Qing-Feng Wang

Generic phylogeny, historical biogeography and character evolution of the cosmopolitan aquatic plant family Hydrocharitaceae

BackgroundHydrocharitaceae is a fully aquatic monocot family, consists of 18 genera with approximately 120 species. The family includes both fresh and marine aquatics and exhibits great diversity in form and habit including annual and perennial life histories; submersed, partially submersed and floating leaf habits and linear to orbicular leaf shapes. The family has a cosmopolitan distribution and is well represented in the Tertiary fossil record in Europe. At present, the historical biogeography of the family is not well understood and the generic relationships remain controversial. In this study we investigated the phylogeny and biogeography of Hydrocharitaceae by integrating fossils and DNA sequences from eight genes. We also conducted ancestral state reconstruction for three morphological characters.ResultsPhylogenetic analyses produced a phylogeny with most branches strongly supported by bootstrap values greater than 95 and Bayesian posterior probability values of 1.0. Stratiotes is the first diverging lineage with the remaining genera in two clades, one clade consists of Lagarosiphon, Ottelia, Blyxa, Apalanthe, Elodea and Egeria; and the other consists of Hydrocharis-Limnobium, Thalassia, Enhalus, Halophila, Najas, Hydrilla, Vallisneria, Nechamandra and Maidenia. Biogeographic analyses (DIVA, Mesquite) and divergence time estimates (BEAST) resolved the most recent common ancestor of Hydrocharitaceae as being in Asia during the Late Cretaceous and Palaeocene (54.7-72.6 Ma). Dispersals (including long-distance dispersal and migrations through Tethys seaway and land bridges) probably played major roles in the intercontinental distribution of this family. Ancestral state reconstruction suggested that in Hydrocharitaceae evolution of dioecy is bidirectional, viz., from dioecy to hermaphroditism, and from hermaphroditism to dioecy, and that the aerial-submerged leaf habit and short-linear leaf shape are the ancestral states.ConclusionsOur study has shed light on the previously controversial generic phylogeny of Hydrocharitaceae. The study has resolved the historical biogeography of this family and supported dispersal as the most likely explanation for the intercontinental distribution. We have also provided valuable information for understanding the evolution of breeding system and leaf phenotype in aquatic monocots.

Trade-offs between sexual and asexual reproduction in a monoecious species Sagittaria pygmaea (Alismataceae): the effect of different nutrient levels

Available resources could influence the trade-offs among different reproductive components in plants. Here, we created three nutrient levels to test the nutrient effects on trade-offs among sexual reproduction, clonal propagation and vegetative growth in a monoecious clonal herb Sagittaria pygmaea. The results of this study showed that the plant exhibited different trade-off patterns among different nutrient levels. When the nutrient level was low, there were weak trade-offs between sexual reproduction and vegetative growth and between clonal propagation and vegetative growth; when the nutrient level was moderate, we found a strong trade-off between sexual reproduction and clonal propagation; but when the nutrient level was high, we found no trade-offs among these three different reproductive components. These results indicated that the plant could adjust its trade-off patterns to fit the nutrient variation and suggested that trade-offs are unlikely to constrain the evolution of reproductive strategy in this species.

Chemical and Genetic Assessment of Variability in Commercial Radix Astragali (Astragalus spp.) by Ion Trap LC-MS and Nuclear Ribosomal DNA Barcoding Sequence Analyses

Radix Astragali (Huangqi) has been demonstrated to have a wide range of immunopotentiating effects and has been used as an adjuvant medicine during cancer therapy. Identity issues in the collection of Radix Astragali exist because many sympatric species of Astragalus occur in the northern regions of China. In order to assess the quality, purity, and uniformity of commercial Radix Astragali, 44 samples were purchased from herbal stores in Hong Kong and New York City. The main constituents, including four isoflavonoids and three saponins, were quantitatively determined by liquid chromatography mass spectrometry (LC-MS). There was significant sample-to-sample variability in the amounts of the saponins and isoflavonoids measured. Furthermore, DNA barcoding utilizing the variable nuclear ITS spacer regions of the 44 purchased Radix Astragali samples were sequenced, aligned and compared. Eight polymorphic point mutations were identified which separated the Radix Astragali samples into three groups. These results indicate that the chemical and genetic variability that exists among Radix Astragali medicinal products is still a consistency and quality issue for this herbal. Two-way ANOVA analysis showed significant effects on the contents of the seven tested compounds when both phylogenetic and geographic (i.e., point of purchase) factors were considered. Therefore, chemical profiles determined by LC-MS and DNA profiles in ITS spacer domains could serve as barcode markers for quality control of Radix Astragali.

