SYDNEY, Jan 3, 2012 (AFP) - Scientists said on Tuesday that they had discovered the world's first hybrid sharks in Australian waters, a potential sign the predators were adapting to cope with climate change.
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, said lead researcher Jess Morgan.
"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.
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This undated handout photo from the New South Wales Department of Primary Industries shows a hybrid black tip shark containing both common and Australian black tip DNA in Australian waters. (AFP) |
"This is evolution in action."
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.
The find was made during cataloguing work off Australia's east coast when Morgan said genetic testing 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 2,000 kilometres down the coast, in cooler seas.
It means the Australian black-tip could be adapting to ensure its survival as sea temperatures change because of global warming.
"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.
If the hybrid was found to be stronger than its parent species -- a literal survival of the fittest -- Simpfendorfer said it may eventually outlast its so-called pure-bred predecessors.
"We don't know whether that's the case here, but certainly we know that they are viable, they reproduce and that there are multiple generations of hybrids now that we can see from the genetic roadmap that we've generated from these animals," he said.
"Certainly it appears that they are fairly fit individuals."
The hybrids were extraorindarily abundant, accounting for up to 20 percent of black-tip populations in some areas, but Morgan said that didn't appear to be at the expense of their single-breed parents, adding to the mystery.
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."
<한글기사>
호주서 세계 최초의 잡종 상어 발견
(연합뉴스) 호주 근해에서 세계 최초의 교잡종 상어가 발견돼 상어들이 기후 변화에 적응하고 있을 가능성을 시사하고 있다고 AFP 통신과 MSNBC 뉴스가 3일 보도했다.
호주 과학자들은 남북으로 약 2천㎞에 이르는 동부 해역에서 호주 블랙팁 상어 와 커먼 블랙팁 상어의 유전자를 모두 갖고 있는 교잡종 상어 57마리를 발견했다고 보존유전학 저널 최신호에 발표했다.
호주 블랙팁 상어의 서식지인 열대 해역과 이보다 몸집이 약간 큰 커먼 블랙팁 상어의 아열대 및 온대 해역 서식지는 다소 겹치긴 하지만 둘 사이의 교잡 종이 발 견되기는 처음이다.
연구진은 열대 해역에서만 사는 호주 블랙팁 상어의 교잡종 후손이 이보다 2천㎞ 떨어진 수온이 낮은 해역에서 발견됐다면서 유전자 분석을 통해 자연 상태에서는 유례가 없는 교잡종의 존재를 확인했다고 밝혔다.
일부 해역에서는 이들 교잡종이 전체 블랙팁 개체수의 20%를 차지할 정도로 흔한 것으로 밝혀지기도 했지만 순혈종 부모들이 이 때문에 희생된 것으로 보이지는 않아 의문을 더하고 있다.
연구진은 이런 교잡 현상은 호주 블랙팁 상어가 온난화에 따른 수온 변화에서 살아남기 위해 적응중이라는 증거가 될 수 있다고 설명했다.
학자들은 "이런 교잡이 가져올 수 있는 효과는 서식지 확대"라면서 열대 해역에서만 살던 호주 블랙팁이 커먼 블랙팁과의 교잡을 통해 서식지를 수온이 차가운 남쪽까지 넓힐 수 있다고 말했다.
이들은 교잡종이 부모 세대보다 강한 것으로 밝혀진다면 이는 문자 그대로 적자생존이 될것이며 이들은 순혈 조상보다 더 오래 생존하게 될 것이라고 지적했다.
연구진은 상어종 사이에 이처럼 유례없는 현상이 일어나고 있는 것은 기후 변화와 인간의 남획 때문인 것으로 추정된다면서 추가적인 유전자 분석을 통해 과거에도 이런 일이 일어났었는지, 아니면 최근에야 시작된 것인지 밝혀낼 계획이라고 말했다 .
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