A Worldwide Perspective on the Population Structure and Genetic Diversity of Bottlenose Dolphins (Tursiops truncatus) in New Zealand

Abstract

Bottlenose dolphins (Tursiops truncatus) occupy a wide range of coastal and pelagic habitats throughout tropical and temperate waters worldwide. In some regions, "inshore" and "offshore" forms or ecotypes differ genetically and morphologically, despite no obvious boundaries to interchange. Around New Zealand, bottlenose dolphins inhabit 3 coastal regions: Northland, Marlborough Sounds, and Fiordland. Previous demographic studies showed no interchange of individuals among these populations. Here, we describe the genetic structure and diversity of these populations using skin samples collected with a remote biopsy dart. Analysis of the molecular variance from mitochondrial DNA (mtDNA) control region sequences (n = 193) showed considerable differentiation among populations (F(ST) = 0.17, Phi(ST) = 0.21, P < 0.001) suggesting little or no female gene flow or interchange. All 3 populations showed higher mtDNA diversity than expected given their small population sizes and isolation. To explain the source of this variation, 22 control region haplotypes from New Zealand were compared with 108 haplotypes worldwide representing 586 individuals from 19 populations and including both inshore and offshore ecotypes as described in the Western North Atlantic. All haplotypes found in the Pacific, regardless of population habitat use (i.e., coastal or pelagic), are more divergent from populations described as inshore ecotype in the Western North Atlantic than from populations described as offshore ecotype. Analysis of gene flow indicated long-distance dispersal among coastal and pelagic populations worldwide (except for those haplotypes described as inshore ecotype in the Western North Atlantic), suggesting that these populations are interconnected on an evolutionary timescale. This finding suggests that habitat specialization has occurred independently in different ocean basins, perhaps with Tursiops aduncus filling the ecological niche of the inshore ecotype in some coastal regions of the Indian and Western Pacific Oceans.

Unexpected patterns of global population structure in melon-headed whales Peponocephala electra

“…Amos et al 1993, Oremus et al 2009, Parsons et al 2013, Martien et al 2014. Haplotypic diversity was similar to that observed in smaller delphinids such as spinner dolphins (Oremus et al 2007, Andrews et al 2010, pantropical spotted dolphins Stenella attenuata (Escorza-Trevino et al 2005), and common bottlenose dolphins (Tezanos-Pinto et al 2009, Martien et al 2012, species that also do not exhibit deep mitochondrial divergences.…”

“…The patterns of genetic differentiation in spinner dolphins and MHWs could result from long-distance dispersal of individuals among populations, or via gene flow with widespread oceanic populations (Oremus et al 2007, Tezanos-Pinto et al 2009). Large oceanic populations of MHWs are known to exist, at least within the Pacific Ocean (Brownell et al 2009b, Hamilton et al 2009), but also most likely in the Indian Ocean (Mannocci et al 2014).…”

Insights about the genetic diversity and population structure of an offshore group of common bottlenose dolphins (Tursiops truncatus) in the Mid-Atlantic

“…Caballero et al (2012) compared the haplotype network of Caribbean bottlenose dolphins with the inshore and offshore individuals of the North Atlantic, and found that haplotypes were shared between the 2 ecotypes. Tezanos-Pinto et al (2009) also observed that gene flow indicates long-distance dispersal among coastal and pelagic bottlenose dolphin populations worldwide. Galov et al (2011) assessed T. truncatus in the Croatian coast of the Adriatic Sea, using microsatellites, and suggested that the mean AR (6.835 ± 0.705) and mean H E (0.692 ± 0.05) indicated a high level of genetic diversity.…”

Population Genetics in the Conservation of Cetaceans and Primates

“…; Natoli et al 2006 ; bottlenose dolphins, Tursiops spp. ; Hoelzel et al 1998b ;Natoli et al 2004 ;Tezanos-Pinto et al 2009 ; pantropical spotted dolphins, Stenella attenuata ; Escorza-Treviño et al 2005 ; and killer whales; Hoelzel et al 2007 ). In some cases, morphological differences have evolved between these genetically differentiated coastal versus pelagic populations, indicating ecological specializations that correspond with habitat preferences (Natoli et al 2004(Natoli et al , 2006Tezanos-Pinto et al 2009 ).…”