Pollen morphology of the tribeHemimerideae: possible evidence of ancestral pollen types and parallel evolution in the basalmost clade ofScrophulariaceaes.str.

Abstract

Abstract: Pollen morphology of nine species belonging to six genera of tribe Hemimerideae (representing the basalmost clade of Scrophulariaceae s.str.) was studied and illustrated with light microscopy (LM) and scanning electron microscopy (SEM). Pollen grains in Hemimerideae are 3- or 6–8-colpate or 3- or 5–8-colporate, prolate, spheroidal or oblate-spheroidal in shape; they are mainly medium-sized or occasionally small. The outline in polar view is 3-lobed, rounded-3-lobed or 5–8-lobed; the outline in equatorial view is elliptic or orbicular. Exine sculpture is rough, rough-foveolate, foveolate, microreticulate, rugulate, rugulate-foveolate or rugulate-microreticulate. Four major pollen types are recognized, based on original data: 3-colpate (Alonsoa), 6–8-colpate (Diclis, Hemimeris), 3-colporate (Colpias) and 5–8-colporate (Diascia, Nemesia). Within two of these pollen types, two subtypes can be further distinguished based on pollen size, exine sculpture, details of the colpi and endoapertures. Based o...