Evolution of apocarpy in Alismatidae using phylogenetic evidence from chloroplast rbcL gene sequence data

The apocarpous groups in the monocotyledons are mainly concentrated in the subclass Alismatidae. The molecular phylogeny of Alismatidae based on analysis of chloroplast rbcL gene sequence data serves as a framework with which to evaluate character evolution with respect to the derivation of apocarpy in the group. 20 of the 27 genera in the subclass that display apocarpy have been included in our study. Our analysis indicates that apocarpy is polyphyletic within the subclass Alismatidae. Two independent origins of apocarpy in Alismatidae are explored in this study. Three separate origins of a single carpel and two separate origins of syncarpy in the subclass are also proposed. Basally connate carpel condition was the ancestral character in Alismatidae and evolved in two directions. It is possible for the unicarpellate condition to have been directly derived by reduction from syncarpy, and it could also be that the unicarpellate state has been derived from apocarpy by reduction in carpel number. The present results indicate that a progression has occurred in the evolution of carpels in Alismatidae from basally connate carpels through syncarpy or apocarpy to a single carpel.

Phylogenetic Relationships of Isoëtes (Isoëtaceae) in China as Revealed by Nucleotide Sequences of the Nuclear Ribosomal ITS Region and the Second Intron of a LEAFY Homolog

Abstract Isoëtes is an ancient lycopod lineage with a highly conserved morphology that provides few morphological characters to resolve the phylogeny of its species. Species appear to have evolved by divergence and allopolyploidy. The basic diploids I. hypsophila, I. taiwanensis, and I. yunguiensis and the tetraploid I. sinensis occur in China. Analysis of ITS sequences indicates that the Chinese Isoëtes species are part of an Australasian clade including I. brevicula from Western Australia and I. kirkii from New Zealand. Two distinct cloned sequences of the second intron of a LEAFY homolog were recovered from I. sinensis supporting the hypothesis that I. sinensis is an allotetraploid. One of the I. sinensis cloned sequences was similar to the I. taiwanensis sequence and the other cloned sequence was similar to the I. yunguiensis sequence identifying I. taiwanensis and I. yunguiensis as the likely parents of I. sinensis. Other cloned sequences recovered from I. sinensis were recombined parts of the two distinct sequences. Morphological evidence supporting an allotetraploid origin of I. sinensis is found in its larger microspore size and intermediate megaspore texture compared to I. taiwanensis, and I. yunguiensis.

The presence of co-flowering species facilitates reproductive success of Pedicularis monbeigiana (Orobanchaceae) through variation in bumble-bee foraging behaviour

Background and Aims The presence of co-flowering species can alter pollinator foraging behaviour and, in turn, positively or negatively affect the reproductive success of the focal species. Such interactions were investigated between a focal species, Pedicularis monbeigiana, and a co-flowering species, Vicia dichroantha, which was mediated by behaviour alteration of the shared bumble-bee pollinator. Methods Floral display size and floral colour change of P. monbeigiana were compared between pure (P. monbeigiana only) and mixed (P. monbeigiana and V. dichroantha) plots in two populations. Pollinator visitation rates, interspecific floral switching and successive within-plant pollinator visits were recorded. In addition, supplemental pollination at plant level was performed, and the fruit set and seed set were analysed in pure and mixed plots with different densities of P. monbeigiana. Key Results Pollinator visitation rates were dramatically higher in mixed plots than in pure plots. The higher pollinator visitation rates were recorded in both low- and high-density plots. In particular, successive flower visits within an individual plant were significantly lower in mixed plots. Supplemental pollination significantly increased fruit set and seed set of individuals in pure plots, while it only marginally increased seed set per fruit of plants in mixed plots. Conclusions The presence of V. dichroantha can facilitate pollination and increase female reproductive success of P. monbeigiana via both quantity (mitigating pollinator limitation) and quality (reducing geitonogamy) effects. This study suggests that successive pollinator movements among flowers within a plant, as well as pollinator visitation rates and interspecific flower switching, may be important determinants of the direction and mechanisms of interaction between species.

