Relationships among Calibrachoa, Fabiana and Petunia (Petunieae tribe, Solanaceae) and a new generic placement of Argentinean endemic Petuniapatagonica.

Calibrachoa Cerv., Fabiana Ruiz & Pav., and Petunia Juss. form a clade within tribe Petunieae (Solanaceae). Phylogenetic studies of Petunieae, either as part of a family-wide analysis or focusing on the genera Calibrachoa and Petunia, have either left Fabiana unsampled or included only a single species. These studies have found conflicting relationships among the three genera with all three possible topologies obtained. Petuniapatagonica (Speg.) Millán, originally described in the genus Nierembergia Ruiz & Pav., is morphologically distinct within Petunia and geographically disjunct from other members of the genus. For the first time, in this study we include multiple species of Fabiana, Calibrachoa, and Petunia, including P.patagonica. Using three chloroplast DNA regions and the nuclear gene GBSSI, or "waxy," our results provide strong support for a sister group relationship between Calibrachoa and Fabiana and for the placement of P.patagonica within Fabiana. Since there is already a species Fabianapatagonica Speg., we provide the new name Fabianaaustralis Alaria nom. nov. to replace Petuniapatagonica.

Andean uplift, drainage basin formation, and the evolution of plants living in fast-flowing aquatic ecosystems in northern South America.

Northern South America is a geologically dynamic and species-rich region. Fossil and stratigraphic data show that mountain uplift in the tropical Andes reconfigured river drainages. These landscape changes shaped the evolution of the flora in the region, yet the impacts on aquatic taxa have been overlooked. We explore the role of landscape change on the evolution of plants living strictly in rivers across drainage basins in northern South America by conducting population structure, phylogenetic inference, and divergence-dating analyses for two species in the genus Marathrum (Podostemaceae). Mountain uplift and drainage basin formation isolated populations of M. utile and M. foeniculaceum in northern South America and created barriers to gene flow across river drainages. Sympatric species hybridize and the hybrids show the phenotype of one parental line. We propose that the pattern of divergence of populations reflects the formation of river drainages, which was not complete until < 4.1 million yr ago (Ma). Our study provides a clear picture of the role of landscape change on the evolution of plants living strictly in rivers in northern South America. By shifting the focus to aquatic taxa, we provide a novel perspective on the processes shaping the evolution of the Neotropical flora.

Phylogeny of the Neotropical tribe Jacarandeae (Bignoniaceae).

PREMISE: The tribe Jacarandeae includes Jacaranda (49 species) and Digomphia (3 species), two genera of trees and woody shrubs with Neotropical distribution. Jacarandeae is sister to the rest of the Bignoniaceae, but not much is known about interspecific and intergeneric relationships within this group. METHODS: We reconstructed the phylogeny of Jacarandeae using chloroplast (ndhF, rpl32-trnL, trnL-F) and nuclear (ETS, PPR62) markers. Evolutionary relationships within Jacarandeae were inferred using Bayesian, Maximum Likelihood, and species tree approaches. The resulting phylogenetic framework was used as the basis to interpret the evolution of key morphological character states (i.e., stamen and calyx traits) and revise the infra-generic classification of the group. RESULTS: Jacaranda and Digomphia belong to a well-supported clade, with Digomphia nested within Jacaranda. We propose the necessary taxonomic changes to recognize monophyletic taxa, including a broadly circumscribed Jacaranda divided into four sections: (1) Jacaranda sect. Nematopogon, species previously included in Digomphia and united by divided staminode apices and spathaceous calyces; (2) Jacaranda sect. Copaia, species with monothecal anthers and cupular calyces; (3) Jacaranda sect. Jacaranda, species with monothecal anthers and campanulate calyces; and (4) Jacaranda sect. Dilobos, species with dithecal anthers and cupular calyces, and including more than half of the species of the genus, all restricted to Brazil. CONCLUSIONS: As circumscribed here, Jacarandeae includes only a broadly defined Jacaranda divided into four sections. Each section is defined by a unique combination of anther and calyx morphologies.

