New Synonymy and Useful Taxonomic Characters in Smilax (Smilacaceae) from the Venezuelan Guayana

Abstract

In conjunction with a treatment of Smilax (Smilacaceae) for the Flora of the Venezuelan Guayana, a number of taxonomic changes are proposed for previously described taxa from southern Venezuela. A discussion of morphological characters used in the revision and a key to the species in the Venezuelan Guayana are also presented. Smilax is a genus of approximately 300 species of dioecious vines inhabiting tropical and temperate areas of both hemispheres, with most species concentrated in tropical Asia and the Neotropics. The genus has a well deserved reputation for being taxonomically difficult. Problems arise from the paucity of fertile collections of both sexes or even a single sex from particular localities (Huft, 1994), the use of characters that are not reliable for species delimitation (Howard, 1979), and conflicting treatment of species across flora boundaries (Sipman, 1979). For future collections of Smilax, collectors should strive to obtain samples from both sexes and, even more importantly, include a section or a description of the lower portion of the stem (where larger spines may be found) as well as an upper, fertile portion of the plant. We recently completed a treatment of the Smilacaceae for the Flora of the Venezuelan Guayana, which includes the states of Amazonas, Bolivar, and Delta Amacuro in southeastern Venezuela. At the onset of our project, there were 37 different species names in Smilax that had been used to identify herbarium specimens from the flora area. Currently, we recognize only 9 species. We dealt with synonymy of names whose types are from the flora area, but we did not attempt this with species described from other countries. The next logical step in the taxonomic study of South American Smilax would be a comprehensive treatment which would include examination of type material and the identification of the many synonyms that undoubtedly exist across national and floristic boundaries. The following discussion addresses our choice of characters, which should prove useful for future work in other areas. Due to the paucity of comparable fertile collections, we focused on vegetative characters more than reproductive ones. Among the type specimens examined for the nine species currently recognized in the Venezuelan Guayana, only three have flowers, and one has fruit. Also missing from these type specimens (and from most other collections in the flora area as well) is a sample of the lower stem and lower leaves of the plant, which are frequently quite different from the younger, higher stems (Killip & Morton, 1936). Stem. The presence of stem spines can be a useful character, but young growth is often unarmed, while the base of the stem can be heavily armed. In Smilax poeppigii Kunth, spines may be absent on most of the stem, while the base, which may be 20 m away, has dense spines (Berry et al. 6239, MO). A character that is more important outside the flora area is the shape of the spines, which can range from terete and needle-like to flattened and triangular. The texture of the stem has been used in many treatments, and Steyermark and Maguire (1972) used the verruculose-tuberculate texture of the stem in S. jauaensis Steyermark & Maguire as virtually the sole character to differentiate it from S. staminea Grisebach. Stem texture has been shown to be a variable character, and verruculose-tuberculate stems also appear in occasional specimens of S. staminea. Another species, S. lappacea Humboldt & Bonpland ex Willdenow, which Steyermark and Maguire (1972) noted as having smooth stems, has some specimens with tuberculate stems, although the bumps are typically not darkned and thus not readily visible (Huber 581, VEN). Only in the case of S. schomburgkiana Kunth did we use stem texture as a diagnostic character. The stem of this species is consistently NovoN 8: 364-370. 1998. This content downloaded from 157.55.39.163 on Fri, 18 Nov 2016 04:22:17 UTC All use subject to http://about.jstor.org/terms Volume 8, Number 4 Gaskin & Berry 365 1998 Smilax from Venezuelan Guayana