Importance of palynology in the taxonomy of Piptolepis Sch.Bip. (Asteraceae: Lychnophorinae), a genus endemic to Brazil

Abstract

Lychnophorinae comprises 19 genera and 117 species. Its representatives are found mostly in the rocky grasslands (“campos rupestres”) of Minas Gerais, Bahia, and Goiás States, Brazil. This study presents a palynological investigation of 10 species belonging to the genus Piptolepis, endemic to the rocky grasslands of the Espinhaço Mountains, in Minas Gerais State. The plant material used in this investigation was obtained from specimens deposited in Brazilian herbaria. Pollen grains were processed by the acetolysis method, measured, described, and photomicrographed in light microscopy and scanning electron microscopy. Morphological observations revealed Piptolepis pollen to be large, prolate spheroidal in most species, 3-colporate, ectoapertures long, sexine subechinolophate or sublophate. Endoapertures vary from almost circular, lalongate or lalongate, with a median constriction observed only in three species. Three types of spines were identified: prostrate and disorganized, elongated and narrow, and conical, erect, apex acute in the other species. This first palynological study of Piptolepis species allowed the separation of representatives of the genus using pollen keys. The most significant characters were pollen shape, ornamentation, endoaperture, and presence of median constriction in the endoaperture. The findings presented here do not support the infrageneric classification of Piptolepis, as pollen characters were not unique to any section.

Key words
rocky grasslands; Lychnophorinae; Minas Gerais; palynotaxonomy; pollen