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Abstract Detail



Population Genetics

Chiang, Yu-Chung [1], Shen, Hsien-Hui [2].

Genetic divergence in three Asian Cycad Sections.

The cycad lineage is ancient, but surviving taxa have recent divergent within 12 million years ago. Cycas is the only genus approbated in the family Cycadaceae and the biggest genus with around 95 species in cycads. In Mainland China and Festoon Islands, 16 cycad species belong to section Asiorientales (ASI), Panzhihuanses (PAN), Wadeanae (WAD), and Stangerioide (STA) are mostly allopatric distribution with unique habitat. In the section Asiorientales, C. taitungensis is restricted to Taiwan whereas C. revoluta is distributed in the Ryukyu Archipelago and on mainland China. Only species belongs to the section Panzhihuanses distributed on the border between Yunnan and Sichuan of Southeastern China. In section Wadeanae, only two species restricted on Culion and Palawan Islands of the Philippines, respectively. In section Stangerioide, there are eleven species, including two island species restricted on Hainan Island and nine inland species, with parapatric or allopatric distribution. In this study, we use multilocus data to evaluate the species divergence, speciation history and coalescence of disjunctive, inter-island, parapatric distribution, or allopatric species of cycad. In total, 125 samples were sampled and 4 chloroplast DNA fragments, 24 nuclear DNA loci, and 425AFLP loci were used for phylogenetic estimation. By Bayesian hierarchical clustering method, best fit model had Kâ=â2, 4, and 2 groups in plastid DNA, 24 nuclear DNA, and 425AFLP loci, respectively. Generally, ASI and STA+WAD are separated into different groups by three different molecular markers, but PAN is either joined to ASI or STA+WAD by different markers. Using models of isolation-with-migration and a coalescent-based hypothesis testing approach, we estimated the divergence time are not older than 6 Mya that sections diverged from the Pliocene to Pleistocene epoch. The extant effective population sizes following growth is may actually large (1.77×106~1.69×107), and the asymmetric gene flows are revealed between different groups. Due to recent diversification, phylogenetic relationships revealed paraphyly or polytomy within the section and may be resulting by incomplete lineage sorting. Briefly, the divergence time is not long than million years ago within four sections of cycads. Long generation time and incomplete lineage sorting caused the genetic admixture among related taxa of cycads.


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1 - National Sun Yat-Sen University, Department Of Biological Sciences, No. 70, Lienhai Road,, Kaohsiung, Taiwan, N/A, 80424, Taiwan
2 - National Sun Yat-Sen University, Department Of Biological Sciences, No. 70, Lienhai Road, Kaohsiung, Taiwan, 80424, Taiwan

Keywords:
Cycas
Phylogeny
divergence time
genetic diversity
phylogenetic diversity
phylogenetic clustering.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PPG006
Abstract ID:837
Candidate for Awards:None


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