Ecology: is speciation driven by species diversity?

Emerson and Kolm show that the proportion of species endemic to an island is positively related to its species richness and, assuming that endemism indexes speciation rate, they infer that greater species diversity accelerates diversification. Here we demonstrate that the same correlation between species richness and percentage endemism can arise even if within-island speciation is negligible, particularly when both endemism and species richness depend on attributes of islands (such as area) that influence the average age of resident populations. Island biogeography theory indicates that, where the average time to extinction is relatively long, diversity increases through colonization, irrespective of whether new species are formed; at the same time, islands on which populations persist for longer accumulate more endemic species as local populations differentiate and populations on neighbouring islands become extinct. We therefore suggest that species richness and endemism are correlated fortuitously owing to their mutual dependence on the life spans of populations on islands, which is unrelated to speciation itself.     

Host plants influence parasitism of forest caterpillars

Patterns of association between herbivores and host plants have been thought to reflect the quality of plants as food resources as influenced by plant nutrient composition, defences, and phenology. Host-plant-specific enemies, that is, the third trophic level, might also influence the distribution of herbivores across plant species. However, studies of the evolution of herbivore host range have generally not examined the third trophic level, leaving unclear the importance of this factor in the evolution of plant-insect herbivore interactions. Analysis of parasitoid rearings by the Canadian Forest Insect Survey shows that parasitism of particular Lepidoptera species is strongly host-plant-dependent, that the pattern of host-plant dependence varies among species of caterpillars, and that some parasitoid species are themselves specialized with respect to tree species. Host-plant-dependent parasitism suggests the possibility of top-down influence on host plant use. Differences in parasitism among particular caterpillar-host plant combinations could select for specialization of host plant ranges within caterpillar communities. Such specialization would ultimately promote the species diversification of Lepidoptera in temperate forests with respect to escape from enemies.     

苯酚-硫酸法测定藏木香中多糖含量

采用传统的水煮醇沉法从藏木香中提取可溶性多糖,通过Sevag法脱蛋白后,以葡萄糖为对照品,使用苯酚-硫酸法测定多糖含量.结果表明,在波长486nm处测定吸光度,10-100μg/mL范围内吸光度与被测含量之间具有良好的线性关系,藏木香中多糖的含量为64.37%.     

Host specificity of Lepidoptera in tropical and temperate forests

For numerous taxa, species richness is much higher in tropical than in temperate zone habitats. A major challenge in community ecology and evolutionary biogeography is to reveal the mechanisms underlying these differences. For herbivorous insects, one such mechanism leading to an increased number of species in a given locale could be increased ecological specialization, resulting in a greater proportion of insect species occupying narrow niches within a community. We tested this hypothesis by comparing host specialization in larval Lepidoptera (moths and butterflies) at eight different New World forest sites ranging in latitude from 15 degrees S to 55 degrees N. Here we show that larval diets of tropical Lepidoptera are more specialized than those of their temperate forest counterparts: tropical species on average feed on fewer plant species, genera and families than do temperate caterpillars. This result holds true whether calculated per lepidopteran family or for a caterpillar assemblage as a whole. As a result, there is greater turnover in caterpillar species composition (greater beta diversity) between tree species in tropical faunas than in temperate faunas. We suggest that greater specialization in tropical faunas is the result of differences in trophic interactions; for example, there are more distinct plant secondary chemical profiles from one tree species to the next in tropical forests than in temperate forests as well as more diverse and chronic pressures from natural enemy communities.     

甘青青兰挥发性成分GC/MS分析

目的：分离鉴定出甘青青兰（Dracocephalum tanguticum Maxim.）挥发油的化学成分.方法：用气相色谱-质谱（GC/MS）联用技术及峰面积归一化法测定各组分的相对含量.结果：共鉴定出23种化合物,占总色谱峰总面积的87.46%.结论：甘青青兰挥发油中的化学成分主要为[-]-反-松香芹乙酯和桉油精,两者分别占总挥发油中化学成分的60.30%和9.31%.     

钢管相贯口变参数变结构建库与数据提取方法研究

零件的批处理和零件库的建立是计算机辅助设计的重要内容之一，以钢管相贯口为例应用UG的几种建库方法，通过分析电子表格、零件族、GRIP编程在变参变结构的复杂零件建库时存在的问题，提出了一种将零件族和GRIP编程相结合的建库方法来建立变参变结构的复杂零件的零件库。     

带有时变时滞的中立型随机系统的鲁棒镇定和H_∞控制

研究了带有时变时滞的中立型随机系统的鲁棒镇定和H∞控制问题.利用Lyapunov泛函方法和It o^公式,基于状态反馈控制器,以线性矩阵不等式(LMI)形式给出了闭环系统鲁棒镇定及H∞控制的新方法.最后,数值算例说明了该方法的有效性.     

Large-scale processes and the Asian bias in species diversity of temperate plants

An important issue in the study of biodiversity is the extent to which global patterns of species richness reflect large-scale processes and historical contingencies. Ecological interactions in local assemblages may constrain the number of species that can coexist, but differences in diversity in similar habitats within different regions (diversity anomalies) suggest that this limit is not firm. Variation in rate of species production could influence regional and perhaps local diversity independently of the ecological capacity of an area to support coexisting species, thereby creating diversity anomalies. Temperate Zone genera of plants that are disjunct between similar environments in eastern Asia and eastern North America (EAS-ENA) have twice as many species in Asia as in North America. Because lineages of these genera in Asia and North America are mostly sister pairs, they share a common history of adaptation and ecological relationship before disjunction. Thus, the diversity anomaly in EAS-ENA genera is not an artefact of taxon or habitat sampling but reflects differences in the net diversification (speciation-extinction) of the lineages in each of the continents. Here we propose that the most probable cause of the EAS-ENA anomaly in diversity is the extreme physiographical heterogeneity of temperate eastern Asia, especially compared with eastern North America, which in conjunction with climate and sea-level change has provided abundant opportunities for evolutionary radiation through allopatric speciation.     

论竞技健美操技术创新的概念与分类

该研究以竞技健美操技术创新为研究对象,采用文献资料法、案例分析法,对查阅的文献和案例进行综合的归纳分析,在研究竞技健美操技术创新发展现状基础上,结合其他项目技术创新的特点,对竞技健美操技术创新的概念进行了阐述;对竞技健美操技术创新进行了系统的分类.