Showing papers by "Lynn Bohs published in 2011"

Molecular delimitation of clades within New World species of the "spiny solanums" (Solanum subg. Leptostemonum).

Abstract: Solanum subg. Leptostemonum contains approximately 350-450 species, including the cultivated eggplant, S. melongena. Most species placed in this subgenus form a monophyletic group, the Leptostemonum clade, characterized by the presence of stellate hairs and prickles, leading to the common name of "spiny solanums". Here we present a phylogenetic analysis that circumscribes the major clades within the spiny solanums and examines the relationships among them, with an emphasis on New World species. Of particular interest is the clarification of the clade limits and species composition of groups that have not been well-sampled. We also increase sampling of taxa that have been previously analyzed in molecular studies, namely those in the Torva, Micracantha, and Erythrotrichum clades. These groups have convergent morphological characteristics that have challenged taxonomists, making classification difficult. Results from our study delimit 14 clades within the spiny solanums, including the newly designated Asterophorum, Gardneri, Sisymbriifolium, and Thomasiifolium clades. We also establish the placement of species not previously sampled, especially those endemic to Brazil. These results give an increased understanding of the evolution of the Leptostemonum clade by defining monophyletic groups within it and identify areas of the phylogenetic tree that remain unresolved and require further taxon sampling.

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

Abstract: 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. 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. 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.

A 10-gene phylogeny of Solanum section Herpystichum (Solanaceae) and a comparison of phylogenetic methods.

Abstract:  Premise of the study: Solanum section Herpystichum is a lineage that comprises both widespread and very narrowly distributed species. This study investigates the phylogenetic relationships of sect. Herpystichum and evaluates several phylogenetic methods for analysis of multiple sequences.  Methods: Sequence data from seven nuclear (ITS, GBSSI, and fi ve COSII) and three plastid ( psbA – trnH , trnT – trnF , and trnS – trnG ) regions were concatenated and analyzed under maximum parsimony and Bayesian criteria. In addition, we used two analytical methods that take into account differences in topologies resulting from the analyses of the individual markers: Bayesian Estimation of Species Trees (BEST) and supertree analysis.  Key results: The monophyletic Solanum sect. Herpystichum was resolved with moderate support in the concatenated maximum parsimony and Bayesian analyses and the supertree analysis, and relationships within the section were well-resolved and strongly supported. The BEST topology, however, was poorly resolved. Also, because of how BEST deals with missing sequences, > 25% of our accessions, including two species, had to be excluded from the analyses. Our results indicate a progenitordescendent relationship with two species nested within the widespread S. evolvulifolium .  Conclusions: Analytical methods that consider individual topologies are important for studies based on multiple molecular markers. On the basis of analyses in this study, BEST had the serious shortcoming that taxa with missing sequences must be removed from the analysis or they can produce spurious topologies. Supertree analysis provided a good alternative for our data by allowing the inclusion of all 10 species of sect. Herpystichum .

A Revision of Solanum Section Herpystichum

Abstract: Solanum section Herpystichum includes 10 species of ground-trailing and climbing vines that root adventitiously at the nodes. Molecular data support section Herpystichum as a member of the Potato clade of Solanum. All of the species inhabit primary and secondary rainforests and occur from southern Mexico to northern Peru. The group is defined by its vining, node-rooting habit, and by its fruit structure; several species have strongly flattened fruits that are unique in Solanum. Most species of sect. Herpystichum have narrow distributions, and four species are endemic to Ecuador and one is endemic to Colombia. Moreover, they tend to be rare in the habitats where they occur and, as a result, are poorly collected and poorly known. Also, because of their restricted distributions, small numbers of populations, and habitat destruction, seven of the 10 species are considered rare and threatened. Descriptions, distribution maps, a phylogeny, photos or illustrations, and a key to the species are presented.

A New Species and Combination in Central American Solanaceae

Abstract: . A new species of Solanum sect. Geminata (G. Don) Walp. (Solanaceae) from Costa Rica and Panama, S. sotobosquense Bohs, is described here from Limon, Costa Rica. It is morphologically most similar to S. rovirosanum Donn. Sm., but differs in its short, usually forked inflorescences and long fruiting pedicels. It has been named in honor of one of its collectors, D. Armando Soto, and in reference to its understory habitat. A new combination, Cuatresia cuneata (Standl.) Bohs, is also published here. Although based on the name Lycianthes cuneata Standl., this species has most commonly been considered to belong to the genus Witheringia L'Her. Morphological and molecular data show that this species is a member of the genus Cuatresia Hunz., not Witheringia.