Genetic analyses identify new giraffe species. Not all giraffes are alike. This apparent truism turned into a hefty surprise after an extensive gene analyses comparison.
Practically every child is familiar with giraffes, because, with a body height of up to 6 meters, they are among the most striking terrestrial mammals and a favorite in every zoo. However, science has only started to analyze scientifically in greater detail in the past few years. This is mainly the work of the Giraffe Conservation Foundation (GCF) – an organization dedicated to the conservation of the species.
Conservation of the giraffe? For a long time, it was assumed that there is only a single species of giraffe with nine subspecies that are distributed from West and East Africa to South Africa. These subspecies are traditionally described and classified
based on their coat pattern, the fur-covered bony protrusions on their forehead, and their geographical distribution. To review this subdivision, GCF members used biopsy darts to collect hundreds of tissue samples from individuals of the different subspecies. These tissue samples were then genetically analyzed at the Senckenberg Biodiversity and Climate Research Center.
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.
joined the SBiK-F and the Goethe University in Frankfurt in 2010 from the University of Lund (Sweden). As a geneticist, he is interested in the evolution of vertebrates, and mammals in particular. Today he and his team study the genetics of speciation in the presence of gene flow. Axel Janke has worked with the GCF on the genetics of the giraffes since 2011 in order to better understand their biodiversity and evolution, thereby contributing to their conservation.
I am interested in the evolution of vertebrates in general, including marsupials, birds, almost every placental mammalian order, lizards, snakes, crocodiles and fishes. Besides reconstructing and dating their evolutionary tree, placing the events into larger contexts of e.g. biogeography, plate tectonics and climate is exciting. The increasing amount of genomic data show that evolution may not be a bifurcating process, but seeing it as a network will enhance our understanding of evolution. Currently – as of January 2017 – I am interested and working on the following topics for which PhD, master or project students are welcome: Giraffe Research
Mammalian phylogenomics (see D2.3)
Arctic adaptation (see D2.4)
Genomics and speciation (see D2.3)
Genomics and climate (environmental) change (see D2.4)
The basic divergences of crocodiles
The evolution of marsupials
Click here for more information about the topics.
Arnason, U., Lammers, F., Kumar, V., Nilsson, M.A. Janke A (2018) Whole-genome sequencing of the blue whale and other rorquals finds signatures for introgressive gene flow. Science Advances
Kumar, V., Lammers, F., Bidon, T., Pfenninger, M., Kolter, L., Nilsson, M.A. and Janke, A. (2017) The
evolutionary history of bears is characterized by gene flow across species. Scientific Reports
Fennessy, J., Bidon, T., Reuss, F., Kumar, V., Elkan, P., Nilsson, M.A., Vamberger, M., Fritz, U. and Janke, A. (2016) Multi-locus analyses reveal four giraffe species instead of one. Current Biology
Bidon, T., Schreck, N., Hailer, F., Nilsson, M.A., Janke A (2015) Genome-wide search identifies 1.9 megabases from the polar bear Y chromosome for evolutionary analyses. Genome Biol Evol
Gallus, S., Hallström, B.M., Kumar, V., Janke, A., Ning, Z., Murchison, E.M., Yang, F., Fu, B., Bertelsen, M.F., Schumann, G.G., Nilsson, M.A. (2015) Evolutionary histories of transposable elements in the genome of the largest living marsupial carnivore, the Tasmanian devil. Mol Biol Evol (early access)
Kutschera, V. E., Bidon, T., Hailer, F., Rodi, J. L., Fain, S. R., Janke, A. (2014) Bears in a forest of gene trees: Phylogenetic inference is complicated by incomplete lineage sorting and gene flow. Molecular Biology and Evolution, MBE2014/06/05/molbev.msu186
studied biology with an emphasis on zoology in Bonn and Vienna. He worked on the ecology of Leopards, Brown Hyenas and Black-backed Jackals in Namibia. Since 2016, he is a PhD student in the Evolutionary Genomics working group. It is his goal to gain a better understanding of the evolution and speciation among the giraffes and to study the population structures and distribution of different giraffe populations.
I am interested in evolutionary biology and taxonomy of mammals. Since visiting Namibia for my Bachelor thesis I am fascinated of large African mammals. Currently, my research focuses on evolutionary genomics and population genetics of giraffe (Giraffa carmelopardalis). The aim is to identify structure and gene flow of wild giraffe populations based on mitochondrial and nuclear markers in order to examine the need for a taxonomic revision in giraffes.
CV Since 2016 PhD student at Biodiversity and Climate Reasearch Centre (BiK-F), Frankfurt am Main, Germany
Working group of Prof. Dr. Axel Janke
2016 Master of Science (Zoology) at University of Vienna, Austria.
Master thesis: “A molecular phylogeny and divergence times of the weevil tribe Apionini (Brentidae, Curculionoidea, Coleoptera”, Supervisor: Prof. Dr. Konrad Fiedler
2014 – 2016 Studies of biology at University of Vienna, Austria
Master degree course: Zoology
2013 Bachelor of Science at Rheinische Friedrich-Wilhelms-Universität Bonn, Germany
Bachelor thesis: “Beutespektren namibischer Prädatoren mit Schwerpunkt auf dem Leopard Panthera pardus auf Farmland in Namibia” (Prey spectra of namibian predators with focus on leopard Panthera pardus on Farmland in Namibia), Supervisor: Dr. Renate van den Elzen
2010 – 2013 Studies of biology at Rheinische Friedrich-Wilhelms-Universität Bonn, Germany. Bachelor degree course: Biology