Genetic diversity of bottlenose dolphin (Tursiops sp.) populations in the western North Pacific and the conservation implications

Shin Nishida,A Rus Hoelzel,Ing Chen,Yuko Tajima,Tomohiko Isobe,Wei-Cheng Yang

doi:10.1007/s00227-017-3232-8

Abstract

The evolutionary processes that shape patterns of diversity in highly mobile marine species are poorly understood, but important towards transferable inference on their effective conservation. In this study, bottlenose dolphins (Tursiops sp.) are studied to address this broader question. They exhibit remarkable geographical variation for morphology, life history, and genetic diversity, and this high level of variation has made the taxonomy of the genus controversial. A significant population structure has been reported for the most widely distributed species, the common bottlenose dolphin (T. truncatus), in almost all ocean basins, though no data have been available for the western North Pacific Ocean (WNP). The genetic diversity of bottlenose dolphins in the WNP was investigated based on 20 microsatellite and one mitochondrial DNA markers for samples collected from Taiwanese, Japanese, and Philippine waters (9°–39°N, 120°–140°E) during 1986–2012. The results indicated that there are at least four genetically differentiated populations of common bottlenose dolphins in the western and central North Pacific Ocean. The pattern of differentiation appears to correspond to habitat types, resembling results seen in other populations of the same species. Our analyses also showed that there was no evident gene flow between the two “sister species”, the common bottlenose dolphins, and the Indo-Pacific bottlenose dolphins (T. aduncus) occurring sympatrically in our study region.

Highlights

A wildlife management unit is usually defined by the significance of morphological, genetic, or demographic differences among populations, often associated with geographic barriers or distance (e.g. Allendorf and Luikart 2006)
Sixty-six CBD and seven IPBD tissue samples collected from various locations in Japan, Taiwan, and the Philippines were included in this study
The clear differentiation between the Hawaiian Islands and Palmyra Atoll populations has been reported in the original paper (Martien et al 2012); here, our analysis further reveals that Hawaiian Islands and Palmyra Atoll populations were differentiated from the western North Pacific Ocean (WNP) populations

Summary

Introduction

A wildlife management unit is usually defined by the significance of morphological, genetic, or demographic differences among populations, often associated with geographic barriers or distance (e.g. Allendorf and Luikart 2006). In our study region in the western North Pacific Ocean (WNP), two species of dolphins in the genus Tursiops have been recognized: the Indo-Pacific bottlenose dolphin (T. aduncus; hereinafter IPBD) and the common bottlenose dolphin (T. truncatus; hereinafter CBD). These two species are distributed parapatrically, or even sympatrically in particular areas. The distribution of IPBD is in the coastal waters of warm-temperate-to-tropical Indo-Pacific regions from southern Japan to western South Africa and southeastern Australia, where the water depth is always less than 200 m (Wang and Yang 2009). The broader taxonomy of the genus remains unresolved, the alpha taxonomy of IPBD and CBD is well supported (LeDuc et al 1999; Wang et al 1999, 2000; Hale et al 2000; Kemper 2004; Natoli et al 2004; Yang et al 2005; Kurihara and Oda 2007; Moura et al 2013)

Methods

Results

Conclusion