Today, relationships among species are assessed by molecular techniques, including dna sequencing. Tillandsia, a large, morphologically diverse and mostly epiphytic neotropical genus that includes nearly one quarter of the species in the entire family, is, however, still in need of alpha-taxonomic investigation. Previous treatments of the 400+ species of Tillandsia were based on characters found on herbarium specimens. Since dried flowers in these species preserve poorly and are sometimes absent, floral characters are difficult to observe in this manner. Smith and Downs were able to find only one character by which to distinguish subgenus Allardtia from subgenus Tillandsia (together 269 species) in their treatment of the Tillandsioideae for Flora Neotropica–whether the stamens were included (Allardtia) or exerted (Tillandsia). Previous field studies of 79 species of subgenus Tillandsia and 12 species of subgenus Allardtia in Mexico showed that rather than two natural groups, five distinct groups could be circumscribed by suites of characters from fresh flowers, and that these groups cut across current taxonomic lines. Subgenus Tillandsia has its center of distribution in Mexico, while subgenus Allardtia is largely centered in the Andes of South America. Current field studies in Ecuador are expanding the number of species examined and support the hypothesis that a thorough examination of flowering specimens in vivo of the majority of the species in these two subgenera can result in a more natural classification for this difficult group.

Key words: Bromeliaceae, Bromeliads, classification, floral characteristics, taxonomy, Tillandsia