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1.
Diatom species grown under non-limiting nutrient availability in multispecific biofilms were sampled from glass substrates immersed in the field and in experimental freshwater microcosms, and their growth responses were determined. The major species that developed on the substrates were common to both experiments and the specific growth rates (k) ranged from 0.06 to 0.41 division day−1. An inverse relationship between k and cell sizes was observed, which is in accordance with allometry results reported by several authors. Although found in lower amounts, the large, slow-growing species accounted significantly in total community biovolume, underlying their significance for ecological purposes. From growth characteristics data, life history strategies were drawn for the dominant species recorded, from small pioneer species to large taxa that are more favoured by high resource supply. Kinetic data measured in both laboratory and in situ experiments stressed that the difficulties to mimic the field in laboratory experiments may have a strong impact on growth kinetics. Handling editor: J. Padisak  相似文献   

2.
Basic assumptions of two distributive network models designed to explain the 3/4 power scaling between metabolic rate and body mass are re-analysed. It is shown that these models could have consistently accounted for the observed scaling patterns if and only if body mass M had scaled as L4, where L is body length, in the model of Banavar et al. (1999, Nature 399, 130-132), or if spatial volume VF occupied by the distributive network had scaled as M3/4 in the model of West et al. (1997, Science 276, 122-126). Lack of agreement between these predictions and observational evidence invalidates both models rendering them mathematically controversial. It is further shown that consideration of distributive networks can nevertheless yield realistic values of scaling exponents under the major assumption that living organisms are designed so as to keep the mass-specific metabolic rate of important functional tissues in the vicinity of a size-independent optimum value. Mass-specific metabolic rate of subsidiary mechanical tissues can be small and vary with body mass. Different patterns of spatial distribution of metabolically active biomass within the organism result in different patterns of allometric scaling. From the available evidence the presumable optimum value of mass-specific metabolic rate of living matter is estimated to be in the vicinity of 1-10 W kg-1.  相似文献   

3.
Studies of the relationship between heart rate (f(H)) and rate of oxygen consumption (V(.) (O(2))), which are then used to predict field metabolic rate, frequently fail to incorporate body mass as a predictive variable. This is a potentially important omission in the study of animals whose body mass fluctuates substantially during their annual cycle. In an attempt further to improve estimates of field metabolic rate from f(H), we re-evaluated data on M(b), f(H) and V(.) (O(2)) from previous studies of macaroni penguins (Eudyptes chrysolophus) and king penguins (Aptenodytes patagonicus) and derived a new relationship to integrate these three quantities. This relationship is at least as accurate and precise as previously determined relationships. We applied this same principle to published data on 11 of the 20 recognised penguin taxa to derive a relationship to predict V(.) (O(2)) from f(H) and M(b) in penguins of any species. This result has interesting implications in terms of reducing the logistical burden in studies of field metabolic rate.  相似文献   

4.
1. The relative growth rate of saplings of 12 species from an oligotrophic lowland rain forest were measured in treefall gaps and understorey. Mean relative height growth ( R H) within treefall gaps was found to be slowest for tall-tree species with branched saplings, intermediate for subcanopy trees and fastest for tall-tree species with unbranched saplings. Most species had similar R H within the understorey. R H values were not related to leaf mass per unit area (LMA) or foliar N concentrations.
2. Allometric relationships between the total leaf area (TLA) and height were dependent upon light conditions; in general saplings of a given height had a greater TLA in treefall gaps than in understorey. The species with the largest estimated TLA values in gaps tended to have the greatest R H values in gaps; no such trend emerged in the understorey. The values of the allometric coefficients were not related to foliar properties.
3. The relationship between stem diameter and height was only weakly dependent on light conditions and the relationship between the growth rates in these dimensions was also weak. The lack of plasticity may reflect the fact that the height–diameter relationship has little bearing on a sapling's tolerance of shade.
4. One way of accommodating the dependence of allometry upon irradiance is to add R H as a covariate. We derive a relationship between growth rates from this resource-dependent allometric equation and show that it reasonably describes measurements taken in the caatinga forest.  相似文献   

