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201610Sep08:58

Genetic analy­sis uncov­ers four species of giraffe, not just one

Infor­ma­tion
pub­lished 10 Sep­tem­ber 2016 | mod­i­fied 10 Sep­tem­ber 2016
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Up until now, sci­en­tists had only rec­og­nized a sin­gle species of giraffe made up of sev­eral sub­species. How­ever, Sci­en­tists from the Senck­en­berg (World of Bio­di­ver­sity – Insti­tute) in Ger­many and the Giraffe Con­ser­va­tion Foun­da­tion recently have analysed the genetic rela­tion­ships of all major pop­u­la­tions of giraffe in the wild. This large study on the genetic make-​up of giraffe, pub­lished on 8 Sep­tem­ber in the jour­nal Cur­rent Biol­ogy, shows that there are four dis­tinct giraffe species. The unex­pected results are based on analy­ses using sev­eral nuclear marker genes of more than 100 ani­mals. The new insights are set to improve pro­tec­tion efforts of these endan­gered ani­mals in Africa.

Nubian giraffeDespite their large size and iconic pres­ence, giraffe have been incom­pletely explored until now, with many aspects of their biol­ogy poorly under­stood. Lat­est esti­mates have revealed that over the past 30 years giraffe num­bers have plum­meted from over 150,000 to less than 100,000 indi­vid­u­als across their range in Africa. Tra­di­tion­ally giraffe are clas­si­fied as one species with nine sub­species based on coat pat­terns, ossi­cone (horn) struc­ture and geo­graph­i­cal dis­tri­b­u­tion – now, this view has to be thor­oughly revised.

We have stud­ied the genetic rela­tion­ships of all giraffe sub­species from across the con­ti­nent. We found, that there are not only one, but at least four genet­i­cally highly dis­tinct groups of giraffe, which appar­ently do not mate with each other in the wild. This we found look­ing at mul­ti­ple nuclear genes con­sid­ered to be rep­re­sen­ta­tive of the entire genome
Pro­fes­sor Axel Janke, co-​author, Senck­en­berg Bio­di­ver­sity and Cli­mate Research, and Goethe Uni­ver­sity in Frank­furt, Germany »

Con­se­quently, giraffe should be rec­og­nized as four dis­tinct species despite their sim­i­lar appear­ance,” added Janke.

About five years ago, Julian Fen­nessy of Giraffe Con­ser­va­tion Foun­da­tion (GCF) 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.

The study
The study that leads to a new clas­si­fi­ca­tion is based on 190 skin biopsy sam­ples from all pre­vi­ously rec­og­nized giraffe sub­species, which were col­lected by the GCF and part­ners over the past decade includ­ing in remote areas and civil war zones. These giraffe DNA sam­ples were then analysed by Janke’s research group at the Senck­en­berg Bio­di­ver­sity and Cli­mate Research Cen­tre in coop­er­a­tion with col­leagues from the Senck­en­berg Nat­ural His­tory Col­lec­tions of Dres­den, Ger­many. The sam­ple set included for the first time the elu­sive Nubian giraffe, the nom­i­nate sub­species (G. c. camelopardalis) – the “camel-​leopard” described by Lin­naeus in 1758 on the basis of a 200-​year-​old record.

Results

The four dis­tinct giraffe species are
(1) south­ern giraffe (Giraffa giraffa), com­pris­ing two dis­tinct sub­species, Angolan (G. g. angolen­sis) and South African giraffe (G. g. giraffa);
(2) Masai giraffe (G. tip­pel­skirchi);
(3) retic­u­lated giraffe (G. retic­u­lata); and
(4) north­ern giraffe (G. camelopardalis), which includes Nubian giraffe (G. c. camelopardalis), West African giraffe (G. c. per­alta) and Kord­o­fan giraffe (G. c. antiquo­rum) as dis­tinct subspecies.

The large-​scale analy­sis of giraffe DNA also yielded fur­ther sur­pris­ing insights. The for­merly rec­og­nized sub­species of Rothschild’s giraffe (G. c. roth­schildi) turned out to be genet­i­cally iden­ti­cal with Nubian giraffe, and thus should be con­sid­ered sim­i­lar to this sub­species. Sim­i­larly, the genetic stud­ies sup­ported pre­vi­ous find­ings by the team that could not dif­fer­en­ti­ate the for­merly rec­og­nized sub­species Thornicroft’s giraffe (G. c. thor­ni­crofti) with Masai giraffe (G. c. tip­pel­skirchi). Addi­tion­ally, research into the his­tory of the dis­tinct species showed that their last com­mon ances­tor lived about 0.42.0 mil­lion years ago, which yields a rate of spe­ci­a­tion that is typ­i­cal for mammals.

Con­se­quences
The dis­cov­ery has sig­nif­i­cant con­ser­va­tion impli­ca­tions, the researchers say, not­ing that the Inter­na­tional Union for Con­ser­va­tion of Nature and Nat­ural Resources (IUCN) Species Sur­vival Com­mis­sion Giraffe and Okapi Spe­cial­ist Group recently sub­mit­ted an updated pro­posed assess­ment of the giraffe on the IUCN Red List tak­ing into con­sid­er­a­tion their rapid decline over the last 30 years.

Species con­ser­va­tion is based on under­stand­ing the num­bers, range and threats to the species. To date, the esti­mated total num­ber of all giraffe has until now not been con­sid­ered a par­tic­u­lar threat for the species’ sur­vival. How­ever, as we now rec­og­nize four dis­tinct species as well as some genet­i­cally unique sub­species, some of their bio­di­ver­sity is very much under threat,” explains Janke. “In par­tic­u­lar, GCF esti­mates that there are maybe as few as 400 West African giraffe remain­ing in the wild and restricted to a small com­mu­nal area in Niger. Although it is not a dis­tinct species, this sub­species is genet­i­cally unique and requires increased spe­cial pro­tec­tion along with the other dis­tinct species.”

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,” Fen­nessy says.

Now that we know that there are four giraffe species, it is even more impor­tant and urgent to sup­port gov­ern­ments and other part­ners across Africa to pro­tect giraffe. We rightly worry about the fate of the African ele­phant, with an esti­mated 450,000 in the wild. By con­trast, the num­bers of three of the four giraffe species are rapidly declin­ing, and two num­ber­ing lees than 10,000 indi­vid­u­als in total. I think we should start work­ing together to secure the future of giraffe in Africa and take action before it is too late.
(Dr. Julian Fen­nessy, lead author, Co-​Director of GCF)

This study was sup­ported by the State of Hesse’s fund­ing pro­gram LOEWE, the Leib­niz Asso­ci­a­tion, the Giraffe Con­ser­va­tion Foun­da­tion, the Lei­den Con­ser­va­tion Foun­da­tion, the Auck­land Zoo, and var­i­ous African gov­ern­ment part­ners and inter­na­tional supporters.

(Source: Senck­en­berg press release, 09.09.2016; Cell Press news release via EurekAlert!, 08.09.2016)


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