黄土高原马栏林区辽东栎林种内、种间竞争研究

利用Hegyi的单木竞争指数模型对黄土高原马栏林区辽东栎(Quercus liaotungensis)的种内和种间竞争强度进行了定量分析.结果显示:(1)辽东栎种内竞争强度与种间竞争强度的总和大致相等,其种内及种间竞争强度均随对象木胸径的增大而逐渐减小,其关系服从幂函数规律,竞争主要发生在胸径小于15 cm的幼树阶段.(2)各组成树种对辽东栎影响程度(竞争指数)的大小顺序为:辽东栎>油松(Pinus tabulaeformis)>白桦(Betulaplatyphylla)>山杨(Populus davidiana)>杜梨(Pyrus betulaefolia)>湖北山楂(Crataegus hupehensis)>茶条槭(Acer ginnala)>陕西鹅耳枥(Carpinus shensiensis)>葛萝槭(A.grosseri).(3)油松是该地区的次优势种,对辽东栎有较大的竞争压力,在群落发展中可能会形成以油松占优势的混交林.(4)辽东栎胸径小于15 cm时,种内种间竞争是导致大量个体死亡的主要原因;胸径超过15 cm时,人为砍伐可能是个体死亡的主要原因.研究结果认为马栏林区混交林油松的密度不宜过大,尤其是在与未成熟辽东栎种群混交时密度应合理,应对该林区的混交林进行人工抚育,及时择伐密度过大的油松,而在辽东栎胸径达到15 cm之前择伐长势较差的植株,以促使森林群落尽快趋于稳定.     

长苞铁杉天然林群落种内及种间竞争关系研究

通过各种竞争指数的比较筛选,得到较能客观反映长苞铁杉种内、种间竞争关系的竞争指数,定量地分析了长苞铁杉种内和种间竞争强度。结果表明:长苞铁杉种内竞争随胸径的增大而逐渐减少;种间与种内竞争关系顺序为:长苞铁杉-长苞铁杉>猴头杜鹃-长苞铁杉>青冈栎-长苞铁杉>其它树种-长苞铁杉。竞争强度与对象木的胸高直径服从双曲线回归关系,利用模型预测了长苞铁杉种内、种间的竞争强度。     

山西稀有濒危植物脱皮榆种内和种间竞争

通过对山西太岳山一块100 m×100 m样地中128株脱皮榆对象木及1093株竞争木的调查,运用Hegyi的单木竞争指数计算分析了脱皮榆的种内和种间竞争强度。结果表明:(1)脱皮榆种群所受到的竞争强度随着对象木胸径的增大而逐渐减小;(2)调查样地内尽管其他物种种类较多,但数量较少,与脱皮榆种间竞争相对较弱,脱皮榆种内与种间竞争关系的顺序为:脱皮榆-脱皮榆>千金榆-脱皮榆>五角枫-脱皮榆>茶条槭-脱皮榆>其他树种-脱皮榆;(3)竞争强度和对象木胸径的关系服从幂函数关系,当脱皮榆胸径在25 cm以上时,竞争强度变化不大,所得的预测模型能很好地预测脱皮榆种内种间竞争强度。     

植物地上竞争与地下竞争研究进展

植物地上光竞争和地下水分与营养的竞争过程十分复杂,并且与竞争机制密切相关。从地上和地下竞争理论、两种竞争过程的相互作用机制以及分离地上和地下竞争的研究方法和表达指标等几个方面综述和分析目前的研究状况,以期为国内研究者在本领域进一步展开实验提供理论依据和实验设计参考。总结了与地上、地下相对竞争强度有关的优化分配理论,地上、地下竞争随生产力梯度的变化,资源异质性对地上、地下竞争机制的影响。介绍了地上竞争和地下竞争相互作用类型以及目前提出的两种作用机制。对常用的3种分离地上、地下竞争的方法:盆分隔、间植分隔和目标植分隔法以及表达竞争强度和竞争重要性的指标和公式进行了归纳。提出未来的研究内容,认为在开展此类研究时,应考虑到实验植物的生理学特性、发育状况、立地生产力跨度范围以及竞争持续时间等方面因素,并认为发展地下竞争研究、深入探讨根系间相互作用的影响因子和过程是当前的研究热点。     

