Taxonomic revision of the dolphin genusLagenorhynchus

Abstract

Evolutionary relationships among cetaceans within the family Delphinidae have been difficult to resolve due to the high number of species and their relatively rapid radiation. This is the case for the dolphin species currently placed in the genus Lagenorhynchus, and their relations to Cephalorhynchus and Lissodelphis species. Phylogenetic relationships among these species have been investigated using multiple lines of evidence, and that evidence consistently suggests that the six species currently assigned to Lagenorhynchus do not form a monophyletic group. Here, we summarize findings from studies of morphology, genetics, historical biogeography, and acoustics that offer insight into the phylogenetics of these taxa. We present the taxonomic basis for revision of Lagenorhynchus, propose retention of Lagenorhynchus albirostris and reassignment of the remaining five species into other existing generic names, namely Leucopleurus acutus, Sagmatias australis, Sagmatias cruciger, Sagmatias obliquidens, and Sagmatias obscurus. Making these revisions now so that the taxonomy better reflects evolutionary relationships among these species will ensure that future studies include the most appropriate taxa for investigating the 1 957 complex phylogenetic and systematic relationships among cetaceans. However, comprehensive analyses using multiple lines of evidence are still needed to clarify the phylogenetic relationships within and among the Lissodelphininae genera Cephalorhynchus, Lissodelphis, and Sagmatias.

3D genital shape complexity in female marine mammals

“…The pygmy sperm whale ( Kogia breviceps ) vagina was the most complex, with multiple deep protrusions of the vaginal wall. Although the genus Lagenorhynchus is no longer considered monophyletic (Vollmer et al., 2019), Pacific white‐sided dolphin ( Sagmatias obliquidens ), dusky dolphins ( Sagmatias obscurus ), and white‐beaked dolphins ( Lagenorhynchus albirostris ) were comparatively complex (Figure 1). The orca ( Orcinus orca) , Blainville's beaked whale ( Mesoplodon densirostris ), and two species of common dolphin ( Delphinus capensis and D. delphis ), had comparatively simple vaginal lumens.…”

“…The pygmy sperm whale (Kogia breviceps) vagina was the most complex, with multiple deep protrusions of the vaginal wall. Although the genus Lagenorhynchus is no longer considered monophyletic (Vollmer et al, 2019), Pacific white-sided dolphin (Sagmatias obliquidens), dusky dolphins (Sagmatias obscurus), and white-beaked dolphins (Lagenorhynchus albirostris) were comparatively complex (Figure 1).…”

Vertebral Morphology in Partially Sympatric Dolphins: A 3D Approach

“…Phylogenetic relationships and species names within the subfamily Lissodelphininae are still a matter of debate, with some genera currently recognized as being polyphyletic (Figure 5; see Vollmer et al, 2019;Committee on Taxonomy, 2020;McGowen et al, 2020). One group consisting of sister species, the Pacific white-side dolphin (Lagenorhynchus obliquidens) and the dusky dolphin, is well distinguished from the clade formed by Cephalorhynchus spp., Peale's dolphin, and the hourglass dolphin; these latter being sister species (Figure 1).…”

“…It is expected that sympatric species should show behavioral and physiological strategies and accompanying morphological adaptations that minimize competition and maximize the possibility of occupying different niches (see Gross et al, 2009). Commerson's dolphin (Cephalorhynchus commersonii), Peale's dolphin (Lagenorhynchus australis), the dusky dolphin (Lagenorhynchus obscurus) and the hourglass dolphin (Lagenorhynchus cruciger) are closely related species belonging to the subfamily Lissodelphininae (Figure 1; see Vollmer et al, 2019;Committee on Taxonomy, 2020;McGowen et al, 2020). They inhabit the Southern Hemisphere with partially sympatric distributions overlapping in different areas of their geographic ranges but differing in their habitat preferences.…”

Disentangling Natural and Anthropogenic Forms of Mortality and Serious Injury in a Poorly Studied Pelagic Dolphin

“…Killer whales prey on more than 20 cetacean species (Jefferson et al, 1991). One small cetacean prey species of mammal-eating killer whales in the North Pacific Ocean is the Pacific white-sided dolphin [Lagenorhynchus obliquidens, but see Vollmer et al (2019)]. Killer whale populations have developed an array of foraging tactics to exploit particular prey species [e.g., carousel feeding on herring (Clupea harengus) in Norway (Simila and Ugarte, 1991), intentional stranding to capture seals (Lopez and Lopez, 1985;Guinet, 1991), and "wave-washing" seals off ice floes (Visser et al, 2008;Pitman and Durban, 2012)].…”