Genetic structure of Metarhizium species in western USA: Finite populations composed of divergent clonal lineages with limited evidence for recent recombination

•Of seven species, Metarhizium robertsii predominates in western North America.•Population sizes are finite, with fewer than 12 genetic individuals per species sampled.•All species display clonal genetic structure and clones may be widely distributed.•Clones evidently long-lived with many uniquely distinguished by private alleles.•A single widespread M. robertsii clone constitutes 45% of total isolates.•No species is panmictic but clone-corrected M. robertsii has a recombining structure.•Mating may preferentially occur between closely related individuals.