Host-jump drives rapid and recent ecological speciation of the emergent fungal pathogen Colletotrichum kahawae

Ecological speciation through host-shift has been proposed as a major route for the appearance of novel fungal pathogens. The growing awareness of their negative impact on global economies and public health created an enormous interest in identifying the factors that are most likely to promote their emergence in nature. In this work, a combination of pathological, molecular and geographic data was used to investigate the recent emergence of the fungus Colletotrichum kahawae (Ck). Ck emerged as a specialist pathogen causing Coffee Berry Disease in Coffea arabica, due to its unparalleled adaptation of infecting green coffee berries. Contrary to current hypotheses, our results suggest that a recent host-jump underlay the speciation of Ck from a generalist group of fungi seemingly harmless to coffee berries. We posit that immigrant inviability and a predominantly asexual behavior could have been instrumental in driving speciation by creating pleiotropic interactions between local adaptation...