Developmental plasticity, Slides of Evolutionary biology

Download Developmental plasticity and more Slides Evolutionary biology in PDF only on Docsity! NES2309 – Evolutionary Biology Sexual selection • Ingredients for sexual selection • (In)direct sexual selection Quantitative genetics • Artificial selection and experimental evolution • Heritability and the Price Equation • Phenotypic plasticity • Individual- and group-level selection Predicting evolution of strategies • Game theory Life • Origins of life • Geological change and evolution • Evidence of evolution • Definition of life Predicting trait evolution with developmental feedback • Developmental plasticity • Pace of life Predicting trait evolution with population feedback • Adaptive dynamics Molecular evolution • Population genetics • Population structure and history • Allele dynamics • Rates of molecular evolution Evolutionary rescue What is evolution? Tools to measure and predict evolution of traits Understanding the evolution of exaggerated traits Understanding the role of trait evolution in ecology Understanding the evolution of genes and genomes Predicting trait evolution NES2309 Evolutionary Biology module outline Coexistence of different genetic strategies: Mixed ESS Remember: mixed ESS (haw-dove game): • If V < C, we have a mixed ESS: • A population with equilibrium frequencies of Hawks and Doves • (Or: a population of individuals who play Hawk some percentage of the time and Dove some percentage of the time can also be stable) • But what maintains this equilibrium frequency of Hawks and Doves? Mixed ESS in Coho salmon Life cycle: : Spawning (fall) erm M Ns (spring) Diagram of general Pacific salmon and steelhead life history phases Mixed ESS in Coho salmon HOOKNOSE Migration to Ocean JACK Migrates back to river early, or stays in river Frequency dependent selection will equate reproductive success of two morphs/genetic strategies Mixed ESS in Coho salmon Shuster & Wade 1991; Nature 350:608-610 3 male morphs: γ β α Mixed ESS in marine isopod (trimorphism) • 3 alleles with dominance relationship β > γ > α • αα males: large, control harems of females inside sponges • ββ, βα, βγ males: female mimics, hide among αα males’ harems • γγ, γα males: tiny “sperm bombs” who hide in crevices of sponges, “strafe” copulating pairs with sperm Shuster & Wade 1991; Nature 350:608-610 3 male morphs: γ β α Mixed ESS in marine isopod (trimorphism) At frequencies observed in the field, average number of mates/male equal across strategies (required for coexistence of genetic strategies) Shuster & Wade 1991; Nature 350:608-610 Equal reproductive succes? • Lethality associated with satellite allele (applies to satellites and feaders) • Satellites and faeders have equal/lower mating rates than independents • Satellites and faeders have larger testes: better in sperm competition? Mixed ESS in the ruff (trimorphism) But what if trait expression is not purely determined by genes? Genotypic value (G): overall effect of all genes carried by individual on its phenotype. It includes: Additive effects of genes (A): sum of individual effects of alleles. Dominance effects of genes (D): interaction between alleles at the same gene Epistatic effects of genes (I): interaction between alleles at different genes G = A + D + I P = A+ D + I + E P = G + E • Quantitative traits (see week 2): Conditional strategy Bullhorned dung beetle Onthophagus taurus Dung beetle males differ in horn morphology (weapons) depending on nutrition during ontogeny Conditional strategy Size reached during ontogeny determines size of male weaponry (A) Hormone signal (B) Sensitive period (C) Threshold time Emlen 2008: In: Alternative Reproductive Tactics by Oliveira et al. (eds) 2008 Male morph expression depends on whether males, during development, cross a threshold body size (switch point), manifested as a threshold of larval sensitivity to a hormone signal During sensitive period, hormone level is assessed against threshold, eliciting all-or-none response Hormone level depends on environmental conditions such as crowding, nutrition, growth and body size, and may be heritable Conditional strategy SUMMARY: in most, if not all conditional strategies: • Fitnesses of alternative phenotypes are unequal (as opposed to fitnesses of genetic strategies in a mixed ESS, which are equal in equilibrium) • We can use quantitative genetics to study threshold evolution and coexistence using the ‘environmental threshold model’ because: • Phenotype expression depends on a threshold body size (switch point) (environmental effect) • The threshold is heritable (genetic effect) Environmental threshold model Individuals larger than the switch point body size develop phenotype A Individuals smaller than the switch point body size develop into phenotype B The threshold (or switch point) is the body size at which the fitness functions cross Deere & Smallegange 2023 https://doi.org/10.1101/2023.02.06.527265 t* Fr eq ue nc y Fi tn es s Body size Here 50% of the population develop phenotype B, the other 50% phenotype A An example Rhizoglyphus echinopus Male morph expression depends on: - Size during ontogeny (large -> fighter) - Population density (low -> more fighters) • Framework: Environmental threshold model • Hypothesis: Selection against fighters shifts mean switchpoint upwards (to larger size) • Test this hypothesis in multigenerational experiment Fi tn es s t* Fr eq ue nc y Body size Tomkins et al. 2011: Curr Biol Environmental threshold model An example Tomkins et al. 2011: Curr Biol Rhizoglyphus echinopus fighters cannot climb straws very well because of their fighter legs • Fighters are not good walkers • Selection against fighters imposed by changing habitat complexity • Experiment lasted 10 generations complex habitat simple habitat also shown in NES2305 Environmental threshold model An example Tomkins et al. 2011: Curr Biol Rhizoglyphus echinopus Results: Evolutionary shift in the threshold in predicted direction (towards larger size) Pr ob ab ilit y of b ei ng a fi gh