Larval competition causes the difference in male ejaculate expenditure in Callosobruchus maculatus

The seed beetle Callosobruchus maculatus larvae exhibit two types of resource competition: scramble, in which a resource is shared, and contest, in which the resource is monopolized. This difference in larval behavior results in different adult densities. Under contest competition, adult density remains constant regardless of larval density, but under scramble competition, adult density increases with larval density. This in turn affects mating frequency during adulthood, and thus, the intensity of sexual selection operating on males. In this study, we examined the relationship between larval competition types and male reproductive investment in mating. We assessed the male ejaculate expenditure per mating across geographic strains of C. maculatus. The male investment (ejaculate expenditure) increased with the degree of scramble competition and decreased with the degree of contest competition. We therefore suggest that males experience different selective pressures depending on the type of larval competition: scramble type males are selected for increased reproductive investment.     

浙江天台山甜槠种内与种间竞争研究

采用Hegyi的单木竞争指数模型对天台山的甜槠种内、种间的竞争强度进行定量分析。结果表明 ,甜槠种内竞争强度随着林木径级的增大而逐渐减小 ,种内竞争较之与其伴生树种间的竞争剧烈。甜槠种内、种间竞争强度的顺序为 :甜楮 >木荷 >马尾松 >尾叶冬青 >虎皮楠 >短柄木包 >珍珠栗。竞争木对对象木的竞争强度与对象木的个体大小服从幂函数关系 ,竞争强度和对象木个体的大小呈极显著的负相关关系。当甜槠胸径达到 30cm后 ,竞争强度变化不明显 ,说明此时该生态系统已基本达到稳定状态。     

Contest and scramble competitions in two bruchid species,Callosobruchus analis andC. phaseoli (Coleoptera: Bruchidae)

Larval competition between contest and scramble strategists was investigated using the two bruchid species, C. analis (contest species) and C. phaseoli (scramble species) with two different sized mung beans (large and small beans). In both sized beans, the adult emergences of each species dependen on total density of the initial larval densities of the two species and the ratio of the two densities. The emergence of one species was suppressed by the existence of the other species when the initial larval density per bean of the former species was less than that of the latter one. There were many cases in which both C. analis and C. phaseoli emerged from one bean in large beans, but such cases were quite rare in small beans. C. analis performed interference behavior only at late larval stages, whereas C. phaseoli was superior in exploitative competition all through their larval stages. These, combined with the niche segregation inside a bean, are throught to be the major factors of observed density- and frequency-dependent competition results. Based on the above experimental results, long-term competition results between the contest and scramble species were predicted.     

阔叶红松林树种间竞争关系及其营林意义

竞争是森林生态系统中的普遍现象 ,其结果是一个有机体阻碍另一个有机体的正常生长和发育[9] 。在生态学上 ,多年来对树种间竞争的研究一直局限于实验的方法 ,而在竞争强度上缺乏数量指标[2 ] 。 2 0世纪 60年代以来 ,很多学者为了更准确地预测林木生长 ,相继提出了许多描述林木间竞争强度的数量指标 ,即竞争指数系统 ,从而形成了用单木生长模型来预测林木生长的方法[2 ,3 ] 。特别是Ｈｅｇｙｉ提出的竞争指数模型对于定量描述树种间的竞争强度有着十分重要的意义。在长白山地区 ,从海拔 5 0 0～ 110 0ｍ分布有温带地区的地带性顶极植被阔叶…     

