Gene flow between Angel fish on a coral reef
Creation of new species often occurs when there is geographic isolation followed by independent evolution over time. However, marine organisms defy this commonly held view, as there is little opportunity for geographical separation but plenty of diversity. The FISHSPECIATIONGENOME (Fish speciation and the origin of marine biodiversity: A comparative genomics approach) project has tackled the question of how genetic divergence and speciation manage to persist when there is overlapping distribution. The researchers looked at Pygmy Angelfishes, Centropyge spp, in the tropical Indo-Pacific Ocean, which have partly overlapping distribution ranges and individual species differing by colour. To identify genomic signatures and establish if there is any gene flow between the species after speciation, they used a high throughput DNA sequencing method, restriction site associated DNA sequencing (RAD). Fish and tissue samples were collected from three sources: three parental pure types from areas where only one species occurs, each of the parental species in hybrid zones, and each of the hybrid combinations in the hybrid zones displaying a range of colour variants. Based on the RAD sequencing system, FISHSPECIATIONGENOME optimised the lab protocol for DNA sequencing libraries. Moreover, they optimised a bioinformatics platform for analysis of key population genetic characteristics. This included estimation of single nucleotide polymorphisms and population allele frequencies as well as analyses of genetic structure, patterns of hybridisation and introgression, and selective sweeps, one type of elimination of variation due to fixation of beneficial alleles. Research results emphasised the complex evolutionary history of Pygmy Angelfishes and revealed patterns of gene introgression by gene flow between interspecific hybrids and a parent species. The work has also explained the genetics of colour variation and demonstrates that angelfish can be used to study colour difference in other fish. As oceans warm up and they are used increasingly for aquaculture and transportation, species conservation, already dwindling, has become even more important. Management of marine resources has widespread economic implications in food, medicine, cosmetics and a host of industrial applications.
Keywords
Coral reef, conservation, FISHSPECIATIONGENOME, speciation, Angelfish
