Phylogeny and Evolution of Bracts and Bracteoles in Tacca (Dioscoreaceae)  

作　　者：Ling Zhang Hong-Tao Li Lian-Ming Gao Jun-Bo Yang De-Zhu Li Charles H. Cannon Jin Chen Qing-Jun Li 

机构地区：[1]Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, the Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China [2]Key Laboratory of Biodiversity and Biogeography, and Germplasm Bank of Wild Species in Southwest China, Kunming Institute of Botany the Chinese Academy of Sciences, Kunming 650204, China [3]Department of Biology, Texas Tech University, Lubbock, TX 79390, USA

出　　处：《Journal of Integrative Plant Biology》2011年第11期901-911,共11页植物学报（英文版）

基　　金：funded by the Key Project of the Chinese Academy of Science (KSCX2-YW-Z-0904);National Natural Science Foundation of China (30670131);Yunnan Provincial Natural Science Foundation (2006C0055M)to Ling Zhang;Laboratory equipment for phylogenetic analyses was provided by the State Key Basic Research and Development Plan of China (973, 2008GA001) to De-Zhu Li

摘　　要：Most species in the genus Tacca （Dioscoreaceae） feature green to black purple, conspicuous inflorescence involucral bracts with variable shapes, motile filiform appendages （bracteoles）, and diverse types of inflorescence morphology. To infer the evolution of these inflorescence traits, we reconstructed the molecular phylogeny of the genus, using DNA sequences from one nuclear, one mitochondrial, and three plastid loci （Internal Transcribed Spacer （ITS）, atpA, rbcL, trnL-F, and trnH-psbA）. Involucres and bracteoles characters were mapped onto the phylogeny to analyze the sequence of inflorescence trait evolution. In all analyses, species with showy involucres and bracteoles formed the most derived clade, while ancestral Tacca had small and plain involucres and short bracteoles, namely less conspicuous inflorescence structures. Two of the species with the most elaborate inflorescence morphologies （T. chantrieri in southeast China and T. integrifolia in Tibet）, are predominantly self-pollinated, indicating that these conspicuous floral displays have other functions rather than pollinator attraction. We hypothesize that the motile bracteoles and involucres may facilitate selfing; display photosynthesis in the dim understory, and protect flowers from herbivory.Most species in the genus Tacca （Dioscoreaceae） feature green to black purple, conspicuous inflorescence involucral bracts with variable shapes, motile filiform appendages （bracteoles）, and diverse types of inflorescence morphology. To infer the evolution of these inflorescence traits, we reconstructed the molecular phylogeny of the genus, using DNA sequences from one nuclear, one mitochondrial, and three plastid loci （Internal Transcribed Spacer （ITS）, atpA, rbcL, trnL-F, and trnH-psbA）. Involucres and bracteoles characters were mapped onto the phylogeny to analyze the sequence of inflorescence trait evolution. In all analyses, species with showy involucres and bracteoles formed the most derived clade, while ancestral Tacca had small and plain involucres and short bracteoles, namely less conspicuous inflorescence structures. Two of the species with the most elaborate inflorescence morphologies （T. chantrieri in southeast China and T. integrifolia in Tibet）, are predominantly self-pollinated, indicating that these conspicuous floral displays have other functions rather than pollinator attraction. We hypothesize that the motile bracteoles and involucres may facilitate selfing; display photosynthesis in the dim understory, and protect flowers from herbivory.

关 键 词：ATPA bracteoles BRACTS ITS molecular phylogeny RBCL Tacca TRNH-PSBA trnL-F. 

分 类 号：S682.13[农业科学—观赏园艺] Q959.722[农业科学—园艺学]