From ABC News in Science, 3 July 2014:
Two dolphin species in north-western Australia are vulnerable to local extinction because they rarely mingle with their own kind outside their immediate location, a new study has found.
The genetic analysis, published today in PLOS ONE, also identified one of the first cases of successful breeding between the two different species.
The Australian snubfin dolphin (Oracella heinsohni) and the Indo-Pacific humpback dolphin (Sousa chinensis) are both listed as ‘near threatened’ by the International Union for the Conservation of Nature.
But little is known about these dolphin populations, and this has hindered efforts to conserve them
“We were looking to get a bit more information about how vulnerable they could be, and a greater understanding to inform environmental impact assessments,” says an author of the new study, Alex Brown, from the Murdoch University Cetacean Research Unit.
Brown and colleagues analysed genetic samples from two Western-Australian populations of each dolphin species, that were separated by more than 200 kilometres.
They used a plastic dart to take small samples of skin from the dolphins and then used nuclear an mitochondrial DNA markers to trace the degree of movement and breeding between the two populations of snubfin dolphins, and between the two humpback dolphins.
“We found there was a considerable differentiation between our different populations, so there was a limited gene flow and limited movement between the populations that we sampled,” says Brown, a PhD candidate.
“This suggests that these species, although you might find them up the coast in a lot of different places, they’re not freely moving up and down hundreds and hundreds of kilometres of coast.” Read more.