, Volume 250, Issue 1-2, pp 39-67
Date: 22 Dec 2004

Phylogenetics of Utricularia (Lentibulariaceae) and molecular evolution of the trnK intron in a lineage with high substitutional rates

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Abstract.

The bladderworts (Utricularia, Lentibulariaceae) are the most diverse carnivorous plant genus, with a nearly worldwide distribution. In the present study, chloroplast DNA sequences of the trnK intron were used to reconstruct phylogenetic relationships within the genus. Parsimony, likelihood, and Bayesian analyses resulted in highly congruent and well-resolved trees. The phylogenetic signal provided by the noncoding trnK intron partition of the dataset is similar to that of the matK coding region, although the latter is twice as long. Within matK, indels appeared in multiples of three except very close to the 3′ end of the gene. Substitutions were found to result in or eliminate stop codons, thus creating a length variable gene end. Indels in both trnK and matK exhibit low degrees of homoplasy, irrespective of their size. A tree based on indels alone is largely congruent to the substitution-based trees but less resolved. Three major clades found within Utricularia are classified as subgen. Utricularia, subgen. Bivalvia, and subgen. Polypompholyx. The immediate common ancestor of Utricularia is suggested to have been a terrestrial plant whereas epiphytic and aquatic habits evolved later in terminal clades.

We are indebted to Wilhelm Barthlott for his support and valuable discussions. Financial support came from the DFG (Deutsche Forschungsgemeinschaft), grant number BA 605/9-1 to Wilhelm Barthlott and Stefan Porembski (Rostock). We thank Werner Höller from the Botanical Garden of the University of Bonn, who took care of the Utricularia collection in the Bonn Botanical Garden, where most of the species used in this study are cultivated. Travel support by the Studienstiftung des deutschen Volkes (Bonn) and EduardRhein-Stiftung (Königswinter) to KM is acknowledged. We thank Laurent Legendre (Sydney) for two sequences of Pinguicula. Finally, we would like to thank Inge Theisen (Bonn) for discussions on Utricularia, and Scot Kelchner and Richard Olmstead for very helpful comments on the manuscript.