Variation in mortality: grey squirrels Requirements for natural selection Mass 200 g Mate 2x / year 4-8 offspring per litter Mass of earth: 5.97 x 1027 g Assume reproduction starts at 6 months (9 in reality) Assume adults die after 2 litters (20 years in zoos) How long until squirrels equal mass of earth? 1 28 24 35 20 16 30 12 8 25 4 0 20 9 11131517192123 28 15 24 20 10 16 5 12 8 0 4 0 0 25 50 75 100 125 150 175 200 225 9 11131517192123 Galen, Zimmer and Newport, 1987. From Galen 1989 Evidence for Heritability Gurevitch 1992. Galen, 1996 2 Floral diameter (mm) Galen and Newport, 1987 Galen 1989 Effect of natural selection: trait mean shifts Bee pollinations Control pollinations Corolla length Corolla length Galen, 1996 3 Evolutionary Longhand Modes of selection Gen. 0 Gen. 1 Gen. 2 Shorthand: Sky pilots with large flowers in the tundra are adapted to bumblebee pollination freq. Longhand: trait, z freq. freq. trait, z trait, z Mode of selection Misconceptions freq. freq. trait, z trait, z freq. freq. trait, z trait, z 4 Sky pilot flowers evolved to become larger in order to colonize the tundra habitat. Men who dive for pearls evolve to have a larger lung capacity. Some species, such as elephants, have only one offspring every five years. This evolved to protect the species from the problems of overpopulation. When the immune system can successfully fight off a disease, new mutations arise that may allow the disease to elude the immune system. [Advanced: why can’t you substitute “groups” for “individuals” in evolutionary longhand and get evolution of groups?] Cannings and Cannings. 1999. 5 References Cannings, R. and Cannings, S. 1999. Geology of British Columbia. Douglas and McIntyre, Vancouver, BC. Galen, C. 1989. Measuring pollinator-mediated selection on morphometric floral traits: bumblebees and the alpine sky pilot, Polemonium viscosum. Evolution 43:882-890. Galen, C. 1996. Rates of floral evolution: adaptation to bumblebee pollination in an alpine wildflower, Polemonium viscosum. Evolution 50:120-125. Galen, C and Newport, M. 1987. Bumble bee behavior and selection on flower size in the sky pilot, Polemonium viscosum. Oecologia 74:20-23. Galen, C, Zimmer, K, and Newport, M. 1987. Pollination in floral scent morphs of Polemonium viscosum: a mechanism for disruptive selection on flower size. Evolution 41: 591-606. Gurevitch, J. 1992. Sources of variation in leaf shape in two populations of Achillea lanulosa. Genetics 130:385-294. Wright, J., Stanton, M, and Scherson, R. 2006. Local adaptation to serpentine and non-serpentine soils in Collinsia verna. Evolutionary ecology research 8:1-21. 6.