Individual Growth Rate as a Measure of Competitive Advantages in Cladoceran Crustaceans

Intra- and interspecific competition for food is one of the main factors governing zooplankton community structure and the evolution of the life history of herbivorous zooplankters. Competitive advantage considered as the ability of a whole population or some developmental stages to survive at low food concentrations is related to individual growth rate rather than to the body size of zooplankters as the “size-efficiency hypothesis” postulates. The slow-growing individuals have been shown to have the most competitive advantage. The outcome of competition among cladoceran species in predator-free waterbodies depends on the trophic status of the latter. In oligo-trophic and mesotrophic waterbodies, small slow-growing cladocerans are the superior competitors, while large rapid-growing species dominate in eutrophic waters and can outcompete the small cladocerans. Small rapid-growing species, which are poor competitors, can temporarily colonize eutrophic waterbodies. Three main types of cladoceran life history represent the compromises between low population mortality during periods of food depletion and high population natality at the abundance of food.     

The Influence of Bauxite Tailings on the Cladoceran Populations of Lake Batata,Amazonia, Brazil

Lake Batata receive tailings from bauxite mining for ten years (1979-1989). This material, with 7-9% of solid particles, changed some ecological conditions of part of the lake. In order to study the influence of this material on the cladoceran populations, seasonal and intensive studies were made of abundance and brood size of the animals and of some environmental parameters such as transparency, suspended material, POC (<30pm), total bacteria and chlorophyll a. Reduced transparency and high suspended matter attested to the greater quantity of tailings in the water column, in the area impacted by tailings. Greater oscillations of density and brood size at stations in the impacted area appear to indicate less stable conditions in this part of the lake.     

History of the community of planktonic Cladocera in Lake Glubokoe (Moscow Region)

A 128-centimeter sediment core of a forest lake in the Moscow Region, for which the recent zooplankton has been well studied, was analysed. The changes in the density and size of organisms in the core points to an important role of fish and interspecific competition in Cladocera and to a minor role of invertebrate predators in the historical development of the plankton. No substantial shifts in the lake trophy seem to have occurred during the last 600 years. A widely used technique of heating the sediment in a 10% KOH solution may account for 5–13-fold losses of planktonic cladocerans' remains.     

Energy Flows in Populations and Communities of Aquatic Animals

The energy assimilated by single individuals of aquatic animals throughout their life times and by populations and communities of aquatic animals during the growth season has been studied with due regard for the definitive weight of the single individual and the mean biomass of populations and communities. Energy assimilated throughout life by invertebrates of different systematic positions, definitive size and life duration is about 2.5 times as high as the energetic content of their definitive mass. The energy flow in populations of benthic animals is about 5 times as high as the seasonal average biomass, and in populations of planktonic animals it is 40 times as high. The energy flow in bottom communities is almost 10 times and in planktonic ones 35 times as high as the average seasonal biomass of communities. Specific production (P/B coefficient per 24 h) for communities of bottom animals was 0.013 per 24 h. The average value of the K₂ coefficient (net growth efficiency) calculated for an individual's life time is about 0.4 in populations of bottom animals, the K₂ for vegetation seasons is 0.26, and for communities it is 0.2 (per vegetation season). Increasing complexity of the biological systems is accompanied by an increase in the specific energy flow and a decline in the efficiency of food energy utilization for production.     

野慈姑自然群体异交率的定量估测

用自然群体取样和同工酶遗传标记的方法对沼生植物野慈姑（Sagittaria trifolia Linn.）及其变型长瓣慈姑［S.trifolia Linn.f.longiloba(Turcz.)Makino］的异交率作了定量研究,3个自然群体的异交率估计值为=91.0％～98.0％,表明该种为异交占绝对优势的交配系统。在野慈姑各群体间未发现异交率的显著差异。 Abstract:The outcrossing rates of Sagittaria trifolia Linn.and S.trifolia Linn.f.longiloba(Turcz.) Makino,a helophyte species and a form under the species,were estimated by sampling from natural habitats and using isozyme locus as genetic marker.According to the values of outcrossing rates in 3 populations( =91.0％～98.0％),the mating system of the species studied was found to be dominated by outcrossing mechanisms.Statistical analysis suggested that there was no significant difference in outcrossing rates among the populations.     

一种计算哺乳动物内禀增长率（rm）的方法

一、概述内禀增长率(r_m)是一个最基本的种群参数,它的测定和计算在动物生态学的研究中占有十分重要的地位。从20年代开始,已发展出多种计算动物r_m值的方法,如下所述。     

滇牡丹天然居群的遗传多样性分析

以云南中部及西北部的6个滇牡丹(Paeonia delavayi)天然居群为研究对象,进行株高、新枝长等9个表型性状的表型多样性分析和ISSR分析。结果表明:9个表型性状变异幅度为0.9%~39.8%,平均值达到了18.9%;居群间生殖器官的变异较大,居群内营养器官更容易产生变异。利用居群间欧式距离进行聚类分析,6个居群聚为4个类群,没有与实际地理位置相吻合,说明表型特征的性状与地理距离的相关性不大。遗传多样性分析结果表明:利用筛选得到的10条引物,在取自6个自然居群、180个个体中,检测到56个多态位点。在居群水平上,多态位点百分率(PPB)为60.2%,Nei's基因多样性指数(H)和Shannon's信息指数(I)分别为0.281和0.414。在物种水平上,Nei's基因多样性指数(H)和Shannon's信息指数(I)分别为0.409和0.596。居群间的遗传分化系数(Gst)达0.319。结果显示,表型性状在居群间和居群内均存在广泛变异。滇牡丹遗传多样性水平较高,居群间遗传分化较大,滇牡丹并不濒危。     

