Major palaeo-environmental changes over the past five million years may explain the surprising genetic differences between Africa's wetland and savanna lions.

Recent genetic studies on the continent's dwindling lion populations have revealed a remarkable distinctiveness between regional lion populations, and particularly between wetland and savanna lions. But there exists very little understanding of why or how this happened.

A recent article in the advance access version of the Journal of Heredity, entitled 'Commentary on the genetic variation of Africa's lions (Panthera leo)' invokes geological and palaeoclimatic evidence to account for this unexpected distinctiveness.

Dr Woody Cotterill, evolutionary biologist and geobiologist at Stellenbosch University and one of five co-authors of the article, says genetically the Etosha and Okavango populations stand apart from their closest neighbours in the more arid habitats of Hwange-Chobe and the Kaladgadi.

"Repeated swings between wet and arid climatic conditions over the past five million years can explain a long-term absence of inter-breeding between lions occupying these contrasting habitats," he explains.

But they are still unsure of how or when the wetland and savanna lion populations became genetically isolated.

"We hypothesise that Africa's ancestral lion populations started out in the inland wetlands of south-central Africa. We argue the key to the puzzle lies in isolation of these wetlands through geological history."

For example, consider Botswana's Okavango Delta, Namibia's Etosha Basin, and the Bangweulu Basin in north-west Zambia. These are the modern representatives of a mosaic or archipelago of wetlands which has evolved in space and time in south-central Africa for at least the past 5 million years.

Depending on the climatic conditions at the time, these wetlands became isolated islands whenever vast desert conditions dominated the high plateau. Several desert expansions have occurred repeatedly over the past three million years. At its largest, a Mega-Kalahari desert extended from the southern Congo basin to the Orange River.

During these arid periods, they argue, ancestral population of lions which became isolated from the wetlands were forced to adapt in order to survive on the open grasslands.

However, during wetter climatic periods Africa's grasslands and moister woodlands expanded at the expense of deserts and stimulated the rapid population expansion and diversification of savanna lions. The result was the evolution of a different suite of behavioural and ecological adaptations to become savanna specialists. This in turn acted to genetically isolate them from the original wetland populations​

According to Dr Cotterill, their finding holds important implications for lion conservation efforts.

In 2015 the International Union for the Conservation of Nature placed Africa's lions on the Red List of Endangered Species.

The other researchers are Dr Andy Moore (Department of Geology, Rhodes University), Christian Winterbach and Hanlie Winterbach (Centre for Wildlife Management, University of Pretoria); Dr Agostinho Antunes (University do Porto, Portugal) and Dr Stephen J. O'Brien (Theodosius Dobzhansky Center for Genome Bioinformatics, St Petersburg State University, Russia).

​Photo 1: Lioness with swimming cubs from the Okavango seasonal wetland. Picture courtesy of Matthew Copham, Safari Footprints, Maun, Botswana

 Photo 2: Aquatic lions from the Okavango Delta. Photo courtesy of Andy Moore

Contact details

Dr Woody Cotterill

T: 021 808 2684

E: fcotterill@gmail.com

Dr Andy Moore

C: +267-71-704005

E: andy.moore.bots@gmail.com

Media release issued by Wiida Fourie-Basson, Media: Faculty of Science, Stellenbosch University, science@sun.ac.za, 021 808 2684, 071 0995721