Inter-Research > ESR > Prepress Abstract

ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01147

Low mitochondrial genetic diversity in the Indian Ocean humpback dolphin Sousa plumbea in South African waters

Sarah Lampert, Robert A. Ingle, Jennifer A. Jackson, Keshni Gopal, Stephanie Plön*

*Corresponding author:

ABSTRACT: The Indian Ocean humpback dolphin (Sousa plumbea) has been described as South Africa’s most endangered marine mammal due to its low abundance, reliance on coastal habitats with increasing anthropogenic threats, and high rates of mortality from bycatch in bather protection nets (BPN). Although the species is well studied in South Africa, only a single study has examined its molecular ecology to date, and the species’ population structure remains poorly understood. However, an understanding of population structure is vital for the conservation and management of a species. To address these research gaps for S. plumbea in South African waters, we analysed the mitochondrial D-loop of 157 museum skin and tooth samples collected between 1963 and 2017 from across the species’ geographic range in South Africa. Our data show that the humpback dolphin has extremely low mitochondrial diversity (haplotype diversity, HD = 0.47; nucleotide diversity, π =0.2%), with only three haplotypes identified, which is comparable to the critically endangered Māui dolphin Cephalorhynchus hectori maui and the critically endangered Mekong population of Irrawaddy dolphin Orcaella brevirostris. Mitochondrial genetic diversity has not changed significantly in the last 50 years, despite the high levels of bycatch in BPN over this time period. Furthermore, we found no evidence of differentiation between dolphins from the KwaZulu-Natal Coast and the Cape South Coast (Western Cape and Eastern Cape). The extremely low mitochondrial diversity we found adds to the growing body of evidence that the humpback dolphin is becoming increasingly vulnerable and that urgent conservation efforts are required for the survival of the species.