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03 Jan 2012 09:50
Scientists say two separate shark species have been found to have interbred to form an unprecedented new species they say is better suited to coping with warmer oceans.
Lead researcher Jess Morgan said the mating of the local Australian black-tip shark with its global counterpart, the common black-tip, was an unprecedented discovery with implications for the entire shark world.
“It’s very surprising because no one’s ever seen shark hybrids before, this is not a common occurrence by any stretch of the imagination,” Morgan, from the University of Queensland, told AFP.
“This is evolution in action.”
The discovery was made during cataloguing work off Australia’s east coast when Morgan said genetic findings showed certain sharks to be one species when physically they looked to be another.
The Australian black-tip is slightly smaller than its common cousin and can only live in tropical waters, but its hybrid offspring have been found 2 000km down the coast, meaning it could be adapting to ocean temperatures.
“If it hybridises with the common species it can effectively shift its range further south into cooler waters, so the effect of this hybridising is a range expansion,” Morgan said.
“It’s enabled a species restricted to the tropics to move into temperate waters.”
Climate change and human fishing are some of the potential triggers being investigated by the team, with further genetic mapping also planned to examine whether it was an ancient process just discovered or a more recent phenomenon.
Colin Simpfendorfer, a partner in Morgan’s research from James Cook University, said initial studies suggested the hybrid species was relatively robust, with a number of generations discovered across 57 specimens.
Simpfendorfer said the study, published late last month in Conservation Genetics, could challenge traditional ideas of how sharks had and were continuing to evolve.
“We thought we understood how species of sharks have separated, but what this is telling us is that in reality we probably don’t fully understand the mechanisms that keep species of shark separate,” he said.
“And in fact this may be happening in more species than these two.”—Sapa-AFP
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