Showing papers by "Robert R. Sokal published in 1964"

Competition among Genotypes in Tribolium Castaneum at Varying Densities and Gene Frequencies (the Black Locus)

Abstract: 1. Mixtures of three genotypes (+/+, +/s, s/s) for the autosomal mutant sooty were reared at five initial gene frequencies and four densities. Replication of the experiments resulted in a total of 59,280 beetles being employed in the experiment. The heterozygote is distinguishable in adults. The frequency and dry weight of emerging adults was recorded by genotypes. A rough measure of total developmental time was also obtained. The wild type strain was found to be contaminated with sooty at a gene frequency of 0.02 for most replicates. 2. Adult survivorship is measured as the percentage of egg input for a given genotype. Figure 1 illustrates the results. The lower three densities did not have any pronounced effects; at density 100/g overall survivorship was markedly reduced. The homozygous wild type has the highest survivorship in the study; the heterozygote is intermediate through the lower densities but lowest in survivorship at the highest density. The relative survivorships of the three genotypes depend on the gene frequency of sooty: at 0.25qs relations may be summarized by +/+ > s/s > +/s, at 0.5qs by +/+ > +/s > s/s and at 0.75qs by +/s > +/+ > s/s. Relationships at 0.5qs are more consistent while those of the other two gene frequencies showed some heterogeneity among replicates. From the results it is clear that the performance of the heterozygote improves with an increase in the gene frequency of sooty. 3. Dry weights of adults were highest at 20/g. The three genotypes weighed as follows when in mixed culture: s/s >> +/+ > +/s. Gene frequency in the cultures has a marked effect on weights of +/+ and +/s individuals. These responses are illustrated in figure 2. Approximation to straight line functions are obtained when weight of +/+ and +/s individuals is graphed as a function of the proportion of +/s plus s/s individuals in the population. Thus, weight is not simply a function of the gene frequency of sooty in a culture, but of the frequencies of the two genotypes carrying the s allele. 4. Heterozygotes are intolerant to crowding, especially with their own genotype. Weight relations among genotypes depend on whether the beetles were reared in pure or mixed culture. Thus, the performance of genotypes when interacting with other genotypes cannot be predicted from their performance in pure culture. 5. At the higher gene frequencies heterozygotes predominate among the early emerging adults, while s/s individuals are largely late emerging ones. 6. The facilitation and interaction among genotypes is discussed from the general point of view of considering quality as well as frequencies of genotypes as comprising part of the milieu of any individual. Such studies will ultimately lead to adding a genetic dimension to our understanding of ecological phenomena.

Competition among genotypes in the housefly at varying densities and proportions (the green strain)

Abstract: The experiments reported below investigate differences in three biological characters affecting fitness in four genotypes of the housefly, Musca domestica L. These biotic properties were studied at seven different densities in pure and mixed culture. Mixtures of genotypes in three different proportions were employed in the study. It is our aim in this and related studies to increase our understanding of the ecology of natural selection in this organism. This study is patterned after several similar ones carried out with a strain homozygous for the bwb locus in M. domestica (Sullivan and Sokal, 1963, 1964; Sokal and Sullivan, 1963). By extending the study to another strain of the same organism marked with a different mutant we hope to test some of the generality of our conclusions as well as increase the range of the modes of response of the biological properties investigated. Parallel work is also being done in this laboratory on competition among genotypes in the red flour beetle, Tribolium castaneum, in which similar experimental designs are yielding both congruent as well as contrasting results (Sokal and Huber, 1963; Sokal and Karten, 1964). No effort has been made to provide an identical genetic background for the mutant and wild type strains. Our emphasis has