Evolution of Mating Systems Flashcards
mating system
how mates are acquired, the type of pair bonds. Summarizes who mates with who, and how.
monogamy
1 male and 1 female mate in a pair bond.
male has 1 female within his territory.
there is social and genetic monogamy
polygyny
1 male, 2+ females. One male forms pair bonds with multiple females.
resource defence polygyny
female defence polygyny
lek polygyny
polyandry
1 female, 2+ males. One female forms multiple pair bonds with several males.
several males may defend one female’s territory
female may defend multiple male territories.
promiscuity
2+ males or females
extra pair copulations
can only occur in pair bonded species. copulations that occur outside the pair
Bateman’s Principle
female reproductive success is limited by access to resources, male reproductive success is limited by access to females
what does the Bateman’s Principle say about mating system organization?
females disperse to where the resources are, and then males will disperse to where the females are. this dispersal pattern makes up the mating system.
ecological factors (resources) dictate the mating system. Highly clumped resources means highly clumped females/mates for the male. It is up to the male to attempt to monopolize these females. (leads to polygyny)
it is harder to monopolize widely distributed females, and this leads to more monogamy.
(depends on size of territory the male can defend and how many females live within it)
synchronous breeding/brief receptivity
all females are sexually active and receptive to breeding at the same time
asynchronous breeding/ prolonged receptivity
females are sexually receptive at different times.
female receptivity duration
influences the temporal distribution of mates, and the mating system
factors influencing mating systems
male and female dispersal patterns
cost and benefits of mate guarding/defence
(size of territory, receptivity duration)
ecology and biology of species determine mating system
social mating system is the same as genetic mating system
false.
social mating is based on observed interactions between individuals, and can be inaccurate
genetic mating system is based on parentage of offspring (DNA)
why does male monogamy exist?
mate assistance (males get net benefit from assisting)
mate guarding (pays to guard when few other opportunities exist)
female enforcement (females chase off other females, or attack males attempting to mate with other females. female imposed monogamy)
maintaining monogamy in dikdiks
both sexes scent mark, and males will scent mark over females to hide the fact that there is a reproductive female from other males.
males will attack females that leave the territory.
resource defence polygyny
males control females indirectly by monopolizing critical resources that females need. Males can become polygynous if they hold onto the resources, or they need to care for young.
usually many female territories in one larger male territory.
female defence polygyny
males directly control females. When females are social, their movements are predictable, and males may defend groups of females seasonally or permanently.
many females live within a male’s territory
lek polygyny
no paternal care
males aggregate at traditional sites (leks) to display
lek sites provide no essential resources to female other than male sperm
females select a mate from the displaying males. The aggregation of males allows for comparison and accurate selection of the best one
why do males aggregate on leks?
hotspot hypothesis: males aggregate on “hotspots”, where female encounter rate is high
hotshot hypothesis: subordinate males cluster around attractive males hoping to interact with the females attracted to hotshots
female preference hypothesis: females prefer large groups of males where they can easily and quickly compare them. Aggregated males are visited more often by receptive females.
consequences of leks
female mate choice and male-male competition is unusually high
lekking males tend to be highly ornamented and perform striking and conspicuous displays (predation)
The paradox of the lek, and a proposed solution
Paradox: with high variance in male reproductive success, within a few generations of selection via female choice, the genetic variation in quality should be depleted, and yet theyre not.
Solution: condition-dependent traits. If a male is to display the most elaborately, he must be able to survive and thrive in harsh conditions. Not all males will handle the stress the same way, and the gene-environment interactions along with stress on development may reduce the size of the trait.
does polygyny benefit females?
females prefer polygyny if the territory is good enough
female mating system choice experiment result
when faced with monogamy and a low quality territory, and polygyny on a high quality territory, females chose the polygyny
Jacanas mating system
sex role reversed, males are smaller and look after chicks. females are polyandrous and have 1-4 mates.
resource distribution affects male distribution.
