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Plastid genome and nuclear ribosomal DNA (nrDNA) arrays, proposed recently as "super-barcodes," might provide additional discriminatory power and overcome the limitations of traditional barcoding loci, yet super-barcodes need to be tested for their effectiveness in more plant groups. Morphological homoplasy among Schima species makes the genus a model for testing the efficacy of super-barcodes. In this study, we generated multiple data sets comprising standard DNA barcodes (matK, rbcL, trnH-psbA, nrITS) and super-barcodes (plastid genome, nrDNA arrays) across 58 individuals from 12 out of 13 species of Schima from China. No samples were correctly assigned to species using standard DNA barcodes and nrDNA arrays, while only 27.27% of species with multiple accessions were distinguished using the plastid genome and its partitioned data sets-the lowest estimated rate of super-barcode success in the literature so far. For Schima and other taxa with similarly recently divergence and low levels of genetic variation, incomplete lineage sorting, hybridization or taxonomic oversplitting are all possible causes of the failure. Taken together, our study suggests that by no means are super-barcodes immune to the challenges imposed by evolutionary complexity. We therefore call for developing multilocus nuclear markers for species discrimination in plant groups.

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Angiosperms are by far the most species-rich clade of land plants, but their origin and early evolutionary history remain poorly understood. We reconstructed angiosperm phylogeny based on 80 genes from 2,881 plastid genomes representing 85% of extant families and all orders. With a well-resolved plastid tree and 62 fossil calibrations, we dated the origin of the crown angiosperms to the Upper Triassic, with major angiosperm radiations occurring in the Jurassic and Lower Cretaceous. This estimated crown age is substantially earlier than that of unequivocal angiosperm fossils, and the difference is here termed the ‘Jurassic angiosperm gap’. Our time-calibrated plastid phylogenomic tree provides a highly relevant framework for future comparative studies of flowering plant evolution. A study reconstructed angiosperm phylogeny on the basis of plastome data representing 2,351 angiosperm and 187 gymnosperm species, and dated the origin of crown angiosperms to be significantly earlier than the estimates based on fossil data.

Aletris megalantha F. T. Wang & Tang is an herbal plant species endemic to Yunnan Province of China. Its complete plastid genome sequence was 154,704 bp in length, with a large single-copy (LSC) region of 83,265 bp, a small single-copy (SSC) region of 18,127 bp, and a pair of inverted repeat regions (IRs) of 26,656 bp. The whole plastid genome encoded 132 genes, including 85 protein-coding genes, 38 tRNA genes, and eight rRNA genes. The overall GC content of A. megalantha plastid genome was 37.4%. Maximum likelihood phylogenetic analysis based on 14 taxa indicated that A. megalantha is evolutionarily close to A. spicata.

Taxus (yew) is both the most species-rich and taxonomically difficult genus in Taxaceae. To date, no study has elucidated the complexities of the plastid genome (plastome) or examined the possibility of whole plastomes as super-barcodes across yew species worldwide. In this study, we sequenced plastomes from two to three individuals for each of the 16 recognized yew species (including three potential cryptics) and Pseudotaxus chienii. Our comparative analyses uncovered several gene loss events that independently occurred in yews, resulting in a lower plastid gene number than other Taxaceous genera. In Pseudotaxus and Taxus, we found two isomeric arrangements that differ by the orientation of a 35 kb fragment flanked by “trnQ-IRs”. These two arrangements exist in different ratios within each sampled individual, and intraspecific shifts in major isomeric arrangements are first reported here in Taxus. Moreover, we demonstrate that entire plastomes can be used to successfully discriminate all Taxus species with 100% support, suggesting that they are useful as super-barcodes for species identification. We also propose that accD and rrn16-rrn23 are promising special barcodes to discriminate yew species. Our newly developed Taxus plastomic sequences provide a resource for super-barcodes and conservation genetics of several endangered yews and serve as comprehensive data to improve models of plastome complexity in Taxaceae as a whole and authenticate Taxus species.

