Cichlids from Lake MalawiCredit: Sabena Jane Blackbird/Alamy Stock Photo

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Gene transfer inhibition in the African cichlids fish might explain the evolution of new species, a study in Nature Ecology & Evolution, has found.

Martin Genner, a professor of Ecology, Population Genomics and Evolutionary Biology at University of Bristol in the United Kingdom, and colleagues from the University of Cambridge, and the Tanzania Fisheries Research Institute, studied the dietary ecology of fishes in Lake Masoko/Kibisa in Southern Tanzania using biochemical tracers in their muscle called stable isotopes.

They also conducted DNA methylation genome-wide, by sequencing chemically altered DNA and looked for tell-tale signatures of methylation in altered DNA. Methylation is a biological process by which methyl groups are added to the DNA molecule, which changes the activity of a DNA segment without changing the sequence, typically repressing gene transcription.

“We found that the ecomorphs (Cichlids) did contrast greatly in the distribution of DNA methylation across the genomes—and that the DNA methylation was very likely to be affecting the expression of genes with ecological importance,” said Genner.

“For example, we found evidence that different patterns of DNA methylation were linked to dietary metabolism and oxygen transport in the blood—and also found that this is passed from parents to offspring,” he added.

“Our focus was on the fish of Lake Masoko because here, one species, the Eastern Happy, is in the process of splitting into two populations with different ecologies that do not freely interbreed. We call these ecomorphs,” he explains.

In East Africa Cichlids have undergone extreme speciation, into more than 2000 species spread across the region, with most in three great Lakes Malawi, Tanganyika and Victoria.