Anatomy of staminal glands in the Stigmaphylloid clade sheds light into new morphotypes of elaiophores and osmophores in Malpighiaceae.

Staminal glands are an important character in the taxonomy of several Malpighiaceae genera, such as Banisteriopsis, Byrsonima, Diplopterys, Peixotoa and Stigmaphyllon, but only recently few studies started to elucidate the anatomy and ecological functions of these glands. Most genera showing staminal glands are placed in the Stigmaphylloid clade, one of the ten major lineages recovered in recent phylogenies for Malpighiaceae. Here, we identified the nature of the staminal glands from 25 Stigmaphylloid species aiming to characterize their micromorphology, anatomy and exudate histochemistry. Scanning electron and light microscopy were applied to examine the stamens of fresh collected or herborized flowers. All Stigmaphylloid representatives showed elaiophores, osmophores or both glands comprising the epidermal cells in the connective, anther or both regions of the stamen. Elaiophores were distinct into three structural patterns: (1) trichomatous, (2) secretory globose epidermis (3) and overlapping globose epidermal cells. These glands were identified mainly by the occurrence of fatty acids composing the secretion within the cells. Osmophores were always identified as unicellular papillae. Elaiophores and osmophores in the stamen seems to be homoplastic in Malpighiaceae, identified in the Stigmaphylloid clade and in the outgroup representative Byrsonima spicata. Osmophores were restricted to the connectives of Camarea and Cottsia, and at different positions in the anther epidermis of Byrsonima spicata, probably linked to their unique pollination syndromes. This is the first effort in understanding the evolutionary patterns of these glands in Malpighiaceae and should shed light on further studies comprising the remaining lineages of this family. [ABSTRACT FROM AUTHOR]