Estudos biossistemáticos para a delimitação de linhagens e espécies no complexo Habenaria parviflora Lindl. (Orchidaceae)

Abstract

In this work, we studied the Habenaria parviflora (Orchidaceae) complex, a group restricted to grassland vegetation in South America, in order to elucidate its systematics both at the sectional level and among the morphologically similar taxa of the complex. At the sectional level, we analysed the phylogenetic relationships of species classified in H. sect. Micranthae, to which H. parviflora belongs, as well as other taxa morphologically associated with this species, using the markers ETS, ITS, matK-trnK and rps16-trnK, through parsimony and Bayesian analysis. We recircumscribed the section in order to establish a monophyletic group that is now formed by eight morphologically related species (H. abscondita sp. nov., H. brachyphyton, H. edwallii, H. gollmeri, H. parviflora, H. paulensis, H. ulei and H. uruguayensis) characterized by their sulcate viscidium. To analyze the patterns of morphological and genetic differentiation within the complex, we sampled 65 populations covering the morphological, taxonomic, ecological and geographical variation of the group. We performed morphometric analyzes using 18 morphological characters on 685 individuals classified into 12 morphotypes. The analyses showed a pattern of overlap, but allowed to differentiate two taxa through an association of characters, H. paulensis and H. ulei. The size of the flower, the width of the leaf and the opening angle of the sepals were the most discriminating characters of the groups. We analyzed the data generated with genotyping by sequencing (GBS) for 196 individuals in the complex through ordering analysis, genetic structuring and phylogenetics. In general, the genetic data showed congruence with the morphological patterns, allowing the recognition of six taxa: H. brachyphyton, H. caaguazensis, H. parviflora, H. paulensis, H. tucumanensis comb. & stat. nov. and H. ulei. The observed patterns of genetic mixture suggest the possibility of hybridization and introgression in the complex, events that have not yet been reported for the genus. In the Cerrado we identified three disjunctions that separate areas of rocky fields: Serra da Canastra and Southern Espinhaço for H. paulensis, and Central-West for H. parviflora. For the Atlantic Forest, we identified two disjunctions, one near the fault zone of Além Paraíba and the other near the Guapiara alignment for H. parviflora and H. paulensis, respectively. Our results indicate that several factors may be involved in the evolution of the complex and additional studies in the group will enable more solid hypotheses regarding the diversification of South American grassland vegetations.