So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

The terms 'antioxidant', 'oxidative stress' and 'oxidative damage' are widely used but rarely defined. This brief review attempts to define them and to examine the ways in which oxidative stress and oxidative damage can affect cell behaviour both in vivo and in cell culture, using cancer as an example.

Biochemistry of oxidative stress

ECOLOGY/EVOLUTION: Phenotypic Plasticity

When the red harvester ant is threatened, nestmates rush to its assistance. The message is a chemical one. Distress is communicated and help summoned by the potential victim ejecting a tiny cocktail of alkanes and terpenoids. Professor E 0 Wilson, who made this discovery, is a distinguished zoologist whose writings have twice been awarded Pulitzer Prizes. His interests extend far beyond entomology, however. Why should human communication be qualitatively different from that of the ant, in being achieved by definable, physicochemical processes? And, if this is the case, surely the same must be true of other social phenomena? Having conceded so much, on what grounds can we exclude other products of human activity such as the social sciences, arts, humanities and ethics? In a mechanistic universe, the whole of human civilization is the ultimate product of the interaction between genes and environment, incredibly complex, as Wilson admits, but susceptible to fundamentally the same analytic techniques as communication in the harvester ant. Consilience (literally, a 'jumping together') is the notion that a common groundwork of explanation applies not only to the sciences but also to the arts, ethics and religion. In his book Consiliencel Wilson applies a combination of broad learning and a style of baroque exuberance to put the case for such a unity of knowledge. Wilson is thus, as he makes clear, a child of the Enlightenment, paying homage to Bacon and Newton but most of all to Condorcet, who trod the same intellectual path (and who came to grief in the Revolution for reasons probably not unrelated to his philosophy). He mourns the triumph at the end of the eighteenth century of revelatory religion fearful of the outcomes of science, and most of all of Romanticism although regrettably overlooking the

Consilience: The Unity of Knowledge.

Unchecked aggression and violence exact a significant toll on human societies. Aggression is an umbrella term for behaviours that are intended to inflict harm. These behaviours evolved as adaptations to deal with competition, but when expressed out of context, they can have destructive consequences. Uncontrolled aggression has several components, such as impaired recognition of social cues and enhanced impulsivity. Molecular approaches to the study of aggression have revealed biological signals that mediate the components of aggressive behaviour. These signals may provide targets for therapeutic intervention for individuals with extreme aggressive outbursts. This Review summarizes the complex interactions between genes, biological signals, neural circuits and the environment that influence the development and expression of aggressive behaviour.

Neural mechanisms of aggression

Animal Communication Networks: Fighting, mating and networking: pillars of poeciliid sociality

Sex steroids can both modulate and be modulated by behavior, and their actions are mediated by complex interactions among multiple hormone sources and targets. While gonadal steroids delivered via circulation can affect behavior, changes in local brain steroid synthesis also can modulate behavior. The relative steroid load across different tissues and the association of these levels with rates of behavior have not been well studied. The bluebanded goby (Lythrypnus dalli) is a sex changing fish in which social status determines sexual phenotype. We examined changes in steroid levels in brain, gonad and body muscle at either 24 hours or 6 days after social induction of protogynous sex change, and from individuals in stable social groups not undergoing sex change. For each tissue, we measured levels of estradiol (E2), testosterone (T) and 11-ketotestosterone (KT). Females had more T than males in the gonads, and more E2 in all tissues but there was no sex difference in KT. For both sexes, E2 was higher in the gonad than in other tissues while androgens were higher in the brain. During sex change, brain T levels dropped while brain KT increased, and brain E2 levels did not change. We found a positive relationship between androgens and aggression in the most dominant females but only when the male was removed from the social group. The results demonstrate that steroid levels are responsive to changes in the social environment, and that their concentrations vary in different tissues. Also, we suggest that rapid changes in brain androgen levels might be important in inducing behavioral and/or morphological changes associated with protogynous sex change.

