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1.
Populations often contain discrete classes or morphs (e.g., sexual dimorphisms, wing dimorphisms, trophic dimorphisms) characterized by distinct patterns of trait expression. In quantitative genetic analyses, the different morphs can be considered as different environments within which traits are expressed. Genetic variances and covariances can then be estimated independently for each morph or in a combined analysis. In the latter case, morphs can be considered as separate environments in a bivariate analysis or entered as fixed effects in a univariate analysis. Although a common approach, we demonstrate that the latter produces downwardly biased estimates of additive genetic variance and heritability unless the quantitative genetic architecture of the traits concerned is perfectly correlated between the morphs. This result is derived for four widely used quantitative genetic variance partitioning methods. Given that theory predicts the evolution of genotype‐by‐environment (morph) interactions as a consequence of selection favoring different trait combinations in each morph, we argue that perfect correlations between the genetic architectures of the different morphs are unlikely. A sampling of the recent literature indicates that the majority of researchers studying traits expressed in different morphs recognize this and do estimate morph‐specific quantitative genetic architecture. However, ca. 16% of the studies in our sample utilized only univariate, fixed‐effects models. We caution against this approach and recommend that it be used only if supported by evidence that the genetic architectures of the different morphs do not differ.  相似文献   
2.
Over the past decade molecular mechanics and molecular dynamics studies have demonstrated considerable flexibility for carbohydrates. In order to interpret the corresponding NMR parameters, which correspond to a time-averaged or 'virtual' conformer, it is necessary to simulate the experimental data using the averaged geometrical representation obtained with molecular modelling methods. This structural information can be transformed into theoretical NMR data using empirical Karplus-type equations for the scalar coupling constants and the appropriate formalism for the relaxation parameters. In the case of relaxation data, the 'model-free' spectral densities have been widely used in order to account for the internal motions in sugars. Several studies have been conducted with truncated model-free spectral densities based on the assumption that internal motion is very fast with respect to overall tumbling. In this report we present experimental and theoretical evidence that suggests that this approach is not justified. Indeed, recent results show that even in the case of moderate-sized carbohydrates internal motions are occurring on the same timescale as molecular reorientation. Simulations of relaxation parameters (NOESY volumes, proton cross-relaxation rates, carbon T1 and nOe values) in the dispersion range (0.1<Tc<5 ns) show that rates of internal motion can be fairly precisely defined with respect to overall tumbling. Experimental data for a variety of oligosaccharides clearly indicate similar timescales for internal and overall motion. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
3.
【目的】研究饲养在西藏高原的放牧藏猪、舍饲藏猪和商品猪(杜长大猪,DLY猪)粪便中真菌群落组成的差异性,获取与饲粮粗纤维消化相关的真菌群落。【方法】以饲养在西藏高原的5月龄放牧藏猪、舍饲藏猪和DLY猪为研究对象,采用消化试验测定放牧藏猪、舍饲藏猪和DLY猪对饲粮粗纤维的表观消化率。采集粪便样品利用单分子实时测序技术(SMRT),测定粪便真菌ITS基因全长序列,分析粪便真菌群落的结构和多样性,采用Pearson相关分析获取饲粮粗纤维表观消化率与真菌群落的相关性。【结果】在放牧藏猪、舍饲藏猪和DLY猪的粪便样品中共鉴定出了4个门、13个纲、23个目、39个科、55个属、58个种,放牧藏猪在各分类水平的分类单元数均显著高于舍饲藏猪与DLY猪(P<0.05)。子囊菌门(Ascomycota)和担子菌门(Basidiomycota)是优势菌门,在门水平下,放牧藏猪、舍饲藏猪和DLY猪间无显著差异(P≥0.05),但在纲、目、科、属、种水平下,放牧藏猪多个真菌类群相对丰度显著高于舍饲藏猪与DLY猪(P<0.05)。放牧藏猪具有更高的菌群丰富度和独有分类操作单元(OTU)(P<0....  相似文献   
4.
