Phylogenetic diversity of forest trees in the Usambara mountains of Tanzania: correlations with altitude

The relationship between diversity of large trees and altitude was investigated in a Tanzanian tropical rain forest. In total, 231 samples of 20 trees of ≥ 20 cm d.b.h. from the East and West Usambara mountains, covering an elevation range from 280 m to 2180 m a.s.l., were analysed. An ordination demonstrated a constant turnover of species, genera, family and orders with elevation. There were no obvious zones or discontinuities. There was no decline in plot richness with respect to altitude for species, genera or orders. Family richness was shown to increase with altitude. A measure of genetic diversity, the avalanche index, was calculated for each plot to investigate the effect of incorporating phylogenetic relatedness of individuals into the diversity measure. Distances between taxa were extracted from a recent molecular phylogeny of the angiosperms. Incorporation of phylogenetic diversity at family level enhanced the positive correlation between plot diversity and altitude.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 217–228.     

Applications of natural orbitals for chemical valence in a description of bonding in conjugated molecules

Natural orbitals for chemical valence (NOCV) were used to describe bonding in conjugated pi-electron molecules. The 'single' C-C bond in trans-1,3-butadiene, 1,3-butadiene-1,1,4,4-tetra-carboxilic acid, 1,3,5,7-octatetraene, and 11-cis-retinal was characterized. In the NOCV framework, the formation of the sigma-bond appears as the sum of two complementary charge transfer processes from each vinyl fragment to the bond region, and partially to the other fragment. The formation of the pi-component of the bond is described by two pairs of NOCV representing the transfer of charge density from the neighboring 'double' C-C bonds. The NOCV eigenvalues and the related fragment-fragment bond multiplicities were used as quantitative measures of the sigma- and pi- contributions. The sigma-component of the 'single' C-C bonds appears to be practically constant in the systems analyzed, whereas the pi-contributions increase from butadiene (ca. 7.5%) to retinal (ca. 14%).     

Seasonal pattern of insect abundance in the Brazilian cerrado

Abstract In Brazil, a severe dry season lasting for approximately 5 months and frequent fires make life difficult for cerrado insects. In certain aspects, the cerrado can be considered to be an understudied ecosystem; even basic information such as knowledge about the annual peak in abundance of different insect orders is unknown. Insect abundance patterns have only been investigated for a few groups in the cerrado region. Thus, our study concerns the temporal distribution of insect abundance in the savanna‐like vegetation of the central Brazilian cerrado (sensu stricto) in Distrito Federal. The region has a well‐defined, long dry season between May and September. The insects were sampled by window, malaise tent and pitfall traps within 1 year. We used a multiple linear regression to analyse the relationship between abundance of insects of each order and climate variables. A total of 50 127 individuals from 15 orders was collected. The orders were Coleoptera (26%), Hymenoptera (23%), Diptera (20.5%), Isoptera (20%), Homoptera (4%), Lepidoptera (4%), Orthoptera (1.5%) and Hemiptera (1%). The abundance of Diptera, Homoptera, Lepidoptera and Orthoptera was randomly distributed over time, Isoptera peaked in the first half of the wet season, Coleoptera and Hemiptera in the second half of the wet season and Hymenoptera in each season. A significant correlation was found only between Coleoptera and delayed climatic variables. There were no obvious trends that might help explain the abundance patterns observed. The study provides baseline information about phenological patterns of insect abundance and permits evaluation of this group as a resource for various food chains and different trophic levels.     

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。     

Effect of vibration magnitude, vibration spectrum and muscle tension on apparent mass and cross axis transfer functions during whole-body vibration exposure

Twelve seated male subjects were exposed to 15 vibration conditions to investigate the nature and mechanisms of the non-linearity in biomechanical response. Subjects were exposed to three groups of stimuli: Group A comprised three repeats of random vertical vibration at 0.5, 1.0 and 1.5 m s⁻² r.m.s. with subjects sitting in a relaxed upright posture. Group B used the same vibration stimuli as Group A, but with subjects sitting in a ‘tense’ posture. Group C used vibration where the vibration spectrum was dominated by either low-frequency motion (2–7 Hz), high-frequency motion (7–20 Hz) or a 1.0 m s⁻² r.m.s. sinusoid at the frequency of the second peak in apparent mass (about 10–14 Hz) added to 0.5 m s⁻² r.m.s. random vibration. In the relaxed posture, frequencies of the primary peak in apparent mass decreased with increased vibration magnitude. In the tense posture, the extent of the non-linearity was reduced. For the low-frequency dominated stimulus, the primary peak frequency was lower than that for the high-frequency dominated stimulus indicating that the frequency of the primary peak in the apparent mass is dominated by the magnitude of the vibration encompassing the peak. Cross-axis transfer functions showed peaks of about 15–20% and 5% of the magnitudes of the peaks in the apparent mass for x- and y-direction transfer functions, respectively, in the relaxed posture. In the tense posture, cross-axis transfer functions reduced in magnitude with increased vibration, likely indicating a reduced fore-aft pitching of the body with increased tension, supporting the hypothesis that pitching contributes to the non-linearity in apparent mass.     

Digit ratio (2D:4D) and the spatial representation of magnitude

Digit ratio (as a putative indicator of prenatal androgen exposure) is related to a range of sexually dimorphic abilities, including spatial skills and mathematical ability. This study examined a phenomenon known as the SNARC effect (Spatial Numerical Association of Response Codes), which is taken as evidence of a mental representation of magnitude along a left-right-oriented number line, with low magnitudes associated with the left side of space, and high numbers with the right side of space. Participants made a parity judgement of numbers with responses made with a left key to odd numbers and a right key to even numbers. This was reversed for a second block of trials. Response times to numbers one to nine with both the right and left hand were calculated, and regression analyses conducted to analyse whether lower magnitudes were responded to faster with the left hand and higher magnitudes with the right hand. Participants with lower (more masculine) digit ratios on the right hand showed a stronger SNARC effect compared to participants with high digit ratios. This pattern of results was also found when the analyses were conducted separately for men and women. Results from left hand digit ratios indicated that only low digit ratio females showed a significant SNARC effect. These findings add to a growing literature on the relationship between digit ratio and cognitive abilities; in this case, simple cognitive representations that are accessed automatically rather than complex skills such as mental rotation or "mathematics" where a variety of solution strategies may be utilised.