MSA - Systematics/Evolution
Ovrebo, Clark L. , Hughes, Karen W. , Halling, Roy E. .
A preliminary phylogeny of Tricholoma based on the rRNA ITS region.
Tricholoma has long been a focus of the first authorís research and most of that work has taken a morphological approach. A current collaborative project is to examine the species in the genus utilizing DNA sequencing of the ribosomal RNA region. For these analyses, DNA was extracted using a modified CTAB buffer followed by alcohol precipitation. Primers ITS1F and ITSF4 were used for PCR of the ribosomal RNA ITS region. Dideoxy sequencing was primed with ITS5 in the forward direction and ITS4 in the reverse direction with alignment and trimming done manually. These sequenced collections have also been examined morphologically. Related sequences were obtained from GenBank. Alignment difficulties required deletion of approximately 100bp of data for analysis of the entire Tricholoma data set. A majority rule consensus tree of 1000 equally parsimonious trees was obtained using PAUP. The resulting tree included two distinct clades comprising ca. 18 subclades. A comparison of the clades to the infrageneric classification of Rolf Singer reveals some similarities when comparing morphology vs. DNA sequencing. In the Singerian classification, Tricholoma subg. Tricholoma is composed of two main sections, sect. Tricholoma and sect. Genuina. Most of section Tricholoma is represented by a monophyletic clade in the ITS phylogeny. The subclades within sect. Tricholoma agree well with stirpes of Singer and pose no alignment problems. Section Genuina, composed of T. caligatum, T. magnivelare, T. colossum, T. fulvum, T. vaccinum, T. ustale and T. focale, appears in a well supported clade together with other morphologically unrelated subgenera Pardinicutis and Contextocutis and a T. myomyces subclade, the latter belonging to sect. Tricholoma. Tricholoma saponaceum and variants belong to subg. Contextocutis and appears as a separate clade but with low bootstrap support.
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1 - University of Central Oklahoma, Biology, 100 N. University Drive, Edmond, OK, 73034-5209, USA
2 - University of Tennessee, Knoxville, Ecology and Evolutionary Biology, 422 Hesler Biology Building, Knoxville, TN, 37996-0830, USA
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Presentation Type: Poster:Posters for Topics
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM