Biossistemática em espécies de Bulbophyllum (Thouars) seção Micranthae Barb.Rodr. (Orchidaceae)

Abstract

Species delimitation has always been a major challenge for taxonomists. Some groups of species are particularly complex, specially those with vegetatively uniform species, in which separation is only possible because of small floral characters that are difficult to discern in herbariums. Biosystematics, a research area that uses data from multiple fields, has been particularly important in taxonomic research of species complexes such as those found in the genus Bulbophyllum (Orchidaceae). In this study, we used genomic molecular markers, morphometry and inter- and intraspecific reproductive system data to understand the evolutionary dynamics of B. sect. Micranthae populations. Phylogenomic analyses provided better resolution for the relationships inferred among species within B. sect. Micranthae. Not all species within for the section are monophyletic. Within the B. epiphytum/B. rupicola species complex there are two different genetic clades, which do not correspond to the current morphological circumsscription. Some species display high population structuring, probably due to different patterns of genetic isolation and distribuition in campos rupestres. The multivariate analyzes performe using floral and vegetative morphometric data showed an overlapping pattern in some species of the section, particularly in specimens from B. epiphytum/B. rupicola complex, suggesting cryptic speciation in the lineages identified by molecular data. Only in the analysis of canonical variables it was possible to recover these two species with a high degree of accuracy. The group is mostly selfincompatible, which is rare in orchids. Pre-zygotic mechanisms contribute significantly to species isolation, but barriers to gene exchange are permeable, especially in closely related species. Furthermore, the great diversity of pollen tube growth phenotypes observed in this small group of orchids provides new insights into the diversity of self-incompatibility reaction sites.