Phylogenetic Analysis of Two Ribosomal Dna Regions Indicates Multiple Independent Losses of a Sexual Talaromyces State Among Asexual Penicillium Species in Subgenus Biverticillium

ABSTRACT

Nucleotide sequences were obtained from the mitochondrial small subunit ribosomal DNA, and the nuclear ribosomal DNA region containing the internal transcribed spacers and 5.8S ribosomal RNA gene for 10 Talaromyces species and six Penicillium species in subgenus Biverticillium. Phylogenetic analysis of the Talaromyces species shows that the majority of the species examined formed a major Talaromyces clade, but that sections and series proposed for these species may not reflect their phylogenetic relationships. Incorporating the strictly mitotic Penicillium species with the meiotic Talaromyces in the phylogenetic analysis demonstrated that the majority of mitotic species have meiotic species as their closest relatives. Thus, multiple independent losses of a meiotic Talaromyces state have occurred among Penicillium species in subgenus Biverticillium. Examination of base substitution patterns for each ribosomal DNA region indicated that the mitochondrial small subunit ribosomal DNA is adenine-thymine rich and biased towards adenine-guanine transitions. The internal transcribed spacers and 5.8S ribosomal RNA gene is guanine-cytosine rich and biased towards cytosine-thymine and thymine-cytosine base transitions. Although these molecules vary in their tempo and mode of evolution, trees generated independently for each ribosomal DNA region from bootstrap analysis had identical topologies in all statistically significant branches.

Key Words:

• ascomyetes
• fungal phylogeny
• internal transcribed spacers-5.8S rRNA gene
• mitochondrial small subunit rDNA
• molecular evolution
• Penicillium subgenus Biverticillium
• Talaromyces