On intraspecific and interspecific competition among Abies yuanbaoshanensis community
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Abies yuanbaoshanensis Y. J. Lu et L. K. Fu is a rare and endangered plant, it is only found on Yuanbaoshan Mountain in Guangxi, China. By using Hegyi,s competition index model for individual tree 〔 CI =∑ N j =1( Dj/Di )·1 Lij 〕, the intraspecific and interspecific competition in A. yuanbaoshanensis community were investigated. The results show that intraspecific competition of A. yuanbaoshanensis is more intensive than interspecific competition. The competition intensity of competitive tree against objective tree and the size of objective tree fit power function CI =A D +{ B }, and competition intensity decreases with the increase of the size of objective tree. The CI change is not significant when the DBH of A. yuanbaoshanensis reaches 35-40 cm. The model can simulate and predict the intraspecific and interspecific competition among Abies yuanbaoshanensis community in Guangxi.=Keywords:
Storage effect
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The roles of intraspecific and interspecific competition in producing differentiation within populations of Veronica peregrina were studied in two populations under controlled, greenhouse conditions. In nature, each population spans an environmental gradient across the center and sides of a temporary, vernal pool in California. Individuals at the center are subjected to intense intraspecific competition produced by high densities (to 30 seedlings/cm2) generated by quasi‐simultaneous germination (90% of seeds germinate in one week). Individuals at the periphery are subjected to interspecific competition with grasses, which shade out the Veronica 4–6 weeks after the onset of winter growth. I predicted that 1) when grown under immediate intraspecific competition in the greenhouse, offspring of plants from the central subpopulation (C) would perform better (i.e., grow larger and produce more seeds) than those from the periphery (P) and that 2) when grown under delayed interspecific competition provided by Agrostis tenuis and Lollium multiflorum, offspring of plants from the periphery would perform better than those from the center. Both predictions were confirmed. The center‐periphery differences were pronounced and statistically significant in an undisturbed population (V‐2), while in a population disturbed by yearly plowing (V‐3), the differences tended to be consistent with those in V‐2 but seldom significant. Distribution of variability tended to be positively skewed and/or leptokurtic in subpopulations grown under "foreign" competition (i.e., intraspecific for P plants and interspecific for C plants) but was normally distributed following exposure to "familiar" competition. Timing of competition affected many results. There were four additional significant differences between the central and peripheral subpopulations. 1) Germination rate: the faster rate in central plants can be advantageous under immediate intraspecific competition. The slower rate in peripheral plants can be advantageous under conditions of erratic and unpredictable soil moisture. 2) Response to nutrient competition: central plants were more sensitive to N‐deficiency and peripheral plants were more sensitive to P‐deficiency. 3) Allocation of biomass: central plants allocated a greater proportion of biomass to seeds, while peripheral plants allocated a greater proportion of biomass to leaves under all growing conditions. 4) Root elongation: at the seedling stage, central plants have longer roots, while at the adult stage, peripheral plants have longer roots (but not more root mass). Most components of this complex pattern of differentiation are interpretable in an adaptive context. Other results defy simple explanations and underline the importance of phenotypic plasticity, which was pronounced in the competition experiments.
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clone (Java method)
Solidago canadensis
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The intraspecific and interspecific competition among the adults of three grasshoppers,Angaracris rhodopa,Oedaleus decorus asiaticus and Chorthippus fallax were studied by field cage method.The results showed that A.rhodopapreferred to feverfew while O.decorus asiaticus and C.fallaxto gramineous plants.A.rhodopahad stronger intraspecific competition than O.decorus asiaticus and C.fallax.The interspecific competition between A.rhodopaand O.decorus asiaticus or C.fallax was weak while competition between O.decorus asiaticus and C.fallax was strong.Intraspecific competition among three species was strong at high densities and decreased along with the densities down.In mixed feeding of two or three grasshopper populations,the mortality of A.rhodopawas higher than that of O.decorus asiaticus or C.fallax,which showed that interspecific competition was asymmetric.
