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Hidden in plain sight: Humpback dolphin species

Not all new species are found in previously unexplored areas; sometimes a new species is hidden in plain sight and revealed with further study.
STEPHANIE PLON: Cetacean taxonomy is very much in flux or has been in flux in the last few years, mainly because of an advancement in technology and analytical techniques in molecular sciences. And we’re seeing a lot of taxonomic revisions at the moment. One example for these is the humpback dolphin which has recently been reclassified into four different species. So it’s the genus Sousa. And remember the definition of a species is that the animals don’t really interbreed and produce viable offspring so we’re not looking at different populations, but we’re really talking about different species. One species has been described from the south Atlantic Ocean, that’s Sousa teuszii.
The second species in the west and northern part of the Indian Ocean so it’s found off South Africa, here’s Sousa plumbea. The third species is more found in towards the Asian side of the Indian Ocean and is called Sousa chinensis. And the fourth species is really in the Pacific region of Australia and it’s Sousa sahulensis. Humpback dolphins are very interesting because they’re a very coastal group of species. They are all found within 500 metres of the shore and, therefore, they are probably very impacted by activities in the coastal zone, mainly human impacts or anthropogenic impacts.
And all of these four species are threatened to a certain degree, and that really highlights the importance of recognising them as separate species and putting them on different levels of protection. Because those coastal species, more than the offshore or oceanic species, are really more impacted by our activities in the coastal zone. So the Graham Ross Marine mammal collection of the Port Elizabeth Museum is the largest marine mammal collection in the southern hemisphere and one of the largest globally. And it’s an important collection for certain taxa, for example, beaked whales and humpback dolphins. And I have a skull of a humpback dolphin here. Recently, four different species were described in this genus, Sousa.
And one of the lines of evidence that was used to describe these different species was skull morphometrics. So what that means is that scientists went and measured the distance between the different landmarks of the skull and compared them across the range of the genus. And basically, based on that evidence and on genetic evidence, they found that there are currently four different species of this genus globally.

Not all new species are found in previously unexplored areas; sometimes a new species is hidden in plain sight and revealed with further study.

New fossil species are occasionally found in museum collections. They may have been originally misidentified but closer inspection can reveal morphological differences that mark the specimen out as a distinct species. In the case of modern plants and animals, advances in the field of genetics and molecular sciences, and the techniques used to study them, have led to new discoveries in environments that humans have already explored.

In this video Stephanie describes recent research undertaken by another international team of scientists. By examining genetical and morphological features, the team discovered that the little-known Humpback dolphin, (Genus name Sousa) can be split into four distinct species:

  • Sousa teuszii (Atlantic, West Africa)
  • Sousa plumbea (Central and western Indian Ocean)
  • Sousa chinensis (Eastern Indian and West Pacific Oceans)
  • Sousa sahulensis (Northern Australia)

This has important conservation implications; especially in the case of coastal species such as Humpback dolphins which are under particular threat from human activities.

The original scientific papers are available online. You will find the links at the bottom of this step.

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Exploring Our Ocean

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