Molecular phylogenetic relationships within Rhizopus based on combined analyses of ITS rDNA and pyrG gene sequences

Liu X.-y., Huang H. & Zheng R.-y. (2007) Molecular phylogenetic relationships within Rhizopus based on combined analyses of ITS rDNA and pyrG gene sequences.

Sydowia 59 (2): 235–253.

DNA sequences from two loci, the entire ITS rDNA and a portion of pyrG, were examined to study relationships within Rhizopus morphospecies. The ITS rDNA sequences from 55 strains representing all 10 currently recognized species showed great differences in length among species ranging from 450 to 788 bp. Phylogenetic analysis of the ITS rDNA resolved seven of the 10 species into separate clades. Three of the species, R. americanus, R. arrhizus and R. niveus, formed a clade, but evolutionary relationships among them were unresolved. In order to clarify relationships among these three species, we analyzed 26 partial sequences of pyrG gene encoding the terminal enzyme in the pyrimidine-biosynthetic pathway. The pyrG gene tree contained seven lineages. R. americanus formed a strongly supported clade with R. sexualis and R. stolonifer, but R. arrhizus was paraphyletic with R. niveus. Although there are 10 recognized species, combined analyses of the ITS rDNA and pyrG gene data only allowed eight species to be distinguished: R. americanus, R. caespitosus, R. homothallicus, R. microsporus, R. reflexus, R. schipperae, R. sexualis and R. stolonifer. The remaining two morphologically distinct species, R. arrhizus and R. niveus, formed an unresolved cluster and need more phylogenetic studies.

Keywords: classification, molecular phylogenetics, ribosomal RNA gene, OMPD.