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991.
The evolutionary relationships among most (143 genera) of the currently recognized genera of the braconid wasp subfamily Doryctinae were investigated using maximum parsimony analysis, employing 100 characters from external morphology and four additional, less well‐studied character systems (male genitalia, ovipositor structure, venom apparatus and larval cephalic structure). We investigated the ‘performance’ of characters from external morphology and the other character systems and the effects of abundant missing entries by comparing the data decisiveness, retention and consistency indices of four different character partitions. The results indicate that the performances of the different partitions are not related to the proportions of missing entries, but instead are negatively correlated to their proportion of informative characters, suggesting that the morphological information in this group is subject to high levels of homoplasy. The external morphological partition is significantly incongruent with respect to a data set comprising the other character systems based on the ILD test. Analyses supported neither the monophyly of the large tribes Doryctini and Hecabolini, nor the monophyly of the Spathiini and Heterospilini. Relationships obtained from successive approximation weighting analysis for the complete data differ considerably from the currently accepted tribal and subtribal classifications. The only exceptions were the Ypsistocerini and the Ecphylini, whose recognized members were recovered in single clades. A close relationship between the Binaerini and Holcobraconini, and also Monarea, is consistently supported by venom apparatus and ovipositor structure characters but is not indicated by external morphological data. Low bootstrap values obtained for most of the recovered clades in all analyses do not allow us to propose a meaningful reclassification for the group at this time. A complete list of the recognized genera and their synonymies is given. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 142 , 369–404.  相似文献   
992.
Aim To analyse quantitatively the biogeographical distribution pattern of species of the Cytiseae Bercht. & J. Presl (= Genisteae Benth.) tribe in the Iberian Peninsula and the Balearic Islands, and to identify environmental variables related to the distributional patterns. Location Iberian Peninsula and Balearic Islands, using the 61 administrative provinces as operational geographical units. Methods In order to identify chorotypes (groups of species with similar geographical distribution), we performed a upgma classification based on the similarity index of Baroni‐Urbani & Buser. The method of McCoy et al. [Ecology 67 (1986), 749] enabled us to detect the significant groups and to differentiate them from those groupings that could be generated at random. Logistic regression analyses and environmental gradient analyses (DCA and CCA) were performed in order to find the relationships between the environmental variables and the observed distributional patterns. Results Sixteen chorotypes were obtained between the Cytiseae species of the Iberian Peninsula and the Balearic Islands. The thermal variables showed the greatest influence in species distribution. Specifically, temperatures (maximum, minimum and mean) of the coldest months were associated with the majority of the chorotypes. Main conclusions The species of the Cytiseae tribe were not randomly distributed in space, and can be classified in groups of species with common distributional patterns. The importance of cold tolerance in the distribution of these species, as well as their preference for acidic soils, was demonstrated. Certain general tendencies seem to exist with respect to the distribution of the biota in the Iberian Peninsula, and these seem to be independent of the taxonomic groups involved and to be determined by convergent macroclimatic factors.  相似文献   
993.
1 Introduction A biological neural system is complicated and ef-ficient. People have tried for years to simulate it to per-form complex signal processing functions. For example,the artificial neural network is a kind of model derivedfrom a biological neural system. Most artificial neuralnetworks simulate some important features such as thethreshold behaviour and plasticity of synapses. However,they are primary simulations and still much simpler incomparison with specific biological neural…  相似文献   
994.
Abstract. We propose a hierarchical approach for plant functional classification in disturbed ecosystems to be used for vegetation modelling and global plant trait comparisons. Our framework is based on the persistence of plants at different levels of organization. We assume that the main parameters to determine persistence in chronically disturbed ecosystems are those related to: I ndividual‐persistence capacity, P ropagule‐persistence capacity (persistence at the population level), C ompetitive capacity (persistence at the community level) and D ispersal capacity (persistence at the landscape level). The IPCD approach is illustrated for fire‐prone and grazed ecosystems from the Mediterranean region and Australia and by assuming a binary classification of the four traits determining persistence which give a total 16 possible functional types. The IPCD framework provides a simple structured and synthetic view from which more elaborated schemes can be developed.  相似文献   
995.
Abstract. Variation of biodiversity over 72 600 km2 of tropical rain forest was mapped by multiple characteristics using a new combined nominal–numerical classification system. Three hundred and sixty-nine tree genera were grouped into classes by eight taxonomic, geographical, phylogenetic and ecological characteristics. Each grid cell was assigned to a nominal biodiversity type by its dominant classes and classified numerically by its share of total variation in study area biodiversity. Differentiation of 0.5° cells by nominal classification was inferior to numerical classification, but improved at higher resolution. The nominal and numerical classifications were shown to have potential for complementary roles in conservation planning.  相似文献   
996.
氨基酸的分子结构与遗传密码简并及二维集合分类   总被引:13,自引:2,他引:11  
根据氨基酸遗传密码子的简并程度,可将64个遗传密码子分为高简并度类(3,4,6度简并组)和低简并度类(1,2度简并组)两大类。高简并度类有9个氨基酸,其分子量比较小,等电点的分布比较集中。低简并度类有11个氨基酸,其分子结构比较复杂,参考Taylor对氨基酸特性的分类图,本文提出以分子量(M)及等电点(P)作为氨基酸的化学特性坐标,作出其二维集合MP分类图,MP分类图可以反映出氨基酸的各种属性,如分子量的大小,简并度的高低,极性与非极性、带电荷或不带电荷,疏水性与亲水性,以及氨基酸残基的种类等。根据氨基酸的分类分析,可以认为:高简并度氨基酸多数是脂烃类和羟脂烃类的氨基酸,分子量比较小,分子结构比较简单,大部分为疏子性,主要组成跨膜结构或蛋白质的结构域,可能是出现较早的氨基酸;而低简并度的氨基酸,分子结构比较复杂,分子量比较大,多数是和蛋白质功能有密切联系的基团,可能是进化出现较晚的结构。  相似文献   
997.
