35-Sex ratio and sex allocation Flashcards
Why is the sex ratio and outcome of frequency dependent selection?
As the portion of females in a sexually reproducing population decreases, one would expect each female to have more mating opportunities and a higher fitness. Likewise, as the portion of males in the population decreases, one would expect male fitness to increase. The tension between these two effects typically brings the sex ratio to some equilibrium value
What does the shaw-mohler equation say in words?
Total fitness of mom is the sum of that of her surviving sons and daughters relative to that of surviving sons and daughters of other females in the population.
What are the examples of how plants and animals allocate sex? How is fitness involved?
Attractive secondary sexual characters or parental quality - produce more sons when mated with males of exceptional quality. Also, sex change in fish represents change in sex allocation.
What is local mate competition and how does that affect sex ration?
Mating may not occur randomly among members of a large population. Wasps: one or a few females emerge from a single host and almost immediately mate with each other. The daughters then disperse in search of new hosts. Within each host (group), the sex ratio favored by individual selection is 0.5. However, groups founded by female-biased genotypes contribute more individuals and genes to the population as a whole than groups founded by unbiased genotypes. This can result in female-biased sex ratios. The greater the number of founders of a group, the more nearly even the optimal sex ratio should be. In the hymenoptera, haploid males have all genes identical by descent from
their diploid mother. Therefore, as inbreeding increases, mothers will transmit more genes to subsequent generations through their daughters