5.
Rodents of the family Heteromyidae are proficient gatherers and hoarders of seeds. A major component of their adaptive specialization for harvesting and transporting seeds is their spacious, fur-lined cheek pouches. Precise measurements of cheek pouch capacities are essential if ecologists are to understand the foraging ecology, possible constraints on locomotion patterns, and competitive relationships of heteromyid rodents. To measure the size of these cheek pouches and the rate at which animals load seeds into their pouches during seed harvest, we attracted 56 individuals representing ten species of heteromyid rodents to bait stations in the field and allowed them to fill their cheek pouches with seeds several times while we observed and timed the events with the aid of night-vision equipment. The largest load taken by each individual was used as an estimate of its cheek pouch capacity. At the end of observations, each subject was captured and its mass and other data gathered. The allometric relationship between cheek pouch capacity and body mass for ten species of heteromyids was significant [pouch capacity (ml) = 0.148 body mass (g)0.992, r 2=0.91, P<0.0001]. The regression coefficient is ≈1.0, which indicates that the volume of the cheek pouches scales in direct proportion to body size. When the data were subdivided into quadrupeds (Perognathus and Chaetodipus) and bipeds (Dipodomys) (n=5 for each), the relationships between pouch capacity and body mass were significant, but the two regressions were not significantly different from each other. When all loads (full and partial) were considered, subjects filled their cheek pouches an average of 93 ± 10% of pouch capacity (n=185). Cheek pouch capacities from published studies of artificially filled pouches of heteromyids in the laboratory averaged about 40% below the field measurements obtained here. The allometric relationship between mean loading rate and body mass was also significant [seeds/s=1.067 bodymass (g)0.830, r 2=0.85,P=0.0011), but when quadrupeds and bipeds were considered separately, the relationships were not significant. Seed densities and bulk densities were used to calculate packing coefficients for seed species, which, when used in conjunction with the allometric relationship between cheek pouch capacity and body size, can be used to estimate the maximum load carried by a heteromyid. Except for the very largest kangaroo rat species, a full pouch load of Indian ricegrass seeds represents less than the daily energy requirements of an active heteromyid. Received: 3 March 1997 / Accepted: 15 July 1997  相似文献   

6.
We compared forage digestion and passage rates among three groups of Nubian ibex (Capra ibex nubiana) — mature males, non-lactating females, and lactating females — to test hypotheses relating intraspecific digestive ability to body mass and reproduction costs. We hypothesized that large males (60 kg) would exhibit longer forage retention times and more complete digestion of fermentable cell walls than adult females (23 kg). We tested these predictions by measuring digestion and retention of a grass hay and an alfalfa hay, forages that exhibited contrasting rates and extents of cell wall digestion. Consistent with predictions, males retained both forages longer than non-lactating females. However, by substantially increasing gut fill, lactating females increased both intake and retention time with respect to non-lactating females. Contrary to predictions, all three groups digested the grass (66% digestible) and alfalfa hay (63%) equally well. Alfalfa cell wall was less digestible than that of grass hay (60% vs 69% digestible), and retention time of alfalfa was consistently, but not statistically significantly, shorter. Fiber digestion was not correlated with retention time, emphasizing the ability of behavioral processes to modify digestion rate. We postulate that females achieved their greater digestion rate by masticating forages much more thoroughly than males.  相似文献   

7.
The surface morphology of the human astragalus (talus) is difficult to represent accurately using landmarks as it is essentially globular in shape. Advances in laser scanning technology allow fast and accurate capture of bone surface morphology. However, methodologies to utilise these new accurate 3D data have not been fully developed. The present study uses canonical sampling of whole surface morphology attained through laser scanning and for the first time applies the technique to analysis of bone morphology. We introduce a new technique for identifying allometric shape characters in whole bone surface morphology. In a sample of adult human astragalus the new technique is successful in identifying and isolating intra-specific allometric shape characters in a bone which typically lacks landmarks and has, consequently, proved difficult to analyse using traditional 3D morphometric methods.  相似文献   

8.
9.
Measurements of metabolic rates of natural populations of zooplankton were made using a closed bottle technique in situ. Results showed a marked seasonality inexplicable in terms of simple temperature functions. For this cladoceran dominated zooplankton, seasonal variations in metabolic response are attributed to a degree of temperature acclimation, to changes in the size structure and species composition of the populations and seasonal variations in food sources.  相似文献   

