Genetic relatedness among species in Aspergillus section Clavati as measured by electrophoretic comparison of enzymes, DNA base composition, and DNA-DNA hybridization.

Aspergillus subgenus Clavati has four recognized species: A. clavatus (the type species), A. clavatonanicus, A. giganteus, and A. longivesica. These species are strictly anamorphic (mitotic) and defined by the morphological species concept. However, their genealogical relationships remain uncertain. In this study, we examined the genetic relatedness among the four species in this section, using electrophoretic comparison of enzymes, DNA base composition, and DNA-DNA hybridization. In a dendrogram based on the calculated similarity values of four enzymes, 10 strains in section Clavati, 3 strains in the xerophilic species, a strain in section Ornati, and a strain in section Cremei were separated into nine major clusters at a 60% similarity level. A. longivesica JCM 10186(T) had Q-10 in our analysis, but Kuraishi et al. (1990) reported A. longivesica JCM 1720(T) had Q-9 (49%) and Q-10 (46%). The G+C contents of the four species of section Clavati ranged from 48 to 50 mol%. The degree of the intraspecific reassociation among the DNAs from the strains of these species ranged from 77 to 99%, whereas the degrees of interspecific relative binding among strains of the four species ranged from 30 to 59%. Our data from enzyme patterns and DNA relatedness support the validity of the three species in section Clavati, except for A. longivesica.