Reassignment of the methine resonances of D-fructose based on the carbon-13 n.m.r. spectrum of 3-O-methyl-D-fructose

Several disagreements in the ¹³C n.m.r. assignments of the methine carbons of D-fructose exist in the literature. In order to settle these inconsistencies, we examined the ¹³C n.m.r. spectrum of 3-O-methyl-D-fructose. By following the methyl induced shift in this spectrum, as compared to the parent sugar, we identified the alkylated C-3 resonance of all four tautomeric forms of D-fructose. This information, together with our previous identification of the C-5 resonances of the α- and β-forms of D-fructofuranose 6-phosphate, allow the unambiguous identification of all methine carbons of D-fructose in its ¹³C n.m.r. spectrum. The tautomeric composition of 3-O-methyl-D-fructose at 16.5°, in aqueous solution, was found to be as follows: α-pyranose 18%, β-pyranose 37%, α-furanose 11% and β-furanose 34%.     

Orders out of chaos – molecular phylogenetics reveals the complexity of shark and stingray tapeworm relationships

Novel molecular data are presented to resolve the long-standing issue of the non-monophyly of the elasmobranch-hosted tapeworm order Tetraphyllidea relative to the other acetabulate eucestode orders. Bayesian inference analyses of various combinations of full ssrDNA, and full or partial lsrDNA (D1–D3), sequence data, which included 134 species representing 97 genera across the 15 eucestode orders, were conducted. New ssrDNA data were generated for 82 species, partial lsrDNA data for 53 species, and full lsrDNA data for 29 species. The monophyly of each of the elasmobranch-hosted orders Cathetocephalidea, Litobothriidea, Lecanicephalidea and Rhinebothriidea was confirmed, as was the non-monophyly of the Tetraphyllidea. Two relatively stable groups of tetraphyllidean taxa emerged and are hereby designated as new orders. The Onchoproteocephalidea n. ord. is established to recognise the integrated nature of one undescribed and 10 described genera of hook-bearing tetraphyllideans, previously placed in the family Onchobothriidae, with the members of the order Proteocephalidea. The Phyllobothriidea n. ord. is established for a subset of 12 non-hooked genera characterised by scoleces bearing four bothridia each with an anterior accessory sucker; most parasitise sharks and have been assigned to the Phyllobothriidae at one time or another. Tentative ordinal placements are suggested for eight additional genera; placements for the remaining tetraphyllidean genera have not yet emerged. We propose that these 17 genera remain in the “Tetraphyllidea”. Among these, particularly labile across analyses were Anthobothrium, Megalonchos, Carpobothrium, Calliobothrium and Caulobothrium. The unique association of Chimaerocestus with holocephalans, rather than with elasmobranchs, appears to represent a host-switching event. Both of the non-elasmobranch hosted clades of acetabulate cestodes (i.e. Proteocephalidea and Cyclophyllidea and their kin) appear to have had their origins with elasmobranch cestodes. Across analyses, the sister group to the clade of “terrestrial” cestode orders was found to be an elasmobranch-hosted genus, as was the sister to the freshwater fish- and tetrapod-hosted Proteocephalidea. Whilst further data are required to resolve outstanding nomenclatural and phylogenetic issues, the present analyses contribute significantly to an understanding of the evolutionary radiation of the entire Cestoda. Clearly, elasmobranch tapeworms comprise the backbone of cestode phylogeny.     

种子重量与海拔的相关性分析：

种子重量与海拔的关系是植物生态学中重要而尚存争议的问题。本文对中国123科853种2879份野生植物种子的重量在海拔上的变化特点以及二者之间的相互关系进行了深入研究,结果显示：种子重量总体上与海拔呈负相关,种子重量级别多样性和生活型多样性随海拔上升呈阶梯状下降。但7级种子中,只有10。级种子的重量与海拔呈负相关;7种生活型中,只有灌木和匍匐草本的种子重量与海拔呈负相关;在种水平上,只有8．2％的物种种子重量与海拔存在相关性。本研究揭示了我国种子重量与海拔之间的复杂关系,以及遗传和环境对种子重量的影响,对植物育种、森林管理以及入侵植物的防治具有一定指导意义。     

Internal consistency as a method to assess the quality of dating estimates using multiple markers

Multiple tools are available to infer time in phylogentic reconstructions and multiple markers/genes are generally used to obtain more solid reconstructions, opening to the issue of which marker performs better in dating. Following the observation that multiple markers, applied to the same group of taxa or even to the same topology, generally produce different time estimates, we suggest two new estimators: DD_jk to quantify the discordance between two ultrametric dated trees with identical topology and ID_j to quantify the discordance of one tree with respect to a study-set of trees in terms of their date estimates. Furthermore we suggest a procedure based on a stepwise exclusion algorithm to rank trees from the most to the least consistent with the study-set of trees based on their time estimates. We name the quality of a tree of having time estimates that agree with the majority of other trees as ‘internal consistency’. We applied this procedure to assess the internal consistency of trees individually obtained from 14 mitochondrial markers in 5 insect orders and to test whether one or more markers repeatedly produce dates that are more consistent. Three genes (nad4, nad5 and cytb) repeatedly perform better than others, one (cox2) worse. We suggest this method could be applied in evaluating the performance of different markers preliminary to a dating analysis.     

