The Strategic Gene

Gene-selectionists define fundamental terms in non-standard ways. Genes are determinants of difference. Phenotypes are defined as a gene’s effects relative to some alternative whereas the environment is defined as all parts of the world that are shared by the alternatives being compared. Environments choose among phenotypes and thereby choose among genes. By this process, successful gene sequences become stores of information about what works in the environment. The strategic gene is defined as a set of gene tokens that combines ‘actor’ tokens responsible for an effect with ‘recipient’ tokens whose replication is thereby enhanced. This set of tokens can extend across the boundaries of individual organisms, or other levels of selection, as these are traditionally defined.Organismic and Evolutionary Biolog

Sarah and Constant Broyer, Pharmacist and Physician, of Carlton

Constant Broyer (1833–1911) trained as a herbalist in Victoria during the 1850s and practised as a medical botanist in Carlton in the 1860s. He obtained medical degrees from the Eclectic Medical College of Cincinnati (1875) and Harvard University (1879). He is perhaps the first Australian to have studied at Harvard. He was twice found guilty of manslaughter by a coroner’s jury in 1874 and 1896. Both cases were much publicised but Broyer was not prosecuted on either charge. His wife, Sarah Broyer (1829–1877), ran the family pharmacy during her husband’s absence in America in the 1870s. She was the first woman to apply for registration as a pharmacist in Victoria in 1877 under the new Pharmacy Act and was represented in her negotiations before the Pharmacy Board by a young barrister, Alfred Deakin. This article traces the chronology and major events shaping the personal, professional and public lives of Constant and Sarah Broyer (and their extended family) from the mid-nineteenth century to the 1940s.Organismic and Evolutionary Biolog

The Epidemiology of Epigenetics

Organismic and Evolutionary Biolog

Games in Tetrads: Segregation, Recombination, and Meiotic Drive

The two alleles at a heterozygous locus segregate during meiosis, sometimes at meiosis I and sometimes at meiosis II. The timing of segregation is determined by the pattern of crossing‐over between a locus and its attached centromeres. Genes near centromeres can exploit this process by driving against spores from which the genes separated at meiosis I. Other genes, located distal to centromeres, can benefit from driving against spores from which they separated at meiosis II. Asymmetric female meiosis is particularly susceptible to such forms of drive. Selection on modifiers of recombination favors changes in the location of chiasmata that increase the proportion of tetrads of high average fitness by changing the timing of segregation. Such changes increase the frequency of driving alleles. This source of selection on recombination does not depend on effects on linkage disequilibrium. Recombinational responses to meiotic drive may contribute to sex differences in overall recombination and sex differences in the localization of chiasmata.Organismic and Evolutionary Biolog

Kinship Asymmetries and the Divided Self

Imprinted genes are predicted to affect interactions among relatives. Therefore, variant alleles at imprinted loci are promising candidates for playing a causal role in disorders of social behavior. The effects of imprinted genes evolved in the context of patterns of asymmetric relatedness that existed within social groups of our ancestors.Organismic and Evolutionary Biolog

Huddling: Brown Fat, Genomic Imprinting and the Warm Inner Glow

Heat generated by huddling animals is a public good with a private cost and thus vulnerable to exploitation, as illustrated by recent work on rabbits and penguins. Effects of imprinted genes on brown adipose tissue suggest that non-shivering thermogenesis is an arena for intragenomic conflict.Organismic and Evolutionary Biolog

Lamarck Ascending! A Review of Transformations of Lamarckism: From Subtle Fluids to Molecular Biology. Edited by Snait B. Gissis and Eva Jablonka, MIT Press, 2011

