LECTURES:
Deepa Agashe (National Center for Biological Sciences, India)
Title 1: Introduction to genetic variation
Title 2: Introduction to molecular evolution
Title 3: Introduction to population genetics III: Revisiting assumptions
Kavita Jain (Jawaharlal Nehru Centre for Advanced Scientific Research, India)
Title: Introduction to stochastic modeling in evolution
Michael Lynch (Arizona State University, USA)
Title 1: The Population-Genetic Environment
Abstract: Evolution is a population-genetic process governed by the joint forces of mutation, recombination, and random genetic drift, all of which vary by more than four orders of magnitude across the Tree of Life. As these three features define the population-genetic playing field upon which evolution operates, such quantitative knowledge is an essential resource for understanding the limits to all adaptive and nonadaptive evolutionary pathways. More
Title 2: Evolution as a Population-Genetic Process
Abstract: Critical to understanding the evolutionary potential and limitations of phylogenetic lineages is information on the distribution of fitness and phenotypic effects of new mutations. Based on bioenergetic considerations alone, few mutations can have absolutely zero effects, and multiple lines of evidence indicate that the vast majority of mutations are deleterious, with most being very mildly so and the mode being near zero. More
Title 3: Evolution of Cellular Complexity
Abstract: To minimize energetic costs and mutational vulnerability, all other things being equal, natural selection is expected to always favor simplicity over complexity. Yet, many aspects of cell biology are demonstrably over-designed, particularly in eukaryotes, and most notably in multicellular species. More
Susanna Manrubia (Centro Nacional de Biotecnología CNB-CSIC, Spain)
Title: Topological structure of genotype spaces and the dynamics of molecular evolution
Guillaume Martin (Universidad de Montpellier II, France)
Title: Mutation, selection and evolutionary rescue in simple phenotype-fitness landscapes
David Nelson (Harvard University, USA)
Title: Introduction to spatial population genetics
RESEARCH SEMINARS:
Deepa Agashe (National Center for Biological Sciences, India)
Title: Evolutionary impacts of biased mutation spectra
Abstract: Biased mutation spectra are pervasive, with widely varying direction and magnitude of mutational biases that influence genome evolution and adaptation. Why are unbiased spectra rare, and how do such diverse biases evolve? We show that changing the mutation spectrum allows populations to sample previously under-sampled mutational space. The resulting shift in the distribution of fitness effects is advantageous: the beneficial mutation supply and beneficial pleiotropy increase, and deleterious load reduces. More broadly, adaptive walk simulations indicate that the evolution of a mutational bias in an unbiased ancestor is selectively neutral; but reversing the direction of a long-term bias is always selectively favoured. Indeed, spectrum changes in the bacterial phylogeny occur frequently, typically involving reversals of ancestral bias. Thus, shifts in mutation spectra evolve under selection, and can directly alter outcomes of adaptive evolution by facilitating access to beneficial mutations.
Sagar Chakraborty (IIT Kanpur, India)
Title: Nonlinear dynamical perspective of evolutionary games: Insights from a replicator map.
Abstract: Probably the simplest mathematical setting for exploring the frequency-dependent selection process in evolution is the replicator equation whose simplest version, arguably, is one-dimensional time-discrete autonomous. The plethora of complex dynamical outcomes and phenomena that this simple equation brings forth is amazing. We shall introduce the equation; and see how it can be used to comprehend connections between game-theoretic and complex dynamical equilibria. Furthermore, we shall put it to use to explore the migration dilemma: In a population with many demes having cooperating and defecting individuals, no cooperator would migrate to a group dominated by defectors lest it should be exploited by them; but unless the migration takes place, there is no hope for the entire population’s cooperator fraction to increase.
Kritika Garg (Ashoka University, India)
Title: Impact of Quaternary glacial cycles on avifauna in Southeast Asia and Australasia
Abstract: The past 2.6 million years, earth has undergone periodic cycles of cooling and warming. Known as the Quaternary glacial cycles, this periodic fluctuations in global climate have been responsible for biotic diversification. Impact of these glacial cycles in the Northern hemisphere is well characterized. However, little is known about the effect of these cyclic fluctuations on the biota in the tropics, especially on the island system in Southeast Asia and Australasia. Islands are natural laboratories and are excellent models to understand evolution. During the cooling phase of the glacial cycles, water is locked up as ice at the poles, leading to drop in sea levels and formation of land bridges across islands. These land bridges allow for gene flow between isolated island populations and can have a varied impact on demography and speciation patterns, depending on the species biology. In this talk, I will discuss the impacts of the Quaternary glacial cycles on gene flow, demographic history, and speciation on birds in Southeast Asia and Australasia using genome-wide data from both fresh and museum samples.
Kavita Jain (Jawaharlal Nehru Centre for Advanced Scientific Research, India)
Title: Evolution in a changing world
Ullasa Kodandaramaiah (IISER - Thiruvananthapuram, India)
Title: Pupal colour plasticity in two tropical butterflies
Abstract: Phenotypic plasticity refers to the ability of organisms to develop multiple phenotypes in response to varying environmental conditions, and this ability is often adaptive. I will introduce phenotypic plasticity broadly, and discuss when this plasticity is considered adaptive. I will then talk about work in our lab in which we attempt to understand pupal colour plasticity in butterflies. We show that pupae of the butterfly Mycalesis mineus are either green or brown. Pupae on leaves are exclusively green, although green pupae are also found on off-leaf substrates. However, brown pupae are found exclusively away from leaves. This sensitivity of pupal colour to pupation substrate may help pupae avoid detection by predators, and may, therefore, be an example of adaptive plasticity. We show that brown pupae are more likely to form when the butterflies grow in drier conditions, when the surrounding foliage is browner. Furthermore, rearing at high density induces a greater frequency of brown pupae, and I discuss how this may benefit the butterfly. In experiments with another butterfly, Catopsilia pomona, we show how butterflies may be able to sense fine-scale differences in the colour of their substrate, and match their pupal colour accordingly. I end with a brief discussion about challenges and exciting avenues of research on adaptive phenotypic plasticity.