Fluctuations in the Size of Isolated Single-Species Populations and Natural Selection

This paper discusses the basic types of dynamical behavior of populations obtained in discrete models, such as monotonous dynamics, stable limited cycles, and chaotic variations. All these modes are shown to have possibly arisen in the evolution of limited populations under the effect of density-independent selection. This effect together with that of density-dependent non-selective factors has been termed F-selection, which is characterized by independence of relative fitnesses from population density, whereas populations may be ecologically limited; in other words, absolute fitnesses prove to be a function of population size. The characteristic of F-selection is to be not sensitive to changes in population size but to lead to fluctuations, that create conditions for achieving density-dependent selection.     

Chromosomal Polymorphism in Korean Natural Populations of Drosophila immigrans

ABSTRACT To analyze chromosome inversions of Drosophila immigrans , wild flies were captured from large vineyards located in the suburbs of Yecheon and Gyeongsan from October 1999 to 2001. With the egg samples obtained singly at each of the 799 females of D. immigrans , cytological examinations were carried out for the type and frequency of inversions. Two types of different inversions were found only in the second chromosome. The inversions detected were known to be the cosmopolitan inversion "A" and "B". The mean frequency of inversion A was estimated to be 0.074 in Yecheon and 0.066 in Gyeongsan and that of B was to be 0.026 in Yecheon and 0.021 in Gyeongsan, respectively. In the frequency ratio, inversion A was significantly higher than that of B. The present populations of D. immigrans showed subtle differences from other Korean populations in inversion frequencies. To account for the local variations observed in inversion frequencies, several hypotheses are discussed such as founding event or selective force.     

自然植物种群的亲本分析及其在生态学研究中的应用

自然植物种群的结构、交配行为、基因流以及个体和基因型的适合度是种群生物学的重要内容,而种群谱系的建立是综合研究以上内容的重要方法。种群谱系的构建最初是在人类中进行研究的,其统计／遗传学方法在１９５０年前就已有详尽的研究［１］,近些年来用于亲子鉴定也已...     

Linkage Disequilibrium in Natural and Experimental Populations of Drosophila Melanogaster

We have studied linkage disequilibrium in Drosophila melanogaster in two samples from a wild population and in four large laboratory populations derived from the wild samples. We have assayed four polymorphic enzyme loci, fairly closely linked in the third chromosome: Sod Est-6, Pgm, and Odh. The assay method used allows us to identify the allele associations separately in each of the two homologous chromosomes from each male sampled. We have detected significant linkage disequilibrium between two loci in 16.7% of the cases in the wild samples and in 27.8% of the cases in the experimental populations, considerably more than would be expected by chance alone. We have also found three-locus disequilibria in more instances than would be expected by chance. Some disequilibria present in the wild samples disappear in the experimental populations derived from them, but new ones appear over the generations. The effective population sizes required to generate the observed disequilibria by randomness range from 40 to more than 60,000 individuals in the natural population, depending on which locus pair is considered, and from 100 to more than 60,000 in the experimental populations. These population sizes are unrealistic; the fact that different locus-pairs yield disparate estimates within the same population argues against the likelihood that the disequilibria may have arisen as a consequence of population bottlenecks. Migration, or population mixing, cannot be excluded as the process generating the disequilibria in the wild samples, but can in the experimental populations. We conclude that linkage disequilibrium in these populations is most likely due to natural selection acting on the allozymes, or on loci very tightly linked to them.     

胭脂花野生居群花粉形态多样性研究

胭脂花是分布于中国北部的报春花科报春花属花柱二型植物,为了阐明胭脂花花粉形态的多样性,对胭脂花分布范围内的7个野生居群的花粉形态进行了测定。结果表明,胭脂花花粉属N3P4C5型,极面观多为三角形,具三孔沟,少数为四边形,具4孔沟;短花柱植株的花粉粒较大(16.53×17.58μm),花粉粒外壁粗糙,表面纹饰多,网眼大;长花柱植株的花粉粒较小(12.95×13.72μm),花粉粒外壁较光滑,表面纹饰少,网眼小。不同居群间花粉粒在大小、网眼直径、外壁纹饰等方面存在显著差异,花粉形态变异系数在4.88%~35.48%之间;短花柱类型各居群的平均变异系数为16.18%,居群间差异较大,其中庞泉沟居群变异系数最大(24.05%),海坨山居群最小(10.13%);长花柱类型各居群的平均变异系数为14.89%,庞泉沟居群的变异系数最大(19.75%),五台山与海坨山居群最小(12.50%),长花柱类型的花粉性状比短花柱植株更为稳定。UPGMA聚类分析发现,7个居群聚为两大类,除庞泉沟居群外,其他居群聚为一组,地理距离相近的居群一般聚在一起。研究结果为胭脂花种质资源遗传多样性及育种研究提供了依据。     

