PHYLOGENETIC ANALYSIS OF 2 RIBOSOMAL DNA REGIONS INDICATES MULTIPLE INDEPENDENT LOSSES OF A SEXUAL TALAROMYCES STATE AMONG ASEXUAL PENICILLIUM SPECIES IN SUBGENUS BIVERTICILLIUM

Nucleotide sequences were obtained from the mitochondrial small subuni t ribosomal DNA, and the nuclear ribosomal DNA region containing the i nternal transcribed spacers and 5.8S ribosomal RNA gene for 10 Talarom yces species and six Penicillium species in subgenus Biverticillium. P hylogenetic analysis of the Talaromyces species shows that the majorit y of the species examined formed a major Talaromyces clade, but that s ections and series proposed for these species may not reflect their ph ylogenetic relationships. Incorporating the strictly mitotic Penicilli um species with the meiotic Talaromyces in the phylogenetic analysis d emonstrated that the majority of mitotic species have meiotic species as their closest relatives. Thus, multiple independent losses of a mei otic Talaromyces state have occurred among Penicillium species in subg enus Biverticillium. Examination of base substitution patterns for eac h ribosomal DNA region indicated that the mitochondrial small subunit ribosomal DNA is adenine-thymine rich and biased towards adenine-guani ne transitions. The internal transcribed spacers and 5.8S ribosomal RN A gene is guanine-cytosine rich and biased towards cytosine-thymine an d thymine-cytosine base transitions. Although these molecules vary in their tempo and mode of evolution, trees generated independently for e ach ribosomal DNA region from bootstrap analysis had identical topolog ies in all statistically significant branches.