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Repens
Trifolium repens
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Populations of Brassica rapa were grown for three generations in each of two environments: intraspecific competition, with four surrounding Brassica rapa neighbors per pot, and interspecific competition, with two Raphanus sativus neighbors per pot. In each environment, the largest (by flower number) 10% of the plants were outcrossed and provided seeds for the next generation. As a control, a randomly chosen 10% of the plants in each environment were outcrossed to produce seed for the next generation. Each of these four treatments, the selected lines in intra- and interspecific competition and the corresponding control lines, was maintained for three generations. After a single generation of growth in a common, no-competition environment, replicate plants from each treatment were grown with no competition and with intra- and interspecific competition for determination of growth responses. After two generations of selection, flower number in the intraspecific-selection line had increased by more than 50% over that in the control line and by more than 19% over that under interspecific selection. After a common-environment generation, plants from the intraspecific-selection line were shown to have significantly faster growth in height and flower number as seedlings. Plants in the interspecific-selection line showed similar but nonsignificant trends. No differences in seed mass, emergence time, or photosynthetic rate were found between control and selected lines in either intra- or interspecific competition. Some differences between control and selected lines were noted in biomass allocation related to differences in phenology. The results demonstrate that performance in competitive environments can evolve through changes in plant development but that rates of evolution will differ in intra- and interspecific competition.
Brassica rapa
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Based on investigation data of the naturally-distributed Cephalotaxus oliveri communities in Yunnan,Guizhou and Jiangxi provinces,the niche breadth,niche overlap,chi-square test,association coefficient( AC) and interspecific covariation based on 2 × 2 contingency table were used to analyze the interspecific relationship of dominant populations of C. oliveri communities. The results showed that the important value and the niche of breadth of C. oliveri in the communities were the highest. Relevant analysis results of important value and index of Levins showed the greater the important value,the greater the niche breadth of populations. The Schooner index showed that for 92. 63% of the species,no or weak niche overlap were found,and the niche overlap was smaller between C. oliveri and other dominant populations. In chi-square test,species pairs of neutral connection were 64. 74%,especially interspecific association between C. oliveri and other dominant populations. The ratio of species pairs of the positive and negative association coefficient between all dominant populations in community was 0. 91. In the same way,the species pairs of negative interspecific covariation were more than that of positive interspecific covariation.C. oliveri and fir showed significant negative interspecific covariation,with the rest of the population,no significantly covariance correlation. The lager utilizing competition did not exist between populations in the community. Bbe-cause C. oliveri was appropriated valleys or stream sides and less external distractions,so its community stability was relative higher.
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The potential importance of interspecific competition for the distribution of three rockpool Daphnia species was examined in a four-year field experiment in artificial rockpools of four different volumes, viz. 4, 12, 50 and 300 l. The three-species, the three two-species combinations, and one-species controls were used. The predictions from island biogeography and metapopulation theory that extinctions rates increase with decreasing patch size and increasing number of species present were also examined. Analyses of reproductive indices and population dynamics indicated that the species used similar resources and that interspecific competition operated during substantial parts of each year
Metapopulation
Storage effect
Extinction (optical mineralogy)
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Recent research has emphasized the importance of investigating the reaction norms of quantitative traits to understand evolution in natural environments. In this study, genetic differences in reaction norms among eight populations of the grass Bouteloua rigidiseta were examined using clonal replicates of genotypes planted in a common garden with two levels of competition (single B. rigidiseta without competition and single B. rigidiseta surrounded by four Erioneuron pilosum). The populations were found to be genetically differentiated for a variety of traits. Differences in reaction norms of size‐specific fecundity (spikelet clusters per tiller number) were detected among the populations: some showed little response to competition; in others size‐specific fecundity was much greater in the absence of competition. This divergence in reaction norms among these populations may be the result of past selection (including the cost of plasticity), or genetic drift.
Tiller (botany)
Divergence (linguistics)
Quantitative Genetics
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