Browsing by Author "Uyenoyama, MK"

Now showing 1 - 8 of 8

Open Access
Evolution of altruism under group selection in large and small populations in fluctuating environments
(Theoretical Population Biology, 1979-01-01) Uyenoyama, MK
A continuous, graded form of group selection which does not involve extinction of demes can effectively oppose selection on the individual level against an altruistic allele under fluctuating environments in infinitely large demes among which uniform mixing occurs every generation. Although group selection cannot alter the conditions necessary for the initial increase of altruistic alleles, group selection can significantly influence the stationary distribution of gene frequency which is attained once stochastic forces have allowed theirintroduction. Drift is a more effective source of variation than fluctuations in selection when the variance in selection is moderate to small. High numbers of demes promote polymorphism under both graded group selection and extinction group selection. © 1979.
Open Access
On relatedness and adaptive topography in kin selection
(Theoretical Population Biology, 1981-01-01) Uyenoyama, MK; Feldman, MW
Open Access
On the evolutionary modification of self-incompatibility: Implications of partial clonality for allelic diversity and genealogical structure
(2008-01-01) Vallejo-Marín, M; Uyenoyama, MK
Experimental investigations of homomorphic self-incompatibility (SI) have revealed an unanticipated level of complexity in its expression, permitting fine regulation over the course of a lifetime or a range of environmental conditions. Many flowering plants express some level of clonal reproduction, and phylogenetic analyses suggest that clonality evolves in a correlated fashion with SI in Solanum (Solanaceae). Here, we use a diffusion approximation to explore the effects on the evolutionary dynamics of SI of vegetative propagation with SI restricted to reproduction through seed. While clonality reduces the strength of frequency-dependent selection maintaining S-allele diversity, much of the great depth typical of S-allele genealogies is preserved. Our results suggest that clonality can play an important role in the evolution of SI systems, and may afford insight into unexplained features of allele genealogies in the Solanaceae.
Open Access
Population genetic theory of kin selection. II. The multiplicative model.
(American Naturalist, 1982-01-01) Uyenoyama, MK; Feldman, M
Analyzes multiplicative kin selection models incorporating fitness functions which involve products of the costs and benefits that are associated with altruistic actions. Multiplicative models exhibit a number of qualitative differences compared to additive models including the dependence of gene frequency change on a more complex covariance and the existence of strongly noninvasible fixation states associated with intermediate levels of performance of altruism. By regarding the multiplicative model as an additive model with genotype-dependent benefit parameters, the multiplicative model can be reconciled with Hamilton's theory. -Authors
Open Access
Population genetic theory of kin selection: Multiple alleles at one locus.
(Proceedings of the National Academy of Sciences of the United States of America, 1981-08) Uyenoyama, MK; Feldman, MW; Mueller, LD
Exact population genetic models of one-locus sib-to-sib kin selection with an arbitrary number of alleles are studied. First, a natural additive scaling is established for the genotypic value associated with probabilities of performance of altruism. Two classes of polymorphic equilibria are possible, one corresponding to the usual one-locus viability equilibria and the other reflecting the kin-selection assumptions of the model. At both, the covariance between additive genotypic value and genotypic fitness vanish. Further, the sign of this covariance determines the fate of rare alleles introduced near the first class of equilibria. In addition, the covariance explains the differences between Hamilton's rule, which results from Hardy-Weinberg assumptions, and exact initial increase conditions.
Open Access
The genetics of sex ratio distortion by cytoplasmic infection under maternal and contagious transmission: an epidemiological study.
(Theoretical population biology, 1978-12) Uyenoyama, MK; Feldman, MW
Nuclear and cytoplasmic determinants jointly influence the sex ratio in several organisms. A mathematical model of a maternally inherited extra-chromosomal agent that affects the fitness of its carriers and distorts the sex ratio in their broods is analyzed. The agent is transmitted through the cytoplasm from mother to daughter, or it may pass contagiously among females of the same generation. It is shown that under natural selection the deviation between the population sex ratio and Fisher's optimum value evolves to a minimum. © 1978.
Open Access
Towards a genetic theory for the evolution of the sex ratio II. Haplodiploid and diploid models with sibling and parental control of the brood sex ratio and brood size
(Theoretical Population Biology, 1981-01-01) Uyenoyama, MK; Bengtsson, BO
Population genetic models involving sister, brother, and father control of the brood sex ratio and brood size in both the haplodiploid and diploid cases are constructed and analyzed. The results are interpreted in light of the verbal theories which predict the evolution of the sex ratio to a value which is proportional to the ratio of relatedness of the controlling members of the family to males and to females produced in the brood. In our models, the sex ratio in a certain class of polymorphic equilibria evolves to equal investment in males and females in those cases where the controlling members of the family are symmetrically related to males and females as predicted by the verbal theory. However, the sex ratio in the case of sister control in haploidiploids does not evolve to 1:3, but rather to a value proportional to the ratio of the regression coefficients of additive genotypes. Even so, the predicted sex ratio, which is proportional to 1:3, is in fact an "ESS" in the sense that fixation of a genotype specifying that sex ratio is resistant to the initial increase of all other genotypes. © 1981.
Open Access
Towards a genetic theory for the evolution of the sex ratio.
(Genetics, 1979-11) Uyenoyama, MK; Bengtsson, BO
A genetical model is formulated in which the sex ratio in broods and the relative size of broods are determined by the genotype at an autosomal locus. The results also apply to the case in which the sex-ratio locus is sex linked and expressed in the homogametic sex and to the case in which the locus is expressed in the diploid sex of a haplodiploid organism. Fisher (1930) argued that the sex ratio evolves under natural selection to a value such that parental expenditure is equalized between the sexes. Shaw and Mohler (1953) and MacArthur (1965) proposed that the sex ratio evolves to increase a certain expression for fitness. The sex ratio suggested by Fisher (1930) is in fact identical to the sex ratio specified by these maximization principles. Further, in our model, the Fisherian sex ratio corresponds exactly to the sex ratio at certain equilibria that are approached whenever they exist.