The Cornales is a relatively small but morphologically diverse order in the basal position of the Asterids clade. Previous study hypothesized that the order might have undergone ancient rapid radiation during the Cretaceous when major angiosperm lineages were established. We conducted the phylogenomic analysis of Cornales using 81 plastid genome sequences with 67 newly generated in this study to test the hypothesis. This sampling represents all the families and 31 out of 48 genera in the order. Phylogenetic analyses were conducted using different datasets to examine the effects of different coding positions and character coding methods. We further conducted divergence time, diversification rate, and biogeographic analyses to understand the early evolutionary history of Cornales in space and time. Our phylogenetic analyses of four datasets (the amino acid characters, the 1st and 2nd codon positions of protein coding genes, nucleotide characters with degenerated coding method, and noncoding regions) resulted in a robust phylogeny congruent with results of previous studies, showing (((Cornaceae-Alangiaceae)-(Curtisiaceae-Grubbiaceae))-(((Nyssaceae-Davidiaceae)-Mastixiaceae)-((Hydrostachyaceae-(Hydrangeaceae-Loasaceae)))). Phylogenetic relationships within families were also well resolved. Conflicts in the placement of Hydrostachyaceae were found from analyses of two datasets, the nucleotide characters of all codon position and the 3rd codon positions, where the family was united with Loasaceae, but not strongly supported. Results from divergence time analyses suggested a mid-Cretaceous origin of Cornales followed by rapid early diversification into major clades/families within 10 million years. The early diversification of Cornales may have been facilitated by divergence in habitat and morphology following geographic dispersals. The ancestral distribution of the order was inferred as a widespread range covering Asia, Europe, North America, and Africa when including fossils in the analyses, suggesting an origin of the order likely along the Tethys Seaway where the areas were connected in the mid-Cretaceous. Inferred geographic origins of each family differed to some extent between analyses including fossils vs excluding fossils. In the analysis with extant and fossil species, the origins of the African Hydrostachyaceae and Grubbiaceae-Curtisiaceae clade were inferred to have involved two independent events, an intercontinental dispersal from the northern hemisphere to Africa and an intercontinental vicariance between the northern hemisphere and Africa, respectively. Other families were inferred to have evolved in the northern hemisphere with subsequent intercontinental dispersal(s) to other areas including to Central and South America, during their subsequent diversification. Net diversification rate analysis based on treePL dated phylogeny using MEDUSA detected a nearly 5-fold decrease in the African endemic Curtisiaceae-Grubbiaceae (CuG) clade and an increase of rate in the Hydrangeaceae-Loasaceae (HL) clade. Within HL, a decrease in the Fendlera-Jamesia clade and an increase in the Philadelphus clade were also detected. The findings are also consistent with the level of present species diversity in these lineages. Our study demonstrated the value of plastid genome in phylogenomic study, but posed an old challenge of biogeographic study with fossil data and raised caution for the synonymous substitution sites of plastid genome in phylogenomics studies.

Angiosperms are by far the most species-rich clade of land plants, but their origin and early evolutionary history remain poorly understood. We reconstructed angiosperm phylogeny based on 80 genes from 2,881 plastid genomes representing 85% of extant families and all orders. With a well-resolved plastid tree and 62 fossil calibrations, we dated the origin of the crown angiosperms to the Upper Triassic, with major angiosperm radiations occurring in the Jurassic and Lower Cretaceous. This estimated crown age is substantially earlier than that of unequivocal angiosperm fossils, and the difference is here termed the 'Jurassic angiosperm gap'. Our time-calibrated plastid phylogenomic tree provides a highly relevant framework for future comparative studies of flowering plant evolution.

