Myth and reality of the subtribe Astephaninae (Decne.) Schumann (Asclepiadaceae)

The subtribe Astephaninae (tribe Asclepiadeae, Asclepiadaceae) is recircumscribed to contain 11 genera: Astephanus, Blyttia, Diplostigma, Goydera, Aiicroloma, Oncinema, Pentatropis, Pteurosteima, Rhyncharrhena, Schizostephanus, and Tylophoropsis. Following a character analysis, phylogeny was analysed by means of a computerized parsimony program (HENNIG86). Astephanus /Microloma is identified as the most stable clade, followed by Tylophopropsis/Pentatropis/Rhyncharrhena, Blyttia/Diplostigma and Schizostephanus/Goydera. A key to the genera is presented, as well as notes on distribution, important characters, and present state of knowledge for each genus. The genus Schizostephanus is resurrected and four new combinations are proposed.     

岛衣型真菌属级分类的初步研究*

本研究对岛衣型真菌Allocetraria ambigua,Allocetraria stracheyi,Nephromopsis pallescens和Tuckneraria laureri的核rDNA ITS序列进行了测定,并结合来自Genbank中的其它21种岛衣型真菌的核rDNA ITS序列进行了同源性分析。分析所用软件为DNAMAN。结果发现,Cetraria、Allocetraria、 Vulpicida、 Flavocetraria、 Tuckermannopsis和Kaernefeltia之间rDNA ITS的同源关系非常密切。这同岛衣型地衣现有细分的小属观点相矛盾。这种矛盾可能是由于持小属观点的作者在分属时对个别表型性状加权的结果。     

基于叶绿体基因组探讨桃金娘目及其近缘类群的系统发育关系

该研究基于叶绿体基因组数据,对桃金娘目(6科44属97种)及其近缘类群(牻牛儿苗目2科5属25种)的系统发育关系进行了分析.结果表明:(1)桃金娘目基因组大小为152～171 kb,包括的蛋白质编码基因数目为74～90个;牻牛儿苗目基因组大小为116～242 kb,包括的蛋白质编码基因数目为75～132个.(2)对比叶...     

Phylogeny and species delimitation of the C-genome diploid species in Oryza

The diploid Oryza species with C-genome type possesses abundant genes useful for rice improvement and provides parental donors of many tetraploid species with the C-genome (BBCC,CCDD).Despite extensive studies,the phylogenetic relationship among the C-genome species and the taxonomic status of some taxa remain controversial.In this study,we reconstructed the phylogeny of three diploid species with C-genome (Oryza officinalis,O.rhizomatis,and O.eichingeri) based on sequences of 68 nuclear single-copy genes.We obtained a fully resolved phylogenetic tree,clearly indicating the sister relationship of O.officinalis and O.rhizomatis,with O.eichingeri being the more divergent lineage.Incongruent phylogenies of the C-genome species found in previous studies might result from lineage sorting,introgression/hybridization and limited number of genetic markers used.We further applied a recently developed Bayesian species delimitation method to investigate the species status of the Sri Lankan and African O.eichingeri.Analyses of two datasets (68 genes with a single sample,and 10 genes with multiple samples) support the distinct species status of the Sri Lankan and African O.eichingeri.In addition,we evaluated the impact of the number of sampled individuals and loci on species delimitation.Our simulation suggests that sampling multiple individuals is critically important for species delimitation,particularly for closely related species.     

Fine-scale cospeciation between Brachycaudus and Buchnera aphidicola: bacterial genome helps define species and evolutionary relationships in aphids

Aphids harbour an obligatory symbiont, Buchnera aphidicola, providing essential amino acids not supplied by their diet. These bacteria are transmitted vertically and phylogenic analyses suggest that they have 'cospeciated' with their hosts. We investigated this cospeciation phenomenon at a fine taxonomic level, within the aphid genus Brachycaudus. We used DNA-based methods of species delimitation in both organisms, to avoid biases in the definition of aphid and Buchnera species and to infer association patterns without the presumption of a specific interaction. Our results call into question certain 'taxonomic' species of Brachycaudus and suggest that B. aphidicola has diversified into independently evolving entities, each specific to a 'phylogenetic' Brachycaudus species. We also found that Buchnera and their hosts simultaneously diversified, in parallel. These results validate the use of Buchnera DNA data for inferring the evolutionary history of their host. The Buchnera genome evolves rapidly, making it the perfect tool for resolving ambiguities in aphid taxonomy. This study also highlights the usefulness of species delimitation methods in cospeciation studies involving species difficult to conceptualize--as is the case for bacteria--and in cases in which the taxonomy of the interacting organisms has not been determined independently and species definition depends on host association.     

