BIOL 201 1st Edition Lecture 7Outline of Previous LectureI. Genetic Drift and Natural Selectiona. Similaritiesb. DifferencesII. ExamplesIII. Genetic Drifta. Definitionb. Sampling errorIV. FixationV. Bottlenecks and Founder’s Effecta. Bottlenecksb. Founder’s EffectVI. Effective Population Sizea. Definitionb. Equationsc. ExamplesVII. Group QuestionsVIII. Coalescent TheoryOutline of Current LectureI. Additions to last lectureII. Mating Systemsa. Monogamyb. Polygamyi. Polygynyii. PolyandryIII. Operational sex ratioIV. Male-male competitiona. Ways males can competeb. Traits that formV. Female choice- direct selectiona. definitionb. ExamplesVI. Female choice- indirect selectiona. definitionb. Good genesi. Handicap hypothesisii. Parasite hypothesisiii. Arbitrary male hypothesisCurrent LectureI. Additions to last lecturei. Selection doesn’t always trump drift.ii. Can tell when it does; if NeS>> 1 then selection will dominate.iii. If NeS<< 1 then drift will dominate so some random outcome will happen. Not necessarily the opposite of selection.iv. Ne with population size changing over time has m- number of generations while the thing in parentheses is the harmonic meanv. Harmonic mean tends to give most influence to the smallest population size involved.vi. Assume even sex ration for this equation and assume constant population size over time for the other equationvii. Nm is number of males who mated not all males in population.viii. Overlapping generations can affect effective population sizes aswell; possibility of mating with parents and grandparents.ix. Drift will ALWAYS reduce variation regardless of population size. II. Mating Systemsa. Monogamy: equal # of males and females will contribute to the next generation because they’re paired, pretty rare, not much opp for evolution to act to improve mating success because everyone has the same chances of matingi. Most birds are monogamous because they lay eggsii. If indiv. of the opposite sex are hard to find then monogamy is best choiceb. Polygamy: unequal # of males and females contributing gametes to zygotes; more common than monogamyi. Polygyny: males mate with more than 1 female so some males don’t get to mate at all; fewer males contribute gametes than females do to zygotes of next generation1. Males varying a lot more in mating success than females2. Types:a. Scramble competition polygyny: males race to get females ex: horseshoe crabsb. Female defense polygyny: females group up and there’s one male that joins to defend the group ex; batsc. Resource defense polygyny: males defend an area/resource and they mate with females who come to their area in exchange for sharing their resources; like prostitutiond. Lek polygyny: lek is mating ground where males defend little patches with no resources; females come by and just pick one to mate with; some males get picked and some don’tii. Polyandry: females mate with more than one male so more males than females contribute gametes to offspring; some females don’t mate and males mate pretty evenly1. Not very common and males raise the offspring in some casesIII. Operational sex ratio: ration of males to females available to mate at one time; skewed towards malesi. w/birds it makes sense that there are more males available because females have to lay eggs and watch over them and their youngii. skew is true for animals with pregnancies like mammalsiii. Peacocks are like poster child of sexual selection1. Bright colors usually for sexual selection if not warning call and this is the case with peacocks.2. Have to mate because fitness= survival and reproduction so genes have no where to go if you don’t reproduceIV. Male-male competitiona. Ways males can compete: male control of resources, scramble competition, males guard femalesi. All link to types of polygynyii. Don’t need resources to survive always but do need them to mate in most instancesb. Traits that form: male weaponry like horns to intimidate others or fight themV. Female choice- direct selectiona. Definition- frequency of an allele changes due to selection directly favoring iti. If female prefers a certain type of male because their traits increase their survival or fecundity and that’s a direct benefitb. Examplesi. Direct benefit- nuptial gift1. Shows that females prefer that males bring them a larger nuptial gift and will let them mate longer2. Beneficial to females because gift – prey she’s eating which increases the proteins needed to lay eggs; increases their fecundityii. Direct benefit- spermatophore1. Spermatophore is a nuptial gift of proteins in sperm thatthe females eat part of to help them lay more eggsiii. Direct benefit- males provide territory1. Bigger males can control more and better territory.2. Females that lay eggs in these areas with big males have lower embryo mortality rates because their babies can survive better in better territories. VI. Female choice- indirect selectiona. Definition- frequency of an allele changes only because it is geneticallyassociated with another allele (at another locus) that is under selectioni. Genetic association: statistical association btwn traits regardless of if the traits are on the same chromosome or not; can be called genetic correlation, statistical correlation, or linkage disequilibriumii. Chose because of good genes or arbitrary male and there is no direct benefit to the femaleb. Good genes- males differ in genetic quality which is heritable and indicated by male ornaments. Females choosing males w/ornaments have offspring with better genes. Ex: peacocksi. Ornaments: tail lengths, fancy spots, pheromones, call volumeii. Indirect benefit because female is not necessarily improving her survival or fecundity; she is improving the quality of her offspring’s genesiii. If male has allele for quality genes then most likely also has allele for the ornament that grabs a female’s attention so her offspring tend to have more quality genes.iv. Handicap hypothesis: elaborate ornaments are a handicap to male survival, males can only support if have high genetic quality1. Fitness- survival times reproduction so it’s worth it to have expensive ornament that hurts survival because it will increase chances for reproductionv. Parasite hypothesis: males with low parasite load can support elaborate ornaments, parasite resistance is heritable1. Females who chose males with elaborate ornaments will have offspring with parasite resistancevi. Arbitrary male