Pollen morphology of some species ofVernonia s. l.(Vernonieae, Asteraceae) from Argentina and Paraguay

Abstract

Pollen morphology is widely used in taxonomic treatments of tribe Vernonieae, and differences in exine structure and aperture form have been described for many species within the genera comprising the tribe. However, in recent years a number of new species have been described and, in the present paper, we describe in detail the pollen of 24 species of the tribe which are either endemic or uncommon to certain regions of Argentina or of Paraguay. The pollen of these species are radially symmetrical and more or less spheroidal, 3-colporate or, in one species, 3-porate; the exine may be tectate or semitectate and microperforate, with echinate lophae or, in the 3-porate example, psilate lophae. Using a range of characteristics related to size, shape, wall thickness, apertures and tectum surface morphology, five of the six pollen types previously described for tribe Vernonieae, and a subtype, are recognized. Our results support the usefulness of pollen morphology in helping to determine the taxonomic position of species within tribe Vernonieae.

Nuevas combinaciones en los géneros sudamericanos Lepidaploa y Lessingianthus (Vernonieae, Asteraceae)

“…Lessingianthus se caracteriza por presentar polen tipo "B", los cuales son tricolporados, equinolofados, con el tectum discontinuo con lagunas ecuatoriales y sin lagunas polares (Dematteis & Pire 2008). Los granos de polen de Lepidaploa pueden ser de tipo "C", "D" o "G".…”

Pollen morphology of the South American genus Lessingianthus (Vernonieae, Asteraceae) and its taxonomic implications

“…ex Baker (Keeley & Robinson, 2009). This pollen, in comparison to the one found in Lessingianthus (type "B-3"), is triporate with lacunae of similar size, without a perforated tectum and spines (Dematteis & Robinson, 1997;Dematteis & Pire, 2008). The echinate pollen seems to be the primitive condition in the family, while the lophate pollen would be derived from it (Wodehouse, 1928).…”

“…The pollen morphology of some Lessingianthus species has been discussed previously (Robinson, 1988a;Dematteis, 2006;Dematteis & Pire, 2008), but these studies were focused on comparative analysis among genera of the tribe Vernonieae. A recent analysis of the genus pollen morphology undertaken by Mendonça et al (in press) includes 30 species of Lessingianthus.…”

“…Robinson (1992a) recognised some additional features and currently, ten main pollen types are recognised within the Vernonieae. The genus Lessingianthus has type "B" pollen grains (Robinson, 1988a), which are characterised by being tricolporate, echinolophate, with a discontinuous tectum, very long germinal furrows that converge at the poles and lacunae disposed in a regular pattern, and by the lack of polar lacuna (Dematteis & Pire, 2008). This pollen type is also characterised by crests with distinct baculae discernible from the point attachment on the foot layer to the point above where they join the ridge of the crest (Robinson, 1988a).…”

“…Several authors have analysed the pollen grains of species of the tribe, mainly belonging to the genus Vernonia s.l. (Wodehouse, 1928;Stix, 1960;Keeley & Jones, 1977, 1979Jones, 1979Jones, , 1981Robinson, 1988a, b, c;Skvarla et al, 2005;Dematteis & Pire, 2008). Wodehouse (1928) studied the pollen grains of the Vernonieae and recognised three patterns of ornamentation: psilate, lophate, and echinate.…”