Are teleomorphs really necessary?: modelling the potential effects of Muller's Ratchet on deuteromycetous entomopathogenic fungi

Teleomorphic, or sexual, phases have not been described for many deuteromycetous fungi and it is debated whether these phases actually exist, or are even necessary for some fungi. Muller's Ratchet is a population genetical mechanism, hypothesized in 1964 by H. J: Muller, which describes how certain asexual populations may undergo an unavoidable and progressive decline in fitness, eventually leading to population extinction. With respect to deuteromycetous fungi, Muller's Ratchet could operate because clonally reproducing populations are not able to reduce their mutational load with each generation. Here we used a model to investigate and quantify some of the potential effects of the lack of sexual recombination on the accumulation of deleterious mutations using parameters derived from two species of deuteromycetous entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana. Our results suggest that, under certain realistic conditions, Muller's Ratchet may not play a critical role in the fitness of these deuteromycetous entomopathogenic fungi and it is at least theoretically possible that these fungi could reproduce through exclusive clonal lineages.