Tree of life for the genera of Chinese vascular plants

We reconstructed a phylogenetic tree of Chinese vascular plants (Tracheophyta) using sequences of the chloroplast genes atpB, matK, ndhF, and rbcL and mitochondrial matR. We produced a matrix comprising 6098 species and including 13 695 DNA sequences, of which 1803 were newly generated. Our taxonomic sampling spanned 3114 genera representing 323 families of Chinese vascular plants, covering more than 93% of all genera known from China. The comprehensive large phylogeny supports most relationships among and within families recognized by recent molecular phylogenetic studies for lycophytes, ferns (monilophytes), gymnosperms, and angiosperms. For angiosperms, most families in Angiosperm Phylogeny Group IV are supported as monophyletic, except for a paraphyletic Dipterocarpaceae and Santalaceae. The infrafamilial relationships of several large families and monophyly of some large genera are well supported by our dense taxonomic sampling. Our results showed that two species of Eberhardtia are sister to a clade formed by all other taxa of Sapotaceae, except Sarcosperma. We have made our phylogeny of Chinese vascular plants publically available for the creation of subtrees via SoTree (http://www.darwintree.cn/flora/index.shtml), an automated phylogeny assembly tool for ecologists.

Testing four barcoding markers for species identification of Potamogetonaceae

Abstract  The pondweeds (Potamogetonaceae) are among the most important plant groups in the aquatic environment. Owing to their high morphological and ecological diversity, species identification of this aquatic family remains problematic. DNA barcoding involves sequencing a standard DNA region and has been shown to be a powerful tool for species identification. In the present study, we tested four barcoding markers (rbcL, matK, internal transcribed spacer (ITS), and trnH–psbA) in 15 Potamogeton species and two Stuckenia species, representing most species of the Potamogetonaceae in China. The results show that all four regions can distinguish and support the newly proposed genera of Stuckenia from Potamogeton. Using ITS and trnH–psbA, significant interspecific genetic variability was shown. However, intraspecific genetic variability of trnH–psbA is high and so it is not suitable for barcoding in Potamogetonaceae. The ITS and matK regions showed good discrimination. However, matK was not easy to sequence using universal primers. The best performing single locus was ITS, making it a potentially useful DNA barcode in Potamogetonaceae.

Phylogeography of a marsh herb Sagittaria trifolia (Alismataceae) in China inferred from cpDNA atpB-rbcL intergenic spacers.

Sagittaria trifolia L. is a perennial, erect herb that is confined to ponds, rice fields, ditches, and freshwater wetlands. Using chloroplast DNA (cpDNA) atpB-rbcL intergenic spacer sequences, we studied the phylogeographic pattern and demographic history of S. trifolia with 108 samples from 42 populations representing the entire geographic range in China. Twenty-seven haplotypes were characterized and two of them were widely distributed in the populations. In the minimum-spanning network, all tip haplotypes were unique to a particular population, while the interior nodes represented widespread haplotypes. Nested clade analysis (NCA) of cpDNA haplotypes indicated that long distance dispersal characterized the post-glacial recolonization of S. trifolia in China. No specific refugia areas were suggested because genetic differentiation was low among the sampled regions and among populations within regions although a large number of the haplotypes were unique to a single population. The present data support that the unique haplotypes in individual population most likely represent recent mutational derivatives after long distance dispersal rather than the relics in refugia. These results for S. trifolia represent the first phylogeographic analysis of a widespread marsh herb in China and support the importance of long distance dispersal events in the post-glacial migrations of plants.

Chloroplast DNA phylogeography reveals repeated range expansion in a widespread aquatic herb Hippuris vulgaris in the Qinghai-Tibetan Plateau and adjacent areas.

Background The Qinghai-Tibetan Plateau (QTP) is one of the most extensive habitats for alpine plants in the world. Climatic oscillations during the Quaternary ice age had a dramatic effect on species ranges on the QTP and the adjacent areas. However, how the distribution ranges of aquatic plant species shifted on the QTP in response to Quaternary climatic changes remains almost unknown. Methodology and Principal Findings We studied the phylogeography and demographic history of the widespread aquatic herb Hippuris vulgaris from the QTP and adjacent areas. Our sampling included 385 individuals from 47 natural populations of H. vulgaris. Using sequences from four chloroplast DNA (cpDNA) non-coding regions, we distinguished eight different cpDNA haplotypes. From the cpDNA variation in H. vulgaris, we found a very high level of population differentiation (G ST = 0.819) but the phylogeographical structure remained obscure (N ST = 0.853>G ST = 0.819, P>0.05). Phylogenetic analyses revealed two main cpDNA haplotype lineages. The split between these two haplotype groups can be dated back to the mid-to-late Pleistocene (ca. 0.480 Myr). Mismatch distribution analyses showed that each of these had experienced a recent range expansion. These two expansions (ca. 0.12 and 0.17 Myr) might have begun from the different refugees before the Last Glacial Maximum (LGM). Conclusions/Significance This study initiates a research on the phylogeography of aquatic herbs in the QTP and for the first time sheds light on the response of an alpine aquatic seed plant species in the QTP to Quaternary climate oscillations.