Filogenia molecular e anatomia da subtribo Cereinae (Cactoideae, Cactaceae)

Abstract

In the light of a recent phylogenetic review, Cereinae was proposed as one of the three subtribes of tribe Cereeae s.l., which includes most of South American columnar cacti lineages in Cactoideae. Current Cereinae comprises species in 14 genera with a remarkable occurrence in eastern Brazil, mainly in dry forest formations such as Caatinga. Nevertheless, the circumscription of the group is still quite controversial, generic delimitations are problematic, and the knowledge of the anatomy of species is incipient. The aims of this study were to test the monophyletism of Cereinae based on multigenic data and in a broad sampling, evaluate the subtribe systematics, in particular the generic circumscriptions, and survey potential diagnostic and phylogenetic anatomical traits of the dermal system and part of the fundamental system of representatives of 11 genera of the subtribe. The results point to a monophyletic Cereinae with high support in Bayesian, maximum parsimony, and maximum likelihood analyses based in combined matrices, and expand the knowledge of generic relationships within the subtribe. Regarding the morphological and the ancestral state reconstruction analyses results, some skin features are phylogenetic informative for some groups within the subtribe, such as the markedly plicate cell outline shared by all Melocactus species, the abundant prismatic crystals in the epidermal cells shared by all species of Arrojadoa and Stephanocereus, the presence of druses with the rounded-oval-shape outline in the spongy parenchyma shared by all species of Cereus and Cipocereus, and the combination of druses with the rounded-oval-shape outline and in concretions in the spongy parenchyma shared by Cereus species. These groups emerge as clades strongly supported by Bayesian analyses in our phylogeny, demonstrating the relevance of anatomical characters for taxonomy. Our results showed novelties both in the anatomy of the species and in the phylogeny of Cereinae as a base of future investigations in a systematic framework also serving to support the study of the evolutionary history and patterns of South American dry forests and the associated biota as a whole.