Background The Cornales is the basal lineage of the asterids, the largest angiosperm clade. Phylogenetic relationships within the order were previously not fully resolved. Fifteen plastid genomes representing 14 species, ten genera and seven families of Cornales were newly sequenced for comparative analyses of genome features, evolution, and phylogenomics based on different partitioning schemes and filtering strategies. Results All plastomes of the 14 Cornales species had the typical quadripartite structure with a genome size ranging from 156,567 bp to 158,715 bp, which included two inverted repeats (25,859–26,451 bp) separated by a large single-copy region (86,089–87,835 bp) and a small single-copy region (18,250–18,856 bp) region. These plastomes encoded the same set of 114 unique genes including 31 transfer RNA, 4 ribosomal RNA and 79 coding genes, with an identical gene order across all examined Cornales species. Two genes (rpl22 and ycf15) contained premature stop codons in seven and five species respectively. The phylogenetic relationships among all sampled species were fully resolved with maximum support. Different filtering strategies (none, light and strict) of sequence alignment did not have an effect on these relationships. The topology recovered from coding and noncoding data sets was the same as for the whole plastome, regardless of filtering strategy. Moreover, mutational hotspots and highly informative regions were identified. Conclusions Phylogenetic relationships among families and intergeneric relationships within family of Cornales were well resolved. Different filtering strategies and partitioning schemes do not influence the relationships. Plastid genomes have great potential to resolve deep phylogenetic relationships of plants. Electronic supplementary material The online version of this article (10.1186/s12864-017-4319-9) contains supplementary material, which is available to authorized users.

Background and Aims The extent to which hybridization leads to gene flow between plant species depends on the structure of hybrid populations. However, if this varies between locations, species barriers might prove permeable in some locations but not in others. To assess possible variation in hybrid population structure, the magnitude and direction of natural hybridization between two Chinese endemic species, Rhododendron spiciferum and Rhododendron spinuliferum, were evaluated. Methods Thirteen nuclear microsatellite markers were employed to characterize 566 individuals collected from 15 non-allopatric populations and nine allopatric parental populations. Chloroplast DNA (cpDNA) sequences were obtained from a subset of samples. Genetic structure and direction of gene flow was determined using a combination of STRUCTURE and NEWHYBRIDS analysis. Key Results Nuclear analysis revealed that parental taxa formed two genetically distinct clusters and hybrids shared the genetic background of both parents and did not form a separate genetic lineage. Overall, hybrid swarms were dominated by early- and later-generation hybrids, with a significantly higher proportion of hybrids (59·6 %) possessing >50 % R. spiciferum-like nuclear germplasm. The cpDNA analysis further indicated that a significantly greater proportion of hybrids (61·1 %) possessed the R. spiciferum cpDNA haplotype. Conclusions Gene flow between R. spiciferum and R. spinuliferum was found to be bidirectional in 14 of the 15 hybrid swarms and asymmetrical in six hybrid swarms. Asymmetrical gene flow was evident for only nuclear DNA (nDNA) in two populations, for only cpDNA in three populations, and for both nDNA and cpDNA in one population. Collectively, the variation in genetic structure found among the 15 hybrid swarms suggests that introgression rather than hybrid speciation is a more likely outcome of hybridization between these hybridizing taxa.

A percent identity plot showing the overall sequence similarity of the fourteen Cornales plastid genomes. Fig. S2. Phylogenetic relationships of Cornales based on three different data sets with light filtered alignment. Fig. S3. Phylogenetic relationships of Cornales based on three different data sets with strict filtered alignment. (PDF 1121Â kb)

The primers newly designed in this study for four junctions and two genes (rpl22, ycf15). Table S2. Molecular models selected for all the data sets of the three alignment strategies. Table S3. Model selected for each data partition identified by software PartitionFinder for unfiltered complete plastid genomes. Table S4. Gene category and gene contained in plastid genomes of Cornales. (DOC 147Â kb)

Carya kweichowensis is an importantly economic tree species in Juglandaceae, which is critically endangered and endemic to Guizhou, China. The plastid genome of C. kweichowensis was assembled and characterized based on Illumina pair-end sequencing data using genome skimming approach. The complete plastid genome is 175,313 bp in length, with a GC content of 35.8%. It is a typical quadripartite structure, containing a large single copy (LSC) region of 89,858 bp and a small single copy (SSC) region of 3569 bp separated by a pair of extremely extensive inverted repeats (IRs) of 40,943 bp. A total of 142 genes were annotated, including 94 protein-coding genes, 40 tRNA genes, and eight rRNA genes. A maximum likelihood (ML) phylogenetic tree on plastid genomes revealed that C. kweichowensis is close to Annamocarya sinensis. The newly characterized complete plastid genome of C. kweichowensis will provide essential data for further studies of this endangered species.

