Phylogenetic relationships, chromosome and breeding system evolution inTurnera(Turneraceae): inferences from its sequence data

Abstract

Turnera provides a useful system for exploring two significant evolutionary phenomena-shifts in breeding system (distyly vs. homostyly) and the evolution of polyploids. To explore these, the first molecular phylogeny of Turnera was constructed using sequences of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA for 37 taxa. We attempted to resolve the origins of allopolyploid species using single-strand conformation polymorphism and sequencing of homeologous copies of ITS. Two allohexaploid species possessed putative ITS homeologues (T. velutina and T. orientalis). A phylogenetic analysis to identify progenitors contributing to the origins of these polyploids was unsuccessful, possibly as a result of concerted evolution of ITS. Breeding system evolution was mapped onto the phylogeny assuming distyly to be ancestral in Turnera. Self-compatible homostyly appears to have arisen independently at least three times in Turnera; however, we were not able to determine whether there have been independent origins of homostyly among hexaploid species in series Turnera. Our phylogenetic analyses suggest that series Turnera is monophyletic. Neither series Microphyllae nor Anomalae, however, appear to be monophyletic. Future taxonomic revisions may require new circumscriptions of these latter series.

Phylogenetic relationships within Turneraceae based on morphological characters with emphasis on seed micromorphology

“…However, the main similarities and differences among them are summarized in Table 1; data from Truyens et al (2005) were not considered because all their results were incorporated in Chafe (2009). The position of the African genera in our analyses is similar to the results of Chafe (2009), they are in a basal position; while in Thulin et al (2012), they are in a derived position.…”

“…There is a better resolution of the series, which are distributed in four main clades. In molecular phylogenetic trees (Truyens et al 2005;Chafe 2009), the only monophyletic series was ser. Turnera, characterized by a base chromosome number x = 5.…”

“…Papilliferae), is associated with T. diffusa with x = 7 (ser. Microphyllae) in molecular analyses (Truyens et al 2005;Chafe 2009). In our clade II, both species of ser.…”

“…Afterwards, cladistic analyses of the genus Turnera (92 species) based on morphological characters and chromosome numbers were made to test the monophyly of the series, and to assess biogeographic patterns (Arbo and Espert 2009). Chafe (2009) conducted further analyses including all the species of Turnera sequenced in Truyens et al (2005), Adenoa, Erblichia, Mathurina, some additional species of Turnera, many other species of Piriqueta and species of four African genera. His results varied depending on the method used to analyze the data (parsimony, maximum likelihood, or Bayesian inference).…”

“…The first molecular phylogenetic study of Turneraceae included 5 species of Piriqueta and 35 American species belonging to seven series of Turnera (Truyens et al 2005). According to their results, Turnera was monophyletic, and series Turnera was the only monophyletic series.…”