This study focuses on a pair of fungal species, Moelleriella libera and M. raciborskii (Ascomycota: Clavicipitaceae) from the neotropics and paleotropics, respectively, that are phenotypically nearly indistinguishable. Molecular analyses based on DNA sequences from RNA polymerase II subunit 2 (RPB2), translation elongation factor 1-alpha (EF1-alpha) and beta-tubulin genes confirm that they are recently derived sister species. Speciation appears to have followed an historical transoceanic dispersal event. Models of population structure and migration from TCS, IM, and coalescent-based analyses suggest there is little gene flow between the two species. The direction of dispersal, investigated using the progression rule and coalescent-based gene genealogies, was likely from the New World to the Old World.