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

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.