AOBPreview originally published online on May 17, 2009
Annals of Botany 2009 104(1):125-142; doi:10.1093/aob/mcp103
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Molecular systematics of Gagea and Lloydia (Liliaceae; Liliales): implications of analyses of nuclear ribosomal and plastid DNA sequences for infrageneric classification
1 Royal Botanic Gardens, Kew, Richmond TW9 3AB, UK
2 School of Biological and Chemical Science, Birkbeck College, University of London, Mallet Street, London WC1E 7HX, UK
3 Department of Biology, College of Basic Science, University of Shahed, PO Box 1815-1159, Tehran, Iran
4 Department of Plant Biology, School of Biology, University College of Sciences, University of Tehran, PO Box 14155-6455, Tehran, Iran
* For correspondence. E-mail zarrei{at}shahed.ac.ir
Received: 3 January 2007 Returned for revision: 15 March 2007 Accepted: 16 March 2009 Published electronically: 17 May 2009
Background and Aims: Gagea is a Eurasian genus of petaloid monocots, with a few species in North Africa, comprising between 70 and approximately 275 species depending on the author. Lloydia (thought to be the closest relative of Gagea) consists of 12–20 species that have a mostly eastern Asian distribution. Delimitation of these genera and their subdivisions are unresolved questions in Liliaceae taxonomy. The objective of this study is to evaluate generic and infrageneric circumscription of Gagea and Lloydia using DNA sequence data.
Methods: A phylogenetic study of Gagea and Lloydia (Liliaceae) was conducted using sequences of nuclear ribosomal internal transcribed spacer (ITS) and plastid (rpl16 intron, trnL intron, trnL-F spacer, matK and the psbA-trnH spacer) DNA regions. This included 149 accessions (seven as outgroups), with multiple accessions of some taxa; 552 sequences were included, of which 393 were generated as part of this research.
Key Results: A close relationship of Gagea and Lloydia was confirmed in analyses using different datasets, but neither Gagea nor Lloydia forms a monophyletic group as currently circumscribed; however, the ITS and plastid analyses did not produce congruent results for the placement of Lloydia relative to the major groups within Gagea. Gagea accessions formed five moderately to strongly supported clades in all trees, with most Lloydia taxa positioned at the basal nodes; in the strict consensus trees from the combined data a basal polytomy occurs. There is limited congruence between the classical, morphology-derived infrageneric taxonomy in Gagea (including Lloydia) and clades in the present phylogenetic analyses.
Conclusions: The analyses support monophyly of Gagea/Lloydia collectively, and they clearly comprise a single lineage, as some previous authors have hypothesized. The results provide the basis for a new classification of Gagea that has support from some morphological features. Incongruence between plastid and nuclear ITS results is interpreted as potentially due to ancient hybridization and/or paralogy of ITS rDNA.
Key words: Gagea, Lloydia, Liliaceae, ITS ribosomal DNA sequences, plastid DNA sequences
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