Four for the price of one

Relationships revealed

In mammals, genetic material in the form of DNA is not only found in the cells’ nuclei but also in their mitochondria. Since mitochondrial DNA is passed on exclusively by the mothers (maternal inheritance), the subspecies can be unequivocally dentified. The analyses revealed that the Thornicroft and Masai Giraffe are genetically identical, as are the Rothschild and the Nubian Giraffe. Thus, genetic analyzes reduced the number of subspecies from nine to seven. Using this method, die GCF and Senckenberg will determine the genotypes of all major giraffe populations in the coming years to scientifically guide reintroduction projects and to learn more about the actual distribution of each subspecies. Initial studies showed, for example, that the Angolan giraffe is more widespread than previously thought.

The results of the mitochondrial DNA analyses raised the question whether similar genetic differences can also be found in the nuclear genome. In fact, the analyses of nuclear-encoded gene loci revealed some astonishing news: The seven subspecies fall into four genetically separated groups. These four groups show significant genetic differences (similar to that of brown and polar bears), and recent studies show that there is only very limited gene flow of about one hybridization in generations across the groups. The latter is a clear indication that these “groups” constitute actual species, because most species concepts are based on reproductive isolation. This means that there is no genetic intermixing among the groups; otherwise, there would be evidence of gene flow.

Based on our results, we described the four new species in collaboration with the taxonomist Uwe Fritz of the Senckenberg institute Dresden. With that in mind it is now evident that the four species are clearly distinguished by their coat patterns. Calculations based on the genetic data show that the split between the giraffe species occurred pproximately 1-2 million years ago, much older a than the split between polar and brown bears. In a follow-up study, we are now sequencing the entire genomes of all subspecies to learn more about the evolution and gene flow in the different giraffe species and subspecies. To date, it is not clear why the four species apparently do not interbreed in the wild – something keeps them separated. Together with the GCF and African partners we will also search for genetic hybrids in Kenya, where three of the four species approach each other geographically. If there are no hybrids, or if they are very rare, it would confirm our pervious results. 

Genetic knowledge contributes to increased protection for the giraffes

The results of the genetic analyses are important for the conservation of giraffes in Africa. In the past 30 years, the giraffe population has decreased by 40 percent to about 100,000 individuals. This is primarily due to loss of its habitat and poaching. Therefore, in 2016 the International Union for Conservation of Nature, the IUCN, listed the giraffe as “vulnerable” in the Red List of Threatened Animal Species. Two of the four new species number fewer than 10,000 individuals and are thus similarly threatened as the White Rhinoceros, which at a population of approx. 5,000 is considered “critically endangered”. As a member of the IUCN Specialist Group, Axel Janke will work toward an improved protection for the individual species, so that our children will be able to marvel at these gentle giants in the wild in the future.