斑翅蝗科部分种类的酯酶同工酶研究:(直翅目:蝗总科)   总被引:10,自引:0,他引:10  
本文采用聚丙烯酰胺凝胶电泳方法,对斑翅蝗科(Oedipodidae)6属8个种进行了酯酶同工酶的研究,共显示30条迁移率不同的酶带,根据酶带迁移距离的不同,可以分为5个泳动区。通过EST同工酶酶带的聚类分析,对斑翅蝗科部分种类的分类问题进行了探讨。  相似文献   
998.
赤潮的分类分级标准及预警色设置   总被引:2,自引:0,他引:2  
江天久  佟蒙蒙  齐雨藻 《生态学报》2006,26(6):2035-2040
为便于赤潮信息的发布、统计和管理,依据我国赤潮发生的特点初步制定了我国赤潮的分类分级及预警色划分的标准。根据形成赤潮的生物种类特性及其对人类健康和近岸水产养殖的影响,将我国赤潮分为有毒赤潮、鱼毒赤潮、有害赤潮和无害赤潮4种类型,考虑到我国沿海赤潮发生面积和持续时间相差巨大,将我国赤潮分为大型、中型和小型3个级别。由此,将我国赤潮分为12种,并依次用不同颜色和符号代表之,以利于在媒体上发布。在此基础上,制定了不同类型赤潮的预警机制和管理措施,为赤潮防灾减灾工作提供参考。  相似文献   
999.
Zhong J C  Chen Z H  Zhao S J  Xiao Y P 《农业工程》2006,26(7):2068-2072
To investigate the genetic resources and to clarify the classification status of the Chinese yak, the Maiwa yak, Jiulong yak, Datong yak, and Tianzhu White yak were intensively studied using microsatellite DNA, RAPD (random amplified polymorphic DNA), and AFLP (Amplified Fragment Length Polymorphism) DNA markers on the basis of the previous study work of the authors' on chromosomes and blood protein polymorphisms of the Chinese yak. The overall results showed that: (1) the genetic distance based on allele frequencies at the microsatellite loci between the Maiwa yak and Jiulong yak was the largest (1.506), and as expected, the two populations of the Maiwa yak had the smallest genetic distance (1.062). The four yak breeds were clustered into two groups: the first group comprised the Jiulong yak, and the second group comprised the remaining three breeds; (2) the genetic distance between the Datong yak and Tianzhu White yak was the smallest (0.0336), whereas the genetic distance between the Jiulong yak and Maiwa yak was the largest (0.0414) based on the data from the RAPD and RFLP analyses. The four yak breeds were again clustered into two groups with the Datong yak and Tianzhu White yak grouped together first, followed by the Maiwa yak; (3) analyses of the chromosomes and blood protein polymorphisms showed a similar pattern of relationship among the breeds. Therefore, it was concluded that the Chinese yak could be considered to be of two types with the Jiulong yak and Maiwa yak as their representatives, respectively. This conclusion was in accordance with the classification proposed later by professor Cai L and his colleagues, according to which the Chinese yak was classified into two types, the ‘Qinghai-Tibetan Plateau yak’ and the ‘Hengduan Mountain Alpine yak’, although this conclusion differed from the other classifications. Considering the geographic distribution, ecological factors, history and development of the Chinese yak, it was believed that this classification is reasonable.  相似文献   
1000.
Objectives: Pediatricians underdiagnose overweight and feel ineffective at counseling. Given the relationship between physicians’ health and health habits and counseling behaviors, we sought to determine the 1) percentage of pediatricians who are overweight; 2) accuracy of pediatricians’ own weight status classification; and 3) relationship between weight self‐perception and perceived ease of obesity counseling. Research Methods and Procedures: This study was a cross‐sectional, mail survey of North Carolina pediatricians that queried about their weight status and ease of counseling. Accuracy of pediatricians’ self‐classification of weight status was compared with BMIs derived from self‐reported height and weight. Using logistic regression, controlling for potential confounding variables, we examined the association between weight perception and ease of counseling. Results: The unadjusted response rate was 62%, and the adjusted response rate was 71% (n = 355). Nearly one‐half (49%) of overweight pediatricians did not identify themselves as such. Men had greater adjusted odds of misclassifying overweight than women [odds ratio (OR), 3.61; 95% confidence interval (CI) = 1.81, 7.21]. Self‐classified “thin” pediatricians had nearly six times the odds of reporting more counseling difficulty as a result of their weight than “average” weight pediatricians (OR = 5.69; 95% CI = 2.30, 14.1), and self‐identified “overweight” pediatricians reported nearly four times as great counseling difficulty as “average” weight physicians (OR = 3.84; 95% CI = 1.11, 13.3), after adjustment for self‐reported BMI weight status and other potential confounders. Discussion: The roles that physician weight misclassification and self‐perception potentially play in influencing rates of obesity counseling warrant further research.  相似文献   
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