为了解三门湾大型底栖动物群落的现状和动态变化,分别于2015年11月、2016年2月、5月和8月在三门湾海域用阿氏拖网对大型底栖动物进行调查。结果表明: 经鉴定,大型底栖动物有119种,主要类群为鱼类、甲壳类和软体动物,占种类总数的79%。大型底栖动物全年优势种为细螯虾、长额超刺糠虾和六丝钝尾虾虎鱼,不同季节优势种的变化明显,种类差异性较大。大型底栖动物的年平均生物量和平均栖息密度分别为0.025 g·m-2和0.07 ind·m-2。三门湾大型底栖动物各季节的Shannon多样性指数为2.21~3.18,Margalef物种丰富度指数为3.25~3.78,Pielou均匀度指数为0.53~0.79。ABC曲线分析显示,在春季和冬季,群落受到中等程度干扰;而在夏季和秋季,群落受到轻微扰动。典范对应分析结果显示,水深、温度、盐度和pH值是影响大型底栖动物群落的最主要环境因子。  相似文献   
5.
Bone-cement interface has been investigated under selected loading conditions, utilising experimental techniques such as in situ mechanical testing and digital image correlation (DIC). However, the role of bone type in the overall load transfer and mechanical behaviour of the bone-cement construct is yet to be fully quantified. Moreover, microdamage accumulation at the interface and in the cement mantle has only been assessed on the exterior surfaces of the samples, where no volumetric information could be obtained. In this study, some typical bone-cement interfaces, representative of different fixation scenarios for both hip and knee replacements, were constructed using mainly trabecular bone, a mixture of trabecular and cortical bone and mainly cortical bone, and tested under static and cyclic compression. Axial displacement and strain fields were obtained by means of digital volume correlation (DVC) and microdamage due to static compression was assessed using DVC and finite element (FE) analysis, where yielded volumes and strains (εzz) were evaluated. A significantly higher load was transferred into the cement region when mainly cortical bone was used to interdigitate with the cement, compared with the other two cases. In the former, progressive damage accumulation under cyclic loading was observed within both the bone-cement interdigitated and the cement regions, as evidenced by the initiation of microcracks associated with high residual strains (εzz_res).  相似文献   
6.
Identifying inbreeding depression early in small and declining populations is essential for management and conservation decisions. Correlations between heterozygosity and fitness (HFCs) provide a way to identify inbreeding depression without prior knowledge of kinship among individuals. In Northern Quebec and Labrador, the size of two herds of migratory caribou (Rivière‐George, RG and Rivière‐aux‐Feuilles, RAF) has declined by one to two orders of magnitude in the last three decades. This raises the question of a possible increase in inbreeding depression originating from, and possibly contributing to, the demographic decline in those populations. Here, we tested for the association of genomic inbreeding indices (estimated with 22,073 SNPs) with body mass and survival in 400 caribou sampled in RG and RAF herds between 1996 and 2016. We found no association of individual heterozygosity or inbreeding coefficient with body mass or annual survival. Furthermore, those genomic inbreeding indices remained stable over the period monitored. These results suggest that the rapid and intense demographic decline of the herds did not cause inbreeding depression in those populations. Although we found no evidence for HFCs, if demographic decline continues, it is possible that such inbreeding depression would be triggered.  相似文献   
7.
Monte Carlo (MC) molecular simulation describes fluid systems with rich information, and it is capable of predicting many fluid properties of engineering interest. In general, it is more accurate and representative than equations of state. On the other hand, it requires much more computational effort and simulation time. For that purpose, several techniques have been developed in order to speed up MC molecular simulations while preserving their precision. In particular, early rejection schemes are capable of reducing computational cost by reaching the rejection decision for the undesired MC trials at an earlier stage in comparison to the conventional scheme. In a recent work, we have introduced a ‘conservative’ early rejection scheme as a method to accelerate MC simulations while producing exactly the same results as the conventional algorithm. In this paper, we introduce a ‘non-conservative’ early rejection scheme, which is much faster than the conservative scheme, yet it preserves the precision of the method. The proposed scheme is tested for systems of structureless Lennard-Jones particles in both canonical and NVT-Gibbs ensembles. Numerical experiments were conducted at several thermodynamic conditions for different number of particles. Results show that at certain thermodynamic conditions, the non-conservative method is capable of doubling the speed of the MC molecular simulations in both canonical and NVT-Gibbs ensembles.  相似文献   
8.
