基因分析显示长颈鹿有四大种类

Up until now, scientists had only recognized a single species of giraffe made up of several subspecies. But, according to the most inclusive genetic analysis of giraffe relationships to date, giraffes actually aren't one species, but four. For comparison, the genetic differences among giraffe species are at least as great as those between polar and brown bears. The unexpected findings reported in the Cell Press journal Current Biology on September 8 highlight the urgent need for further study of the four genetically isolated species and for greater conservation efforts for the world's tallest mammal, the researchers say.

"We were extremely surprised, because the morphological and coat pattern differences between giraffe are limited," says Axel Janke, a geneticist at the Senckenberg Biodiversity and Climate Research Centre and Goethe University in Germany. Giraffes are also assumed to have similar ecological requirements across their range, he added, "but no one really knows, because this megafauna has been largely overlooked by science." 

Giraffes are in dramatic decline across their range in Africa. Their numbers have dropped substantially over the last three decades, from more than 150,000 individuals to fewer than 100,000. Despite that, the researchers say that there has been relatively little research done on giraffes in comparison to other large animals, such as elephants, rhinoceroses, gorillas, and lions.

About five years ago, Julian Fennessy of Giraffe Conservation Foundation in Namibia approached Janke to ask for help with genetic testing of the giraffe. Fennessy wanted to know how similar (or not) giraffes living in different parts of Africa were to each other, whether past translocations of giraffe individuals had inadvertently "mixed" different species or subspecies, and, if so, what should be done in future translocations of giraffes into parks or other protected areas. 

In the new study, Janke and his research group examined the DNA evidence taken from skin biopsies of 190 giraffes collected by Fennessy and team all across Africa, including regions of civil unrest. The extensive sampling includes populations from all nine previously recognized giraffe subspecies.