10.
11.
Allometric scaling relationships of the form Y = aX b are widely utilized in many types of models and analyses of tree structure. They are often viewed as static relationships where both the scaling exponent (b) and the normalization constant (a) obtain empirical values that are fixed within a single set of data. Among different sets of data, their values can show environmental variability. However, there have been only few attempts to give a mechanistic interpretation for this variability. We used field data to demonstrate how the scaling relationships in trees can be modified by ecological interactions. Moreover, we show how such processes can be incorporated into the scaling models to improve the fit and the information content of the scaling equations. When fixed theoretical scaling exponents were used instead of empirical exponents and when the effect of competitive interactions between trees was described by separate submodels that predicted the value of the normalisation constant in the scaling equations, it was possible to obtain 4–10% improvement in the model fit of three different structural scaling relationships. Our results suggest that unexplained variation in the values of the scaling parameters can be substituted by an identified effect of ecological factors on the value of the normalisation constant. This agrees with recent theoretical suggestions stating that ecological factors can directly influence the value of normalisation constants.  相似文献   

12.
Mathematical relations that use easily measured variables to predict difficult-to-measure variables are important to resource managers. In this paper we develop allometric relations to predict total aboveground biomass and individual components of biomass (e.g., leaves, stems, branches) for three species of mangroves for Everglades National Park, Florida, USA. The Greater Everglades Ecosystem is currently the subject of a 7.8-billion-dollar restoration program sponsored by federal, state, and local agencies. Biomass and production of mangroves are being used as a measure of restoration success. A technique for rapid determination of biomass over large areas is required. We felled 32 mangrove trees and separated each plant into leaves, stems, branches, and for Rhizophora mangle L., prop roots. Wet weights were measured in the field and subsamples returned to the laboratory for determination of wet-to-dry weight conversion factors. The diameter at breast height (DBH) and stem height were also measured. Allometric equations were developed for each species for total biomass and components of biomass. We compared our equations with those from the same, or similar, species from elsewhere in the world. Our equations explained ≥93% of the variance in total dry weight using DBH. DBH is a better predictor of dry weight than is stem height and DBH is much easier to measure. Furthermore, our results indicate that there are biogeographic differences in allometric relations between regions. For a given DBH, stems of all three species have less mass in Florida than stems from elsewhere in the world.  相似文献   

13.
The Michaelis-Menten equation was fitted to simulated data containing different sorts of error by using the three linear transformations, and the methods of S. R. Cohen [Anal. Biochem. (1968) 22, 549-552], R. Eisenthal & A. Cornish-Bowden [Biochem. J. (1974) 139, 715-120], F. de M. Merino [Biochem. J. 143, 93-95] and G. N. Wilkinson [Biochem. J. (1961) 808 324-332). The best methods were those of Eisenthal & Cornish-Bowden (1974) and Wilkinson (1961).  相似文献   

14.
Andrea Peitsch 《Hydrobiologia》1995,311(1-3):127-137
Production rates of the calanoid copepod Eurytemora affinis were estimated from field studies in the Elbe estuary and from an enclosure experiment. As one basic parameter of production rates, the body length, was compared between both investigations. Most of the copepodid stages in the enclosure experiment reached a significant greater length than the copepodids in the estuary. The differences in length between copepods from the field and the experiment could mainly be explained by a four times higher chlorophyll-a level in the enclosure experiment. The better food supply also results in a higher individual growth rate for all instars in the enclosure experiment. Therefore the population of Eurytemora affinis in the Elbe estuary was regarded as food limited during certain times of the year, especially in late spring and summer.Maximum daily production rate in the enclosure experiment (40 µg dw l–1 d–1) was four times higher than in the estuary (12 µg dw l–1 d–1). The mean daily P:B ratio in the enclosure was 0.301 d–1 compared to 0.11 d–1 in the estuary.  相似文献   

15.
Abstract. Isothermal heat-conductance calorimetry was used to monitor responses of tomato and carrot metabolism to changes in temperature and oxygen concentrations. Calorimetric measurements of metabolic heat evolution from tissue segments and cultured cells was found to be a sensitive, nondestructive estimate of metabolic rates. Short-term measurements of metabolic rates of cells in culture correlate well with calorimetric measurements made on tissue sections. The results accurately predict the growth properties of intact plants based on the generally recognized characteristics of these two species. The calorimetric method provides another means for rapid evaluation of plant responses to physical and chemical stresses and is of value for screening and selection.  相似文献   

