Howard Levene

INTERACTION OF THE ADAPTIVE VALUES IN POLYMORPHIC EXPERIMENTAL POPULATIONS OF DROSOPHILA PSEUDOOBSCURA

Genetic diversification is an evolutionary mechanism which enables MIendelian populations to master a wide variety of environments in the territories which they inhabit. In many species of Drosophila, some of the genetic diversification takes the form of chromosomal polymorphism. Thus, in Drosophila pseudoobscura several (up to seven) different gene arrangements occur in the third chromosomes in many natural populations. The chromosomal polymorphism can be studied not only in natural but also in artificial laboratory populations (Wright and Dobzhansky, 1946; Dobzhansky, 1949). Such studies have shown that the fitness of the structural heterozygotes which carry two third chromosomes with different gene arrangements derived from the same population is, not invariably but usually, superior to that of the corresponding structural homozygotes. The polymorphism is, therefore, balanced, and the gene arrangements are maintained in the populations with frequencies which are determined, for a given environment, by the relative adaptive values of the different karyotypes (Dobzhansky, 1948, 1949; Dobzhansky and Levene, 1948). The great interest of the chromosomal polymorphism in Drosophila is that it makes the processes of natural selection and evolutionary adaptation amenable to experimental study. The work in this

Development of Heterosis Through Natural Selection in Experimental Populations of Drosophila pseudoobscura

Hybrids of the California and the Mexican races of Drosophila pseudoobscura were kept in population cages for approximately 15 generations. A preliminary study of viability, and the early course of the population in the cages, showed no heterosis for the heterozygotes which carried a California and a Mexican third chromosome. Heterosis has, however, developed during the experiment, as indicated by the attainment of equilibrium and by a study of the viability of flies derived from the cage. Both tests gave statistically significant results. Methods were developed for estimating adaptive values and viability in such experiments, and for investigating the possible range of values of these constants consistent with the sampling error involved.

Population dynamics of a variant t-allele in a confined population of wild house mice.

Variant alleles at one locus, T, have been found in many populations of wild house mice (Dunn and Suckling, 1956; Dunn, 1957b), but reliable estimates of gene frequency have not been obtained since most of the population samples tested have been small. One such population, breeding in confinement, has now been tested over a period of 7/2 years, and a reliable estimate obtained of the frequency in it of one t-allele for which it is polymorphic. Since the allele is favored by high transmission ratio from male heterozygotes, and is subject to strong negative selection because of the sterility of males homozygous for it, the results are of interest in the study of evolutionary forces which influence the equilibrium frequencies of such genes (Dunn, 1957a). The wild population tested is that maintained since 1944 by Dr. Howard A. Schneider at the Rockefeller Institute, New York City. The origin and maintenance of this population have been described by Dr.

DEPENDENCE OF THE ADAPTIVE VALUES OF CERTAIN GENOTYPES IN DROSOPHILA PSEUDOOBSCURA ON THE COMPOSITION OF THE GENE POOL

In a previous publication (Levene, Pavlovsky, Dobzhansky, 1954) we have reported experiments on laboratory populations of Drosophila pseudoobscura in which three different gene arrangements were present among the third chromosomes. The adaptive values of six karyotypes (three inversion homozygotes and three heterozygotes) were estimated from the observed changes in the relative frequencies of the gene arrangements in the experimental populations. The results indicated that the adaptive values of at least some of the karyotypes were not constant; they depended upon the presence or absence of certain other karyotypes in the same population. Thus, individuals homozygous for the CH gene arrangement in third chromosome (CH/ CH) had a fitness apparently superior to AR homozygotes (AR/AR) in populations in which ST third chromosomes were also present, but CH/CH were inferior to AR/AR in fitness when ST chromosomes were absent. ST homozygotes (ST/ST) were superior to ST/CH heterozygotes in populations which also had AR chromosomes, but ST/CH were superior to ST/ST in the absence of AR. Lewontin (1955) reported some elegant experiments in which constant numbers of larvae of certain genotypes of Drosophila melanogaster were introduced

The Effectiveness of Quality Control Charts

Abstract The spacing and effectiveness functions of a quality control chart used either alone or in sets of two or more are derived for production at a constant level and for erratic production. The spacing of decision points is considered from a general point of view. The theory developed is fundamental in deciding which of two different decision techniques in quality control, each using the same spacing function, is the more effective. * Many of the results given herewith were obtained independently by the two authors.

