Ty. Chiang et Ba. Schaal, Molecular evolution of the atpB-rbcL noncoding spacer of chloroplast DNA in the moss family Hylocomiaceae, BOTAN B A S, 41(2), 2000, pp. 85-92
Molecular evolution of the chloroplast noncoding region between the atpB an
d rbcL genes was investigated in the moss family Hylocomiaceae. Nucleotide
substitution contributed to most of the variation among taxa, although an i
nsertion of 29 base pairs was found in Rhytidiopsis robusta. The evolution
of atpB-rbcL intergenic spacer was constrained in Hylocomiaceae compared to
the evolutionary rates of this chloroplast spacer, and even of the rbcL ge
ne, in angiosperms. Using a relative rate test procedure, substitution rate
s of the chloroplast spacer were found to be consistent with the hypothesis
of a molecular clock, except for three taxa. Based on previous knowledge o
f the evolutionary rate of this spacer in true mosses, the divergence of th
e Hylocomiaceae from their common ancestor was estimated to be 29.0 million
years ago, which is consistent with the fossil record. The chloroplast seq
uences supported the monophyly of the Hylocomiaceae with a bootstrap value
of 82%. The effects of long branch attraction caused the erroneous placemen
ts of Rhytidiopsis and Rhytidium in the parsimony analysis. In contrast, ne
ighbor-joining analysis provided a more congruent estimate of the phylogeny
of the Hylocomiaceae based on the cpDNA variation observed.