Sexual Selection & Secondary Characters Potential for Sexual Selection: Ratio Variance in Reproductive Success, Lesser PI Sex / Greater PI Sex Monogamy.

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Sexual Selection & Secondary Characters Potential for Sexual Selection: Ratio Variance in Reproductive Success, Lesser PI Sex / Greater PI Sex Monogamy vs Polygyny (Polyandry)

Sexual Selection & Secondary Characters J. L. Hoogland, D. W. Foltz (1982) Variance in Male and Female Reproductive Success in Harem-Polygynous Mammal, the Black-Tailed Prairie Dog (Sciuridae: Cynomys ludovicianus) Behav. Ecol. Socio. 11, Colonial rodent, coterie (harem) Operational sex ratio < 1 Blood-protein polymorphism, electrophoresis: parentage

Males: Greater Variance in Reproduction Same pattern, 4 of 5 years studied

Black-Tailed Prairie Dog Males disperse from natal colony; Females philopatric: male-male competition, access to coterie Female choice: “Ranking adult male” (RAM) in multi-male coteries

Sexual Selection & Secondary Characters V[Male Rep Success] > V[Female Rep Success] Sexual Selection More Intense in Males: Benefit/Cost of Secondary Sexual Characters in Males

Secondary Sexual Characters Females: Likely Choose Males with Greater PI, Higher Quality Resources, … But when Male PI lower Bright Colors, Ornaments, Elaborate Displays of Males Common Sexual Selection: Advance Mating Success & Enhance Fitness, Despite Cost

Breden, F., Stoner, G Nature 329:831. Trinidad guppy (Poecilia reticulata): dichromatism, males brightly colored

Breden, F., Storer, G Nature 329:831. Most streams: Females prefer brighter males as mates, AND Brighter males suffer more predation. Exception: Intense predation (cost); male coloration reduced “Fits;” but why do females prefer brighter males?

Secondary Sexual Characters R.A. Fisher: runaway process of sexual selection IF secondary sexual characteristic M expressed in one sex genetically correlated with preference for this trait in the other sex, mate choice for M also selects for strong preference. Self-reinforcing (runaway) until another force balances sexual selection.

Runaway process of sexual selection One Allele: bright color in male genome preference for bright color in female genome Fisher’s “genetic correlation” Balance: mortality?

Secondary Sexual Characters & Female Choice “Sexy Son” Hypothesis: Given Female Preference, Female Chooses Male Genes Likely to Render Her Sons Attractive Doesn’t Answer Question ?

Secondary Sexual Characters & female Choice “Good Genes” Hypothesis: Females Choose Mates with Genes Increasing Mean Fitness of her Offspring Circular? Correlates of good genes?