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31.
Current challenges for the study of population ecology of microtine rodents are reviewed. Comparisons with other taxonomic
groups (other mammals, birds and insects) are given throughout. A major challenge is to link patterns and processes (i.e.
mechanisms) better than is the case today. Other major challenges include the furthering of our understanding of the interaction
between deterministic and stochastic processes, and as part thereof, the interaction between density-dependent and density-independent
processes. The applicability of comparative studies on populations exhibiting different temporal dynamical patterns is, in
this connection, emphasized. Understanding spatiotemporal dynamical patterns is another major challenge, not the least from
a methodological point of view. Long-term and large-scale ecological data on population dynamics (in space and time) are critical
for this purpose. Looking for consistency between hypothesized mechanisms and observed patterns is emphasized as a good platform
for further empirical and theoretical work. The intellectual feedback process between different approaches to the study of
microtine population ecology (observational studies, experimental manipulative studies, statistical modeling and mathematical
modeling) are discussed. We recommend a pluralistic approach (involving both observational and experimental as well as theoretical
studies) to the study of small rodent ecology. 相似文献
32.
Ottar N. Bj?rnstad Nils Chr Stenseth Takashi Saitoh Ole Chr Lingj?rde 《Researches on Population Ecology》1998,40(1):77-84
We study the regional transitions in dynamics of the gray-sided vole,Clethrionomys rufocanus, within Hokkaido, Japan. The data-set consists of 225 time series of varying length (most from 23 to 31 years long) collected
between 1962 and 1992 by the Forestry Agency of the Japanese Government. To see clearly how the periodic behavior changes
geographically, we estimate the spectral density functions of the growth rates of all populations using a log-spline method.
We subsequently apply functional data analysis to the estimated densities. The functional data analysis is, in this context,
analogous to a principal component analysis applied to curves. We plot the results of the analysis on the map of Hokkaido,
to reveal a clear transition from relatively stable populations in the southwest and west to populations undergoing 3–4 year
cycles in the northeast and east. The degree of seasonality in the vegetation and the rodent demography appear to be strongest
in the cyclic area. We briefly speculate that the destabilization of the rodent dynamics is linked to increased seasonalforcing
on the trophic interactions in which the gray-sided voles are involved. 相似文献
33.
Takashi Saitoh 《Researches on Population Ecology》1990,32(2):391-406
Summary A population of the grey red-backed vole,Clethrionomys rufocanus bedfordiae, was investigated on a 1 ha control grid and a 1 ha grid on which the voles were fed within a 2.1 ha outdoor enclosure in
Hokkaido, Japan by live trapping from 1984 to 1986, for testing the Reproductive Suppression Model of Wasser and Barash (1983)-females
can optimize their lifetime reproductive success by suppressing reproduction when future conditions for the survival of offspring
are likely to be sufficiently better than present ones as to exceed the costs of the suppression itself. Age at the first
pregnancy more varied in a higher density population on the experimental grid and females could be classified into the early
and the late reproductive type in two generations (A: females born from February to June 1985; B: females born from September
to November 1985). Lifetime reproductive success (the number of pregnancies, the number of successful litters, and the number
of offspring) was not different between the early and the late reproducing females. The late reproducing females lived for
longer periods than the early reproducing females, so that the loss by delayed start of reproduction was compensated for by
a longer life span. Life span was not different between offspring of the early and the late reproducing females. These facts
supported the Reproductive Suppression Model. 相似文献
34.
Takashi Saitoh 《Researches on Population Ecology》1995,37(1):49-57
The natal dispersal distance of the grey-sided vole,Clethrionomys rufocanus (Sundevall), was measured in a large outdoor enclosure (2.1 ha) in Hokkaido, Japan. Voles in about half of the enclosure
(1 ha) were fed. Distance from the natal site to the site of reproduction was significantly greater in males (64.9 m) than
in females (35.3 m). In males, 24.8% settled within one home range length of their natal site and 49.6% settled further than
two range lengths from their natal site. In femles, the respective percentages were reversed: 51.2% and 22.0%. The timing
of large movements (≥50 m) was related to body mass in both sexes. The population density was always higher on the fed grid
than on the control grid, which resulted in the frequency of large movements being greater on the fed grid that on the control
grid. Thus, the percentage of voles performing a large movement was not different between the grids in both sexes. 相似文献
35.
We present the censored regression model with the error term following the asymmetric exponential power distribution. We propose three Markov chain Monte Carlo (MCMC) algorithms: the first one uses the probability integral transformation; the second one uses a combination of the probability integral transformation and random walk draws; while the third one uses random walk draws. Using simulated data we compare the performance of the three MCMC algorithms. Then we compare the posterior means, or Bayes estimates, with maximum likelihood estimates. We estimate the stock option portion of executive compensation as an example of the empirical application. 相似文献
36.
The explicit form of the reference prior bayes estimator due to Yang and Ber-ger (1994) for bivariate normal covariance matrix under entropy loss is given in terms of Legendre polynomials when degrees of freedom is even and in terms of hypergeometric functions in general case. The finite series expression of the density function of the ratio of latent roots of bivariate Wishart matrix is obtained and the exact risk is compared with those of James-Stein minimax estimator and other orthogonally equivariant estimators. It is found numerically that the reference prior bayes estimator has the smallest risk among the class of equivariant estimators compared, when the ratio of the largest to the smallest population latent roots of covariance matrix lies in the middle of the interval [1, ∞]. It has larger risk than that of James-Stein minimax estimator when the ratio is large. Moreover it has larger risk than that of MLE when, for instance, degrees of freedom is 20 and the ratio lies between 4 and 8. 相似文献