Lecture 10 - 1 Lecture 10 Linkage and Sex Continued Monday...

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Lecture 10: Linkage and Sex Continued Monday, Jan.27th 1
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Learning Objectives 1. Explain how the Tangled Bank and Red Queen Hypothesis account for the persistence of sexual lineages in competition with asexuals. 2
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Selection and Sex Two related models Variation generated by sex as a way to deal with environmental variability and unpredictability 3
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The Tangled Bank Name from the close of Darwin’s “Origin” “It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.” 4
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The Tangled Bank Spatial heterogeneity in environment If offspring disperse, variation produced by sex increases probability that some will do well in several different patches (like a lottery with different winning tickets in each patch) With limited dispersal, variation will reduce sibling competition 5
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Variation within patches and an asexual fish Sexual populations are more variable, and have broader niches (i.e. feeding niches) Sexuals outcompete asexuals that have narrower niches by using resources unavailable to asexuals (hatched area) Sexual Asexual Resource type Efficiency After Vrijenhoek 1994 6
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Sexuals do have lower dietary overlap among individuals than clones (translation: broader niche for sexuals) Gray and Weeks 2001. Can. J. Fish. Aquat. Sci. Vol. 58, 1313-1318 clones sexual 7
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The Red Queen Name from Lewis Carroll’s “Through the Looking Glass” “… in our country," said Alice, still panting a little, "you'd generally get to somewhere else -- if you ran very fast for a long time, as we've been doing." "A slow sort of country!" said the Queen. "Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!" 8
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The Red Queen Hypothesis “Arms races” between parasite and host, or predator and prey create unpredictable environments = temporal variation
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  • Spring '11
  • DAVIDSON
  • Genetics, variation, VE, Quantitative Traits

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