Intercontinental and intracontinental biogeography——patterns and methods

The study of biogeography has benefited from the exponential increase of DNA sequence data from recent molecular systematic studies, the development of analytical methods in the last decade concerning divergence time estimation and geographic area analyses, and the availability of large-scale distributiofi data of species in many groups of organisms. The underlying principle of divergence time estimation from DNA and protein data is that sequence divergence depends on the product of evolutionary rate and time. With their molecular clock hypothesis, Zuckerkandl and Pauling （1965） separated rates of molecular evolution from time by incorporating fossil evidence. Originally,

Diploid species phylogeny and evolutionary reticulation indicate early radiation of Ephedra in the Tethys coast

Reconstructing a robust species phylogeny and disentangling the evolutionary and biogeographic history of the gymnosperm genus Ephedra,which has a large genome and rich polyploids,remain a big challenge.Here we reconstructed a transcriptome-based phylogeny of 19 diploid Ephedra species,and explored evolutionary reticulations in this genus represented by 50 diploid and polyploid species,using four low-copy nuclear and nine plastid genes.The diploid species phylogeny indicates that the Mediterranean species diverged first,and the remaining species split into three clades,including the American species(Clade A),E.rhytidosperma,and all other Asian species(Clade B).The single-gene trees placed E.rhytidosperma sister to Clade A,Clade B,or Clades A+B in similar proportions,suggesting that radiation and gene flow likely occurred in the early evolution of Ephedra.In addition,reticulate evolution occurred not only among the deep nodes,but also in the recently evolved South American species,which further caused difficulty in phylogenetic reconstruction.Moreover,we found that allopolyploid speciation was pervasive in Ephedra.Our study also suggests that Ephedra very likely originated in the Tethys coast during the late Cretaceous,and the South American Ephedra species have a single origin by dispersal from Mexico or North America.

Floral nectary, nectar production dynamics, and floral reproductive isolation among closely related species of Pedicularis

Floral nectar is thought to be one of the most important rewards that attract pollinators in Pedicularis; however, few studies have examined variation of nectary structure and/or nectar secretion in the genus, particularly among closely related species. Here we investigated nectary morphology, nectar quality, and nectar production dynamics in flowers of Pedicularis section Cyathophora. We found a conical floral nectary at the base of the ovary in species of the rex-thamnophila clade. Stomata were found on the sudace of the nectary, and copious starch grains were detected in the nectary tissues. In contrast, a semi-annular nectary was found in flowers of the species of the superba clade. Only a few starch grains were observed in tissues of the semi-annular nectary, and the nectar sugar concentration in these flowers was much lower than that in the flowers of the rexthamnophila clade. Our results indicate that the floral nectary has experienced considerable morphological, structural, and functional differentiation among closely related species of Pedicularis. This could have affected nectar production, leading to a shift of the pollination mode. Our results also imply that variation of the nectary morphology and nectar production may have played an important role in the speciation of sect. Cyathophora.

Evolution of the platycodonoid group with particular references to biogeography and character evolution

The Qinghai‐Tibet Plateau（QTP）is an important center of origin and diversification for many northern temperate plants.The hypothesis＂out‐of‐QTP＂suggests that the majority of northern temperate plants have originated and dispersed from the QTP and adjacent regions.An interesting question is whether the biogeographic history of the platycodonoids（Campanulaceae）,a group mainly distributed in the QTP and adjacent regions,coincides with the hypothesis＂out‐of‐QTP＂？Furthermore,how have the diagnostic characters of the platycodonoids evolved？In the present study,all 10genera of the platycodonoids were sampled for molecular phylogeny and dating analyses,and ancestral states of distribution and characters were reconstructed.The results do not support the platycodonoids as an＂out‐of‐QTP＂group,but instead they might have descended from Tethyan ancestors.The dispersal and diversification of the platycodonoids in Asia might have been driven by the uplift of the QTP.The present study highlights the importance of the Tethyan Tertiary flora for the origin of the Sino‐Himalayan flora and the influence of the uplift of QTP on diversification of northern temperate plants.In addition,character state reconstruction reveals that the inferior ovary,capsule,long‐colpate pollen,and chromosome number 2n=14 are probably ancestral states.

A Test of Seven Candidate Barcode Regions from the Plastome in Picea (Pinaceae)

DNA barcoding, as a tool for species discrimination, has been used efficiently in animals, algae and fungi, but there are still debates on which DNA region（s） can be used as the standard barcode（s） for land plants. Gymnosperms, especially conifers, are important components of forests, and there is an urgent need for them to be identified through DNA barcoding because of their high frequency of collection in the field. However, the feasibility of DNA barcoding in gymnosperms has not been examined based on a dense species sampling. Here we selected seven candidate DNA barcodes from the plastome （matK, rbcL, rpoB, rpoC1, atpF-atpH, psbA-trnH, and psbK-psbI） to evaluate their suitability in Picea （spruce）. The results showed that none of them or their different combinations has sufficient resolution for spruce species, although matK＋rbcL might be used as a two-locus barcode. The low efficiency of these candidate barcodes in Picea might be caused by the paternal inheritance of the chloroplast genome, long generation time, recent radiation, and frequent inter-specific hybridization aided by wind pollination. Some of these factors could also be responsible for the difficulties in barcoding other plant groups. Furthermore, the potential of the nuclear LEAFY gene as a land plant barcode was discussed.