Why African elephants are becoming hybrids
Poaching and habitat loss have led to hybridisation between forest and savannah elephants in Africa, say researchers.
The forest elephants of Central and Western Africa are easily distinguishable, both physically and genetically, from the more familiar savannah type. Among other differences they are smaller, with straighter tusks and rounder ears.
However, the two types produce fertile hybrids where their ranges meet, and many conservation bodies, including the IUCN, now regard African elephants as a single species.
Biologists led by Samuel Wasser of the University of Washington have now found three significant zones of hybridisation: one on the border of Uganda and the Democratic Republic of the Congo; another in the Central African Republic; and a third in Benin and Burkina Faso.
This could be seen as evidence against separateness. However, genetic analyses show little gene flow between the two types historically, suggesting the hybrid zones are a recent development. Wasser argues that they are a consequence of poaching and habitat loss leading to shifts in both types’ ranges.
“The fact that hybrids are fertile simply shows how effective reproductive isolation has been in the past, since historically these hybrids did not spread,” Wasser told BBC Wildlife. This, say the scientists, bolsters the case for two species, not one.
According to a spokesperson, the IUCN’s African Elephant Specialist Group is currently reviewing the new evidence. Wasser believes that hybrids could have a positive impact on the future of African elephants. “Hybrids may be important to species’ persistence in a rapidly changing world,” he said. But there are potentially other, less desirable consequences. “The major hybrid zone we found is in the Albertine Rift, which has some of the highest endemism in Africa. Are these rare endemics now in danger of increased consumption by hybrids? Has poaching created the world’s largest invasive species?”
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According to Wasser, we have lost over 90 per cent of forest elephants in the past 50 years and over 60 per cent in the past decade. Savannah elephants, while more abundant, are being affected two to three times as badly.
Source Molecular Ecology