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Trade-off Relationship (trade-off + relationship)
Selected AbstractsADAPTIVE CHANGE IN THE RESOURCE-EXPLOITATION TRAITS OF A GENERALIST CONSUMER: THE CEOLUTION AND COEXISTENCE OF GENERALISTS AND SPECIALISTSEVOLUTION, Issue 3 2006Peter A. Abrams Abstract Mathematical models of consumer-resource systems are used to explore the evolution of traits related to resource acquisition in a generalist consumer species that is capable of exploiting two resources. The analysis focuses on whether evolution of traits determining the capture rates of two resources by a consumer species produce one generalist, two specialists, or all three types, when all types are characterized by a common fitness function. In systems with a stable equilibrium, evolution produces one generalist or two specialists, depending on the second derivative of the trade-off relationship. When there are sustained population fluctuations, the nature of the trade-off between the consumer's capture rates of the two resources still plays a key role in determining the evolutionary outcome. If the trade-off is described by a choice variable between zero and one that is raised to a power n, polymorphic states are possible when n > 1, which implies a positive second derivative of the curve. These states are either dimorphism, with two relatively specialized consumer types, or trimorphism, with a single generalist type and two specialists. Both endogenously driven consumer-resource cycles, and fluctuations driven by an environmental variable affecting resource growth are considered. Trimorphic evolutionary outcomes are relatively common in the case of endogenous cycles. In contrast to a previous study, these trimorphisms can often evolve even when new lineages are constrained to have phenotypes very similar to existing lineages. Exogenous cycles driven by environmental variation in resource growth rates appear to be much less likely to produce a mixture of generalists and specialists than are endogenous consumer-resource cycles. [source] Do shade-tolerant tropical tree seedlings depend longer on seed reserves?FUNCTIONAL ECOLOGY, Issue 4 2002Functional growth analysis of three Bignoniaceae species Summary 1.,A functional growth analysis was used to determine the duration of strict dependency on seed reserves for energy and nitrogen in three woody Bignoniaceae species (Tabebuia rosea DC., Challichlamys latifolia K. Schum. and Pithecoctenium crucigerum A. Gentry) which differed in cotyledon function (photosynthetic, semi-photosynthetic and storage) and shade tolerance (probability of seedling establishment and survival in the understorey). 2.,Seedlings were raised from seeds in sand culture under combinations of three nitrogen levels (daily supply of nutrient solution containing 100, 10 and 0% of 2ˇ6 mm N) and two irradiances (27 and 1% full sun). Time course of biomass, non-cotyledonous biomass and leaf area for 40 days post-germination were compared to identify when the external availability of nitrogen or light began to affect seedling growth. 3.,Seedlings of all species became dependent on external energy supply earlier than they did on nitrogen supply. In all species seed nitrogen was sufficient to support positive seedling growth for 40 days in shade, but not in sun. 4.,Tabebuia rosea with photosynthetic cotyledons responded to light availability earlier than more shade-tolerant species with storage cotyledons. Challichlamys latifolia, the most shade-tolerant species, had the highest nitrogen concentration in seeds and was the last to respond to external nitrogen availability. Thus seedlings of the most shade-tolerant species depended on seed reserves for the longest period for both energy and nitrogen. 5.,Relative growth rate after seedlings initiated autotrophic growth was in a trade-off relationship with seedling survivorship in the understorey across the three species. Tabebuia rosea, the least shade-tolerant species, had the highest positive net carbon balance in sun and shade. 6.,Functional morphology of cotyledons and concentration of seed nitrogen deserve as much attention as seed size as correlates of contrasting seedling regeneration strategies. [source] Resource distribution and the trade-off between seed number and seed weight: a comparison across crop speciesANNALS OF APPLIED BIOLOGY, Issue 1 2010B.L. Gambín In grain crops, total sink capacity is usually analysed in terms of two components, seed number and individual seed weight. Seed number and potential individual seed weight are established at a similar timing, around the flowering period, and seed weight at maturity is highly correlated with the potential established earlier. It is known that, within a species, available resources during the seed set period are distributed between both yield components, resulting in a trade-off between seed number and seed weight. Here we tested if this concept could apply for interspecific comparisons, where combinations of numbers and size across species could be related to the total available resources being either allocated to more seed or larger potential individual seed weight during the seed set period. Based on this, species differences in seed weight should be related to resource availability per seed around the period when seed number is determined. Resource availability per seed was estimated as the rate of increase in aboveground biomass per seed around the period of seed set. Data from 15 crop species differing in plant growth, seed number, seed weight and seed composition were analysed from available literature. Because species differed in seed composition, seed weight was analysed following an energy requirement approach. There was an interspecific trade-off relationship between seed number per unit of land area and seed weight (r = 0.92; F(1, 13) = 32.9; n = 15; P < 0.001). Seed weight of different species was positively correlated (r = 0.90; F(1, 13) = 52.9; n = 15; P < 0.001) with resource availability per seed around the seed set period. This correlation included contrasting species like quinoa (Chenopodium quinoa; ,100000 seeds m,2, ,4 mg equivalent-glucose seed,1) or peanut (Arachis hypogaea; ,800 seeds m,2, ,1000 mg equivalent-glucose seed,1). Seed number and individual seed weight combinations across species were related and could be explained considering resource availability when plants are adjusting their seed number to the growth environment and seeds are establishing their storage capacity. Available resources around the seed set period are proportionally allocated to produce either many small seeds or few larger seeds depending on the particular species. [source] HUB-AIRPORT COMPETITION: CONNECTING TIME DIFFERENTIATION AND CONCESSION CONSUMPTION,AUSTRALIAN ECONOMIC PAPERS, Issue 4 2006MING HSIN LIN This paper develops a network model to analyse the economic effects resulting from the non-price competition between the home country's and neighbouring country's hub-airports. Focusing on the trade-off relationship between the length of the connecting time in the hub-airport and the consumption opportunities of the transfer passengers, we demonstrate theoretically that even though the hub-airport bears a cost disadvantage over its rival in providing the hub-airport service, it still has a chance to earn more profits than its rival by the setting of the connecting time. This finding suggests a new methodology for hub-airports that attempt to alleviate price competition. [source] | ||||||||||