A comparative study of metal levels in leaves of some Al-accumulating Rubiaceae

Concentrations of Al, Si, Fe, Mn, Cu and Ca were analysed in leaves of ten Rubiaceae species, most of which are Al accumulators, and these were compared with concentrations in one species of Melastomataceae. Quantitative data confirmed the distribution of Al accumulation as previously determined by semi-quantitative tests, and suggest that there is an apparent congruency between the shoot Al concentration and the number of accumulators within a certain genus or tribe. Al accumulators within the Rubiaceae are most characteristic of the Rubioideae subfamily, although a second origin is likely in at least a few members of the tribes Vanguerieae and Alberteae. While the leaf Si concentration in Melastomata malabathricum L. (Melastomataceae) was negligible, all Rubiaceae studied showed relatively high Si levels (mostly >3000 mg kg(-1)). It is hypothesized that an Al-Si complex is formed in the shoot tissues of Al-accumulating Rubiaceae and that this may contribute to Al detoxification. However, the Si : Al mole ratio tended to differ widely among species. There was no significant correlation between Al and the other metals analysed. A remarkably high Mn concentration was found in Coptosapelta olaciformis Elm.     

Systematic significance of tepal surface morphology in tribes Persicarieae and Polygoneae (Polygonaceae)

In order to improve understanding of the systematic relationships between taxa and of tepal-pollinator and tepal-habitat relationships, a detailed scanning electron microscopy (SEW study of the adaxial tepal surface of 135 taxa belonging to c. 14 genera in the tribes Persicarieae and Polygoneae (Polygonoideae-Polygonaceae) was carried out. The tepal surfaces have revealed some striking differences among the genera studied. Three main patterns of sculpturing and cell shape can be recognized. Type I: mostly rectangular to elongate cells with straight or undulating anticlinal walls; the cuticles smooth or striate in longitudinal direction and often continuous (Persicaria, Bistortu, Aconogonon, Koenigia and some species of Fagopyrum). Type II: irregular tesselated to elongated cells, rarely rectangular with mostly sinuate anticlinal walls; the cuticles rarely with longitudinal striation, but with strong orthogonal to reticulate ridges or striae, often without correlation between cells (Polygonum s.s., Polygonella, Fallopia, Parapteropyrum, Pteropyrum, Atraphaxis and Calligonum). Type III: mostly irregular, mammilliform, papillose cells with either longitudinal tightly pressed or randomly ridged cuticles (some species of Fagotyrum and Oxygonum). The present data generally support the division of Polygoneae and Persicarieae by Ronse Decraene & Akeroyd. The mammilliform, papillate epidermis of tepals in Oxygonum and some Fagopyrum is probably well-adapted to entomophily either as a foothold or even as a light-trap, and also shows some correlation with heterostyly. It is noteworthy that the tepal structure of Polygonella (tesselated form) is highly similar to that of Polygonum s. s. (especially P. sect. Duravia). Cuticular striation alone does not appear to have much systematic value, but has a mechanical function in affording extra strength to the cell walls. Some correlations between the degree/shape of cuticles and the pollination mechanisms or the habitat of each taxon are also briefly discussed. It is concluded that the studied tepal characters can be useful in improving the classification of tribes Persicarieae and Polygoneae, arid give additional support at the infrageneric level.     

Phytochemistry and the systematics and ecology of Loasaceae and Gronoviaceae (Loasales)

A screening for iridoid compounds of 78 of 315 species from all major groups in Gronoviaceae and Loasaceae has been carried out. The results were compared to the systematic concepts in the family and distribution and ecology of the taxa. Iridoids are present in at least some species of all genera screened. Some simple, monomeric compounds (e.g., loganin, sweroside) are found in all major groups of the two families and represent the basic iridoid inventory. Other compounds are restricted to certain taxonomic groups: nine-carbon iridoids (e.g., deutzioside) are restricted to Mentzelia (Loasaceae subfam. Mentzelioideae), hetero-oligomeric iridoids (e.g., tricoloroside methyl ester, acerifolioside) are restricted to two small groups in Loasa (Loasa ser. Macrospermae and ser. Floribundae, Loasaceae subfam. Loasoideae), and oleosides (e.g., 10-hydroxyoleoside dimethyl ester) are restricted to the large genus Caiophora sensu Weigend). The distribution of certain iridoid compounds thus confirms some of the generic limits. Iridoid phytochemistry does not correlate with systematic entities above the generic level nor does it in any way correlate with the morphological evolution of taxa. Conversely, the amount and complexity of iridoid compounds present in taxa correlate positively with the aridity of their habitat and the extent of mammalian herbivore pressure.