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Sex © BBC 2001, distributed under license from BBC Worldwide Limited |, downloaded from http://dsc.discovery.com/convergence/beasts/photo/slide_05.html Brian O’Meara EEB464 Fall 2015 Learning objectives Why is sex weird? Why has it evolved? How does sex ratio evolve? How does sexual selection evolve? Sex No Sex Two-fold cost Two-fold cost Sex No Sex Half mother’s genes All mother’s genes Groups with parthenogenetic species Cnemidophorus inornatus, C. neomexicanus, C. tigris Stick insects Many plants Aphids Lizards Bees etc... Alistair J. Cullum Sex No sex Wikimedia commons Muller’s ratchet http://www.youtube.com/watch?v=KjH9MwulnV0 Muller’s ratchet Muller’s ratchet ♥ ♥ Jokela et al. The maintenance of sex, clonal dynamics, and host-parasite coevolution in a mixed population of sexual and asexual snails. The American Naturalist (2009) vol. 174 (S1) pp. 43-53 Mean (±SE) proportion of sexual snails (male %) in the shallow-habitat zone of Lake Alexandrina (black) and mean (±SE) prevalence of infection by Microphallus sp. (gray) between 1994 and 2005. Proportion of males corresponds closely to proportion of asexual females and can be used as a surrogate of frequency of sexuals in the population (Jokela et al. 2003). Jokela et al. The maintenance of sex, clonal dynamics, and host-parasite coevolution in a mixed population of sexual and asexual snails. The American Naturalist (2009) vol. 174 (S1) pp. 43-53 http://www.youtube.com/watch?v=hHdaEbcIOSM Even sex ratio What is expected fitness of each of these? Jordal et al. Extraordinary sex ratios and the evolution of male neoteny in sib-mating Ozopemon beetles. Biol J Linn Soc (2002) vol. 75 (3) pp. 353-360 Sexual selection Male-male competition http://www.youtube.com/watch?v=DU4xW79ASsg Female choice http://www.youtube.com/watch?v=GPbWJPsBPdA http://www.youtube.com/watch?v=Wz9h-5z60Xc Ryan 1990 Andersson and Iwasa. Sexual selection. Trends Ecol Evol (1996) vol. 11 (2) pp. 53-58