Evolution will be fast when selection is strong and heritability high. Native to Florida: Balloon vine Seed deep inside of fruit. Introduced to Florida: Golden rain tree. Fruit not so puffy. Soapberry bugs feeding on introduced (flatter) fruits have shorter mouthparts than those that feed on native (puffier) fruits. Length of mouthparts (mm) Number of bugs Directional selection has caused evolution of shorter mouthparts in soapberry bugs. Length of mouthparts (mm) Rain tree Introduced in the 1930s. Date that insect was collected Directional selection on cliff swallows, caused by a winter storm. Cold spells are rare and large swallows less agile. Will selection continue to favor increase in body size? Downy Woodpecker on Goldenrod Gall by Robert Bateman Gall = structure produced by plant in response to insect secretion (mimics plant hormone) Insect larva develops inside Goldenrod galls are made by a fly; the fly can control, to some extent, the size of the gall. Birds like to eat the fly larva, and they prefer large galls. Should selection favor small galls, so the flies can escape Predation by birds? No, because a wasp parasite prefers small galls. The wasp larva eats the fly larva. EEEeeeew! Stabilizing selection reduces variation Gall size # of individuals Wasp parasite Bird predators (big)Benthic form eats invertebrates on lake bottom. Sticklebacks -- disruptive selection on feeding morphology (little) Limnetic form eats plankton in surface waters. F1 progeny of these forms are bad at feeding anywhere! Disruptive selection can lead to speciation. Natural selection cant explain sexual dimorphism. Watch film clip. Batemans principle: Female RS typically limited by resources Male RS typically limited by access to mates. Number of mates Reproductive success males females Male elephant seals fight to control territory, and Sexual selection has two components: Male-male competition (for access to mates) Female choice (to obtain best mates possible) Bright beak color demonstrates health in birds. Carotenoids used to fight infection. Bird on right has duller bill because carotenoids diverted to fight infection. Do females prefer to mate with males who have bright beaks? (Used zebra finches for this experiment; easier to handle. 9/10 females chose the bright males. Sexual dimorphism of body size in humans is about 10%. Less than in our ancestors. Humans also differ from other species in the extent to which paternal care increases male reproductive success. Dont uncritically apply sexual selection theory to humans.