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Premise of the Study: The South American genus Gymnocalycium (Cactoideae-Trichocereae) demonstrates how the sole use of morphological data in Cactaceae results in conflicts in assessing phylogeny, constructing a taxonomic system, and analyzing trends in the evolution of the genus., Methods: Molecular phylogenetic analysis was performed using parsimony and Bayesian methods on a 6195-bp data matrix of plastid DNA sequences (atpI-atpH, petL-psbE, trnK-matK, trnT-trnL-trnF) of 78 samples, including 52 species and infraspecific taxa representing all the subgenera of Gymnocalycium. We assessed morphological character evolution using likelihood methods to optimize characters on a Bayesian tree and to reconstruct possible ancestral states., Key Results: The results of the phylogenetic study confirm the monophyly of the genus, while supporting overall the available infrageneric classification based on seed morphology. Analysis showed the subgenera Microsemineum and Macrosemineum to be polyphyletic and paraphyletic. Analysis of morphological characters showed a tendency toward reduction of stem size, reduction in quantity and hardiness of spines, increment of seed size, development of napiform roots, and change from juicy and colorful fruits to dry and green fruits., Conclusions: Gymnocalycium saglionis is the only species of Microsemineum and a new name is required to identify the clade including the remaining species of Microsemineum; we propose the name Scabrosemineum in agreement with seed morphology. Identifying morphological trends and environmental features allows for a better understanding of the events that might have influenced the diversification of the genus.

Molecular phylogenetic studies of seven plastid DNA regions were used to resolve circumscriptions at generic and infrageneric levels in subfamily Tillandsioideae of Bromeliaceae. One hundred and ten tillandsioid samples were analyzed, encompassing 10 genera, 104 species, and two cultivars. Two species of Bromelioideae, eight species of the polymorphic Pitcairnioideae, and two species of Rapateaceae were selected as outgroups. Parsimony analysis was based on sequence variation of five noncoding (partial 5' and 3' trnK intron, rps16 intron, trnL intron, trnL-trnF intergenic spacer, atpB-rbcL intergenic spacer) and two coding plastid regions (rbcL and matK). Phylogenetic analyses of individual regions produced congruent, but mostly weakly supported or unresolved clades. Results of the combined data set, however, clearly show that subfamily Tillandsioideae is monophyletic. The earliest divergence separates a lineage comprised of Glomeropitcairnia and Catopsis from the "core" tillandsioids. In their present circumscriptions, genera Vriesea and Tillandsia, and their subgenera or sections, as well as Guzmania and Mezobromelia, are poly- and/or paraphyletic. Genera Alcantarea, Werauhia, Racinaea, and Viridantha appear monophyletic, but separation of these from Vriesea and Tillandsia makes the remainder paraphyletic. Nevertheless, Tillandsioideae separates into four main clades, which are proposed as tribes, viz., Catopsideae, Glomeropitcairnieae, Vrieseeae, and Tillandsieae.