秦岭太白山巴山冷杉种内和种间竞争特性的研究

通过对不同方法的比较分析,提出了确定巴山冷杉(Abies fargesii)植株间竞争强度和竞争范围的新方法,并利用改进的方法研究了其种内和种间竞争强度。结果表明:随对象木胸径的增大,由于巴山冷杉种群自然稀疏过程中密度调节作用,植株距离增加,种内竞争强度降低;巴山冷杉主要分布于亚高山地段,群落内太白红杉(Larixchinensis)数量较多,胸径较大,种内与种间竞争关系顺序为:太白红杉-巴山冷杉>巴山冷杉-巴山冷杉>牛皮桦(Betula utilis)-巴山冷杉>其它树种-巴山冷杉;竞争强度和对象木胸径的关系服从幂函数关系(CI=AD-B),当巴山冷杉胸径达到25 cm以上时,种内和种间竞争强度变化较小。研究表明,改进的方法能很好地预测巴山冷杉种内和种间的竞争强度。     

舟山群岛红楠林种内和种间竞争研究

红楠（Machilus thunbergii）林是浙江沿海地区典型森林类型之一,研究竞争强度的动态变化规律及红楠种群的生态适应机制,对舟山群岛常绿阔叶林的保护与可持续利用具有重要意义。利用Hegyi单木竞争指数模型,对舟山桃花岛次生林优势种红楠的种内和种间竞争强度进行定量分析。结果表明：红楠3种类型的竞争强度均随对象木胸径的增大而逐渐减小,小径级的红楠承受的竞争压力较大;红楠的种内和种间竞争强度分别占总竞争强度的44.55%和55.45%,两者大致相等,说明其受到的种内和种间竞争压力均衡;落叶树种的平均竞争指数大,常绿树种的平均竞争指数小,使红楠受压的主要树种是朴树和枫香树;红楠种内和种间竞争强度的顺序为：红楠种内 > 朴树 > 枫香树 > 椿叶花椒 > 柘 > 梾木 > 化香树 > 赛山梅 > 黄檀 > 日本珊瑚树 > 天仙果等;3种类型的竞争强度与对象木胸径均呈显著负相关,且服从幂函数关系CI=AD^-B,当红楠胸径达到20 cm以上时,竞争强度变化很小,利用所得的预测模型能很好地预测红楠种内和种间竞争强度。当红楠胸径小于20 cm时,应对其进行抚育管理以提高红楠成活率和促进植被恢复。     

Competition components along productivity gradients – revisiting a classic dispute in ecology

Competition is ubiquitous in plant communities with various effects on plant fitness and community structure. A long-standing debate about different approaches to explain competition is the controversy between David Tilman and Philip Grime. Grime stated that the importance of competition relative to the impact of the environment increases along a productivity gradient, while Tilman argued that the intensity of competition is independent of productivity. To revisit this controversy, we assumed that the effects of plant–plant interactions are additive and applied the new competition indices by Díaz-Sierra et al. (2017) in a field experiment along a productivity gradient in S-Germany, using the rare arable plant Arnoseris minima as a study species. The ‘target technique' was applied, to separate the effects of root and shoot competition. The study plants were exposed to five competition treatments with three replicates in 18 sites, respectively. We investigated the expectation that root competition is more intense in unproductive sites than shoot competition. Additionally, we predicted survival to be less affected by competition than growth-related plant parameters. Using the biomass of individuals without competition as a proxy for site productivity there was a positive relationship with competition importance but no relationship with competition intensity when plants experienced full competition. Survival of the target plants was unaffected by competition. Root competition was the main mechanism determining the performance of the target plants, whereas the effect of shoot competition was relatively low albeit increasing with productivity. We conclude that when considering plant–plant interactions additive both Grime's and Tilman's theories can be supported.     

