Abstract

Subspecies recognition can affect how people (scientists and non-scientists alike) view organisms and thus has important implications for research on, as well as the conservation of, these entities. Recently, a small group of Indo-Pacific humpback dolphins was discovered inhabiting the waters off central western Taiwan. This geographically isolated population possesses pigmentation patterns that are subtly, but noticeably, different from their nearest conspecifics in the neighbouring waters of the Jiulong River Estuary and Pearl River Estuary of mainland China. Due to this population's low and declining numbers and the numerous threats it faces, it was assessed as critically endangered by the Red List of Threatened Species of the International Union for Conservation of Nature. The purpose of this study is to examine the degree of differentiation of the Taiwanese population to determine if subspecies recognition iswarranted. Analysis of the degree of differentiation in pigmentation patterns revealed nearly non-overlapping distributions between dolphins from Taiwanese waters and those from the Jiulong River + Pearl River estuaries of mainland China (the nearest known populations). The Taiwanese dolphins were clearly diagnosable from those of the Jiulong River + Pearl Riverestuaries under the most commonly accepted '75%rule' for subspecies delimitation (with 94% of one group being separable from 99+% of the other). Evidence of geographical isolation and behavioural differences also provided additional support for the distinctiveness of the Taiwanese dolphins. Together, the evidence strongly demonstrated that the Taiwanese humpback dolphin population is differentiated at the subspecies level and on an evolutionary trajectory that is independent from that of dolphins from adjacent waters of mainland China (i.e. Jiulong River + Pearl River estuaries). As a result, the taxonomy of Sousa chinensis was revised to include two subspecies: the Taiwanese humpback dolphin, Sousa chinensis taiwanensis subsp. nov., and the Chinese humpback dolphin, Sousa chinensis chinensis (the nominotypical subspecies). These subspecies are described, and the holotype and paratype specimens for S. c. taiwanensis are established.

Highlights

  • IntroductionSubspecies recognition can affect how people (scientists and non-scientists alike) view organisms and has important implications for research on, as well as the conservation of, these entities

  • Subspecies recognition can affect how people view organisms and has important implications for research on, as well as the conservation of, these entities

  • The discriminant analysis showed very clear separation of the Taiwanese dolphins from the Jiulong River Estuary + Pearl River Estuary dolphins (Wilk’s lambda = 0.307, F2,245 = 276.25, p < 0.0001) with very little overlap (Figure 3) and provided more confirmation that the Taiwanese dolphins were differentiated. [Note: a discriminant analysis was conducted on the original data, without the new specimens, which were reserved for cross-validation of the classification functions

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Summary

Introduction

Subspecies recognition can affect how people (scientists and non-scientists alike) view organisms and has important implications for research on, as well as the conservation of, these entities. A small group of Indo-Pacific humpback dolphins was discovered inhabiting the waters off central western Taiwan This geographically isolated population possesses pigmentation patterns that are subtly, but noticeably, different from their nearest conspecifics in the neighbouring waters of the Jiulong River Estuary and Pearl River Estuary of mainland China. The subspecies category is the only non-species taxonomic rank that is accompanied by formal taxonomic treatment, scientific (trinomial) naming and establishment of type specimens, and recognized and governed by the International Code of Zoological Nomenclature (ICZN 1999). In this regard, it is treated to species. Ignoring subspecies designations because of personal philosophy can be damaging to the conservation of some taxa because they may not receive the same recognition and attention as distinct taxa that possess trinomial names

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