Plants exist across varying biotic and abiotic environments, including variation in the composition of soil microbial communities. The ecological effects of soil microbes on plant communities are well known, whereas less is known about their importance for plant evolutionary processes. In particular, the net effects of soil microbes on plant fitness may vary across environmental contexts and among plant genotypes, setting the stage for microbially mediated plant evolution. Here, we assess the effects of soil microbes on plant fitness and natural selection on flowering time in different environments. We performed two experiments in which we grew Arabidopsis thaliana genotypes replicated in either live or sterilized soil microbial treatments, and across varying levels of either competition (isolation, intraspecific competition or interspecific competition) or watering (well‐watered or drought). We found large effects of competition and watering on plant fitness as well as the expression and natural selection of flowering time. Soil microbes increased average plant fitness under interspecific competition and drought and shaped the response of individual plant genotypes to drought. Finally, plant tolerance to either competition or drought was uncorrelated between soil microbial treatments suggesting that the plant traits favoured under environmental stress may depend on the presence of soil microbes. In summary, our experiments demonstrate that soil microbes can have large effects on plant fitness, which depend on both the environment and individual plant genotype. Future work in natural systems is needed for a complete understanding of the evolutionary importance of interactions between plants and soil microorganisms.  相似文献   
9.
Worldwide there is a rush toward wind power development and its associated infrastructure. In Fennoscandia, large‐scale wind farms comprising several hundred windmills are currently built in important grazing ranges used for Sámi reindeer husbandry. In this study, reindeer habitat use was assessed using reindeer fecal pellet group counts in relation to two relatively small wind farms, with 8 and 10 turbines, respectively. In 2009, 1,315 15‐m2 plots were established and pellet groups were counted and cleaned from the plots. This was repeated once a year in May, during preconstruction, construction, and operation of the wind farms, covering 6 years (2009–2014) of reindeer habitat use in the area. We modeled the presence/absence of any pellets in a plot at both the local (wind farm site) and regional (reindeer calving to autumn range) scale with a hierarchical logistic regression, where spatial correlation was accounted for via random effects, using vegetation type, and the interaction between distance to wind turbine and time period as predictor variables. Our results revealed an absolute reduction in pellet groups by 66% and 86% around each wind farm, respectively, at local scale and by 61% at regional scale during the operation phase compared to the preconstruction phase. At the regional, scale habitat use declined close to the turbines in the same comparison. However, at the local scale, we observed increased habitat use close to the wind turbines at one of the wind farms during the operation phase. This may be explained by continued use of an important migration route close to the wind farm. The reduced use at the regional scale nevertheless suggests that there may be an overall avoidance of both wind farms during operation, but further studies of reindeer movement and behavior are needed to gain a better understanding of the mechanisms behind this suggested avoidance.  相似文献   
10.
One of the current challenges of evolutionary ecology is to understand the effects of phylogenetic history (PH) and/or ecological factors (EF) on the life‐history traits of the species. Here, the effects of environment and phylogeny are tested for the first time on the reproductive biology of South American xenodontine snakes. We studied 60% of the tribes of this endemic and most representative clade in a temperate region of South America. A comparative method (canonical phylogenetic ordination—CPO) was used to find the relative contributions of EF and PH upon life‐history aspects of snakes, comparing the reproductive mode, mean fecundity, reproductive potential, and frequency of nearly 1,000 specimens. CPO analysis showed that PH or ancestry explained most of the variation in reproduction, whereas EF explained little of this variation. The reproductive traits under study are suggested to have a strong phylogenetic signal in this clade, the ancestry playing a big role in reproduction. The EF also influenced the reproduction of South American xenodontines, although to a lesser extent. Our finding provides new evidence of how the evolutionary history is embodied in the traits of living species.  相似文献   
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