Cytonuclear interactions affect adaptive traits of the annual plant Arabidopsis thaliana in the field

Although the contribution of cytonuclear interactions to plant fitness variation is relatively well documented at the interspecific level, the prevalence of cytonuclear interactions at the intraspecific level remains poorly investigated. In this study, we set up a field experiment to explore the range of effects that cytonuclear interactions have on fitness-related traits in Arabidopsis thaliana. To do so, we created a unique series of 56 cytolines resulting from cytoplasmic substitutions among eight natural accessions reflecting within-species genetic diversity. An assessment of these cytolines and their parental lines scored for 28 adaptive whole-organism phenotypes showed that a large proportion of phenotypic traits (23 of 28) were affected by cytonuclear interactions. The effects of these interactions varied from slight but frequent across cytolines to strong in some specific parental pairs. Two parental pairs accounted for half of the significant pairwise interactions. In one parental pair, Ct-1/Sha, we observed symmetrical phenotypic responses between the two nuclear backgrounds when combined with specific cytoplasms, suggesting nuclear differentiation at loci involved in cytonuclear epistasis. In contrast, asymmetrical phenotypic responses were observed in another parental pair, Cvi-0/Sha. In the Cvi-0 nuclear background, fecundity and phenology-related traits were strongly affected by the Sha cytoplasm, leading to a modified reproductive strategy without penalizing total seed production. These results indicate that natural variation in cytoplasmic and nuclear genomes interact to shape integrative traits that contribute to adaptation, thereby suggesting that cytonuclear interactions can play a major role in the evolutionary dynamics of A. thaliana.

Patterns of Interaction in Family Triads with High-Achieving and Low-Achieving Children

The patterns of interaction between the parents and the child in family triads of high-achieving and low-achieving boys and girls and their parents were compared. Forty family triads were studied. The mean age of the children was 12 yr., 1 mo. Fathers of boys and girls did not differ in over-all dominance in the family process. Parents shared dominance but fathers of boys differed from fathers of girls in how this dominance was applied. Fathers' interactional pattern with their wives was flexible, influenced by the sex and achievement level of the children. These factors influenced fathers' interaction with their children and also mothers' interaction with their husbands. Mothers' behaviour toward their children was influenced by sex but much less so by achievement level. The sex of the child significantly influenced his behaviour toward his mother but the achievement level not to the same extent. In essence, the interaction of the parental pair with their children seemed to be the important factor in achievement.

Mathematical contributions to the theory of evolution. IX.—On the principle of homotyposis and its relation to heredity, to the variability of the individual, and to that of the race. Part I.—homotyposis in the vegetable kingdom

(1.) If we take two offspring from the same parental pair, we find a certain diversity and a certain degree of resemblance. In the theory of heredity we speak of the degree of resemblance as the fraternal correlation, while the intensity of the diversity is measured by the standard deviation of the array of offspring due to given parents. Both correlation and standard deviation are determined for any given character or organ by perfectly definite well-known statistical methods. Passing from the case of bi-parental to asexual reproduction, we may still determine the correlation and variability of the offspring.