Palynotaxonomy of tribe Hippomaneae A. Juss. (Euphorbioideae, Euphorbiaceae)

Abstract

Abstract Pollen grains of 23 species distributed in 15 genera and represented by 64 specimens were analysed using light and scanning electron microscopy to characterise the neotropical genera of Hippomaneae. Five of these species are palynologically characterised for the first time. Hippomaneae pollen is shed in monads, being small to large, isopolar, oblate-spheroidal to prolate, with an amb ranging from circular, three-lobed to distinctly three-lobed, tricolporate, very long colpi (except for Hura crepitans in which is long), margo psilate (rugulate only in Colliguaja brasiliensis), narrow to wide, and endoapertures circular, lalongate to very lalongate, with costae. Sexine thicker than the nexine. Sexine is psilate-perforate except for Algernonia brasiliensis, C. brasiliensis, Gymnanthes multiramea, G. schottiana, Microstachys corniculata, Pleradenophora membranifolia, and Sebastiania brasiliensis where it is microreticulate. Only in M. corniculata the sexine is separated from the nexine at the mesocolpus, forming a cavea. Although the Hippomaneae are considered stenopalynous in the literature, our results showed variation between species and genera groups, reinforcing the relevance of pollen morphology in the systematics of this tribe.