ANALYSIS OF THE RIBOSOMAL DNA-SEQUENCES OF THE MICROSPORIDIA THELOHANIA AND VAIRIMORPHA OF FIRE ANTS

Sequences of the 16SrRNA gene of three microsporidia pathogenic to imp orted fire ants, Solenopsis invicta and Solenopsis richteri, were dete rmined and compared to each other and 15 other species of microsporidi a. The sequences of 2 Thelohania species are nearly identical (99.2% i dentity), supporting light-microscopic and ultrastructural evidence th at Thelohania solenopsae and Thelohania sp. are closely related but pr obably not conspecific. Sequence comparisons further revealed that Vai rimorpha sp. has a sequence identity of about 73% with the two Theloha nia species and Vairimorpha necatrix, the type species of the genus Va irimorpha. This, together with information on spore morphology, sugges ts that Vairimorpha sp. represents a genus distinct from that of the f ire ant Thelohania. Its placement in the genus Vairimorpha must also b e reevaluated. Two new sister taxa, one containing T. solenopsae and T helohania sp. and one containing Vairimorpha sp., were found to have d iverged early in the microsporidian lineage. (C) 1998 Academic Press.