New evidence of heterosis in naturally occurring inversion heterozygotes in Drosophila pseudoobscura

New evidence of heterosis in naturally occurring inversion heterozygotes in Drosophila pseudoobscura

CHROMOSOMAL POLYMORPHISM IN DROSOPHILA PSEUDOOBSCURA USED FOR DIAGNOSIS OF GEOGRAPHIC ORIGIN

Natural populations of many species of Drosophila are polymorphic for gene orders in at least some of their chromosomes. In Drosophila pseudoobscura the polymorphism is found mostly in the third chromosomes in which no fewer than 22 inversions of gene blocks have been found in nature (Dobzhansky, 1944, 1948). In no population have all the inversions been encountered; the number of polymorphic inversions varies from zero (monomorphism) to nine. Some inversions are widespread, others endemic; neighboring populations have similar or identical frequencies, while remote localities may show quantitative or even qualitative differences in the inversions present. Smooth as well as stepwise gradients of the inversion frequencies are found, the latter usually coinciding with topographic barriers or environmental breaks. D. pseudoobscura is a complex of chromosomal geographic races. The accumulation of data now permits inquiry into the extent to which knowledge of the gene orders in the chromosomes of a single individual enables one to infer from which race or population that individual or its ancestors came. We report here the results of such an inquiry. Further, we compare the results of diagnosing the geographic origin of a fly by using chromosal data with the results obtained by using single locus data (allozymes). We also show how the probability of correctly identifying the population of

A Conservative Procedure for the Estimation of Multiple Insemination in Drosophila

For certain Drosophila females, observation of the genotypes at an autosomal locus of a sample of their progeny confirms that they used the sperm from at least two males in fertilizing their offspring. In addition to these observably multiply mated females there are other females whose multiple matings are not apparent in the progeny sample. We relate the observed level of concurrent multiple paternity (CMP) to the true level of CMP by a multiplier which depends only on the gene frequencies and the progeny sample size. The simplicity of the relation between observed and estimated actual CMP is purchased at the cost of ignoring sperm displacement and triple mating. We argue that the resulting estimate still errs on the conservative side.

On the Foundations of Statistical Inference: Discussion

Author(s): L. J. Savage, George Barnard, Jerome Cornfield, Irwin Bross, George E. P. Box, I. J. Good, D. V. Lindley, C. W. Clunies-Ross, John W. Pratt, Howard Levene, Thomas Goldman, A. P. Dempster, Oscar Kempthorne and Allan Birnbaum Source: Journal of the American Statistical Association, Vol. 57, No. 298 (Jun., 1962), pp. 307-326 Published by: Taylor & Francis, Ltd. on behalf of the American Statistical Association Stable URL: http://www.jstor.org/stable/2281641 Accessed: 25-12-2017 20:48 UTC

POSSIBLE GENETIC DIFFERENCE BETWEEN THE HEAD LOUSE AND THE BODY LOUSE (PEDICULUS HUMANUS L.)

The head louse and the body louse are human parasites which are distinguishable by their morphological traits, as well as by their preferred location on the host. The nature of the differences between them is, however, by no means clear. Many investigators regarded them as full-fledged species (Pediculus capitis and P. vestimenti), and even alleged that the hybrids between them were sterile intersexes. Other investigators united them in a single species (Pediculus hum anus), and treated the differences between the head and the body forms as mere environmental modifications. New evidence has been obtained in the careful experiments of Alpatov and his collaborators, conducted in 1942-1946, and published in concise but most workmanlike papers by Alpatov, Nastjukova, and Khartulari (1945) and by Alpatov and Nastjukova (1955).