/pdf/differential-responses-of-brain-gonad-and-muscle-steroid-55k9bxy198.pdf

Differential Responses of Brain, Gonad and Muscle Steroid Levels to Changes in Social Status and Sex in a Sequential and Bidirectional Hermaphroditic Fish

In addition to genetic variation, epigenetic mechanisms such as DNA methylation might make important contributions to heritable phenotypic diversity in populations. However, it is often difficult to disentangle the contributions of genetic and epigenetic variation to phenotypic diversity. Here, we investigated global DNA methylation and mRNA expression of the methylation-associated enzymes during embryonic development and in adult tissues of one natural isogenic lineage of mangrove rivulus fish, Kryptolebias marmoratus. Being the best-known self-fertilizing hermaphroditic vertebrate affords the opportunity to work with genetically identical individuals to examine, explicitly, the phenotypic effects of epigenetic variance. Using the LUminometric Methylation Assay (LUMA), we described variable global DNA methylation at CpG sites in adult tissues, which differed significantly between hermaphrodite ovotestes and male testes (79.6% and 87.2%, respectively). After fertilization, an immediate decrease in DNA methylation occurred to 15.8% in gastrula followed by re-establishment to 70.0% by stage 26 (liver formation). Compared to zebrafish, at the same embryonic stages, this reprogramming event seems later, deeper, and longer. Furthermore, genes putatively encoding DNA methyltransferases (DNMTs), Ten-Eleven Translocation (TET), and MeCP2 proteins showed specific regulation in adult gonad and brain, and also during early embryogenesis. Their conserved domains and expression profiles suggest that these proteins play important roles during reproduction and development. This study raises questions about mangrove rivulus' peculiar reprogramming period in terms of epigenetic transmission and physiological adaptation of individuals to highly variable environments. In accordance with the general-purpose genotype model, epigenetic mechanisms might allow for the expression of diverse phenotypes among genetically identical individuals. Such phenotypes might help to overcome environmental challenges, making the mangrove rivulus a valuable vertebrate model for ecological epigenetic studies. The mangrove rivulus, Kryptolebias marmoratus, is the best-known self-fertilizing hermaphroditic vertebrate that allows to work with genetically identical individuals to examine, explicitly, the phenotypic effects of epigenetic variance. The reprogramming event is later, more dramatic and longer than in other described vertebrates. High evolutionary conservation and expression patterns of DNMT, TET, and MeCP2 proteins in K. marmoratus suggest biological roles for each member in gametogenesis and development.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.4141

DNA methylation in adults and during development of the self-fertilizing mangrove rivulus, Kryptolebias marmoratus.

Prior work has demonstrated that, following a predator inspection visit of their own, guppies prefer to associate with individuals who inspected a predator most closely. Based on this work, as well as studies of social learning in the context of mate choice, we predicted that male guppies that observed but did not participate in an inspection trial would subsequently choose to associate with the closer of two inspectors. Our experimental protocol consisted of three treatments: a control test in which an observer watched two fish consecutively, only one of which was exposed to a predator, a sequential test in which an observer watched two fish consecutively, both of which were exposed to the predator, and a social test in which an observer watched two fish inspect simultaneously. We found no preferences by the observer for either of the fish in any of the trials. Our results suggest that direct interaction is a critical component to the development of preferences in male guppies. We discuss our findings in light of game theoretical treatments of cooperation.

Ryan L. Earley

Papers

Animal Communication Networks: Fighting, mating and networking: pillars of poeciliid sociality

Differential Responses of Brain, Gonad and Muscle Steroid Levels to Changes in Social Status and Sex in a Sequential and Bidirectional Hermaphroditic Fish

DNA methylation in adults and during development of the self-fertilizing mangrove rivulus, Kryptolebias marmoratus.

Observational Learning and Predator Inspection in Guppies (Poecilia reticulata)

Innate immune performance and steroid hormone profiles of pregnant versus nonpregnant cottonmouth snakes (Agkistrodon piscivorus).