CAMERON, KENNETH M.* AND CHENGXIN FU. The Lewis B. & Dorothy Cullman Program for Molecular Systematics Studies, The New York Botanical Garden, Bronx, NY 10458 USA; Laboratory of Plant Systematics, Department of Biology, Zhejiang University, Hangzhou 310029, China. - Untangling the catbriers: phylogenetic studies in Smilacaceae.
Smilacaceae are a family of monocotyledons typically characterized by
climbing habit, reticulate leaf venation, paired tendrils on the
petioles, unisexual flowers with six stamens, and superior ovaries
found throughout the world. Deviations from this generalized
description of growth form and floral morphology have led to the
division of Smilacaceae into at least two different families, two
subfamilies, seven different genera, and five sections within the
largest genus, Smilax. In particular, taxa with either fused
perianth, more than six stamens, or herbaceous habit have been
difficult to classify. Moreover, the affinity of the family among
monocots has been a matter of debate. Current treatments of
Smilacaceae based partly on molecular evidence recognize three genera:
Smilax, Heterosmilax, and Rhipogonum positioned
near Philesiaceae and Liliaceae. Our cladistic analyses of 61 taxa
using 51 morphological characters show that Heterosmilax,
Pseudosmilax, Oligosmilax, Pleiosmilax, and
Nemexia are monophyletic clades embedded within Smilax
itself and that Rhipogonum is a monophyletic sister genus.
Within Smilax, the erect woody habit has evolved from climbers
on several occasions, but herbaceous species are monophyletic and
those with inflorescence of more than one umbel also share a common
ancestor. Preliminary DNA sequence data derived from the trnL-F
intergenic spacer conflict with the morphological trees and support
the view that Heterosmilax is sister to Smilax with
Rhipogonum sister to this pair. These molecular data are
limited and weakly supported, however, and continued sampling with
more variable gene regions is required before the catbriers can be
fully untangled.
Key words: molecular systematics, monocots, monocotyledons, phylogenetics, Smilacaceae, Smilax, trnL-F