Natural hybridisation isn’t uncommon among marine life. Two different species often mate and produce hybrid offspring.
However, a new study has found that, among coral reef species at least, angelfish (Pomacanthidae) are the most enthusiastic; 48% of them – 42 species in all – can have viable offspring with different angelfish species.
And it’s not limited to not limited to closely related species, according to a paper in the journal Proceedings of the Royal Society B.
“We found that hybrids are frequently produced even between angelfish species that are distantly related to each other; some separated by over 10 million years in evolutionary time,” says lead author Yi-Kai Tea from Australia’s University of Sydney, who worked with colleagues from the Australian Museum, the University of Queensland and Edith Cowan University.
The team used photographs, previous studies and records from the researchers to identify hybrids across 87 species based on abnormal or mid-way colouration patterns between parent species.
Hybrids were found between species with over 12% pairwise distance – differences in pairs of DNA sequences – in mitochondrial DNA.
“This genetic separation is quite astounding, considering that hybrids are rarely reported between species that share more than 2% in genetic distance,” says Tea. “Though coral reef fish hybrids are common, they are usually formed by closely-related species.”
The researchers also found that angelfish hybridise wherever different species exist, whereas other coral reef species tend to hybridise within certain zones of shared habitats.
Hybridisation has been observed in 173 species of coral fish, yet further research is needed to better understand many factors.
“In terms of coral reef fish hybridisation, much remains unanswered, particularly in the context of why, and how hybrids are formed,” Tea says.
“We still don’t know why some species hybridise and others don’t. For example, the regal angelfish, Pygoplites diacanthus, is found throughout the Indian and Pacific Oceans, yet no hybrids have ever been reported for this species.
“In terms of cracking the secrets to hybridisation in coral reefs, we’ve only just scratched the surface.”
Amelia Nichele is a science journalist at The Royal Institution of Australia.
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