Variability and Phylogenetic Incongruence of an SSU nrDNA Group I Intron in Artomyces, Auriscalpium, and Lentinellus (Auriscalpiaceae: Homobasidiomycetes)

Previous research has shown that a group I intron occurs in the SSU ribosomal DNA gene of isolates of Artomyces (Clavicorona, in part) and Lentinellus, but apparently it is absent in an Auriscalpium isolate. However, further investigation revealed that the intron is apparently absent in some species of Artomyces and Lentinellus and is present in at least one species of Auriscalpium. To examine this further, the presence or absence of the group I intron is reported for 13 species of Lentinellus, two species of Auriscalpium, and 16 species of Artomyces. The presence of the intron among the species was variable and is documented for seven species of Lentinellus, one species of Auriscalpium, and 12 species of Artomyces. Furthermore, the presence of the intron was variable among the isolates of several species, and variability of its presence was observed within single isolates, indicating inter-ribosomal repeat heterogeneity. Independent phylogenetic estimations were generated for the intron and nuclear ribosomal internal transcribed spacer regions (ITS). Tests of congruence for the two trees indicated that the data were heterogeneous. Some of the discontinuity between the two phylogenies is due to placement of the Ar. austropiperatus intron within the Lentinellus intron clade. Variability in the length of the intron was observed in populations of the pan-Northern Temperate species Ar. pyxidatus. This was due to the presence of an additional unknown insertional element found only within North American collections of Ar. pyxidatus and absent from European and Asian collections.