Study Reveals Significant Diversity Among Giraffes

A research team studying the genetic diversity of giraffes has shown that there may be more than just one species of giraffe. The team, lead by David M. Brown from the University of California, Los Angeles, examined the mitochondrial DNA sequences obtained from wild giraffes from various populations throughout Africa.

The classification of giraffes into various species and subspecies has been the subject of ongoing debate for many decades. Previous schemes defined one or two species of giraffes with up to ten subspecies. The most widely accepted current classification scheme—the one that could well be overturned by the Brown team's findings—consists of a single species (Giraffa camelopardalis) and five subspecies (G. c. giraffa, G. c. reticulata, G. c. rothschildi, G. c. thorncrofti, and G. c. tippelskirchi).

Large mammals that are highly mobile and widespread throughout continuous ranges (ranges not subdivided by habitat or topographical boundaries) are expected to display relatively low levels of genetic differentiation. In other words, without barriers to interbreeding such as mountain ranges and deserts, such mammal populations are expected to mix and individuals from the overlapping regions would interbreed, keeping diversity relatively low. Such interbreeding between populations over a large range would be expected to retain low levels of speciation among the overall population of the mammal.

But giraffes run counter to this expectation. Despite the high potential for genetic mixing between giraffe populations—they can roam over hundreds of kilometers and they form loose social groups—giraffes exhibit significant variation in pelage patterns and ossicone number between the various populations. And now, Brown and team's findings have revealed that significant genetic variations underpins these morphological differences.

The genetically distinct groups of giraffes noted by Brown and his team include:

• Rothschild's Giraffe (currently G. c. rothschildi)
• West African Giraffe (currently G. c. peralta)
• Angolan Giraffe (currently G. c. angolensis)
• Reticulated Giraffe (currently G. c. reticulata)
• Masai Giraffe (currently G. c. tippelskirchi)
• South African Giraffe (currently G. c. giraffa)

Find out more:

• Six Species of Giraffe Discovered (Mongabay.com)
• Not One But 'Six Giraffe Species' (BBC News)

Photo © Purdy Photography / iStockphoto.