16.
探讨鳄蜥(Shinisaurus crocodilurus)的体温调节和静止代谢率及其热依赖性特征,测定了在自然和实验室条件下的环境温度、鳄蜥体温以及静止代谢率(RMR)等热生物学指标。结果显示:在自然条件下,鳄蜥的野外活动体温(Th)稍高于基质温度(Tc)和空气温度(Td)并与后二者呈正相关关系(Tb=11.65+0.47Tc,r^2=0.34,F1.75=39.11,P〈0.0001;Tb=11.61+0.46Td,r^2=0.56,F1.75=96.56,P〈0.0001)。鳄蜥在野外的活动体温存在明显的月份间差异,但无性别及年龄上的差异。环境温度为15℃-30℃的实验条件下,鳄蜥的静止体温(Tb)与环境温度(Ta)呈正相关关系:Tb=12.450+0.5641Ta(F1.110=11.34,r^2=0.997,P〈0.001);在缺乏温度梯度的环境中,尽管鳄蜥的体温、空气温度和基质温度都有显著的昼夜差异,但体温、空气温度和基质温度的日平均温度之间无显著差异。鳄蜥的RMR不存在雌雄个体间的差异,并与环境温度呈正相关关系。分析显示鳄蜥的体温既有行为调节也有生理调节,其体温调节及RMR符合变温动物的热生物学特征,但是相对于其他活动较多的蜥蜴而言,鳄蜥的生理调节能力较强,这可能与其活动时间分配中静栖占绝大部分的行为特点是相适应的[动物学报54(6):964-971,2008]。  相似文献   

17.
18.
Summary Phylogenetic trees were constructed for 25 Cu-Zn superoxide dismutases and 31 Mn/Fe superoxide dismutases. The latter set includes seven new sequences that we determined in an effort to make the two phylogenies equally representative. We analyzed all pairwise differences in each set in an attempt to estimate rates of change. As reported by others, the Cu-Zn enzyme has experienced significant changes in its evolutionary rate. In contrast, the clock for the Mn/Fe enzyme is ticking quite regularly. The comparison of these two independently evolved superoxide dismutases that catalyze the same reaction and occur together throughout much of the biological world suggests that adaptation to environmental stress is not the basis for the erratic rate of change observed in the Cu-Zn enzyme. Offprint requests to: R.F. Doolittle  相似文献   

19.
The hypothesis that sperm competition should favour increases in sperm size, because it results in faster swimming speeds, has received support from studies on many taxa, but remains contentious for mammals. We suggest that this may be because mammalian lineages respond differently to sexual selection, owing to major differences in body size, which are associated with differences in mass-specific metabolic rate. Recent evidence suggests that cellular metabolic rate also scales with body size, so that small mammals have cells that process energy and resources from the environment at a faster rate. We develop the 'metabolic rate constraint hypothesis' which proposes that low mass-specific metabolic rate among large mammals may limit their ability to respond to sexual selection by increasing sperm size, while this constraint does not exist among small mammals. Here we show that among rodents, which have high mass-specific metabolic rates, sperm size increases under sperm competition, reaching the longest sperm sizes found in eutherian mammals. By contrast, mammalian lineages with large body sizes have small sperm, and while metabolic rate (corrected for body size) influences sperm size, sperm competition levels do not. When all eutherian mammals are analysed jointly, our results suggest that as mass-specific metabolic rate increases, so does maximum sperm size. In addition, species with low mass-specific metabolic rates produce uniformly small sperm, while species with high mass-specific metabolic rates produce a wide range of sperm sizes. These findings support the hypothesis that mass-specific metabolic rates determine the budget available for sperm production: at high levels, sperm size increases in response to sexual selection, while low levels constrain the ability to respond to sexual selection by increasing sperm size. Thus, adaptive and costly traits, such as sperm size, may only evolve under sexual selection when metabolic rate does not constrain cellular budgets.  相似文献   

20.
The allometric relationships for plant daily biomass production rates, different measures of body size (dry weight and length) and photosynthetic biomass per plant are reported for two mutants of Arabidopsis thaliana (abi1-1, insensitive to ABA; era1-2, hypersensitive to ABA). Scaling relationships, such as daily rate of growth (G) vs body mass (M), plant body length or plant height (L) vs body mass (M), photosynthetic biomass (M p ) vs non-photosynthetic biomass (M n ), and daily rate of growth (G) vs. photosynthetic biomass (M p ) were significantly different in abi1-1 and era1-2. It is implied that the sensitivity to abscisic acid may change the scaling relationships for plant biomass production rate and body size in Arabidopsis thaliana. Because these scaling relationships are closely related to sensitivity to abscisic acid, they are of importance for phytohormonal ecology.  相似文献   

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