Right Whale - Taxonomy

Taxonomy

The right whales were first classified in the Balaena genus in 1758 by Carolus Linnaeus, who at the time considered all of the right whales (including the bowhead) as a single species. Through the 1800s and 1900s, in fact, the Balaenidae family has been the subject of great taxonometric debate. Authorities have repeatedly recategorized the three populations of right whale plus the bowhead whale, as one, two, three or four species, either in a single genus or in two separate genera. In the early whaling days, they were all thought to be a single species, Balaena mysticetus. Eventually, it was recognized that bowheads and right whales were in fact different, and John Edward Gray proposed the Eubalaena genus for the right whale in 1864. Later, morphological factors such as differences in the skull shape of northern and southern right whales indicated at least two species of right whale—one in the Northern Hemisphere, the other in the Southern Ocean. As recently as 1998, Rice, in his comprehensive and otherwise authoritative classification, Marine mammals of the world: systematics and distribution, listed just two species: Balaena glacialis (the right whales) and Balaena mysticetus (the bowheads).

In 2000, Rosenbaum et al. disagreed, based on data from their genetic study of DNA samples from each of the whale populations. Genetic evidence now clearly demonstrates that the northern and southern populations of right whale have not interbred for between 3 million and 12 million years, confirming the southern right whale is a distinct species. What some scientists found more surprising was the discovery that the Northern Hemisphere Pacific and Atlantic populations are also distinct, and that the North Pacific species is more closely related to the southern right whale than to the North Atlantic right whale.

In 2001, Brownell et al. re-evaluated the conservation status of the North Pacific right whale as a distinct species, and in 2002, the Scientific Committee of the International Whaling Commission (IWC) accepted Rosenbaum's findings, and recommended that the Eubalaena nomenclature be retained for this genus. A 2007 study by Churchill provided further evidence to conclude the three living right whale species do comprise a phylogenetic lineage, distinct from the bowhead, and are rightly classified into two separate genera.

The cladogram is a tool for visualizing and comparing the evolutionary relationships between taxa; the point where each node branches is analogous to an evolutionary branching – the diagram can be read left-to-right, much like a timeline. The following cladogram of the Balaenidae family serves to illustrate the current scientific consensus as to the relationships between the three right whales and the bowhead whale.

Whale lice, parasitic cyamid crustaceans that live off skin debris, offer further information through their own genetics. Because these lice reproduce much more quickly than whales, their genetic diversity is greater. Marine biologists at the University of Utah examined these louse genes and determined their hosts split into three species 5–6 million years ago, and these species were all equally abundant before whaling began in the 11th century. The communities first split because of the joining of North and South America. The rising temperatures of the equator then created a second split, into northern and southern groups, preventing them from interbreeding. "This puts an end to the long debate about whether there are three species of right whale. They really are separate beyond a doubt", Jon Seger, the project's leader, told BBC News.