Nishad Matange (IISER Pune, India)
Title: The Evolutionary Logic of Antimicrobial Resistance
Abstract: The evolution of antimicrobial resistance (AMR) is akin to natural selection. Bacterial populations challenged with antibiotics rapidly evolve drug resistance due to the fixation of resistance-conferring mutations. In recent years, genome sequencing has revealed that mutations in bacteria that are selected by antibiotics can have a variety of different mechanisms by which they confer resistance. Further, different mutations that confer resistance show strong genetic interactions, i.e. epistasis, which produces a variety of interesting effects at the cellular and population levels. My group has been trying to understand what the evolutionary logic of mutation fixation is in bacteria challenged with antibiotics. In this talk, I will describe some of our efforts in trying to relate mutation, mechanism, environment and selection using laboratory evolution of drug resistance in E. coli to ultimately understand why certain sequences and combinations of mutations are successful during the evolution of AMR.
Saskya Van Nouhuys (IISc, India)
Title: Spatio-temporal dynamics of interacting species across a fragmented and changing landscape
Abstract: Species in a community, even those that interact closely, experience their shared landscape differently because they have different dispersal abilities and availability of their limiting resources vary. Using long-term survey and population genetic markers I show the impact of habitat fragmentation and environmental change on a butterfly, two of its parasitoids, and a hyperparasitoid in Åland, Finland. Climate change has led to increased spatial synchrony of butterfly population dynamics, resulting in large-scale destabilizing population fluctuation. High trophic level species such as parasitoids are disproportionally affected by environmental change because they depend on their unstable host as a resources. The vulnerability of many parasitoid species is amplified because of their sex determination mechanism, which leads to male sterility with inbreeding when populations become small. In this system genetic structures of the parasitoid populations show that while one dispersive species has so far managed to ride out the storm, it’s own parasitoid species, a hyperparasitoid, may not.
Samay Pande (IISc, India)
Title: Bacterial predator mediated enrichment of antibiotic resistance in complex microbial communities
Himani Sachdeva (University of Vienna, Austria)
Title: Effects of linkage disequilibria and genetic drift on polygenic local adaptation in sub-divided populations.
Abstract: Environmental adaptation often involves spatially heterogeneous selection at many genetic loci. Thus, the evolutionary consequences of hybridisation between populations adapted to different environments depend on the coupled dynamics of multiple loci under selection, migration and genetic drift, making them challenging to predict. In this talk, I will introduce theoretical approximations that accurately capture the effect of such coupling on allele frequencies at individual loci, while also accounting for the stochastic effects of genetic drift. These approximations will then be used to analyse hybridisation in a subdivided population that includes multiple habitats under divergent selection. This analysis clarifies the conditions under which associations between immigrating deleterious alleles allow these to be collectively eliminated despite drift, causing sharper and (under certain conditions) shifted migration thresholds for the collapse of local adaptation. I will also briefly discuss how local adaptation influences neutral (relative) divergence, resulting in counter-intuitive patterns of FST.
Supreet Saini (IIT-Bombay, India)
Title: An example of metabolic cooperation driving same sex fusion in yeast.
Abstract: Metabolic cooperation is thought to be ubiquitous among microbial populations in the wild. Laboratory studies have demonstrated that, in several contexts, metabolic cooperation can lead to faster growth of a population. Several theoretical frameworks have also been proposed to explain how cooperation is adaptive. In this talk, I will discuss an observation of same sex ("a-a") fusion in yeast, in a particular experimental context. The fusion event is contingent on (a) metabolic cooperation, (b) cell-cell proximity, and (c) the cells crossing an energy threshold barrier. I will also discuss the wider implications of this novel mechanism of cooperation.
Sudipta Tung (Ashoka University, India)
Title: Evolution of dispersal components, kernel and syndromes: the Drosophila story
Abstract: Dispersal is a central life-history trait. Consequently, a variation in dispersal properties is expected to modulate other vital traits of an individual. Although several past studies have alluded to the evolution of dispersal in the context of contemporary rapid habitat fragmentation, habitat destruction and climate change, the exact nature of the changes in life- history, behavioural and physiological traits in conjunction with dispersal evolution is not clear. Predicting these changes becomes further difficult for individuals with stage-structured life-history, where alteration of a trait in one life-stage does not always imply a similar change in other stages. Here, using four outbred laboratory populations of Drosophila melanogaster, selected for increased dispersal for >70 generations, we have investigated the impact of dispersal evolution on an array of larval and adult traits. We showed that larval activity, pre-adult developmental time and larval viability did not alter in response to dispersal evolution. In contrast, locomotor activity, exploratory tendency and aggression in adults were significantly greater in dispersal-selected populations. Mating behaviours in both the sexes seem to remain unaffected by this selection. Among adult life-history traits, body size, fecundity, lifespan and starvation resistance remained unaltered, but interestingly, desiccation resistance of the selected populations had reduced significantly despite the level of stored glycogen remained identical to the controls. Furthermore, assays after relaxing the selection pressure for 20 generations reveal a negligible cost of evolved dispersal and associated traits. These results have serious implications on species invasion, range expansion and ecosystem stability in this changing world.