Individual based simulations of population dynamics require the availability of growth models with adequate complexity. For this purpose a simple-to-use model (non-linear multiple regression approach) is presented describing somatic growth and reproduction of Daphnia as a function of time, temperature and food quantity. The model showed a good agreement with published observations of somatic growth (r2 = 0.954, n = 88) and egg production (r2 = 0.898, n = 35). Temperature is the main determinant of initial somatic growth and food concentration is the main determinant of maximal body length and clutch size. An individual based simulation was used to demonstrate the simultaneous effects of food and temperature on the population level. Evidently, both temperature and food supply affected the population growth rate but at food concentrations above approximately 0.4 mg Cl−1Scenedesmus acutus temperature appeared as the main determinant of population growth.
Four simulation examples are given to show the wide applicability of the model: (1) analysis of the correlation between population birth rate and somatic growth rate, (2) contribution of egg development time and delayed somatic growth to temperature-effects on population growth, (3) comparison of population birth rate in simulations with constant vs. decreasing size at maturity with declining food concentrations and (4) costs of diel vertical migration. Due to its plausible behaviour over a broad range of temperature (2–20 °C) and food conditions (0.1–4 mg Cl−1) the model can be used as a module for more detailed simulations of Daphnia population dynamics under realistic environmental conditions. 相似文献
Samples of the estuarine-spawning teleostAcanthopagrus butcheri were collected from nine estuaries and a coastal lake, located in the Pilbara and South-western drainage divisions of Western
Australia and distributed along a coastline covering a distance of nearly 2,000 km. The patterns of allozyme variation in
these samples were used to explore the extent to which there was variation in the genetic compositions of black bream assemblages
in geographically-isolated estuarine systems, and whether or not any such variation could be related to the geographical location
or type of estuary. Although only three of 36 scorable loci (Gpi-1, Ldh andMdh-2) exhibited variation that could be used for analysis, there was considerable variation in allele frequencies at these loci
among the different samples (mean FST=0.166). Much of the detected variation was attributable to differences between the samples collected from the two drainage
divisions, which are located in very different climatic regions. Furthermore, the genetic compositions of samples from neighbouring
estuaries were typically more similar to each other than to those of samples collected from more distantly-located systems.
However, the assemblages in one west coast and two south coast estuaries, that are closed to the ocean for extensive periods
of time during the year, all showed very similar genetic compositions. Nevertheless, it is crucial to recognise that, pairwise
comparisons of samples collected from the different estuaries, both within and between the two drainage divisions, almost
invariably showed statistically significant differences in allele frequencies at one or more loci. Thus, our results indicate
that the local populations of black bream in individual estuaries are genetically distinct, which is probably a consequence
of both a limited movement by individuals between estuaries and the effects of differences in regional and local environmental
conditions. 相似文献
This article discusses the issue of whether to use a variable mean and describes a test that can be used to evaluate whether
it is justified to add terms to the drift (deterministic part) of a geostatistical model. The basic model could be the intrinsic
one, where the deterministic part is a constant, and the alternate model could be any model that includes a constant term
in the expression for the drift. Also, differences between constant- and variable-mean models are discussed. 相似文献
This paper presents a new approach for estimating unknown ore grades within a mining deposit in a fuzzy environment using
fuzzy c- means clustering and a fuzzy inference system. Based on a collection of cluster centers obtained from fuzzy c- means,
a fuzzy rule base and fuzzy search domains are established to compute grades at these cluster centers. These cluter center-
grade pairs act as control information in the fuzzy space- grade system in order to infer unknown grades on the basis of fuzzy
interpolation, fuzzy extrapolation, and a defuzzification process of fuzzy control. 相似文献