Sj. Brunsfeld et al., PHYLOGENETIC-RELATIONSHIPS AMONG THE GENERA OF TAXODIACEAE AND CUPRESSACEAE - EVIDENCE FROM RBCL SEQUENCES, Systematic botany, 19(2), 1994, pp. 253-262
DNA sequences from the plastid gene rbcL were used to assess relations
hips among genera of the conifer families Taxodiaceae and Cupressaceae
s. str. Phylogenetic analyses produced four most parsimonious trees t
hat differ only in the positions of three genera (Athrotaxis, Taxodium
, and Taiwania) and the degree of resolution of a trichotomy within Cu
pressaceae s. str. Taxodiaceae and Cupressaceae form a monophyletic gr
oup. The major lineages of Taxodiaceae diverged first, and a monophyle
tic Cupressaceae s. str. are derived from within Taxodiaceae. These re
sults are consistent with recent suggestions that the two families be
treated as a single family, Cupressaceae s.l. Sciadopitys, often class
ified in Taxodiaceae, is not closely related to Cupressaceae s.l. and
should be excluded from the family. Sequence evolution of rbcL is extr
emely slow in this group of long-lived trees. The rate of silent nucle
otide substitutions is 2.5 x 10(-11) per site per year, approximately
13 times slower than rates estimated in short-lived monocots.