These two chapters deal with some fundamental topics in quantitative genetics and evolutionary biology. Again, they are fairly technical in the details and sometimes the methods are a bit outdated, but the questions that are covered are still relevant and of great interest to evolutionary biologists.
In chapter 22, I would especially like to highlight Fig. 22.1 (p. 658) which shows how genotype-by-environment interactions ("G x E":s) can arise in several different ways, i. e. changed additive genetic variances between environments (B), changed rank ordering of genotypes (C) or a combination of changed additive genetic variances and changed rank ordering in the different environments (D). Discuss the evolutionary consequences of these different settings in terms of maintenance of genetic variation in heterogeneous environments. Is there any principal difference in terms of evolutionary consequences between scenario B and C, for instance?
(Hint: think of the character being "Fitness" (Y-axis), instead of an ordinary trait to answer this question).
In chapter 24, there is a principally interesting discussion about sex-specific additive genetic variances and the central role of the intersexual genetic correlation in "constraining" the evolution of sexual dimorphism (SD). How much of an "absolute" genetic constraint do you think the intersexual genetic correlation really is? Can sexual dimorphism ever evolve if the intersexual genetic correlation is equal to one? Can it become negative, and if so, how? And why would it become negative?
What is the relationship between sex-specific genetic variances and the intersexual genetic correlation? Can the sex-specific genetic variances differ between males and females, and the intersexual genetic correlation still be equal to one? Or is it impossible?
Also, try to think of the two sexes as different "environments" and the intersexual genetic correlation as the between-environment genetic correlation, as it was formulated by Falconer, and which is also discussed in chapter 22 (return to Fig. 22.1 and replace "Environment 1" with males and "Environment 2" with females.
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