Sperm competition mechanisms in birds: models and data

This study presents three models to explain the mechanism oflast male sperm precedence in birds. Because passive loss ofsperm from the female reproductive tract occurs, all modelsincorporate this process. The three models are passive spermloss alone, stratification with passive sperm loss, and displacementwith passive sperm loss. With two inseminations containing thesame number of sperm, the models make the following predictions.For passive sperm loss alone, (1) differential paternity ispositively and linearly related to the time interval betweeninseminations, (2) with a slope that is equal to rate of lossof sperm from the female reproductive tract, (3) with an interceptthat is the same as the differential fertilizing capacity betweenthe semen of the two inseminations, and (4) the ratio of offspringfrom two inseminations remains constant over time. For stratification,(1) the relationship between differential paternity and theinterval between inseminations is nonlinear and exhibits a "brokenstick" pattern, with a substantial first-insemination precedencefor short intervals, and (2) the proportion of offspring fatheredby the first insemination increases over time. For displacement,the relationship between differential paternity and the intervalbetween inseminations is nonlinear and also exhibits a "brokenstick" pattern, but in contrast to the stratification model,sperm from the last insemination have precedence. Data fromthree experimental studies of the domestic fowl and one forthe turkey provide the opportunity to test these models, albeitto different extents. The data from all studies are consistentwith the passive sperm-loss model, except that one aspect ofone data set provided ambiguous support for stratification.None of the data provided any support for the displacement model.     

子午岭天然油松林乔木层种内与种间竞争关系研究

采用改进的竞争指数模型研究了甘肃省子午岭天然油松林乔木层种内和种间竞争强度。结果发现:(1)随对象木胸径的增大,油松种群因自疏作用使植株距离增加,种内竞争强度降低。(2)油松群落内其它物种虽较多,但个体普遍较小,种间竞争相对较弱,种内与种间竞争关系顺序为:油松种内>辽东栎>漆树>春榆。(3)竞争强度与对象木胸径的关系服从幂函数关系,当油松胸径达25cm以上时,竞争强度变化不大,所得的预测模型能很好地预测油松种内和种间的竞争强度。(4)改进的竞争指数模型能很好地度量油松的种内和种间竞争强度。     

Variation in the relative magnitude of intraspecific and interspecific competitive effects in novel versus familiar environments in two<Emphasis Type="Italic">Drosophila</Emphasis> species

Models of competitor coevolution, especially the genetic feedback hypothesis, suggest that a negative correlation between intraspecific and interspecific competitive effects may be important in sustaining competitor coexistence, and can give rise to oscillatory dynamics with repeated reversals of competitive superiority. I reanalyzed previously published census data from an experiment in which populationsof Drosophila melanogaster andD. simulans underwent competitive coevolution in one familiar and two novel environments, to specifically look for any evidence of a negative relationship between intraspecific and interspecific competitive effects on population growth rates, and for any indication of short period cycling in the relative magnitude of intraspecific and interspecific competitive effects. While there was considerable variation in the relative magnitude of intraspecific and interspecific competitive effects over generations, among both populations and environments, there was no clear evidence supporting the genetic feedback hypothesis. Intraspecific and interspecific competitive effects on population growth rates were strongly positively correlated in novel environments, and uncorrelated in the familiar environment. Data from the familiar environment indicated that indices of competition of populations of the initially superior competitor,D. melanogaster, might be showing some cyclic behaviour, but I argue that this is likely to be transient, and not suggestive of sustained oscillatory dynamics predicted by the genetic feedback model. I discuss the results in the context of the importance of the genetic architecture of intraspecific and interspecific competitive abilities in determining the coevolutionary trajectory of competitive interactions.     

Contest‐type competition between age classes in scramble‐type Callosobruchus maculatus (Coleoptera: Bruchidae)

We examined the effect of age differences on competition type in individuals of a scramble‐type strain of Callosobruchus maculatus (F.). When oviposition of two individuals on a bean was manipulated to introduce time intervals using two lines with different adult body colors, the frequency of two‐adult emergence decreased with the introduction of sequential oviposition. This result indicates that an age difference between two individuals induces contest competition. The frequency of adult emergence in older individuals decreased, whereas in younger individuals it increased with the introduction of sequential oviposition. Using a dissecting microscope, we observed that bodies of older individuals that died in the bean during the 4‐day oviposition interval were crushed at the pupal stage under the pupal chambers of younger individuals. These results show that an age difference between two larvae in a bean causes contest competition due to one‐sided interference by a younger individual during pupation of an older individual. Based on these experimental results, we discuss the ecological cause of contest competition and the population‐level consequences of identified interactions in scramble‐type C. maculatus.     

