Phylogeny of Paullinia L. (Paullinieae: Sapindaceae), a diverse genus of lianas with dynamic fruit evolution.

Paullinia L. is a genus of c. 220 mostly Neotropical forest-dwelling lianas that display a wide diversity of fruit morphologies. Paullinia resembles other members of the Paullinieae tribe in being a climber with stipulate compound leaves and paired inflorescence tendrils. However, it is distinct in having capsular fruits with woody, coriaceous, or crustaceous pericarps. While consistent in this basic plan, the pericarps of Paullinia fruits are otherwise highly variable-in some species they are winged, whereas in others they are without wings or covered with spines. With the exception of the water-dispersed indehiscent spiny fruits of some members of Paullinia sect. Castanella, all species are dehiscent, opening their capsules while they are still attached to the branch, to reveal arillate animal-dispersed seeds. Here we present a molecular phylogeny of Paullinia derived from 11 molecular markers, including nine newly-developed single-copy nuclear markers amplified by microfluidics PCR. This is the first broadly sampled molecular phylogeny for the genus. Paullinia is supported as monophyletic and is sister to Cardiospermum L., which together are sister to Serjania Mill + Urvillea Kunth. We apply this novel phylogenetic hypothesis to test previous infrageneric classifications and to infer that unwinged fruits represent the ancestral condition, from which there were repeated evolutionary transitions and reversals. However, because the seeds of both winged and unwinged fruits are dispersed by animals, we conclude that the repeated transitions in fruit morphology may relate to visual display strategies to attract animal dispersers, and do not represent transitions to wind dispersal.

Differential gene retention in plastids of common recent origin.

The cyanobacterium-derived plastids of algae and plants have supported the diversification of much of extant eukaryotic life. Inferences about early events in plastid evolution must rely on reconstructing events that occurred over a billion years ago. In contrast, the photosynthetic amoeba Paulinella chromatophora provides an exceptional model to study organelle evolution in a prokaryote-eukaryote (primary) endosymbiosis that occurred approximately 60 mya. Here we sequenced the plastid genome (0.977 Mb) from the recently described Paulinella FK01 and compared the sequence with the existing data from the sister taxon Paulinella M0880/a. Alignment of the two plastid genomes shows significant conservation of gene order and only a handful of minor gene rearrangements. Analysis of gene content reveals 66 differential gene losses that appear to be outright gene deletions rather than endosymbiotic gene transfers to the host nuclear genome. Phylogenomic analysis validates the plastid ancestor as a member of the Synechococcus-Prochlorococcus group, and the cyanobacterial provenance of all plastid genes suggests that these organelles were not targets of interphylum gene transfers after endosymbiosis. Inspection of 681 DNA alignments of protein-encoding genes shows that the vast majority have dN/dS ratios <<1, providing evidence for purifying selection. Our study demonstrates that plastid genomes in sister taxa are strongly constrained by selection but follow distinct trajectories during the earlier phases of organelle evolution.

Purine alkaloids in Paullinia.

Among the few purine alkaloid-containing genera consumed as stimulants, Paullinia is the least investigated with respect to both chemotaxonomy and within-the-plant allocation of caffeine and its allies. Since purine alkaloids (PuA) have been proved to be valuable marker compounds in chemotaxonomy, 34 species of Paullinia and related genera were screened for them, but only one, P. pachycarpa, was positive in addition to the already known P. cupana and P. yoco. The PuA allocation in P. pachycarpa was examined and found to be restricted to theobromine in the stem, leaves and flowers. Moreover, the theobromine concentration in the stem cortex increased significantly towards the base of the plant. Since the stem cortex of P. yoco is traditionally used by the natives of Colombia and Ecuador to prepare a caffeine-rich beverage, we suspected that within the genus Paullinia the PuA are preferentially allocated to the older parts of the stem and not to young shoots like e.g., in the coffee plant (Coffea spp.). Indeed, the axis (greenhouse) of P. cupana (guaraná), known for its caffeine-rich seeds, exhibited a basipetal PuA gradient (0.005-0.145%). Moreover, the analysis of young cortex samples (herbarium) and of one piece of old stem (museum collection) revealed the same for P. yoco, even though we found much less (0.5 vs 2.5%) caffeine in the old cortex as compared to the only two analyses in 1926 of similar material. However, this discrepancy may be explained by the high variability of the PuA pattern we detected among yoco, the diversity of which the Indians take advantage.