Post on 04-Jan-2016
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Mating SystemsMating Systems
Psychology 3107Psychology 3107
IntroductionIntroduction
For the most part, males’ involvement in For the most part, males’ involvement in mating, well, ends after the matingmating, well, ends after the mating
Females pay for the mating a lot moreFemales pay for the mating a lot more PhysiologicallyPhysiologically Post birth/hatch carePost birth/hatch care
Therefore, we should expect Polygyny Therefore, we should expect Polygyny where males have more than one matewhere males have more than one mate Male variance > female varianceMale variance > female variance
PolygynyPolygyny
There are several There are several theories about polygynytheories about polygyny
Resource defense Resource defense polygynypolygyny Male defends some Male defends some
good resourcegood resource
Example, hummingbirdsExample, hummingbirds
The resource is some The resource is some nectar giving flowernectar giving flower
HummingbirdsHummingbirds
Male sets up territoryMale sets up territory
Excludes other males Excludes other males
Basically, the male exchanges letting Basically, the male exchanges letting females feed in exchange for copulationsfemales feed in exchange for copulations
Sort of like nuptial gifts in some sinsects, Sort of like nuptial gifts in some sinsects, but the ‘gift’ is stationarybut the ‘gift’ is stationary
Females then set up breeding territory Females then set up breeding territory withing male’s teritorrywithing male’s teritorry
Polygyny ThresholdPolygyny Threshold
Polygyny may occur Polygyny may occur when the ‘polygyny when the ‘polygyny threshold’ is crossedthreshold’ is crossed
Example here is Example here is migratory songbirdsmigratory songbirds Males arrive, set up Males arrive, set up
territoriesterritories Females choose Females choose
matesmates
Polygyny ThresholdPolygyny Threshold
When differences in qualities of available When differences in qualities of available territories crosses the polygyny threshold, territories crosses the polygyny threshold, then polygyny resultsthen polygyny results It is more profitable for the female to become It is more profitable for the female to become
a secondary female with a high end male, a secondary female with a high end male, then a primary femle with a mid rangethen a primary femle with a mid range
What about monogamyWhat about monogamy
Monogamy should happen if:Monogamy should happen if: Curves are far apartCurves are far apart Curves are flatCurves are flat
In other words, little variation in quality of males In other words, little variation in quality of males and their territoriesand their territories
Verner and Wilson did a really cool study Verner and Wilson did a really cool study that looked at these ideasthat looked at these ideas
Verner and WilsonVerner and Wilson
Marsh birdsMarsh birds Quality varies greatlyQuality varies greatly
vsvs
Non Marsh birdsNon Marsh birds Not so much variationNot so much variation
Prediction is that there should be much Prediction is that there should be much more monogamy in non marsh living more monogamy in non marsh living songbirdssongbirds
So, what happenedSo, what happened
Marsh species Marsh species 44 % are polygynous 44 % are polygynous
Non Marsh Non Marsh 2 % are polygynous 2 % are polygynous
You can also get female defense polygynyYou can also get female defense polygyny Males basically guard the femalesMales basically guard the females Good example here is in BisonGood example here is in Bison
But you said we’d talk about But you said we’d talk about monogamy…monogamy…
OK, OK……OK, OK……
When should mongamy happen?When should mongamy happen? When the young are in need of lots of When the young are in need of lots of
parental careparental care When Territories or resources are poorWhen Territories or resources are poor When females actually enforce it!When females actually enforce it!
Some ‘monogamous’ species aren’t…..Some ‘monogamous’ species aren’t…..
Extra Pair CopulationsExtra Pair Copulations
Happens a lot in birdsHappens a lot in birds
Ummm, happens a lot Ummm, happens a lot in peoplein people
‘‘sperm competition’sperm competition’ Usually when female is Usually when female is
unguarded or when unguarded or when male can get away male can get away with it…..with it…..
Sperm WarsSperm Wars
PolyandryPolyandry
One female, many One female, many malesmales
Exceedingly rareExceedingly rare
Usually only happens Usually only happens when there is when there is complete sex role complete sex role reversalreversal Sea horsesSea horses Spotted sandpipersSpotted sandpipers
ConclusionsConclusions
Many theories as to why different animals Many theories as to why different animals have different mating systemshave different mating systems
Polygyny is by far the most commonPolygyny is by far the most common
When you think about it, the system When you think about it, the system correlates nicely with the gametes!correlates nicely with the gametes!