Mol Phylogenet Evol 2019 11 13;140:106580. Epub 2019 Aug 13.
Ecologie Systématique Evolution, Univ. Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France.
The identification and delimitation of species boundaries are essential for understanding speciation and adaptation processes and for the management of biodiversity as well as development for applications. Ophiocordyceps unilateralis sensu lato is a complex of fungal pathogens parasitizing Formicine ants, inducing zombie behaviors in their hosts. Previous taxonomic works with limited numbers of samples and markers led to the "one ant-one fungus" paradigm, resulting in the use of ant species as a proxy for fungal identification. Here, a population genomics study with sampling on three ant species across Thailand supported the existence of host-specific species in O. unilateralis s.l. with no footprints of long term introgression despite occasional host shifts and first-generation hybrids. We further detected genetic clusters within the previously delimited fungal species, with each little footprints of recombination, suggesting high levels of inbreeding. The clusters within each of O. camponoti-leonardi and O. camponoti-saundersi were supported by differentiation throughout the genome, suggesting they may constitute further cryptic species parasitizing the same host, challenging the one ant-one fungus paradigm. These genetic clusters had different geographical ranges, supporting different biogeographic influences between the north/center and the south of Thailand, reinforcing the scenario in which Thailand endured compartmentation during the latest Pleistocene glacial cycles.