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Genetic Analysis Reveals Giraffes Actually Divided Into Four Species

NEW YORK (GenomeWeb) – A team of researchers from Germany and the US working with the Giraffe Conservation Foundation (GCF) in Namibia performed genetic testing on giraffes (Giraffa camelopardalis) across different parts of Africa and discovered that what was once thought to be one far-roaming species with nine sub-species can actually be separated into four genetically distinct species.

Giraffe numbers have dropped from more than 150,000 individuals to fewer than 100,000 across Africa over the past thirty years. But despite their place on the endangered species list, there has been relatively little research done on giraffes to date compared to other large animals such as elephants, rhinoceroses, gorillas, and lions.

Up to this point, scientists have only recognized one giraffe species and nine subspecies (West African, Kordofan, Nubian, reticulated, Rothschild, Masai, Thornicroft, Angolan, and South African). However, based on the study published today in Current Biology, this team determined that the genetic differences between the four giraffe species are comparable to those between polar and brown bears.

"We were extremely surprised, because the morphological and coat pattern differences between giraffes are limited," Axel Janke, a geneticist at the Senckenberg Biodiversity and Climate Research Centre and senior author on the paper, said in a statement.

The researchers obtained biopsy samples from 141 wild giraffes — including samples from all recognized subspecies — through the GCF. They extracted mitochondrial and nuclear DNA, and sequenced the samples on an Applied Biosystems ABI 3730 instrument. They then aligned and analyzed mitochondrial sequences using BEAST software, created phylogenetic trees using TreeAnnotator software, and performed population genetic analyses on the nuclear sequences.

Based on their data, the researchers determined some of the currently recognized subspecies were actually distinct giraffe species: a southern cluster called Giraffa giraffa, which includes South African (G.g. giraffe) and Angolan (G.g. angolensis) giraffes; a Masai cluster called G. tippelskirchi; a reticulated giraffe cluster called G. reticulata; and a northern cluster called G. camelopardalis which includes the West African (G.c. peralta), Kordofan (G.c. antiquorum), and Nubian (G.c. camelopardalis) giraffes.

They further noted that two previously recognized subspecies — Thornicroft’s and Rothschild’s giraffe — are actually identical to the Masai and Nubian giraffes, respectively, and synonymized them.

"Our findings provide the most inclusive analysis of giraffe relationships to date and show that their genetic complexity has been underestimated, highlighting the need for greater conservation efforts for the world's tallest mammal," the researchers wrote.

In a statement, GCF researcher and first author Julian Fennessy further added that dividing giraffes into four species presents a more accurate picture of how endangered they really are. "Northern giraffe number less than 4,750 individuals in the wild, and reticulated giraffe number less than 8,700 individuals — as distinct species, it makes them some of the most endangered large mammals in the world," he said. "With now four distinct species, the conservation status of each of these can be better defined and in turn added to the IUCN Red List."

The researchers have made the four giraffe genomes available for conservation research.