New publication: Population differentiation and hybridisation of Australian snubfin and Indo-Pacific humpback dolphins in north-western Australia

Home / Kimberley dolphin research project / New publication: Population differentiation and hybridisation of Australian snubfin and Indo-Pacific humpback dolphins in north-western Australia

We are pleased to announce publication of the following article in the open access journal PLOS ONE:

Population differentiation and hybridisation of Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins in north-western Australia

Authors: Alex Brown*, Anna Kopps*, Simon Allen, Lars Bejder, Bethan Littleford-Colquhoun, Guido Parra, Daniele Cagnazzi, Deborah Thiele, Carol Palmer, Celine Frère. (*co-lead authors)

The collaborative study, led by Murdoch PhD student Alex Brown and Dr. Anna Kopps (University of Groningen, Netherlands), represents the first estimates of population genetic structure of two little-know inshore dolphin species of north-western Australia. Both the Australian snubfin and Indo-Pacific humpback dolphin are listed as ‘near threatened’ by the IUCN, but a detailed assessment of their conservation status is precluded by a lack of information. This is of particular concern in the north-west of Australia, where coastal development is resulting in considerable modification of the nearshore habitats upon which these species rely. The findings of this study, which was funded by the Australian Marine Mammal Centre, provide valuable information to inform the conservation and management of these two species.

Humpback dolphins. Photo: Alex Brown.

Indo-Pacific humpback dolphins. Photo: Alex Brown.

The study found that sampled populations of both species showed significant population structure and low levels of gene flow. This suggests that they may be existing as a series of small populations with limited gene flow, making them more vulnerable to environmental change and localised extinctions compared to a single, larger population. The authors make several recommendations, including efforts to protect local populations and maintain opportunities for movement between populations.

The paper also documents the first reported hybridisation of snubfin and humpback dolphins. These coastal delphinids are sympatric throughout the the majority of their range in Australia, and aggressive and sexual interactions have been previously been observed between the two species. Genetic analyses of a small tissue sample from the hybrid dolphin, which was observed in Cygnet Bay on the Dampier Peninsula, revealed it to be the offspring of a female snubfin and male humpback dolphin. The hybrid dolphin is female, appears healthy and fully-grown, but we no nothing of her fertility at present. Several other species of cetacean have been reported to form hybrids both in the wild and captivity, but this is the first reported case between snubfin and humpback dolphins.

See a video clip of the hybrid dolphin here.

 

A composite of images comparing the dorsal proportions and head shape of the hybrid (top) alongside both snubfin and humpback dolphins.

A composite of images comparing the dorsal proportions and head shape of the hybrid (top) alongside both snubfin and humpback dolphins.

The full article is freely available from PLOS ONE here.

Abstract

Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). All sampling locations were separated by geographic distances > 200 km. For each species, we found significant genetic differentiation between sampling locations based on 12 (for snubfin dolphins) and 13 (for humpback dolphins) microsatellite loci (FST = 0.05-0.09; P < 0.001) and a 422 bp sequence of the mitochondrial control region (FST = 0.50-0.70; P < 0.001). The estimated proportion of migrants in a population ranged from 0.01 (95% CI 0.00-0.06) to 0.13 (0.03-0.24). These are the first estimates of genetic diversity and differentiation for snubfin and humpback dolphins in Western Australia, providing valuable information towards the assessment of their conservation status in this rapidly developing region. Our results suggest that north-western Australian snubfin and humpback dolphins may exist as metapopulations of small, largely isolated population fragments, and should be managed accordingly. Management plans should seek to maintain effective population size and gene flow. Additionally, while interactions of a socio-sexual nature between these two species have been observed previously, here we provide strong evidence for the first documented case of hybridisation between a female snubfin dolphin and a male humpback dolphin.

Full citation: BROWN, A., KOPPS, A. M., ALLEN, S. J., BEJDER, L., LITTLEFORD-COLQUHOUN, B., PARRA, G. J., CAGNAZZI, D., THIELE, D., PALMER, C. & FRÈRE, C. (2014). Population differentiation and hybridisation of Australian snubfin and Indo-Pacific humpback dolphins in north-western Australia. PLOS ONE 9(7): e101427. doi:10.1371/journal.pone.0101427

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