Synopsis of some important, non-DNA character states in the asterids with special reference to sympetaly
Erbar, Claudia; Leins, Peter
published: Jun 1, 2011
ArtNo. ESP145012972001, Price: 29.00 €
Character states of sympetaly (early or late formation of corolla tubes), phytochemistry (mainly iridoids, polyacetylenes, inulin) and ovule conditions (bi- or unitegmic, crassi- or tenuinucellate) are — on family level — transferred onto cladograms based on DNA sequences. Though the sub-clades cannot be definitely circumscribed by means of non-DNA characters, nevertheless, there are some evolutionary trends, particularly in the modes of corolla tube formation and ovule morphology.Early sympetaly has become canalized in the upper asterids (euasterids II = campanulids) as the single mode of development, whereas in the euasterids I (= lamiids), besides early sympetaly in a few groups, mostly late sympetaly occurs. In the basal asterids (Cornales, Ericales) late sympetaly is uncommon (Polemoniaceae); if corollas are sympetalous, the early mode is dominant (as far as investigated). In advanced taxa of the euasterids I and in all euasterids II investigated so far, ovules are unitegmic. Bitegmic ovules (but which are mostly tenuinucellate) occur only in the basal asterids and in taxa basal within the euasterids I. Unitegmy is very seldom combined with a crassinucellate condition of the ovules (see Fig. 6-8).