GOFFINET, BERNARD* AND A. JONATHAN SHAW. Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs CT, 06269 and Department of Botany, Duke University, Durham NC, 27708. - Phylogenetic inferences in the Orthotrichoideae based on trnL-F and rps4 (cpDNA) sequence data.
The genus Orthotrichum Hedw. is one of the largest genera of
mosses. Together with Ulota, Stoneobryum, Muelleriella and
Orthomitrium it composes the Orthotricheae. Generic concepts in
the Orthotrichaceae are based primarily on gametophytic features,
whereas the infrageneric classification of Orthotrichum has
traditionally relied almost exclusively on sporophytic features, and
particularly the architecture of the peristome teeth and the degree of
exposure of the stomatal guard cells. The classification of the
Orthotrichaceae has recently been tested against a phylogenetic
concept of taxa. This study revealed among others that species of
Orthotrichum do not compose a monophyletic genus. Paraphyly
is partially due to the recognition of oligospecific genera but also
to the close affinities of some species of Orthotrichum to
Ulota. Analysis of sequences of two chloroplast loci
(trnL-trnF and rps4) obtained for nearly 80 exemplars of
Orthotrichoideae lead to following results: Orthotrichum, and
most of all speciose subgenera are para- or polyphyletic;
Muelleriella , a genus of saxicolous subantarctic mosses is
nested within a clade that can be defined by immersed vs. superficial
stoma; subg. Orthophyllum is sister to the latter forming a
lineage characterized by n=11 vs n=6. The hypotheses that
diploidization and immersion of the stoma occurred twice in the
Orthotricheae can be rejected. Similarly it is likely that dioicy is
not a plesiotypic conditions, but rather evolved multiple times from
monoicy. The loci sequenced hold about 10% parsimony informative
characters and the trnL intron comprises about 20 unambiguous indels
which define lineages within the clade of aneuploid taxa. Noteworthy
is also the observation that the doubling of chromosome number is
accompanied by a conspicuous acceleration of the rate of molecular
evolution.
Key words: Bryophytes, cytology, Orthotrichum, phylogeny, rps4, trnL