Evolution of morphological traits in Verbenaceae.

PREMISE OF THE STUDY: A new infrafamilial circumscription of the Verbenaceae with eight tribes: Casselieae, Citharexyleae, Duranteae, Lantaneae, Neospartoneae, Petreeae, Priveae, and Verbeneae, has been recently proposed, on the basis of molecular phylogenetic studies. Two genera, Dipyrena and Rhaphithamnus, remain unplaced. The aim of this work is to reconstruct the evolutionary history of morphological characters traditionally employed in the classification of the Verbenaceae, with special attention to tribes Verbeneae and Lantaneae. METHODS: Twenty-one characters, related to habit and vegetative morphology, inflorescence and floral morphology, ovary and fruit morphology, as well as chromosome number, were optimized over a molecular phylogeny of Verbenaceae. KEY RESULTS: All tribes are supported by at least one morphological trait except tribes Duranteae and Citharexyleae. Suffrutescent habit, sessile flowers, and four cluses are synapomorphies for tribe Verbeneae. Gynoecium with short style and entire stigma are synapomorphic traits for tribe Lantaneae. Sessile flowers and unicarpellate ovaries are morphological synapomorphies for the new tribe Neospartoneae. Suffrutescent habit is a synapomorphic trait for tribe Priveae. Homothetic pleiobotrya and absence of the adaxial staminode are synapomorphic traits for tribe Casselieae. Undivided fleshy fruits are probably a synapomorphic trait for tribe Petreeae. Putative plesiomorphies for the ancestor of the Verbenaceae are discussed as well as synapomorphic traits within other Verbenaceae clades. CONCLUSIONS: Many of the characters traditionally employed in classification have proven to be very homoplastic, or have been shown not to support relationships within the family. Moreover, traditional assumptions concerning character polarity have in some cases been shown to be incorrect.

Multiple recent horizontal transfers of the cox1 intron in Solanaceae and extended co-conversion of flanking exons.

BACKGROUND: The most frequent case of horizontal transfer in plants involves a group I intron in the mitochondrial gene cox1, which has been acquired via some 80 separate plant-to-plant transfer events among 833 diverse angiosperms examined. This homing intron encodes an endonuclease thought to promote the intron's promiscuous behavior. A promising experimental approach to study endonuclease activity and intron transmission involves somatic cell hybridization, which in plants leads to mitochondrial fusion and genome recombination. However, the cox1 intron has not yet been found in the ideal group for plant somatic genetics - the Solanaceae. We therefore undertook an extensive survey of this family to find members with the intron and to learn more about the evolutionary history of this exceptionally mobile genetic element. RESULTS: Although 409 of the 426 species of Solanaceae examined lack the cox1 intron, it is uniformly present in three phylogenetically disjunct clades. Despite strong overall incongruence of cox1 intron phylogeny with angiosperm phylogeny, two of these clades possess nearly identical intron sequences and are monophyletic in intron phylogeny. These two clades, and possibly the third also, contain a co-conversion tract (CCT) downstream of the intron that is extended relative to all previously recognized CCTs in angiosperm cox1. Re-examination of all published cox1 genes uncovered additional cases of extended co-conversion and identified a rare case of putative intron loss, accompanied by full retention of the CCT. CONCLUSIONS: We infer that the cox1 intron was separately and recently acquired by at least three different lineages of Solanaceae. The striking identity of the intron and CCT from two of these lineages suggests that one of these three intron captures may have occurred by a within-family transfer event. This is consistent with previous evidence that horizontal transfer in plants is biased towards phylogenetically local events. The discovery of extended co-conversion suggests that other cox1 conversions may be longer than realized but obscured by the exceptional conservation of plant mitochondrial sequences. Our findings provide further support for the rampant-transfer model of cox1 intron evolution and recommend the Solanaceae as a model system for the experimental analysis of cox1 intron transfer in plants.