• Premise of the study: Tropical regions have high species diversity, and polyploidization is a major mechanism of speciation in plants. However, few cases of natural polyploidy have been reported in tropical regions. Lippia alba, is a tropical, aromatic shrub with a wide distribution, extensive morphological plasticity, and several chemotypes. The species has long been recognized as a diploid with 2n = 30 chromosomes. Recently, two variations in chromosome number (2n = 60; 2n = 12-60) have been reported, suggesting the occurrence of polyploidy within the species.• Methods: Flow cytometry was used to investigate the genome size in 106 accessions from 14 Brazilian States. Conventional and molecular cytogenetic techniques and pollen viability analysis were employed to characterize each chromosome number observed.• Key results: The DNA 1C-value varied from 1.17 to 3.45 pg, showing a large variation in genome size. Five distinct chromosome numbers were observed (2n = 30, 38, 45, 60, 90); three are cytogenetically described here for the first time. The 5S rDNA signals varied proportionally according to each chromosome number, but 45S rDNA sites did not. High rates of meiotic irregularity were observed, mainly in cytotypes with higher chromosome numbers.• Conclusions: The data provide new support for the occurrence of a polyploid series in Lippia alba. We provide a hypothesis for how this complex may have arisen. Other cryptic polyploid complexes may remain undiscovered in tropical regions.

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Four new species of Habenaria restricted to the Espinhaço Range in the states of Minas Gerais and Bahia are described: H. reflexicalcar, H. hippocrepica, H. quadriferricola, and H. espinhacensis. Specimens were collected as long ago as 1816, but they were misidentified or unidentified in herbarium collections. Molecular phylogenetic analyses based on nuclear and plastid DNA sequences showed that these species form a highly supported clade, denominated Espinhacenses, which is related to other species having linear, grass-like leaves that are concentrated in the cerrado and campos rupestres vegetation of central and southeastern Brazil, although the closest relatives to the Espinhacenses clade were not resolved. There are no apparent morphological synapomorphies for the clade, it being characterized by a combination of characters, including slender plants, linear leaves, spiral inflorescences, few to many small and glabrous flowers, a pedicel that is shorter than the ovary, and separate hemipollinaria.

Habenaria bicornis fue descrita por primera vez en 1835, para Cuba, y era conocida apenas para este país y unos pocos registros de Panamá, de 1920. En el presente estudio, demostramos que H. bicornis y H. goyazensis, esta última conocida para Brasil y Guiana, son específicas y la especie se distribuye desde México hasta el sudeste de Brasil. El modelado de nicho y la recolección de datos indican que esta especie posee una preferencia por sabanas húmedas de tierras bajas y es predicho que su distribución incluye gran parte del Neotrópico con hábitats favorables. Los análisis filogenéticos moleculares con secuencias del ADN nuclear (ITS) y plastidial (matK) ubicaron H. bicornis en una posición aislada próximo a la base del clado Neotropical, aunque con bajo soporte. En términos de su morfología, sus relaciones no están aclaradas, ya que no hay similitudes evidentes entre H. bicornis y los subclados básales o cualquier otro subclado Neotropical. Los análisis citogenéticos indican un número cromosómico básico de x=21, similar a las otras especies basales del Neotrópico.

Th ree new species of Habenaria (Orchidaceae) section Nudae from Rio Grande do Sul, southern Brazil, are described and illustrated: Habenaria australis , H. kleinii and H. sobraliana . Th ese are the fi rst records of H. sect. Nudae for the state. Based on the examination of living and dried specimens, a total of 33 species and 400 collections of Habenaria were recorded for Rio Grande do Sul. Based on this survey, an updated checklist of the genus Habenaria for Rio Grande do Sul has been compiled. Four species are known only from this state, while seven other species are restricted to southern Brazil, Argentina and Uruguay. Habenaria hieronymi , previously known only from Argentina, is recorded for the fi rst time from Brazil, and H. brachyphyton , H. ekmaniana and H. melanopoda are new records for Rio Grande do Sul.