Compensatory growth is a phase of accelerated growth apparent when favourable conditions are restored after a period of growth depression. To investigate if F-2 common 'all-fish' growth hormone gene transgenic common carp (Cyprinus carpio) could mount compensatory growth, a 9 week study at 29 degrees C was performed. The control group was fed to satiation twice a day throughout the experiment. The other two groups were deprived of feed for 1 or 2 weeks, respectively, and then fed to satiation during the re-feeding period. At the end of the experiment, the live masses of fish in the deprived groups were still significantly lower than those of the controls. During the re-feeding period, size-adjusted mean specific growth rates and mean feed intakes were significantly higher in the deprived fish than in the controls, indicating a partial compensatory growth response in these fish. No significant differences were found in food conversion efficiency between the deprived and control fish during re-feeding, suggesting that hyperphagia was the mechanism responsible for increased growth rates. The proximate composition of the deprived fish at the end of the experiment was similar to that of the control fish. This study is, to our knowledge, the first to report that fast-growing transgenic fish can achieve partial compensation of growth following starvation. (c) 2007 The Authors Journal compilation (c) 2007 The Fisheries Society of the British Isles.

The growth and energy budget for F-2 'all-fish' growth hormone gene transgenic common carp Cyprinus carpio of two body sizes were investigated at 29.2 degrees C for 21 days. Specific growth rate, feed intake, feed efficiency, digestibility coefficients of dry matter and protein, gross energy intake (I-E), and the proportion of I-E utilized for heat production (H-E) were significantly higher in the transgenics than in the controls. The proportion of I-E directed to waste products [faecal energy (F-E) and excretory energy loss (Z(E) + U-E) where Z(E) is through the gills and U-E through the kidney], and the proportion of metabolizable energy (M-E) for recovered energy (R-E) were significantly lower in the transgenics than in the controls. The average energy budget equation of transgenic fish was as follows: 100 I-E = 19.3 F-E + 6.0 (Z(E) + U-E) + 45.2 H-E + 29.5 R-E or 100 M-E = 60.5 H-E + 39.5 R-E. The average energy budget equation of the controls was: 100 I-E = 25.2 F-E + 7.4 (Z(E) + U-E) + 35.5 H-E + 31.9 R-E or 100 M-E = 52.7 H-E + 47.3 R-E. These findings indicate that the high growth rate of 'all-fish' transgenic common carp relative to their non-transgenic counterparts was due to their increased feed intake, reduced lose of waste productions and improved feed efficiency. The benefit of the increased energy intake by transgenic fish, however, was diminished by their increased metabolism.

The F-4 generation of human growth hormone (hGH) transgenic red common carp Cyprinus carpio had significantly higher growth rates than the non-transgenic controls. Protein and energy intakes were significantly higher in the transgenic carp than in the controls fed the 20% protein diet, but were not different between the two strains fed diets with 30 and 40% protein. Faecal protein loss, as a proportion of protein intake, was significantly lower in the transgenics than in the controls fed diets with 20 and 30% protein, but was not different between the two strains Fed diet with 40% protein. Faecal energy loss, as a proportion of energy intake, was significantly lower in the transgenics than in the controls fed diet with 20% protein, but was not different between the two strains fed diets with 30 and 40% protein. Recovered protein, as a proportion of protein intake, was significantly higher in the transgenics than in the controls fed all diets, whereas recovered energy was significantly higher in the transgenic fish fed the 40% protein diet. For fish fed each diet, the transgenics had significantly higher body contents of dry matter and protein, but lower contents of lipid than the controls. It was concluded that transgenics were more efficient in utilizing dietary protein than the controls. it a lower dietary protein level; transgenics achieved higher growth rates mainly by increasing feed intake; at higher levels of dietary protein, transgenics achieved higher growth rates mainly through a higher energy conversion efficiency. (C) 1998 The Fisheries Society of the British Isles.