Hotrod ants!

Nokuthula Nhleko and Simon van Noort

(Research and Exhibitions Department, Iziko Museums of South Africa)

Ocymyrmex resekhes with captured insect prey. Photograph by Hamish Robertson.

So named for their excessive, high-speed activity in the extreme heat of the day. Highest species richness and endemicity of the genus Ocymyrmex is centred in the arid environments of south-western Africa where ambient temperatures reach over 45 degrees Celsius, and ground surface temperatures can reach 60 degrees Celsius. They have long legs, enabling them to raise their body away from the hot ground surface, and probably also facilitate their running at high speed. One of the reasons why they are so thermophilic may be because this gives them an adaptive advantage over their insect prey. 

We recently published a paper demonstrating that the genus Ocymyrmex likely radiated as a result of past climatic oscillations, characterized by long periods of aridification. Phylogenomic relationships were analysed within a biogeographical and paleoclimatic framework. Dating analyses estimated that the crown age of Ocymyrmex dates to the Oligocene, around 32 million years ago. Diversification within this group occurred between the mid-Miocene (∼12.5 Ma) and Pleistocene (∼2 Ma). The biogeographic analyses suggested that Ocymyrmex species originated in the south-western region of southern Africa and diversified into eastern subtropical areas during the Pliocene.

Ocymyrmex velox photographed in Namibia. Photograph by Hamish Robertson.

Mbanyana N, Blaimer BB, Le Roux JJ, van Noort S, Brady SG, Wossler TC. 2023. Out of the desert: paleoclimatic changes drove the diversification of arid-adapted Ocymyrmex ants in southern Africa. Molecular Phylogenetics and Evolution 107977

https://doi.org/10.1016/j.ympev.2023.107977

This work was one of the components of Nokuthula Mbanyana-Nhleko’s PhD on the systematics, phylogeography and physiology of this ant genus conducted at the Iziko South African Museum and Stellenbosch University.

Ocymyrmex resekhes with brood. Photograph by Hamish Robertson.

Close up of head of Ocymyrmex afradu. Photograph by Nokuthula Mbanyana-Nhleko.

This video shows Hotrod ants in action!

https://www.instagram.com/p/BckQ3CahSUPrsr8xGAS6s9Lhl9KgN4bOuKafZI0/?igsh=MTBnaXJhMXQ4MWY3Zg==

In the video, workers of Ocymyrmex gariepensis are cleaning out their nest in Tswalu Kalahari reserve. The video is in real time, demonstrating the speed and tenacity that these Hotrod ants work at in extreme environments. Each of the trips carried out by an individual worker entails removing a grain of sand from within the nest and depositing it on the heap surrounding the entrance. They have a special basket of bristly hairs beneath the head to facilitate transportation of sand grains. Given the sandy environment in which they live this is clearly a never-ending task! 

Ocymyrmex afradu. Photograph by Nokuthula Mbanyana-Nhleko.