A Taxonomic Study On Pterocypsela Shih(Lactuceae-Compositae)

Pterocypsela Shih, belonging to subtribe Lactucinae Less, tribe Lactuceae Cass, family Compositae/Asteraceae, was a genus that newly isolated from Lactuca L. Because of the complication of characters and the serious crossing between the genus of Pterocypsela shih, Lactrcal L and other relative genera, it is hard to classify them. So, we could not determine that whether the genus of PterocyPsela Shih can be a independent genus, and the systematic relationships between this genus and other relative genera are not clear. For this reason, basing on the herbarium specimens and observation of the field populations, the range and trend of variation of morphological traits of Pterocypsela Shih and the related genera were analyzed, combining the research of anatomy and micro-morphology characteristics, the independent status of this genus was Determined.1.The analysis of morphological traits of PterocypselaInspection on the basis of a large number of specimens and observation of wild populations, we made a detailed analysis on morphological traits of the genus Pterocypsela. The traits of bracts between this genus and relative genera are the foundation in their classification. Achene characters of Pterocypsela is also stable, but there are also having some differences in interspecific, this can be used as one basis of interspecific division. Leaf as the main basis of its division or the only basis is not very reliable, but the size of the leaves and hair types in interspecific division can only be used as a secondary character and must be treated carefully; there are some differences in base of the leaf among the species and it is more stable within species, and could be used in classification.2. The observication of achene’s anatomical characteristicsThe anatomic features of Pterocypsela’s achenes is the wing type, mesocarp compose by parenchyma cells and fiber cells., there was a funnel-shaped fiber bundle in the central part of the wing, which is composed of3-5layers of fibroblasts; in the base of fiber bundle surrounding2-4layers of thin-walled cells; In the base of funnel-shaped fiber bundle have the heart reavy vascular, at the top the rib is composed of3-4layers of fiber cells and the subsequent1-2layers of parenchyma cells. In the ribs and between the ribs and wings only have1-2layers of parenchyma cells. This is a obvious distinction when comparing with other genus, some or little supporting that, the Pterocypsela are a independent genus.3.The observation of the achene surface’s micromorphologyThis paper use electron microscope to scan the achenes of Pterocypsela, We found that there is a large difference between the genus Pterocypsela and related genera, but they are similar in the same genus. This indicates that the observation of the achenes surface’s micro-features has a certain value on the case of inter-division. The achenes of Pterocypsela elata and P. raddeana have three ribs on each side, and is different from the remaining species of the genus which only have one rib on each side in the achenes and angle clavate in the epidermal cells of the apex acute. Achene surface’s micro-features in related traits of difference also can be used between species classification.4. Taxonomic revisionAbove the analysis results and referencing large numbers of specimens and literatures, the concept of Pterocypsela was redefine and the genus was taxonomically revised. A key to species of this genus was given. One species and one variety are reduced to synonyms, the altogether6species are recognized, that are:P. elata, P. raddeana, P. triganulata, P. indica, P. sonchus and P. formosana. Because no specimens (including the type) were examined, P. lyrata C. X. Yang is not completely understood, and needs to be further studied in future. Each species is described and their distributions are mapped. Flowering phenology, habitat preference, and interspecific relationships are also discussed.