Climate change effects on animal and plant phylogenetic diversity in southern Africa

Much attention has been paid to the effects of climate change on species' range reductions and extinctions. There is however surprisingly little information on how climate change driven threat may impact the tree of life and result in loss of phylogenetic diversity (PD). Some plant families and mammalian orders reveal nonrandom extinction patterns, but many other plant families do not. Do these discrepancies reflect different speciation histories and does climate induced extinction result in the same discrepancies among different groups? Answers to these questions require representative taxon sampling. Here, we combine phylogenetic analyses, species distribution modeling, and climate change projections on two of the largest plant families in the Cape Floristic Region (Proteaceae and Restionaceae), as well as the second most diverse mammalian order in Southern Africa (Chiroptera), and an herbivorous insect genus (Platypleura) in the family Cicadidae to answer this question. We model current and future species distributions to assess species threat levels over the next 70 years, and then compare projected with random PD survival. Results for these animal and plant clades reveal congruence. PD losses are not significantly higher under predicted extinction than under random extinction simulations. So far the evidence suggests that focusing resources on climate threatened species alone may not result in disproportionate benefits for the preservation of evolutionary history.     

Asymmetric hydrolysis of dimethyl 3-phenylglutarate catalyzed by Lecitase Ultra: Effect of the immobilization protocol on its catalytic properties

The asymmetric hydrolysis of dimethyl 3-phenylglutarate (1) by different immobilized preparations of a phospholipase A₁ (Lecitase Ultra (LECI)) at pH 7 and 25 °C has been studied. Agarose beads coated with octyl, cyanogen bromide (CNBr), polyethylenimine (PEI) or glyoxyl groups were used as supports for the immobilization of LECI. The different derivatives behaved very differently in terms of activity, discrimination between 1 and methyl 3-phenylglutarate (2) resulting from the hydrolysis of 1, enantioselectivity (in the hydrolysis of 1 to produce R or S-2) and enantiospecificity in the hydrolysis of R-2 and S-2. Using 1 mM of 1, CNBr-LECI showed the highest activity (13 × 10⁻³ μmol/min mg protein) while octyl-LECI was about 20 times less active. All the enzyme preparations mainly produced (S)-2, but with different enantioselectivity. CNBr-Lecitase was the most enantioselective, producing the S-2 10 fold more rapidly than the R-2, while octyl-Lecitase gave only half of that difference.LECI adsorbed on octyl-agarose allowed to get a yield up to 99% of S-2 (ee was 66%). The reaction stopped in the monoester and no isomer of this compound was further hydrolyzed by the enzyme. However, when the reaction was catalyzed by the other immobilized LECI preparations, the enzyme was able to hydrolyze mainly the minority isomer, permitting to improve the ee of the remaining S-2. The best results were obtained using CNBr-LECI, which gave (S)-methyl-3-phenylglutarate with a yield of 80% and an ee exceeding 99%.     

应用BioMod集成多种模型研究物种的空间分布——以铁杉在中国的潜在分布为例

新型统计方法和多源、多尺度空间信息数据的产生促进了物种空间分布模型的快速发展。不同的物种空间分布模型在生态学理论的运用以及前提假设上存在差异。选用不同的模型方法和输入数据会带来预测结果的不确定性。对比并集成多个物种空间分布模型,同时利用多组输入数据可降低预测的不确定性,提高物种分布模拟的精度。本文以中国特有种铁杉（Tsuga chinensis）为例,运用基于R语言开发的BioMod软件包对比9个物种空间分布模型对铁杉的模拟效果。最后以曲线下面积（ROC）为权重集成9个模型的模拟结果,产生和筛选最佳的铁杉潜在空间分布图。研究发现随机森林模型（RF）的模拟效果最好,其次是多元适应回归样条函数模型（MARS）和广义相加模型（GAM）,模拟效果最差的是表面分布区分室模型（SRE）。模型集成结果显示,最适宜铁杉分布的区域集中在中国的西南及四川盆地周围,其次零星分散于华南和台湾部分地区。这一结果与前人对铁杉自然分布的描述和研究结果较为吻合。研究进一步表明,通过模型的集成能有效地降低由于单个模型所带来的模拟结果不确定性,从而提高模拟的精度和效果。     

Immobilization of functionally unstable catechol-2,3-dioxygenase greatly improves operational stability

