Biosystematics of the Didymium iridis super species complex: Additional isolates

Abstract

Forty-six isolates referable to the Didymium iridis super species complex were cultured and their reproductive system determined. Thirty of the isolates were nonheterothallic and presumptive apomicts, while the remaining 16 isolates were heterothallic and found to belong to seven biological species: A0 or D. ovoideum (one isolates), A1 or Caribbean (five isolates), A2 or Northeastern US (one isolate), A5 or D. megalosporum (five isolates), A8 or Hawaii (one isolate), A9 or Costa Rican B (two isolates), and A10 or Mexican (one isolate). As such, most of the sexual isolates of this cosmopolitan complex conformed to the pattern of geographically based sibling species that are part of a more widely distributed species complex. However, the A5 and A0 groups have worldwide distributions and are primarily the basis of the Didymium megalosporum and D. ovoideum morphospecies descriptions to which they partially conform. These results suggest that the long non-calcareous stalked Didymium are an extremely complicated series of species complexes, each consisting of one or more biological species and countless apomictic lines with overlapping morphology. While the morphological defined species are, in a few cases, correlated with a reproductive group, the reproductive groups, in general, are not assignable to a morphologically based taxon.