Interaction of genotype and parental environment in the adaptation of wild House mice Mus musculus to cold

Myopia, intelligence, and the expanding human neocortex: behavioral influences and evolutionary implications

The first two parts of this monograph document that areas of the human neocortex heavily used to cope with a complex, language-driven society have been expanding rapidly and suggest strongly that this is linked with the huge upsurge that's occurred in myopia, and with the large gradual 20th-century increase in measured intelligence. Part III proposes mechanisms capable of supporting such rapid changes, without violating the basic precepts of Darwin's thinking. Part IV discusses the social and evolutionary ramifications of our apparent proclivity for rapid, progressive, adaptive neocortical change, and suggests areas for productive research.

Multiple selection responses in house mice bidirectionally selected for thermoregulatory nest-building behavior: crosses of replicate lines

Replicate high-selected, control, and low-selected lines were crossed at generation 46 of bidirectional selection for thermoregulatory nest-building behavior. Previous analysis of the lines at their limits had revealed multiple responses to uniform selection, where each of the four selected lines responded differently to reverse selection (Laffan, 1989). The reciprocal F1 crosses showed significant heterosis for nest-building behavior compared to the contemporaneous generations of the parental lines. This pattern of heterosis in all three crosses is consistent with the finding that nest-building behavior in each of the four replicate lines had a different genetic basis, in spite of the phenotypic similarity between the two replicate lines in the high and low direction of nesting. This heterosis effect and the larger number of young weaned in all three crosses compared to their respective contemporaneous generation of the parental lines also support earlier findings that larger nests are closely related to fitness.

Neophenogenesis: a developmental theory of phenotypic evolution

An important task for evolutionary biology is to explain how phenotypes change over evolutionary time. Neo-Darwinian theory explains phenotypic change as the outcome of genetic change brought about by natural selection. In the neo-Darwinian account, genetic change is primary; phenotypic change is a secondary outcome that is often given no explicit consideration at all. In this article, we introduce the concept of neophenogenesis: a persistent, transgenerational change in phenotypes over evolutionary time. A theory of neophenogenesis must encompass all sources of such phenotypic change, not just genetic ones. Both genetic and extra-genetic contributions to neophenogenesis have their effect through the mechanisms of development, and developmental considerations, particularly a rejection of the commonly held distinction between inherited and acquired traits, occupy a central place in neophenogenetic theory. New phenotypes arise because of a change in the patterns of organism-environment interaction that produce development in members of a population. So long as these new patterns of developmental interaction persist, the new phenotype(s) will also persist. Although the developmental mechanisms that produce the novel phenotype may change, as in the process known as "genetic assimilation", such changes are not necessary in order for neophenogenesis to occur, because neophenogenetic theory is a theory of phenotypic, not genetic, change.

Wild mice in the cold: some findings on adaptation

The house mouse, Mus domesticus, can thrive in natural environments much below its optimum temperature. Thermogenesis is then above that at more usual temperatures. In addition, body weight, and the weights of brown adipose tissue and the kidneys, may be higher than usual. In free populations of house mice cold lowers fertility and may prevent breeding. Other possible limiting factors on breeding are food supply, shelter for nesting and social interactions. In captivity, wild-type house mice exposed to severe cold (around 0 degrees C) at first adapt ontogenetically by shivering and reduced activity. But raised thermogenesis is soon achieved without shivering; nest-building improves; and readiness to explore may be enhanced. Endocrine changes probably include, at least initially, a rise in adrenal cortical activity and in catecholamine secretion. Some females become barren, but many remain fertile. The maturity of fertile females is, however, delayed and intervals between births are lengthened; nestling mortality rises. A limiting factor during lactation may be the capacity of the gut. Similar adaptive changes are observed during winter in some species of small mammals that do not hibernate. But neither the house mouse nor other species present a single, universal pattern of cold-adaptation. Wild-type mice bred for about 10 generations in a warm laboratory environment (20-23 degrees C) change little over generations. In cold they become progressively heavier and fatter at all ages; they mature earlier, and nestling mortality declines. The milk of such 'Eskimo' females is more concentrated than that of controls. If 'Eskimo' mice are returned to a warm environment, they are more fertile, and rear heavier young, than controls that remained in the warm. Despite the heavier young, litter size is not reduced: it may be increased, probably as a result of a higher ovulation rate. Parental effects have been analyzed by cross-fostering and hybridizing. Survival, growth and fertility are all favourably influenced by the intra-uterine and nest environments provided by 'Eskimo' females. 'Eskimo' males are also better fathers. Hence after ten generations the phenotype of cold-adapted house mice shows the combined effects of (a) an ontogenetic response to cold, (b) a superior parental environment and (c) a change genotype. The secular changes in the cold that lead to this phenotype give the appearance of evolution in miniature; but it is equally possible that they represent a genetical versatility that allows rapid, reversible shifts in response to environmental demands.(ABSTRACT TRUNCATED AT 400 WORDS)

Hybrids show parental influence in the adaptation of wild house mice to cold

Wild house mice, Mus musculus, were bred (a) at 3 °C (‘Eskimo’) and (b) at 23 °C. Mice of the ninth generation bred at 23°C were transferred to the cold environment. Their young, and Eskimo of the same (tenth) generation, were mated to give the four possible types of pairs: controls; the two reciprocal hybrid pairings; and Eskimo. In the resulting (eleventh) generation there were therefore two hybrid classes, genetically identical but with different parentage. The growth and reproduction of the eleventh generation were studied. At all ages from birth, mice with Eskimo mothers were heavier than those with control mothers. They were also better breeders: (1) they matured earlier; (2) their litters were larger; (3) the mortality of their young in the nest was lower. In one feature there was heterosis: of the four classes, the hybrids with Eskimo mothers produced the largest litters. These and previous findings suggest rapid selection, in the cold, for changes in growth, reproductive physiology and other aspects of metabolism. The cold-adapted mice of a given generation differed from the controls partly as a result of favourable parental effects, which acted in conjunction with genetical differences. It is hypothesized that the ecological versatility of Mus musculus depends partly on the presence, in each population, of alternative genotypes which allow rapid adaptation to new conditions.