Molecular phylogenetic analysis of Leibnitzia Cass.(Asteraceae:Mutisieae:Gerbera-complex),an Asian-North American disjunct genus

作     者：Kristen E.BAIRD Vicki A.FUNK Andrea WEEKS 

作者机构：Department of Environmental Science and PolicyGeorge Mason University US National HerbariumSmithsonian InstitutionMRC 166P.O.Box 371012WashingtonDC 20013-7012USA 

出 版 物：《Journal of Systematics and Evolution》 (植物分类学报(英文版))

年 卷 期：2010年第48卷第3期

页      面：161-174页

核心收录：

学科分类：0710[理学-生物学] 0830[工学-环境科学与工程（可授工学、理学、农学学位）] 090706[农学-园林植物与观赏园艺] 0907[农学-林学] 09[农学] 0901[农学-作物学] 0902[农学-园艺学] 0713[理学-生态学] 

主　　题：Beringia biogeography Gerbera-complex Mutisieae. 

摘      要：Leibnitzia comprises six species of perennial herbs that are adapted to high elevation conditions and is one of only two Asteraceae genera known to have an exclusively disjunct distribution spanning central to eastern Asia and North America.Molecular phylogenetic analysis of Leibnitzia and other Gerbera-complex members indicates that Leibnitzia is monophyletic,which is in contrast with our expectation that the American Leibnitzia species L. lyrata and L.occimadrensis would be more closely related to another American member of the Gerbera-complex,namely Chaptalia.Ancestral area reconstructions show that the historical biogeography of the Gerbera-complex mirrors that of the entire Asteraceae,with early diverging lineages located in South America that were followed by transfers to Africa and Eurasia and,most recently,to North America.Intercontinental transfer of Leibnitzia appears to have been directed from Asia to North America.Independent calibrations of nuclear(ribosomal DNA internal transcribed spacer region)and chloroplast(trnL-rpl32 intron)DNA sequence data using relaxed clock methods and either mean rate or fossil-based priors unanimously support Miocene and younger divergence times for Gerbera-complex taxa.The ages are not consistent with most Gondwanan vicariance episodes and,thus,the global distribution of Gerbera-complex members must be explained in large part by long-distance dispersal.American species of Leibnitzia are estimated to have diverged from their Asian ancestor during the Quaternary(ca.2 mya)and either migrated overland to North America via Beringia and retreated southwards along high elevation corridors to their present location in southwestern North America or were dispersed long distance.