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1.
2.
Leo S. Luckinbill Michael J. Clare Walter L. Krell William C. Cirocco Paula A. Richards 《Evolutionary ecology》1987,1(1):37-46
Summary Although many different physiological and biochemical changes characterize the process of senescence, little is understood of the genetic elements that determine its age of onset. We provide here the first estimates of the number of genetic factors that extend longevity inDrosophila melanogaster. Life span was measured in F1, F2 and backcrosses of true-breeding long and short-lived stocks ofD. melanogaster, established by selection. Estimates of the number of effective factors delaying senescence range from about 0.3 to 1.5, indicating control by a single factor. The distribution of longevity shows this to arise as selection acts on the short-lived parental stock. Life span is extended at the cost of early fecundity. 相似文献
3.
Synopsis We present ways to test the assumptions of the Petersen and removal methods of population size estimation and ways to adjust
the estimates if violations of the assumptions are found. We were motivated by the facts that (1) results of using both methods
are commonly reported without any reference to the testing of assumptions, (2) violations of the assumptions are more likely
to occur than not to occur in natural populations, and (3) the estimates can be grossly in error if assumptions are violated.
We recognize that in many cases two days in the field is the most time fish biologists can spend in obtaining a population
estimate, so the use of alternative models of population estimation that require fewer assumptions is precluded. Hence, for
biologists operating with these constraints and only these biologists, we describe and recommend a two-day technique that
combines aspects of both capture-recapture and removal methods. We indicate how to test: most of the assumptions of both methods
and how to adjust the population estimates obtained if violations of the assumptions occur. We also illustrate the use of
this combined method with data from a field study. The results of this application further emphasize the importance of testing
the assumptions of whatever method is used and making appropriate adjustments to the population size estimates for any violations
identified. 相似文献
4.
On nonparametric discrimination using density differences 总被引:2,自引:0,他引:2
5.
Estimation in linear models with censored data 总被引:1,自引:0,他引:1
6.
Improvements of jackknife confidence limit methods 总被引:1,自引:0,他引:1
7.
8.
Radial estimates and the test for sphericity 总被引:1,自引:0,他引:1
9.
在系统调查分析和特尔斐测定的基础上,选取人口密度、耕地人口负荷量、土地工业经济密度、居民点、厂矿用地、>25°土地面积、单位森林蓄积占用土地、耕地非旱涝保收面积7项指标,应用分值权重累加、系统聚类分析和模糊综合评价3种方法对杭州湾6市土地生态环境作综合分析评价,结果可应用于国土规划实践,对探讨土地生态环境评价的理论与方法有参考价值。 相似文献
10.
C. S. Wang B. S. Yandell J. J. Rutledge 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,85(1):79-88
Summary At least two common practices exist when a negative variance component estimate is obtained, either setting it to zero or not reporting the estimate. The consequences of these practices are investigated in the context of the intraclass correlation estimation in terms of bias, variance and mean squared error (MSE). For the one-way analysis of variance random effects model and its extension to the common correlation model, we compare five estimators: analysis of variance (ANOVA), concentrated ANOVA, truncated ANOVA and two maximum likelihood-like (ML) estimators. For the balanced case, the exact bias and MSE are calculated via numerical integration of the exact sample distributions, while a Monte Carlo simulation study is conducted for the unbalanced case. The results indicate that the ANOVA estimator performs well except for designs with family size n = 2. The two ML estimators are generally poor, and the concentrated and truncated ANOVA estimators have some advantages over the ANOVA in terms of MSE. However, the large biases may make the concentrated and truncated ANOVA estimators objectionable when intraclass correlation () is small. Bias should be a concern when a pooled estimate is obtained from the literature since <0.05 in many genetic studies. 相似文献