Cladistic relationships among thePleurotus ostreatuscomplex, thePleurotus pulmonariuscomplex, andPleurotus eryngiibased on the mitochondrial small subunit ribosomal DNA sequence analysis

The cladistic analysis of the V4 domain sequences, performed by UPGMA, the neighbor-joining, and parsimony methods, revealed that the 19 Pleurotus strains tested in this study evolved along three lineages, each corresponding to a separate biological species: the Pleurotus ostreatus complex, the Pleurotus pulmonarius complex, and Pleurotus eryngii. Moreover, the cladistic positions of the 3 biological species show that the P. ostreatus complex and P. eryngii were derived from a common ancestor at a later stage of evolution, and that the common ancestor had diverged from the lineage of the P. pulmonarius complex during an earlier evolutionary event. The sequences of the 5′ portion of the mt SSU rDNA among the strains of the P. ostreatus complex had 99.2%-99.6% homology. All test strains in the P. pulmonarius complex had completely identical sequences. The homology of the strain sequences between the P. ostreatus complex and the P. pulmonarius complex ranged from 96.0% to 96.3%. The sequence of the strain of P. eryngii showed 97.8%-98.3% and 96.5% homologies with those of the strains in the P. ostreatus and the P. pulmonarius complexes, respectively.