Tradeoffs, Conflicts and Cooperation in the Evolution of Behaviour and Reproduction

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The research in my group focuses on three of the most important unresolved questions in biology: (1) why most species have sexual reproduction and two sexes, rather than asexual reproduction and only females; (2) how new species originate; and (3) how and why people differ in cognitive traits (mental traits and abilities), and if different skills tend to trade off with one another. (1) Sexual versus asexual reproduction. Most animals have two sexes. This pattern is unusual because only females produce offspring, and any female that produced all daughters (without mating) could have twice as many grand-offspring as a female who had half sons and half daughters. Theory thus predicts that all species should be asexual and all-female, unless there are large benefits to reproducing sexually, or large, long-term costs to reproducting asexually. We study of group of insects in which asexuality has evolved at least seven times, and occurs by mitosis (self-cloning). In these insects, we are (1) conducting gene-sequencing and phylogenetic work that allows us to infer whether or not asexuals really have a large advantage in offspring production, in the field, (2) determining whether asexuals have lower rates of new mutations in their offspring than do sexuals, because they undergo cloning, and (3) evaluating if asexuals are better at DNA repair, or more resistant to DNA damage, and (4) studying how their immune system genes evolve, because asexuals may have evolved new ways of genetically-resisting parasites. These studies will help us to understand why sex predominates in animals, and how good and bad mutations originate and evolve. (2) Origins of new species. Determining how new biodiversity arises is a fundamental question in biology. Species are populations within which individuals can successfully mate and produce fertile offspring. We are studying this process in a group of insects where each species lives on different species of plants, to which they are closely adapted. Host plant changes are associated with the formation of new species. In these insects, mating is based in part on smell: the set of chemicals that individuals have on their body surfaces. We have shown that divergence in these chemicals is positively correlated with divergence in tendencies to mate. We are now studying the roles of host plants in chemical profiles of individuals, by rearing individuals on different host plants and quantifying their chemical profiles and their tendencies to mate with one another. These studies will uncover the roles of host plant changes, and chemical signals, in the generation of new species of insects. The results will be of general importance to understanding how ecological and behavioral traits are involved in origins of species. (3) Evolution of cognitive traits. Humans have extraordinary cognitive abilities, with regard to both social interactions with other humans, and with regard to non-social abilities such as visual-spatial skills and technology. We have developed a model of human cognition that centres on an important role for tradeoffs between social and non-social abilities and interests, such that enhancements in one domain tend to go along with reductions in the other. This model is supported by a suite of data from psychology, neuroscience and psychiatry, but has yet to be tested directly. We are genotyping large numbers of individuals for a set of genes that are involved in social and non-social cognition, to determine if alternative alleles and genotypes for such genes mediate social, relative to non-social, interests and skills. The results will have important implications for understanding how the human brain works, and how human mental disorders can develop.