Phylogenetic relationships within phylum Rotifera: orders and genus Notholca

We investigated evolutionary relationships among orders in phylum Rotifera and among species in genus Notholca (Rotifera) by computing parsimonious cladograms. All of the most-parsimonious cladograms generated for the ordinal level confirm the view that class Monogononta, superclass Eurotatoria, and phylum Rotifera are monophyletic. Species within the genus Notholca were separated into six groups (clades), but some species have been defined based on highly variable characters not reliably studied using cladistics. Therefore, phenetic studies are warranted, especially for species possessing caudal processes.     

The effect of irrigation regimes on plum (Prunus cerasifera) root system development dynamics

Prunus genus species are widely spread in semi-arid regions due to their ability to adjust to the limited water supply. Former research described the effect of water deficit on their aboveground development. However, less is known about the effects of water stress on the development of the root system. In order to investigate the effects of the irrigation regime on the root system development, young plum (Prunus cerasifera) trees were grown under three irrigation regimes for a period of five months. The effects of the irrigation regime on different root order and total root system elongation, biomass growth and tip numbers were analyzed. The results indicate that the responses vary according to the stress level. Under moderate stress, the total root system biomass decreases relative to the full irrigation treatment. However, low-order root formation remains similar to that found under no stress conditions. Under severe stress, the formation of low-order roots is also inhibited. Our results suggest that plum trees’ response to water deficit stress escalates according to the stress level. Namely, moderate stress affects the growth rate of the root system but does not alter the relative contribution of different orders, while severe stress both inhibits the total growth and changes the relative contribution of the different root orders. The combined measurements of the total root system and the different orders enable the identification of a stepwise response to water stress.     

种子重量与海拔的相关性分析

种子重量与海拔的关系是植物生态学中重要而尚存争议的问题。本文对中国123科853种2879份野生植物种子的重量在海拔上的变化特点以及二者之间的相互关系进行了深入研究,结果显示：种子重量总体上与海拔呈负相关,种子重量级别多样性和生活型多样性随海拔上升呈阶梯状下降。但7级种子中,只有100级种子的重量与海拔呈负相关;7种生活型中,只有灌木和匍匐草本的种子重量与海拔呈负相关;在种水平上,只有82%的物种种子重量与海拔存在相关性。本研究揭示了我国种子重量与海拔之间的复杂关系,以及遗传和环境对种子重量的影响,对植物育种、森林管理以及入侵植物的防治具有一定指导意义。     

The relative importance of environment, human activity and space in explaining species richness of South African bird orders

Aim To assess the relative importance of environmental (climate, habitat heterogeneity and topography), human (population density, economic prosperity and land transformation) and spatial (autocorrelation) influences, and the interactions between these predictor groups, on species richness patterns of various avifaunal orders. Location South Africa. Methods Generalized linear models were used to determine the amount of variation in species richness, for each order, attributable to each of the different predictor groups. To assess the relationships between species richness and the various predictor groups, a deviance statistic (a measure of goodness of fit for each model) and the percentage deviation explained for the best fitting model were calculated. Results Of the 12 avifaunal orders examined, spatially structured environmental deviance accounted for most of the variation in species richness in 11 orders (averaging 28%), and 50% or more in seven orders. However, orders comprising mostly water birds (Charadriiformes, Anseriformes, Ciconiformes) had a relatively large component of purely spatial deviance compared with spatially structured environmental deviance, and much of this spatial deviance was due to higher‐order spatial effects such as patchiness, as opposed to linear gradients in species richness. Although human activity, in general, offered little explanatory power to species richness patterns, it was an important correlate of spatial variation in species of Charadriiformes and Anseriformes. The species richness of these water birds was positively related to the presence of artificial water bodies. Main conclusions Not all bird orders showed similar trends when assessing, simultaneously, the relative importance of environmental, human and spatial influences in affecting bird species richness patterns. Although spatially structured environmental deviance described most of the variation in bird species richness, the explanatory power of purely spatial deviance, mostly due to nonlinear geographical effects such as patchiness, became more apparent in orders representing water birds. This was especially true for Charadriiformes, where the strong anthropogenic relationship has negative implications for the successful conservation of this group.