Origin and radiation of Southern Hemisphere coastal dolphins (genus Cephalorhynchus)

Abstract

The genus Cephalorhynchus (Gray 1846) consists of four species of small coastal dolphins distributed in cool temperate waters around the Southern Hemisphere. Each species is sympatric with other members of the subfamily Lissodelphininae but widely separated from other congeners. To describe the origin and radiation of these species, we examined 442 bp of mitochondrial DNA control region sequences of 307 individuals from the genus Cephalorhynchus and compared these to sequences from other members of the subfamily Lissodelphininae. We investigate the hypotheses that Cephalorhynchus is a monophyletic genus or, alternatively, that the four species have arisen separately from pelagic Lissodelphine species and have converged morphologically. Our results support the monophyly of Cephalorhynchus within the Lissodelphininae and a pattern of radiation by colonization. We confirm a pattern of shallow but diagnosable species clades with Heaviside's dolphin as the basal branch. We further examine the monophyly of maternal haplotypes represented by our large population sample for each species. Based on this phylogeographic pattern, we propose that Cephalorhynchus originated in the waters of South Africa and, following the West Wind Drift, colonized New Zealand and then South America. The Chilean and Commerson's dolphins then speciated along the two coasts of South America, during the glaciation of Tierra del Fuego. Secondary radiations resulted in genetically isolated populations for both the Kerguelen Island Commerson's dolphin and the North Island Hector's dolphin. Our results suggest that coastal, depth-limited odontocetes are prone to population fragmentation, isolation and occasionally long-distance movements, perhaps following periods of climatic change.

Mitochondrial DNA variation and population structure of Commerson’s dolphins (Cephalorhynchus commersonii) in their southernmost distribution

“…2, 3). A small number of sequence errors were detected in the previous haplotypes of Pichler et al (2001). The original electropherograms of these were reviewed and the submitted sequences have now been corrected (Supplementary Material).…”

“…No heteroplasmy, either in the nucleotide sequence or in the length of the amplified fragments was detected. Five of the 20 haplotypes had been identified previously by Pichler et al (2001) and the 15 new haplotypes were submitted to GenBank (Accession numbers HM368538-HM368552). One (C.com-M) of the three haplotypes found previously by Pichler et al (2001) only from the Kerguelen Islands was represented by a single individual in the larger sample from South America presented here (Figs.…”

“…All Cephalorhynchus species are characterized by relatively low abundance (\10 4 ) and all are subjected to some degree of incidental or directed mortality in fishing nets (Dawson 1991;Goodall et al 1988aGoodall et al , b, 1994Pichler et al 2001;Best 2007). Species of the genus Cephalorhynchus also have relatively low reproductive rates (Lande 1991;Slooten 1991), and appear to be depth-limited coastal species with small home ranges (Bräger et al 2002).…”

Bayesian inference of cetacean phylogeny based on mitochondrial genomes

“…It has been widely accepted that Balaenidae is the basal group of Mysticeti (Arnason et al 1992;Milinkovitch et al 1994;Arnason & Gullberg 1996;Rychel et al 2004;Sasaki et al 2005;May-Collado & Agnarsson 2006;Nishida et al 2007). However, some issues remain controversial: the relationships among the groups within Odontoceti and Mysticeti (Adegoke et al 1993;Milinkovitch et al 1993;Rosel et al 1995;Arnason & Gullberg 1996;Waddell et al 2000;Nikaido et al 2001;Pichler et al 2001), and the relationships among several subgroups within Balaenopteridae (Arnason et al 1992;Adegoke et al 1993;Arnason & Gullberg 1994Messenger & McGuire 1998).…”

Review of the occurrence of multiple pulse echolocation clicks in recordings from small odontocetes

“…All the members of this genus have habitats that are confined or nearly confined to shallow waters [17]. This genus comprised the following animals: Commerson's dolphin (Cephalorhynchus commersonii), Hector's dolphin (Cephalorhynchus hectori), the Chilean/ [18]. The other species that are discussed in this paper are northern hemisphere members of the family Phocoenidae which includes the finless porpoise (Neophocoena phocaena) and Dall's porpoise (Phocoena dalli).…”