福建山樱花天然居群表型变异研究

以闽、赣、粤三省天然分布的福建山樱花(Cerasus campanulata Maxim.)为研究对象,调查了11个居群226个单株的17个表型性状指标,运用变异系数和单因子方差分析研究了居群间和居群内的表型变异;应用相关分析揭示了表型性状间及其与地理、气候因子间的相关性以及表型变异的地理格局;并且运用聚类分析进行了居群分类.结果表明,福建山樱花天然居群内的变异远大于居群间的变异,居群分化较小;花色、花量与经度、纬度间显著或极显著相关,花瓣宽与纬度、海拔显著或极显著相关,花色、花量与年降雨量极显著相关,花量、花瓣宽、开花习性与年日照时数显著相关,花瓣宽与年均温、无霜期显著或极显著相关,存在较明显的地理变异趋势.而居群间马氏距离聚类分析结果与参试居群分布地域性呈现高度一致,二者之间相关显著.     

Molecular Mechanisms of Stress Adaptation in Plant Natural Populations

Recent advances in studies of genetic variation at protein and DNA levels in plant natural populations and its relationship with environmental changes were reviewed with special reference to the works on the wild barley ( Hordeum spontaneum C. Koch.). On one side, adaptation was shown in statistic data, on the other side, the fact that a considerable part of genetic variation does exist within populations (subpopulations) under same ecological condition indicated its maintainability of neutral or near-neutral mutations in natural populations. The researches on adaptive populations of plants, especially on wild soybean ( Glycine soja Sieb. et Zucc.) mainly conducted in author's laboratory, have shown that the most part of molecular variation within and among populations can not be explained by selection particularly as far as the individual uniqueness was concerned. There are some data shown that adaptation may be caused by accumulation of a few near-neutral mutations. Recent publications on molecular mechanisms of morphological evolution has been received special attention to elucidate the discrepancy between molecular evolution and morphological adaptive evolution. A frame on the unified evolution theory has been built. Finally some related viewpoints of philosophy were discussed.     

The Structure of Morphological and Genetic Diversity in Natural Populations of Carica papaya (Caricaceae) in Costa Rica

In Costa Rica, dioecious Carica papaya has been observed growing in disturbed areas and within secondary lowland forests. Such populations can serve as a reservoir of genetic and morphological diversity for this tropical fruit crop. We quantify the levels and patterns of the diversity of naturally occurring populations of C. papaya and address the demographic history of these populations. We measured 29 vegetative and reproductive morphological traits in situ from 252 plants and found significant heterogeneity among regional populations in the majority of these traits. Significant variation was found among regional populations with respect to fruit size and shape, with plants in the Nicoya Peninsula possessing smaller, less fleshy fruit, a characteristic of previously described wild populations of papaya. We then assessed the levels and patterns of genetic diversity in 164 plants from natural populations and 20 cultivars. Natural populations exhibit a deficiency of heterozygotes; however, this is much more pronounced within the cultivars. Although there is little genetic differentiation among natural populations, we did find evidence of cryptic genetic population structure. Analyses of population demography indicate that these natural populations have undergone a recent genetic bottleneck, followed by recent population expansion, possibly promoted by the transformation of the Costa Rican landscape for agricultural use. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

Variation in the temperature preference and growth rate of individual fish reconciles differences between two growth models

1. A growth model, originally developed for brown trout (Salmo trutta), has now been fitted to data for Atlantic salmon (S. salar) and stone‐loach (Barbatula barbatula) from English populations, and Arctic charr (Salvelinus alpinus) from Sweden. The model relates growth rate to temperature for a fish of standard size and the functional relationship has a triangular shape with a sharp peak at the optimal temperature for growth and zero growth at the base of the triangle. It was unsuitable for growth data for Norwegian salmon, and a curvilinear Ratkowsky model provided a better fit, though the experimental protocol was different in the Norwegian and English experiments. 2. The Norwegian salmon were kept in groups in each tank, had to compete for food, and had to be divided into slow, moderate and fast growers before the Ratkowsky model could be fitted. Each English salmon was kept in its own tank and fed individually. For replicate experiments, fish of similar size were selected. Variation among fish kept under similar conditions was therefore small, and the triangular model was essentially for individual fish, not groups of fish. 3. The present simulation study tests the hypothesis that individual differences in the growth response could account for the curvilinear growth‐temperature relationship for the Norwegian salmon. The triangular model was used to generate the growth response to temperature for a group of salmon, each fish having a slightly different temperature preference and growth rate. The result was a curvilinear response, well approximated by the Ratkowsky model (adjusted R² = 0.96). When the variability in individual temperature preference was increased, the Ratkowsky model was an even better fit (adjusted R² = 0.98). Therefore, the apparent discrepancy between the two models was reconciled by allowing for individual differences in temperature preference and growth rate within groups of fish.