LITTLE, DAMON P. L.H. Bailey Hortorium, Cornell University, Ithaca, NY 14853. - Phylogenetic relationship and monophyly of Cupressus and Chamaecyparis (Cupressaceae): molecular and organismal evidence
Most 19th and early 20th century works treated Chamaecyparis
Spach as an infrageneric taxon within Cupressus L.
(Cupressaceae). In recent works Cupressus and
Chamaecyparis are recognized as separate genera on the basis of
a single constant character: the presence of vermiform (a.k.a.
trabeculate) thickenings on the pits of leaf transfusion tracheids in
Cupressus and the absence of such thickenings in
Chamaecyparis. Other characters commonly used to circumscribe
these taxa (e.g. the configuration of the ovulate cone, the anatomy of
the seed, the timing of embryo development) are not constant within
each genus, largely due to the conflicting suite of characters
observed in Chamaecyparis nootkatensis (D. Don) Spach. As a
result of limited taxon sampling and/or the reliance on composite
terminals, the monophyly of these genera in the Cupressaceae was not
tested by previous phylogenetic efforts. The monophyly of
Cupressus and Chamaecyparis is tested with a
simultaneous cladistic analysis of organismal data and rbcL
sequences. Organismal data, including morphology, anatomy,
biochemistry, and embryological development, comprise ca. 50% of the
informative characters in the combined matrix. Preliminary analysis
suggests that, as currently circumscribed, Cupressus and
Chamaecyparis are not monophyletic.
Key words: Chamaecyparis, Cupressaceae, Cupressus, monophyly, phylogeny, rbcL