The strong genetic differentiation between southeastern Caatinga and the remaining regions may indicate the occurrence of a cryptic species in . The unique genetic composition of each inselberg population suggests in situ conservation as the most appropriate protection measure for this plant lineage.

No abstract

Encholirium is a genus of 31 xerophytic terrestrial or epilithic bromeliad species endemic to eastern Brazil. Together with Dyckia and Deuterocohnia, it forms the so-called xeric clade of the Pitcairnioideae subfamily of Bromeliaceae. Encholirium species are adapted to rocky landscapes, and many of them are found in the rocky grassland fields of the Espinhaço in the state of Minas Gerais, which is considered the diversity center of the genus. Encholirium species and other bromeliads growing on isolated, island-like habitats like rock outcrops and "inselbergs" are often characterized by high levels of genetic structure and limited gene flow among populations, but there are also exceptions. In the present study, we applied nuclear and chloroplast microsatellite markers to investigate the genetic diversity and population structure of E. magalhaesii L.B.Sm., an endemic species of the Espinhaço, collected in four localities of the Diamantina municipality in southeastern Brazil. Moderate genetic differentiation among localities was revealed by the nuclear markers (F st = 0.199), whereas genetic structuring was much higher with plastid markers (F st = 0.496). Estimations of pollen/seed flow ratios suggest that pollen flow is more efficient in maintaining the genetic connectivity among E. magalhaesii populations than seed flow.

Th e taxonomy of Cyperaceae is complex, with genera like Cyperus harboring species complexes. We analyzed the genetic similarity between Cyperus ligularis L. and C. odoratus L. based on DNA fi ngerprinting and cytogenetics. Signifi cative genetic diff erentiation (G ST = 0.363) and low gene fl ow (N m = 0.877) indicated a clear genetic distinction between the two species. Moreover, the clustering analysis showed two distinct genetic groups, suggesting a lack of evidence for hybridization. Th e phenogram revealed two diff erent lineages, and although all individuals of C. odoratus were collected from plots close to each other, they possessed greater genetic diversity than that observed among individuals of C. ligularis, which were sampled over a wider geographic range. Variation in chromosome number within the two species exhibited the opposite pattern, indicating greater karyotype stability in C. odoratus with 2n = 72 and 2n = 76, while the diploid number for C. ligularis varied from 2n = 66 to 88. Th e lower genetic variation in C. ligularis may be a result of the founder eff ect associated with seed dispersion and clonal reproduction. Field observations and analysis of reproductive biology should enrich the understanding of the genetic structure of the investigated populations and their role in successional processes.

Hohenbergia isepponae (Bromeliaceae), a new species from the Atlantic Forest of Pernambuco, Brazil is described and illustrated herewith. We also compared it with the morphologically similar species.

Plant evolution may be triggered by significant chromosome changes. In some plant groups, karyoevolution played an important role, influencing speciation processes. Hohenbergia comprises 48 species distributed through eastern Brazil. Previous cytological information includes few species and only chromosome counts, lacking information about genome size and more accurate karyomorphological investigation. Here, we compare cytomolecular features and genome sizes of 12 Hohenbergia spp. Besides, new measurements of genome sizes of 32 species are reported. All studied species presented 2n = 50, a number prevalent in Bromelioideae. The genome sizes (2C) varied from 0.74 to 1.52 pg. Despite the apparent homogeneity in chromosome number and genome size in Hohenbergia, significant polymorphism was observed in regard to the distribution of CMA+/DAPI0 bands and sites of 35S and 5S rDNA in metaphase chromosomes. Seven out of 12 analysed species presented heteromorphic pairs regarding 35S rDNA and/or 5S rDNA. Hohenbergia thus shows karyotypic diversity despite the conservation in chromosome number.