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