World's First Shark Hybrids Discovered Near Australia

For the first time ever, scientists have discovered a species of hybrid shark (a cross between two different species of the cartilaginous fishes) off the coast of Australia.

Close to sixty of the hybrids (one of which is pictured up top), spanning numerous generations, have been discovered so far; and here's the intriguing bit: this new shark breed appears to be thriving in waters thought to be too cold for its genetic forebears.

The hybrid shark in question is a mix between the Australian black-tip shark and its global counterpart, the common black-tip shark. In the past, Australian black-tip had only been found in warm, relatively isolated tropical waters; but these hybrids have been found along over 1200 miles of Australian coastline, in comparably cooler seas.

So why the change in habitat? Researchers say we could be seeing evidence of evolution in action:

"If [the Australian black-tip] hybridizes with the common species it can effectively shift its range further south into cooler waters, so the effect of this hybridizing is a range expansion," said Jess Morgan, who led the team of researchers that made the unprecedented discovery.

"It's enabled a species restricted to the tropics to move into temperate waters."

Of course, if the hybrid species is able to outcompete its predecessors for resources and continue producing viable offspring, it's entirely possible that this new breed of shark could, in time, supplant the Australian black-tip entirely.

But this hybrid coup isn't necessarily a bad thing. Morgan and his colleagues speculate that the success of the hybrid sharks could be tied back to climate change that has already lead to changes in sea temperature. If these cross-bred hybrid sharks allow the genes of the Australian black-tip to live on in a more successful organism, then evolutionarily this discovery makes sense.

Of course, whether these hybrids stand the test of time remains to be seen. But so far, things are looking pretty good for the genetic mashups.

"Certainly we know that they are viable," explained Colin Simpfendorfer, a member of Morgan's research team. "They reproduce and that there are multiple generations of hybrids now that we can see from the genetic road map that we've generated from these animals."

"Certainly it appears that they are fairly fit individuals."

The researchers' findings were published last month, in Conservation Genetics

[Conservation Genetics via Discovery News]
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