Molecular phylogeny of the endemic fern genera Cyrtomidictyum and Cyrtogonellum (Dryopteridaceae) from East Asia
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ORIGINAL ARTICLE
Molecular phylogeny of the endemic fern genera Cyrtomidictyum and Cyrtogonellum (Dryopteridaceae) from East Asia Hong-Mei Liu & Xian-Chun Zhang & Wei Wang & Hui Zeng
Received: 13 December 2008 / Accepted: 18 April 2009 / Published online: 9 March 2010 # Gesellschaft für Biologische Systematik 2010
Abstract Cyrtomidictyum Ching and Cyrtogonellum Ching are two eastern Asian endemic genera whose taxonomic affinities and phylogenetic relationships have long been controversial. The main uncertainty surrounds the separation of the two genera from the species-rich genus Polystichum. Here we present a phylogenetic study focusing on the phylogenetic relationships of these polystichoid ferns. We reconstructed the relationships based on DNA sequence variation in four chloroplast genome regions, rbcL, atpB, and the intergenic spacers (IGS) rps4-trnS and trnL-trnF. Maximum likelihood and Bayesian inference analyses confirm earlier results that were based on less comprehensive taxon sampling and either only a single gene (rbcL) or two IGS (rps4-trnS and trnL-trnF). Cyrtomidictyum is the sister of the clade of polystichoid ferns that includes Cyrtogonellum, Cyrtomium subser. Balansana and three sections of Polystichum. Cyrtogonellum groups with several species of Polystichum, and constitutes the sister taxon to Polystichum sect. Sphaenopolystichum. We support the recognition of Cyrtomidictyum as circumscribed initially, rather than expansion of the genus to include either several Polystichum species or Cyrtogonellum, some Polystichum and Cyrtomium species. The monophyly of Cyrtomidictyum is supported by morphological characters such as once-pinnate leaves, free H.-M. Liu : H. Zeng (*) The Key Laboratory for Environmental and Urban Sciences, Shenzhen Graduate School, Peking University, Shenzhen 518055, People’s Republic of China e-mail: [email protected] X.-C. Zhang : W. Wang State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, People’s Republic of China
venation, prolongated leaf apices, and exindusiate sori. Two synapomorphic indels in the chloroplast genome, one 15-bp deletion in rps4-trnS, and one 3-bp insertion in trnL-trnF further differentiate Cyrtomidictyum from other polystichoid ferns. The close affinity of Cyrtogonellum to section Sphaenopolystichum of Polystichum s.s. is highly supported by molecular data. However, no shared morphological characters or molecular indels have been detected, although the distinctness of Cyrtogonellum is shown by a 13-bp insertion in the rps4-trnS alignment. Keywords East Asia . Molecular phylogeny . atpB . rbcL . rps4-trnS . trnL-trnF . IGS
Introduction Polystichum Roth is one of the ten most species-rich genera of ferns and has its main centre of diversity in southwest China and adjacent regions (Kung et al. 2001). Several small genera with restricted distribution ranges—Acropelta Nakai, Cyrtomium C. Presl, Cyrtomidictyum Ching, Cyrtogonellum Ching, Papuapteris C. Chr., Phanerophlebia C. Presl,
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