WHEELER, JOHN A.*, DENNIS P. WALL, KIRSTEN JOHANNES, AND BRENT D. MISHLER. University Herbarium, Jepson Herbarium, and Department of Integrative Biology, University of California, Berkeley, CA 94720-2465. - Congruence and convergence in the moss family Calymperaceae: phylogenetic analysis of
two chloroplast genes (rbcL and rps4) and Morphology
.
Morphological homoplasy is reputed to be prevalent in plants, perhaps
especially in mosses and other haploid-dominant ‘bryophytes’. The
Calymperaceae is a diverse and ecologically important family of mosses
in the tropics that has proven difficult to place phylogenetically and
circumscribe taxonomically; single characters are not often definitive
and supra-specific taxa are mostly defined by tenuous combinations of
morphological features. Using morphological characters, as well as
sequence data from the plastid-encoded genes rbcL and
rps4, we reconstructed a phylogenetic framework in which to
explore character evolution in the Calymperaceae and putative
relatives, particularly, the origin and evolution of a distinctive
leaf anatomy seen most prominently in Leucobryum and similar taxa.
This generalized ‘leucobryoid’ leaf type contains living green cells
that are covered with empty dead hyaline cells. We showed that a
monophyletic Calymperaceae can only be defined by including several
leucobryoid genera within the traditional family; in fact, our
topologies confirm that the leucobryoid leaf architecture evolved
independently at least four times within our taxon sample. The
phylogenetic patterns probably denote both convergence and
parallelism. When mapped to the phylogenies (using several different
quantitative comparative methods), coarse habitat characterizations of
sampled leucobryoid taxa appear to falsify previous adaptive
hypotheses and yet provide no obvious clues about why this leaf
architecture might be favored. If one considers all the various
extant moss taxa with hyalocyst-dominated architectures then there
might conceivably be one common denominator: their respective
oligotrophic habitats.
Key words: Calymperaceae, convergence, homoplasy, leaf architecture, oligotrophy, parallelism