te r complex simple low density high density simple, complex Relative juvenile size Environmental threshold model Conditional strategy: anticipatory developmental plasticity (QG) • Daphnia (top-left) grow ‘helmets’ if they perceive cues that inform on predator presence • Some salamanders (top-right) metamorphose, or not, in response to cues signalling population density • Some butterflies show different colour morphs in response to environmental cues • The plant in the bottom-right corner develops different leave types depending on whether it grows above or below the water. Conditional strategy: anticipatory developmental plasticity (QG) What do they all have in common? Fitness proxy is adult performance Can we ignore ontogeny and development? The role of development in the conditional strategy Hercules beetles fighting Hercules beetle ontogeny (https://www.youtube.com/watch?v=AFbu21AGSho) Reproductive state Develop structures to prepare for reproduction Protect important physiological processes Acquire resources to prepare for reproduction Escape from risky non-reproductive state Trade-offTrade-off Mitigating developmental plasticity (stress-mitigating) Information Mating niche 1 Mating niche 2Anticipatory developmental plasticity (alternative mating tactics) Developmental perspective: Focus lies on process of development Genotype-specified reaction norm perspective: Focus lies on outcome of development Two types of selection pressures explain conditional strategy Reproductive state Mitigating developmental plasticity (stress-mitigating) Information Mating niche 1 Mating niche 2Anticipatory developmental plasticity (alternative mating tactics) Resource budget Fi tn es s ( vi ab ili ty an d re pr od uc tio n) fu ll lif e cy cl e Fighter Scrambler Body/weapon sizeFi tn es s ( m at in g su cc es s) Fighter Scrambler Two types of selection pressures explain conditional strategy - Evolutionary change generally defined as genetic changes over time - But: the environment imposes selection on phenotypes - The role of the environment in evolutionary change is captured in quantitative genetics, where the environment affects the expression of genotypes - What is missing?? • Development can be a crucial player in evolutionary change • For one, it can transform the response to selection and thus break the genotype-phenotype link Laland et al. 2015 Proceedings B (available on canvas week 1) Broadening our view of evolutionary explanations slide from week 1! Key evolutionary concepts Figure from Yuen Sizhe et al. 2023. Epigenetic opportunities for evolutionary computation R. Soc. open sci. 10 221256221256 Broadening our view of evolutionary explanations “Plasticity is well accepted in developmental biology [...] and yet, to biologists in many other fields, it is virtually unknown. Undergraduates beginning their education are unlikely to hear anything about it.” Broadening our view of evolutionary explanations See this week’s Discussion on canvas Broadening our view of evolutionary explanations on why sneakers exist • Sneakers are generally described as ‘making the best of a bad job’ • Males in bad condition salvage fitness by e.g.: • reducing maturation time (e.g. bulb mites) • accelerating development relative to the slow growth trajectory • skipping developmental stages to mature precocially (e.g. coho salmon) Sneaker benefit through stress-mitigating mechanism Broadening our view of evolutionary explanations on why sneakers exist Mitigating developmental plasticity (see earlier slides): Males that, under stress, salvage somatic functioning by developing into a scrambler, as opposed to suffering great, perhaps fatal costs when developing into a fighter Fighter Scrambler Bulb mite Rhizoglyphus robini Rhebergen et al. 2022, Ecol & Evol Final instar size Rich food Fighter Scrambler Bulb mite Rhizoglyphus robini Poor food Final instar size Fighters take longer to mature Fighter legs are costly to develop Broadening our view of evolutionary explanations on why sneakers exist Final instar size Nutritionally rich food Nutritionally poor food Final instar size - Size threshold for phenotype expression strongly depends on nutrition - Size threshold is cued by resource budget Rhebergen et al. 2022, Ecol & Evol Broadening our view of evolutionary explanations on why sneakers exist - Size threshold for phenotype expression strongly depends on nutrition - Size threshold is cued by resource budget - Phenotype expression is predicted by body size and growth immediately prior to the final moulting stage - Males accelerate metamorphosis when perceiving decline in food: adaptive, plastic response Coexistence explained by males that, under stress, salvage somatic functioning by developing into a scrambler, as opposed to suffering great, perhaps fatal costs when developing into a fighter Broadening our view of evolutionary explanations on why sneakers exist Alcock et al. 1977: Am Nat females produce both morphs Centris pallida Maximising fitness of the mother: 3 fighter offspring = 6 sneaker offspring Broadening our view of evolutionary explanations on why sneakers exist Bonus material: conditional strategy with three phenotypes Rowland and Emlen 2009, Science Odontolabis cuvera (stag beetle) Bonus material: conditional strategy with three phenotypes Bonus material: do alternative reproductive tactics occur in females? • Limited evidence; why? • ARTs typically arise in taxa with strong sexual selection • In what sex is sexual selection typically strongest? Steeper BG means stronger sexual selection on the limited sex Bateman’s Gradient Week 9 – Developmental plasticity To do this week: • Discussion board (on canvas): Does evolutionary biology need a rethink? • Quiz (on canvas) We discussed: • The differences between a mixed ESS and a conditional strategy • How frequency-dependence maintains a mixed ESS, and how crossing fitness functions maintain a conditional strategy • The difference between anticipatory and mitigating developmental plasticity (both of which are a conditional strategy)