We describe the chromosome numbers and genome sizes of species of the cryptanthoid complex of Bromeliaceae in a phylogenetic framework and their relationship with habitat preferences. The 2C DNA contents varied 2.13-fold among species, ranging from 0.76 to 1.66 pg. A significant difference in DNA content was found among Cryptanthus, Hoplocryptanthus and Rokautskyia. Moreover, species from campos rupestres and the Atlantic Forest had lower and higher genome size values, respectively. The smaller genome sizes of Hoplocryptanthus spp. from campos rupestres may be related with the large genome constraint. The species show a highly conserved ploidy (with 2n = 32 and 34), although the genome sizes varied considerably. The observed variation in chromosome numbers seems to be influenced by dysploidy, but additional investigations are needed. Our study demonstrates that the genome size variation in the cryptanthoid complex species is not strictly related to the phylogenetic relationships and has probably been influenced by different evolutionary processes.

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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.