J Integr Plant Biol ›› 2011, Vol. 53 ›› Issue (11): 901-911.DOI: 10.1111/j.1744-7909.2011.01076.x

• Molecular Ecology and Evolution • Previous Articles    

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

Ling Zhang1*, Hong-Tao Li2, Lian-Ming Gao2, Jun-Bo Yang2, De-Zhu Li2, Charles H. Cannon1,3, Jin Chen1 and Qing-Jun Li1   

  1. 1Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China
    2Key Laboratory of Biodiversity and Biogeography, and Germplasm Bank of Wild Species in Southwest China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, 650204, China
    3Department of Biology, Texas Tech University, Lubbock, TX 79390, USA
  • Received:2011-04-28 Accepted:2011-09-15 Published:2011-09-25
  • About author:*Corresponding author: Tel: +86 691 871 5948; Fax: +86 691 871 5070; E-mail: zhangl@xtbg.org.cn

Abstract:

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.

Zhang L, Li HT, Gao LM, Yang JB, Li DZ, Cannon CH, Chen J, Li QJ (2011) Phylogeny and evolution of bracts and bracteoles in Tacca (Dioscoreaceae). J. Integr. Plant Biol. 53(11), 901–911.

Key words: atpA, bracteoles, bracts, ITS, molecular phylogeny, rbcL, Tacca, trnH-psbA, trnL-F

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