Ural Federal University: Scientists Have Compiled an Evolutionary Tree of Rhinos

An international team of scientists reconstructed the evolutionary history of rhinoceroses from eight genomic sequences (five currently living and three extinct species). This made it possible to determine the stages of rhinoceros evolution, as well as the reasons for their extinction. An article describing the study and its results was published in the journal Cell.

The study used previously obtained genome sequences of black, white and Sumatran rhinoceros. Genomes of Indian and Javanese species were also independently sequenced. The genome of the Javanese rhinoceros was extracted from a museum specimen from 1838. In addition, the authors studied the DNA sequences of three extinct species – the Siberian elasmotherium, the Merck rhinoceros and the woolly rhinoceros. The scientists obtained these data from fossils dating back to the Late Pleistocene (about 10,000-100,000 years ago).

In the past, rhinoceroses were characterized by considerable diversity. Up to 100 extinct species were known and were distributed in Africa, Eurasia, North and Central America. Now there are only five rhinoceros species, and all of them are threatened with extinction. Ancient species were not numerous, but the rate of decline in their populations was low. Modern rhinoceroses, on the other hand, are subject to population decline at a higher rate than their ancestors. There could be several reasons: low genetic diversity, rhinoceros lifestyle, environmental problems and poaching.

“The level of genetic diversity is due to the peculiarities of rhinoceros biology. They are peculiar animals that cannot live in herds; they are individualists. Males and females are characterized by separation, close kinship within the same species, which affects the number of cubs born. Moreover, low genetic diversity is characteristic of all rhinoceros species,” explains Pavel Kosintsev, senior researcher at the Institute of Plant and Animal Ecology of the Ural Branch of the Russian Academy of Sciences, leading researcher at the Laboratory of Natural Science Methods in Humanities Research at UrFU.

The rhinoceros population is more seriously affected by anthropogenic and environmental factors. Rhinoceroses never migrate, remaining in their chosen territory for their entire lives. Environmental problems affecting rhino habitat lead to changes in their life cycle and decreases in numbers.

“Extermination is the main anthropogenic factor that reduces rhino numbers. In addition to the fact that low genetic diversity is inherent in rhinos, their numbers are declining due to constant hunting. If poaching could be stopped, environmental factors would not affect the population size as much. The rhinoceros population density and diversity would be higher,” says Pavel Kosintsev.

The scientists plan to continue their work. The obtained genomic sequences will help to study genetic changes and mutational features of existing species. This will create the most favorable conditions for the conservation of the remaining rhinoceros species.