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According to natural selection, what are both females and males selected to do ?. Survive and reproduce Certain traits favor survival and reproduction. When those traits have a genetic basis, they are passed on to successful offspring.
implies no durable associations, mating a matter of temporary contact (also called polygynandry)
Female resources clumped, males can defend these and attract females
When females cannot be herded, or guarded in one place, males have to find them, or attract them from far away.
Flightless firefly (brief call by female)
Male wood frogs (all females receptive on same single night each year)
Why the group display?
Display where females tend to aggregate (“hot spot”)
Display near dominant male (“hot shot”)
Display with other males so females can pick among rivals (“female preference”)
Display in groups to avoid predators (“safety in numbers”)
When females remain receptive after mating
or are widely dispersed/hard to find ---
guard your mate.
When offspring survival requires two parents
assist your mate.
Mating with one partner for breeding season
Rare in mammals
More common in birds - why?
Male birds can incubate, feed young
Young require two parents.
20%-50% of nestlings in songbird nests are from EPCs.
Advantage to males of promiscuity?
Advantage to females of promiscuity?
Matings outside pair bond:
Higher hatch rate (redwing blackbirds)
Fewer still born (adders)
Blue tit bird - males of stay-at -home females are more attractive
Experiment 1 (Zeh): when females mated to several males. Results:
Less embryo failure
Higher offspring survival
Experiment 2 (Zeh): when different females mated to same males. Results:
No “good” and “dud” males.
Depended on particular male-female genetic match or genetic compatibility .
Diverse mating types within the same species
Dunnocks eat seed and small insects.
Males mate-guard a group of females if food is concentrated enough.
More concentrated food, more monogamy.
Experiment 1. Added food in clumps over years.
Female territory size decreased by 40 feet.
Males guarded females in territory.
Female monogamous to one males (polygyny)
But… female behavior interfered with male ability to monopolize females.
Females chased off other females (from food and male parental care).
Females solicited copulations from “beta” males.
Illustrates how distribution of females and resources and conflict between the sexes affects evolution of mating systems.