Evolutionary Biology BIOL 3350 Dr Lisa Rapaport Lecture 11 Part 2 Notes I II III IV Sexual Selection Parental Investment continued Male male competition in humans A The violence within a tribe ended up in higher reproductive success Brown Laland Borgerhoff Mulder 2009 A The graph with the steeper line has the higher rate of sexual selection because there is more benefit in that set than on the other set B Every additionally mating brings the same reproductive success as the previous mating for fruit flies this is not the same for all species C Female redback spiders take part in sexual suicide they summer salt into the females mouse and they reproduce as the female eats the male thus the male only gets to reproduce once because it is eaten during the process of reproduction D Female guppies store sperm it increases and then it levels off E Intermediate optimum the males who have lots of females lose their reproductive success overtime about 4 females is the optimum for reproductive success F You will not always do better if you mate more it depends on a G number of aspects If there are numerically more females than males then males should emphasize mate selection and be more choosy about who they mate with H If males are investing a lot into each reproductive event then the males should be more selective because any poor reproductive event will cost them more energy I Males should be more selective when there is a high amount of J For the majority males do have more variance in reproductive variance in female quality success than females K Polygynous societies have more variance than monogamous societies Alternative male strategies A Orangutans can go on 2 different developmental tracks B During development orangutans have two different ways to develop one is much larger than the other Male reproductive tactics infanticide A When females are pregnant or lactating and nursing frequently then B their ovulatory cycle is repressed so they cannot get pregnant If a male comes in and kills an offspring the female will become more sexually receptive V Female counterstrategies to infanticide 1 A A male is more likely to mate with one of his female friends rather than a female that he is unfamiliar with VI VII Arbitrary selection R A Fisher A Females who have a preference for males with long tails will produce daughters who have a preference for males with long tails Correlated preference and display equilibrium A Females who have a low preference for the trait will mate with males who have a low expression of the trait B Females who have a high preference for the trait will mate with males who have a high expression of the trait VIII C Thus there is an equilibrium Sexual displays can be costly A Females like loud males and males who produce fast clucks B The bats the prey on these frogs also like what the females like C The 2 forces act against each other which keeps the preferred traits IX How does the good genes model work A The trait is costly to produce and it is an honest reflection of male from going to fixation health and survivability B Red spots signify good health C Unhealthy males are unable to produce these beautiful red spots D Reliable association between the trait and male quality E Females prefer the trait because it is a reliable indicator of the male s health F There is a benefit to the sons and daughters of the females 2