Behavior influences range limits and patterns of coexistence across an elevational gradient in tropical birds

Does competition influence patterns of coexistence between closely related taxa? Here we address this question by analyzing patterns of range overlap between related species of birds (‘sister pairs’) co‐occurring on a tropical elevational gradient. We explicitly contrast the behavioral dimension of interspecific competition (interference competition) with similarity in resource acquisition traits (exploitative competition). Specifically, we ask whether elevational range overlap in 118 sister pairs that live along the Manu Transect in southeastern Peru is predicted by proxies for competition (intraspecific territorial behavior) or niche divergence (beak divergence and divergence times, an estimate of evolutionary age). We find that close relatives that defend year‐round territories tend to live in non‐overlapping elevational distributions, while close relatives that do not defend territories tend to broadly overlap in elevational distribution. In contrast, neither beak divergence nor evolutionary age was associated with patterns of range limitation. We interpret these findings as evidence that behavioral interactions – particularly direct territorial aggression – can be important in setting elevational range limits and preventing coexistence of closely related species, though this depends upon the extent to which intraspecific territorial behavior can be extended to territorial interactions between species. Our results suggest that interference competition can be an important driver of species range limits in diverse assemblages, and thus highlight the importance of considering behavioral dimensions of the niche in macroecological studies.     

Avoidance of reproductive interference causes resource partitioning in bean beetle females

Reproductive interference is any interspecific sexual interaction that adversely affects female fitness through indiscriminate reproductive activities. It can be a driving force of resource partitioning in conjunction with resource competition. We previously showed that the bean beetle Callosobruchus maculatus is superior in larval resource competition, but vulnerable in reproductive interference, compared with its congener C. chinensis. We hypothesized that these two species might use two resources differently if one of the resources modified the intensity of reproductive interference or resource competition. We observed that C. maculatus females often enter gaps between beans to avoid mating attempts of heterospecific males, and hypothesized that removing bean gaps would strengthen reproductive interference. Therefore, we provided normal beans with gaps and split beans without gaps to females of the two species housed with conspecific or heterospecific males or no males and compared the number of eggs on each bean type among treatments. Callosobruchus maculatus females housed with heterospecific males were more likely to oviposit on normal beans than C. chinensis females. As a result, more C. chinensis adults hatched from split beans and more C. maculatus hatched from normal beans when females and males of both species were housed together. Thus, oviposition resource partitioning resulted from the combination of female avoidance of reproductive interference and resource competition.     

天柱山黄山松种内与种间竞争的研究

采用改进的竞争指数模型研究安徽天柱山黄山松的种内和种间竞争强度。结果发现:(1)随对象木胸径的增大,黄山松种群因自然稀疏过程中密度调节作用,植株距离增加,种内竞争强度降低;(2)黄山松群落内其它物种虽然较多,但个体普遍较小,结果种间竞争相对较弱,种内与种间竞争关系顺序为:黄山松—黄山松>杉木—黄山松>枹栎—黄山松>其它树种—黄山松;(3)竞争强度和对象木胸径的关系服从幂函数关系(CI=AD-B),当黄山松胸径达到20cm以上时,竞争强度变化不大,所得的预测模型能很好地预测黄山松种内和种间的竞争强度;(4)改进的竞争指数模型能很好地度量黄山松的种内和种间竞争强度,改进的确定邻体范围的方法能有效地确定黄山松的竞争范围。     

天然东北红豆杉(Taxus cuspidata)种内和种间竞争

竞争是植物种内和种间关系的主要形式之一。通过对黑龙江穆棱东北红豆杉自然保护区的95株东北红豆杉对象木及980株竞争木的调查,运用Hegyi的单木竞争指数计算分析了东北红豆杉的种内和种间竞争强度。东北红豆杉的种内竞争强度不大,占总竞争的4%。竞争压力更多的来自于种间竞争,占总竞争的96%。与东北红豆杉竞争激烈的树种主要是冷杉、紫椴、色木槭和红松等地带性植被的优势种。随着东北红豆杉胸径的增大,所受到的竞争压力逐渐减小,胸径在20cm以前所受到的竞争压力最大,竞争强度与对象木胸径符合幂函数（CI=AD^-B）关系。