Chapter 2 - Dusky Dolphin Life History and Demography

Abstract

With five other dolphin species, dusky dolphins (Lagenorhynchus obscurus), are currently classified in the genus Lagenorhynchus, but that is likely to change in the near future once the details are better understood. Analysis of full-length cytochrome b DNA sequences by LeDuc and coauthors gave the first evidence that the current naming scheme, which implies that all six species are closely related by placing them in a single genus, is incorrect. Although the final assignment of genus names to the species awaits detailed study and formal taxonomic review and publication, the new understanding of evolutionary relationships within this group has been recognized in several recent papers, which place all but the two North Atlantic species into subfamily Lissodelphininae. Morphological evidence suggests differentiation, possibly at the subspecies level, between geographically distinct dusky dolphin populations. Molecular data provide further evidence for significant differentiation. There is tantalizing evidence that dusky dolphins from Argentina and Southern Africa recently separated from an ancestral Atlantic population, although not all agree with this conclusion and instead suggest a Pacific/Indian Ocean source population. Formal taxonomic consideration of subspecies status awaits concentrated study utilizing both morphological and molecular analysis.