Study On The Subtribe Lactucinae Of Compositae From Shandong

Lactucinae belong to Lactuceae, Compositae. Lactuca and the related ones form a complex named"Lactuca-Prenathes"in Lactuceae with unclear circumscription. The complex is of unstable and variable characters, which make it one of the most problematic groups in Compositae. The systematics of the subtribe Lactucinae need to be further studied.The aim of the present study is to evaluate the separate genus status of Lactucinae and to finally clarify the systematic relationship between some genera and related ones, and to make a taxonomic revision based on evidence from pollen micro-morphology, epidermal micro-morphology, acheae micro-morphology and molecular study . Based on these evidences, systematics of 11 genera (Ixeridium (A.Gray) Tzvel., Ixeris Cass. , Chorisis DC., Paraixeris Nakai, Lactuca L., Mulgedium Cass., Pterocysela Shih, Sonchus L., Youngia Cass., Prenanthes L. and Taraxacum F. H. Wigg. ) of the subtribe Lactucinae from Shandong was studied , and we took out the following conclusions.1. Based on experimental data, genera Ixeris Cass.s.str. , Ixeridium (A.Gray) Tzvel. and Chorisis DC. should be combined as the genus Ixeris Cass. s. lat. . But it can be divided into three sections: Section Ixeris, Section Ixeridium and Section chorisis.2. Based on experimental data, genera Lactuca L.s.str., Mulgedium cass. and Pterocypsela Shih should be united as the genus Lactuca L. s. lat. .But it can be divided into three Sections: Section lactuca , Section mulgedium and Section Pterocypsela.3. Based on experimental data, the genus Paraixeris Nakai shoud be considered as a distinct genus.