The researchers at the STRI (Smithsonian Tropical Research Institute), and Naos Molecular and Marine Laboratories gathered ancient coral reef fossils and determined their ages by using high-resolution geologic dating methods. The coral species fossilized at different points of time were compared. They found that the species in the Orbicella genus, a class of reef-building corals, were among the best-represented ones.
They further evaluated the existing and past numbers of various Orbicella species by genome sequencing them. They found that even single individuals contained their genetic material in two copies. In some cases, one copy differed from the other which is termed as a genetic variant.
The population sizes of different species at different periods were estimated by analyzing the degree of genetic variation at specific intervals across the genome. Findings revealed that about 1 and 2 million years ago, half of the coral species in the Caribbean had become extinct mostly due to drastic environmental changes.
The particular group that survived was the Orbicella genus. Thanks to their genetic variation. The scientists believe that this will enable their continuous adaption to future climatic changes as well.