Chamaecrista belongs to subtribe Cassiinae (Caesalpinioideae), and it comprises over 330 species, divided into six sections. The section Xerocalyx has been subjected to a profound taxonomic shuffling over the years. Therefore, we conducted a phylogenetic analysis using a cpDNA trnE-trnT intergenic spacer and nrDNA ITS/5.8S sequences from Cassiinae taxa, in an attempt to elucidate the relationships within this section from Chamaecrista. The tree topology was congruent between the two data sets studied in which the monophyly of the genus Chamaecrista was strongly supported. Our analyses reinforce that new sectional boundaries must be defined in the Chamaecrista genus, especially the inclusion of sections Caliciopsis and Xerocalyx in sect. Chamaecrista, considered here paraphyletic. The section Xerocalyx was strongly supported as monophyletic; however, the current data did not show C. ramosa (microphyllous) and C. desvauxii (macrophyllous) and their respective varieties in distinct clades, suggesting that speciation events are still ongoing in these specimens.

Foi caracterizada a composição florística da vegetação de carrasco do sul do planalto da Ibiapaba em Novo Oriente, Ceará (5°28’ - 5°43’S e 40°52’ - 40º55’W ; 750-850 m de altitude), ocorrendo em Areias Quartzosas profundas. Foram coletadas 184 espécies, incluindo ervas, cipós, subarbustos, arbustos e árvores, distribuídas em 52 famílias. As famílias com maior número de espécies foram Caesalpiniaceae (17), Fabaceae (16), Euphorbiaceae (15), Myrtaceae (11), Bignoniaceae (10) e Mimosaceae (9). De 102 espécies arbustivas e arbóreas da área estudada, 24 ocorreram em áreas de caatingas e cerrados, 29 em cerrados, 17 em caatinga, uma espécie em mata e 31 foram exclusivas do carrasco. Não foi possível definir se o carrasco é um cerradão degradado ou um tipo próprio de vegetação, sendo necessária para isso a realização de levantamentos em outras áreas similares.

The floristic composition of the vegetation in the southern part of the Ibiapaba plateau was studied at Novo Oriente, Ceará - Brazil (5°28’ - 5°43’S and 40°52’ - 40º55’W ; 750-850 m altitude). A total of 184 species in 52 families was collected, including herbs, vines, shrubs and trees. Families with the highest number of species were Caesalpiniaceae (17 species), Fabaceae (16 species), Euphorbiaceae (15 species), Myrtaceae (11 species), Bignoniaceae (10 species) and Mimosaceae (9 species). Of 102 shrub and tree species in the area, 24 occurred in both caatinga and cerrado, 29 in cerrado, 17 in caatinga, one in forest and 31 only in carrasco. It is not yet possible to define whether carrasco is a degraded cerradão or a type vegetation on its own. Surveys in other carrasco areas are necessary in order to contribute to solve this problem.