and spotted dolphins inhabiting the pelagic waters of the Northeast Atlantic

“…in Tursiops sp. : Hoelzel et al 1998b;Krützen et al 2004). Even though it was not possible to obtain reliable estimates of the amount of gene flow, our results indicated that gene flow was sufficient to prevent differentiation within and between archipelagos in common and spotted dolphins at the scale of the study area.…”

“…Fourteen polymorphic dinucleotide microsatellite loci were analysed: d08, d22 (Shinohara et al 1997), EV14, EV37 Amos 1996), FCB1, FCB17 (Buchanan et al 1996), Kwm2a, Kwm12a, Kwm9b (Hoelzel et al 1998b), Mk6, Mk8 (Krützen et al 2001), Sw10, Sw19 (Richard et al 1996) and TexVet5 (Rooney et al 1999). Loci TexVet5 and Kwm2a were not analysed in S. frontalis because they failed to amplify.…”

“…South Pacific spinner dolphins, Stenella longirostris, Oremus et al 2007) or ecological specialisation in relation with habitat features (e.g. killer-whales, Orcinus orca, Hoelzel et al 1998a; common bottlenose dolphins, Tursiops truncatus, Hoelzel et al 1998b;Natoli et al 2004, pantropical spotted dolphins, Stenella attenuata, Escorza-Treviño et al 2005). In the latter case, forms specialised for different habitats (called "ecotypes") are often both genetically and morphologically differentiated (e.g.…”