An international team of researchers has sequenced and analyzed the genomes 50 giraffe individuals representing all traditionally recognized subspecies. Their results strengthen previous findings of limited gene flow and admixture among giraffe species and establish a genomic foundation for recognizing four species, which seemingly do not mate with each other in the wild.
An adult female Masai giraffe (Giraffa tippelskirchi) in the Masaai Mara National Park, Kenya. Image credit: Bjørn Christian Tørrissen / CC BY-SA 3.0.
“New mammal species are only rarely discovered and described,” said senior author Professor Axel Janke, a researcher at the LOEWE Centre for Translational Biodiversity Genomics, Goethe University, and the Senckenberg Biodiversity and Climate Research Centre.
“Genomics, that is studying all genetic information of a living being, opens up new possibilities and can broaden our perspective on species and their evolution — as now happened in the case of giraffes.”
Until recently, giraffes (genus Giraffa) were widely recognized as one single species with several subspecies.
In 2016, a genetic study suggested otherwise by first introducing the concept for four distinct species.
The new whole-genome analysis supports four distinct species and seven subspecies.
Those taxa include: the northern giraffe (Giraffa camelopardalis), including the Kordofan (G. c. antiquorum), the Nubian (G. c. camelopardalis), and the West African giraffe (G. c. peralta); the reticulated giraffe (Giraffa reticulata); the Masai giraffe sensu lato (Giraffa tippelskirchi), including the Masai giraffe sensu stricto (G. t. tippelskirchi) and the Luangwa or Thornicroft’s giraffe (G. t. thornicrofti); and the southern giraffe (Giraffa giraffa), including the Angolan (G. g. angolensis) and the South African giraffe (G. g. giraffa).
Population structure and phylogenomic analyses identified that the four separately evolving lineages diverged between 230,000 and 370,000 years ago.
Coimbra et al. confirm four separate giraffe lineages with distinct demographic histories. Image credit: Coimbra et al., doi: 10.1016/j.cub.2021.04.033.
“The results of the genome analysis have great significance for giraffe conservation,” said co-author Dr. Julian Fennessy, director of the Giraffe Conservation Foundation.
“The populations have declined sharply in the past century to around 117,000 wild giraffes.”
“It now becomes clear now that the remaining giraffes belong to four different species. This further exacerbates the situation.”
“For example, we estimate that there are less than 6,000 northern giraffes remaining in the wild. As a species, they are one of the most threatened large mammals in the world.”
As part of the study, the authors generated the first-ever high-quality genome assembly for the critically endangered Kordofan giraffe (G. c. antiquorum).
They also performed a comprehensive whole-genome analysis of 50 giraffe individuals from all previously recognized subspecies.
“The data available is more informative than ever before,” said first author Dr. Raphael Coimbra, a researcher at the Senckenberg Biodiversity and Climate Research Centre and Goethe University.
“Our genome analyses are based on significantly more genetic data than previous studies.”
The results were published in the journal Current Biology.
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Raphael T.F. Coimbra et al. Whole-genome analysis of giraffe supports four distinct species. Current Biology, published online May 5, 2021; doi: 10.1016/j.cub.2021.04.033
Source link: https://www.sci.news/biology/four-giraffe-species-09632.html
