EEB318H1 Lecture Notes - Lecture 18: Red Queen Hypothesis, Directional Selection, Nasonia
19 Nov 2015
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Sex ratios: they do not have to be 50:50: not a necessary consequence of the. Xy, xx sex determination system e. g. , meiotic drive -- sperm carrying an x chromosome out-competes those with y (or vise versa) -- can skew the sex ratio: sex ratio is subject to frequency- dependent selection. A gene that causes a mother to produce more of the rare sex will be favored. Assume: every mother makes 10 offspring, every mating of offspring makes 10 grandchildren, daughters mate once, sons mate opportunistically, son:daughter ratio is genetically determined, population is very large and mating is random. The mutation increases in frequency, nudging the sex ratio closer to 50:50. Once the population reaches a 50:50 ratio, both genotypes equally t. Nasonia vitripenis: parasitoid, mothers lay dozens of eggs per host, males mate with females as they emerge, occasionally several mothers lay eggs in same host, haplo-diploid sex determination (females 2n, males 1n); mothers control sex of offspring.
