AsianScientist (Jan. 3, 2012) – Australian marine scientists have discovered widespread hybridization in the wild between two shark species commonly caught in Australia’s east coast shark fisheries.
The Australian black tip shark (Carcharhinus tilstoni) and the common black tip shark (C. limbatus) have overlapping distributions along the northern and eastern Australian coastline.
Although closely related, the two species grow to different maximum sizes and are genetically distinct.
Working with 57 hybrid animals from five locations spanning 2000 kilometers from northern New South Wales to far northern Queensland, the researchers identified a species mismatch using mitochondrial DNA sequencing and morphological characters such as body length and number of vertebrae.
Nuclear DNA sequencing later confirmed the hybrid status of the 57 sharks.
“Wild hybrids are usually hard to find, so detecting hybrids and their offspring is extraordinary. To find 57 hybrids along 2000 km of coastline is unprecedented,” said Dr. Jennifer Ovenden, an expert in genetics of fisheries species and a member of the scientific team.
“Hybridization could enable the sharks to adapt to environmental change as the smaller Australian black tip currently favors tropical waters in the north, while the larger common black tip is more abundant in sub-tropical and temperate waters along the south-eastern Australian coastline,” she said.
Dr. Ovenden believes that other closely related shark and ray species around the world may also be interbreeding to adapt to climate changes.
The scientists are now investigating the full extent of the hybrid zone and are attempting to measure hybrid fitness of the animals.
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Source: University of Queensland.
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