Transformations of Lamarckism is an edited volume arising from a workshop to commemorate the bicentenary of the publication of Philosophie Zoologique. The contributed chapters discuss the history of Lamarckism, present new developments in biology that could be considered to vindicate Lamarck, and argue for a revision, if not a revolution, in evolutionary theory. My review argues that twentieth and twenty-first century conceptions of Lamarckism can be considered a reaction to August Weismann’s uncompromising rejection of the inheritance of acquired characters in the late nineteenth century. Weismann rejected the inheritance of acquired characters both as a proximate mechanism of heredity and as an ultimate cause of adaptation. I argue that Weismann’s proximate claim is still valid for the kind of mechanism that he had in mind but that the inheritance of acquired characters has come to refer to many different processes, some of which undoubtedly do occur. However, processes of physiological adaptation and adaptive plasticity, even if transgenerational, do not challenge Weismann’s claim about the ultimate causes of adaptation because these processes can be understood as evolving by natural selection. Finally, I discuss some of the emotional and aesthetic reasons why many find Lamarckism an attractive alternative to hard-core neo-Darwinism.Organismic and Evolutionary Biolog

Sexual Antagonism and the Evolution of X Chromosome Inactivation

In most female mammals, one of the two X chromosomes is inactivated early in embryogenesis. Expression of most genes on this chromosome is shut down, and the inactive state is maintained throughout life in all somatic cells. It is generally believed that X-inactivation evolved as a means of achieving equal gene expression in males and females (dosage compensation). Following degeneration of genes on the Y chromosome, gene expression on X chromosomes in males and females is upregulated. This results in closer to optimal gene expression in males, but deleterious overexpression in females. In response, selection is proposed to favor inactivation of one of the X chromosomes in females, restoring optimal gene expression. Here, we make a first attempt at shedding light on this intricate process from a population genetic perspective, elucidating the sexually antagonistic selective forces involved. We derive conditions for the process to work and analyze evolutionary stability of the system. The implications of our results are discussed in the light of empirical findings and a recently proposed alternative hypothesis for the evolution of X-inactivation.Organismic and Evolutionary Biolog

Fitness Variation Due To Sexual Antagonism and Linkage Disequilibrium

Extensive fitness variation for sexually antagonistic characters has been detected in nature. However, current population genetic theory suggests that sexual antagonism is unlikely to play a major role in the maintenance of variation. We present a two-locus model of sexual antagonism that is capable of explaining greater fitness variance at equilibrium than previous single-locus models. The second genetic locus provides additional fitness variance in two complementary ways. First, linked loci can maintain gene variants that are lost in single-locus models of evolution, expanding the opportunity for polymorphism. Second, linkage disequilibrium results between any two sexually antagonistic genes, producing an excess of high and low fitness haplotypes. Our results uncover a unique contribution of conflicting selection pressures to the maintenance of variation, which simpler models that neglect genetic architecture overlook.Organismic and Evolutionary Biolog

Coleochaete and the origin of sporophytes

Premise of the study: Zygotes of Coleochaete are provisioned by the maternal thallus before undergoing 3–5 rounds of division to produce 8–32 zoospores. An understanding of the selective forces favoring postzygotic divisions would be relevant not only to the interpretation of Coleochaete life history but also to the origin of a multicellular diploid phase in embryophytes. Methods: Simple optimization models are developed of the number of zygotes per maternal thallus and number of zoospores per zygote. Key results: Zygotic mitosis is favored once zygotic size exceeds a threshold, but natural selection usually promotes investment in additional zygotes before zygotes reach this threshold. Factors that favor production of fewer, larger zygotes include multiple paternity, low fecundity, and accessory costs of zygote production. Such factors can result in zygotes exceeding the size at which zygotic mitosis becomes profitable. Conclusions: Coleochaete may possess large zygotes that undergo multiple fission because of accessory costs associated with matrotrophy, including costs of cortical cells and unfertilized oogonia. The unpredictability of fertilization on land is proposed to have increased accessory costs from unfertilized ova and, as a consequence, to have favored the production of larger zygotes that underwent postzygotic division to produce diploid sporophytes.Organismic and Evolutionary Biolog