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Size Inequality (size + inequality)
Selected AbstractsDensity-Induced Plant Size Reduction and Size Inequalities in Ethylene-Sensing and Ethylene-Insensitive TobaccoPLANT BIOLOGY, Issue 2 2004R. Pierik Abstract: Plant competition for light is a commonly occurring phenomenon in natural and agricultural vegetations. It is typically size-asymmetric, meaning that slightly larger individuals receive a disproportionate share of the light, leaving a limited amount of light for the initially smaller individuals. As a result, size inequalities of such stands increase with competition intensity. A plant's ability to respond morphologically to the presence of neighbour plants with enhanced shoot elongation, the so-called shade avoidance response, acts against the development of size inequalities. This has been shown experimentally with transgenic plants that cannot sense neighbours and, therefore, show no shade avoidance responses. Stands of such transgenic plants showed a much stronger development of size inequalities at high plant densities than did wild type (WT) stands. However, the transgenic plants used in these experiments displayed severely hampered growth rates and virtually no response to neighbours. In order to more precisely study the impact of this phenotypic plasticity on size inequality development, experiments required plants that have normal growth rates and reduced, but not absent, shade avoidance responses. We made use of an ethylene-insensitive, transgenic tobacco genotype (Tetr) that has wild type growth rates and moderately reduced shade avoidance responses to neighbours. Here, we show that the development of size inequalities in monocultures of these plants is not affected unambiguously different from wild type monocultures. Plots of Tetr plants developed higher inequalities for stem length than did WT, but monocultures of the two genotypes had identical CV (Coefficient of Variance) values for shoot biomass that increased with plant density. Therefore, even though reduced shade avoidance capacities led to the expected higher size inequalities for stem length, this does not necessarily lead to increased size inequalities for shoot biomass. [source] Effects of elevated CO2 on the size structure in even-aged monospecific stands of Chenopodium albumGLOBAL CHANGE BIOLOGY, Issue 4 2003HISAE NAGASHIMA Abstract To investigate the effect of elevated CO2 on the size inequality and size structure, even-aged monospecific stands of an annual, Chenopodium album, were established at ambient and doubled CO2 with high and low nutrient availabilities in open top chambers. The growth of individual plants was monitored non-destructively every week until flowering. Elevated CO2 significantly enhanced plant growth at high nutrients, but did not at low nutrients. The size inequality expressed as the coefficient of variation tended to increase at elevated CO2. Size structure of the stands was analyzed by the cumulative frequency distribution of plant size. At early stages of plant growth, CO2 elevation benefited all individuals and shifted the whole size distribution of the stand to large size classes. At later stages, dominant individuals were still larger at elevated than at ambient CO2, but the difference in small subordinate individuals between two CO2 levels became smaller. Although these tendencies were found at both nutrient availabilities, difference in size distribution between CO2 levels was larger at high nutrients. The CO2 elevation did not significantly enhance the growth rate as a function of plant size except for the high nutrient stand at the earliest stage, indicating that the higher biomass at elevated CO2 at later stages in the high nutrient stand was caused by the larger size of individuals at the earliest stage. Thus the effect of elevated CO2 on stand structure and size inequality strongly depended on the growth stage and nutrient availabilities. [source] Reproductive Allocation Patterns in Different Density Populations of Spring WheatJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 2 2008Jing Liu Abstract The effects of increased intraspecific competition on size hierarchies (size inequality) and reproductive allocation were investigated in populations of the annual plant, spring wheat (Triticum aestivum). A series of densities (100, 300, 1 000, 3 000 and 10 000 plants/m2) along a gradient of competition intensity were designed in this experiment. The results showed that average shoot biomass decreased with increased density. Reproductive allocation was negatively correlated to Gini coefficient (R2 = 0.927), which suggested that reproductive allocation is inclined to decrease as size inequality increases. These results suggest that both vegetative and reproductive structures were significantly affected by intensive competition. However, results also indicated that there were different relationships between plant size and reproductive allocation pattern in different densities. In the lowest density population, lacking competition (100 plants/m2), individual reproductive allocation was size independent but, in high density populations (300, 1 000, 3 000 and 10 000 plants/m2), where competition occurred, individual reproductive allocation was size dependent: the small proportion of larger individuals were winners in competition and got higher reproductive allocation (lower marginal reproductive allocation; MRA), and the larger proportion of smaller individuals were suppressed and got lower reproductive allocation (higher MRA). In conclusion, our results support the prediction that elevated intraspecific competition would result in higher levels of size inequality and decreased reproductive allocation (with a negative relationship between them). However, deeper analysis indicated that these frequency- and size-dependent reproductive strategies were not evolutionarily stable strategies. [source] Size variation and mating success in the stag beetle, Lucanus cervusPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2006DEBORAH J. HARVEY Abstract The stag beetle, Lucanus cervus, is Britain's largest beetle, with a patchy distribution in southern England. The literature suggests that it displays exceptional size variation, particularly in the males, but no analysis of size inequality has ever been conducted. In the present study, stag beetle adults are measured and allometric relationships derived between various parameters and total body length. Most of the specimens found each year are fragments and head width can be used as a good predictor of total body length in each sex. Body size differs between years and between localities and male beetles show a greater degree of size inequality than females. However, L. cervus does not show greater inequality in size than many other beetle species and populations of males are composed of a relatively large number of small individuals. These males are not at a disadvantage in mating because it is the ratio of male : female size that determines mating success. Very large males are less successful in mating and it is suggested that lack of mating success may act as an additional constraint on mandible size in this species. Size variation is most likely caused by variation in larval food resources, coupled with variation in local climatic conditions. [source] Firm Size Distribution in Small SamplesBULLETIN OF ECONOMIC RESEARCH, Issue 4 2004Luigi Buzzacchi D40; L11; G22 Abstract Sutton (1998) has recently proposed a theoretical lower bound to firm size inequality when a market is made of several independent submarkets. His results are valid asymptotically, as the number of submarkets becomes arbitrarily large. We show that, in small samples, his results can be interpreted as a positive relationship between an index of firm size inequality and the number of submarkets. We also test this relationship in the Italian motor insurance market. [source] | ||||||||||