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Lecture 11 - BIO220

Consider virtually all interactions between the sexes

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Unformatted text preview: interests and sexually antagonistic selection How wide spread is sexual conflict I? Consider virtually all interactions between the sexes. In the absence of life-long genetic monogamy, all will be subject to conflict. Parental Investment Theory (R.L. Trivers) • Sexes differ in their reproductive investment • Members of the sex that invest little in offspring will compete among themselves to mate with members of the sex that invest more in offspring • Male (female) competition and female (male) choice Geoff Parker Sexual conflict 1. The evolutionary interests of the sexes differ 2. Therefore selection acting on the two sexes in an interaction (or on a single shared trait) will often be antagonistic Benefit to Males: Mating rate and duration Costs to female: -More eggs more Mate choice -Longer mating, Sperm use o ffspring l onger predation Egg laying rate -No parental r isk Parental investment i nvestment :) -More eggs, more There will be battles over these interactions, c ost! with the potential for evolutionary arms races. -More investment more cost -Evidently, the sexes have very, very different evolutionary i nterests Waterstriders Gigantometra gigas Gerris Rheumatobates -Flies -Females resist mating, males jump on top of them Antagonistic Adaptations in Rheumatobates Sexual Conflict: sexually antagonistic selection on a “shared trait”. Often resulting from sexual selection. M F w w Male antennae Mating Rate Female antennae -Male appendages are modified to hold the female -Every appendage is sexually dimorphic Mating Rate Mating Rate -Males benefit linearly when it comes to mating: more mating = more benefit -Females benefit maximally when mating rate is intermediate (not too high, not too low) -It is at this point where the mating costs become high for the f emale: this is where CONFLICT begins 4 2/13/2013 -When females become mated MORE than one time in several d ays, it becomes costly to the female -The female cannot look for food during mating (men are on t op of them) Hunger effects on resistance Economics of mating in females Mating is costly (beyond once per several days) • predation • energy expenditure • for...
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