Abstract
The recent evidence that extant cycads are not living fossils triggered a renewed
search for a better understanding of their evolutionary history. In this study, we
investigated the evolutionary diversification history of the genus Encephalartos,
a monophyletic cycad endemic to Africa. We found an antisigmoidal pattern
with a plateau and punctual explosive radiation. This pattern is typical of a
constant radiation with mass extinction. The rate shift that we found may
therefore be a result of a rapid recolonization of niches that have been emptied
owing to mass extinction. Because the explosive radiation occurred during the
transition Pliocene–Pleistocene, we argued that the processes might have been
climatically mediated.