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Sex
Brian O’MearaEEB464 Fall 2015
© BBC 2001, distributed under license from BBC Worldwide Limited |, downloaded from http://dsc.discovery.com/convergence/beasts/photo/slide_05.html
Learning objectivesWhy 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
Stick insectsMany plants
AphidsLizardsBeesetc...
Groups with parthenogenetic species
Alistair J. Cullum
Cnemidophorus inornatus, C. neomexicanus, C. tigris
No sex
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
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).
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
Andersson and Iwasa. Sexual selection. Trends Ecol Evol (1996) vol. 11 (2) pp. 53-58
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