Higher level phylogenetic relationships of euascomycetes (Pezizomycotina) inferred from a combined analysis of nuclear and mitochondrial sequence data |
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Authors: | H Thorsten Lumbsch Nora Wirtz Ralf Lindemuth Imke Schmitt |
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Institution: | 1. Botanisches Institut, Universit?t Essen, D-45117, Essen, Germany
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Abstract: | A combined data set of nuclear SSU rDNA, LSU rDNA, and mitochondrial SSU rDNA sequences was analyzed in order to examine the
relationships of the major clades of euascomycetes. Partial sequences of 14 ascomycetes were determined and aligned with the
corresponding sequences of 16 other ascomycetes retrieved from Genbank. The alignment was analyzed using maximum parsimony
(MP) and a Bayesian analysis with Markov chain Monte Carlo (B/MCMC). The classification based on single-gene studies is supported,
but the confidence is enhanced in the concatenated analysis. The monophyly of the superclass Leotiomyceta, which includes
all euascomycetes with inoperculate asci, is strongly supported. The polyphyly of ascolocularous fungi is supported. The group
is divided into two groups: the Dothideomycetes basal to all other Leotiomyceta and the Chaetothyriomycetes as sister-group
to Eurotiomycetes. The Lecanoromycetes appear as a monophyletic group with strong support and form a sister-group to the Chaetothyriomycetes/Eurotiomycetes
clade, but this lacks support. The Leotiomycetes and Sordariomycetes form a strongly supported sister-group. Alternative topologies
are tested using parametric bootstrapping; a basal position of the Eurotiomycetes and Leotiomycetes in the Leotiomyceta cannot
be rejected, while such a position can be rejected for Chaetothyriomycetes, Lecanoromycetes and Sordariomycetes. The character
evolution with regard to ascoma type, ascus type and ascoma-ontogeny is examined using MP and maximum likelihood (ML). While
it appears most likely that the ancestor of the inoperculate ascomycetes had apothecia and an ascohymenial ascoma-ontogeny
using MP methods, the ML approach shows that there is some uncertainty at the current state of knowledge. The improvement
of confidence of the combined data set in comparison with single-gene studies makes us confident that analyses with additional
data sets will further improve the confidence and eventually uncover the branching order of euascomycetes. |
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