Pollen morphology of selected species of Piriqueta Aubl. (Passifloraceae sensu lato)

Abstract

ABSTRACTPassifloraceae sensu lato currently encompasses Malesherbiaceae, Turneraceae and Passifloraceae sensu stricto, with Malesherbiaceae being the sister of Turneraceae + Passifloraceae sensu stricto. In Brazil, Turneraceae is represented by the genera Piriqueta and Turnera, and Piriqueta in turn is represented by 38 species. The main objective of this study was to characterise the pollen grains of species of Piriqueta, since few works have addressed the pollen morphology of this genus. The intention is to contribute to a more precise delimitation of taxa, compare pollen morphology between Piriqueta and Passifloraceae sensu lato, and provide characters for future phylogenetic analyses. The pollen of 14 species of Piriqueta occurring in Brazil was studied. The pollinic material was acetolysed, measured and described, electron photomicrographs were taken, and multivariate analysis was conducted. The species analysed are characterised by having pollen grains that are in monads, isopolar, medium sized (25.0–49.9 µm) or large (50.0–100.0 µm), 3-colporate, with short or long colpi, a lalongate or nearly circular endoaperture, and a microreticulate or reticulate sexine, and are heterobrochate and simplicolumellate. The principal component analysis (PCA) and hierarchical cluster analysis (HCA) confirm the separation of species using quantitative pollen grain variables. In relation to the patterns of the exine and the number of apertures, the genus Piriqueta differs from Passiflora in possessing pollen that is 3-colporate and has only a microreticulate or reticulate exine. The analysis of pollen morphology of the genera Piriqueta and Passiflora does not support the inclusion of the family Turneraceae (here represented by Piriqueta) in Passifloraceae sensu lato since the pollen characters do not correspond to the monophyletic grouping of Passifloraceae sensu lato.