Thermophilic catechol 2,3-dioxygenase (EC 1.13.11.2) from Bacillus stearothermophilus has been immobilized on highly activated glyoxyl agarose beads. The enzyme could be fully immobilized at 4 degrees C and pH 10.05 with a high retention of activity (around 80%). Enzyme immobilized under these conditions showed little increase in thermostability compared with the soluble enzyme, but further incubation of immobilized enzyme at 25 degrees C and pH 10.05 for 3 h before borohydride reduction resulted in conjugates exhibiting a 100-fold increase in stability (c.f. the free enzyme). The stability of catechol 2,3-dioxygenase immobilized under these conditions was essentially independent of protein concentration whereas free enzyme was rapidly inactivated at low protein concentrations. An apparent stabilization factor of over 700-fold was recorded in the comparison of free and immobilized catechol 2,3-dioxygenases at protein concentrations of 10 μg/ml. Immobilization increased the 'optimum temperature' for activity by 20 degrees C, retained activity at substrate concentrations where the soluble enzyme was fully inactivated and enhanced the resistance to inactivation during catalysis. These results suggest that the immobilization of the enzyme under controlled conditions with the generation of multiple covalent links between the enzyme and matrix both stabilized the quaternary structure of the protein and increased the rigidity of the subunit structures.     

Determination of protein-protein interactions through aldehyde-dextran intermolecular cross-linking

A very simple strategy, based on the intermolecular cross-linking of associated proteins by using aldehyde-dextrans, has been proposed to detect protein-protein interactions. Aldehyde-dextran was able to cross-link different enzymes composed of several polypeptide chains (e.g., trypsin and penicillin G acylase), proteolyzated proteins (e.g., extracts from porcine pancreas) and finally, an immunocomplex (horseradish peroxidase/anti-horseradish peroxidase). This cross-linked immunocomplex could be selectively adsorbed on immobilized anti-rabbit IgG. The presence of unspecific covalent attachment between unrelated protein molecules was not detected. Thus, this strategy permits the cross-linking of different protein components and avoids the formation of nonspecific protein-protein associations.     

Regioselective enzymatic hydrolysis of acetylated pyranoses and pyranosides using immobilised lipases. An easy chemoenzymatic synthesis of alpha- and beta-D-glucopyranose acetates bearing a free secondary C-4 hydroxyl group

Protected sugars with only one free hydroxyl group are useful building blocks for the synthesis of a large number of glycoderivatives. In order to avoid the problems of the classical chemical synthesis, we studied the regioselective enzymatic hydrolysis of different fully acetylated glycopyranoses and glycopyranosides. The main challenge was to obtain the hydrolysis of the substrates in only one position, with high regioselectivity, while avoiding any further hydrolysis towards partially acetylated sugars. Candida rugosa (CRL) and Pseudomonas fluorescens (PFL) lipases (EC 3.1.1.3) immobilised on octyl agarose afforded regioselective hydrolysis only in the 6- and 1-positions, respectively. Furthermore, a new one-pot chemoenzymatic approach has been developed in order to obtain alpha- and beta-protected glucopyranoses bearing a free secondary C-4 hydroxyl group. For instance, 1,2,3,6-tetra-O-acetyl-alpha-D-glucopyranose was easily synthesised in good overall yield (70%) starting from 1,2,3,4,6-penta-O-acetyl-alpha-D-glucopyranose by regioselective enzymatic hydrolysis in the 6-position, catalysed by CRL, followed by a temperature- and pH-controlled acyl migration.     

Modelling plant species distribution in alpine grasslands using airborne imaging spectroscopy

Remote sensing using airborne imaging spectroscopy (AIS) is known to retrieve fundamental optical properties of ecosystems. However, the value of these properties for predicting plant species distribution remains unclear. Here, we assess whether such data can add value to topographic variables for predicting plant distributions in French and Swiss alpine grasslands. We fitted statistical models with high spectral and spatial resolution reflectance data and tested four optical indices sensitive to leaf chlorophyll content, leaf water content and leaf area index. We found moderate added-value of AIS data for predicting alpine plant species distribution. Contrary to expectations, differences between species distribution models (SDMs) were not linked to their local abundance or phylogenetic/functional similarity. Moreover, spectral signatures of species were found to be partly site-specific. We discuss current limits of AIS-based SDMs, highlighting issues of scale and informational content of AIS data.     

Climate niche conservatism does not explain restricted distribution patterns in Tynanthus (Bignonieae,Bignoniaceae)

Studies on niche evolution allow us to establish how species niches have changed over time and to identify how long‐term evolutionary processes have led to present‐day species distributions. Here, we investigate the patterns of climatic niche evolution in Tynanthus (Bignonieae, Bignoniaceae), a genus of narrowly distributed species. We test the hypothesis that niche conservatism has played an important role in the history of this group of Neotropical lianas. We perform univariate and multivariate comparisons between climatic niches of species and associated environmental data with information on phylogenetic relationships. We encountered considerable divergence in niches among species, indicating that niche conservatism in climatic variables does not seem to have played a key role in the history of the genus. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 95–109.