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Abstract Detail


Xiao, Long-Qian [1], MÖLLER, Michael [2].

Vicariance and transoceanic dispersal drove the late Miocene rapid radiation of Cycas: evidence from phylogenetic relationships based on functional nrDNA ITS arrays.

Background and aims Cycas is the most widespread and diverse genus among the ancient cycads, but the extant species could be the product of late Miocene rapid radiations. Taxonomic treatments to date for this genus are quite controversial, which makes it difficult to elucidate its evolutionary history and biogeography. Methods We cloned 161 genomic ITS sequences from 31 species representing all sections of Cycas. The divergent ITS paralogs were examined within each species and identified as putative pseudogenes, recombinants and functional paralogs. Functional paralogs were used to reconstruct phylogenetic relationships with pseudogene sequences as outgroup, since ITS sequence alignment with their closest relatives is impossible. BEAST was taken to estimate the divergence times for the main nodes, and Lagrange was used for biogeographical reconstruction. Key Results A fully resolved and highly supported tree topology was obtained at the section level, with the genus divided into two major clades including six minor monophyletic groups. The results supported the classification scheme proposed by Hill at the section level (2004). The most recent common ancestor of Cycas had likely occupied a wide distribution in both South China and Indochina region in the late Miocene, and a vicariant event had separated the ancestral Cycas into two lineages. Subsequently, Cycas experienced a series of dispersal events and expanded the distribution range. Conclusions The obtained pattern of phylogenetic relationships, combined with the estimated divergence times and reconstructed ancestral areas, and the different seed dispersal capabilities, allowed us to propose that the late Miocene rapid radiation of Cycas might have been promoted by vicariant events associated with the complex topography and orogeny of South China and adjacent regions. In contrast, transoceanic dispersals might have played an important role in the rapid diversification of sect. Cycas, whose members have evolved a spongy layer in their seeds aiding water dispersals.

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1 - Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Key Laboratory of Tropical Forest Ecology, 88, Xuefu Road, Kunming, Yunnan, 650223, China
2 - Royal Botanical Garden Edinburgh, Edinburg EH3 5LR, Scotland, United Kingdom

Transoceanic dispersal

Presentation Type: Poster:Posters for Topics
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:30 PM
Number: PBG008
Abstract ID:935
Candidate for Awards:None

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