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Mate Choice + Sexual Selection - Coggle Diagram
Mate Choice + Sexual Selection
Sexual Selection
: "
A mode of natural selection where members of one sex choose mates of the other sex to mate with
"
Intersexual selection ("between")
:
1 sex chooses mates of the other sex
--> females choosing males based on exaggerated traits (Ex. Guppy fish)
Intrasexual selection ("within"):
Competing with members of the same sex for access to members of the opp. sex
--> males fighting with other males to gain access to females (Ex. antlers in deer)
Sexual selection occurs due to a conflict over
reproductive investment
Promotes
:
conflict between males
(arms race- extreme features
) --> to establish dominance, controlling of resources that females require + control over groups of females
choosiness by females --> choose males w/most advantageous traits (
Ex. Bowerbirds)
Conflict between males favors large, well-armed males ("arms race)
Female choice favors elaborate male behaviour or morphology
Conflict between sexes present
: male + female gametes= not aligned
Female gametes:
large, immobile,
invest in small n. of offspring
,
reproductive success limited to resources
Male gametes:
small, mobile, large quantities produced at once,
reproductive success is limited by access to females
Example of conflict between sexes
:
Trinidadian guppy
: Male --> spent give engaging in sexual behaviour through displaying their colors to females (
elaborate courtship
) + sneakily successfuly mating w/females (
sneaky-mating
)
Females
--> prefer males w/brighter colors but males r harassing them, have behaviourally adapted to this by going to areas where males cannot go (areas high in predation)
Anisogamy (root of the problem)
: "
sexual reproduction involving fusion of 2 gametes of unequal size
"
Ex Domestic pigs
:
Male
--> produces billions of sperm + have quick recovery,
Female
--> produce less than 20 eggs, slow recovery, huge investment
Ex Killer Whales
: Females --> important for keeping family alive, when offspring experience death of mother =
decline in male survival
Females killer whales= providing life-long investment into their offspring
Males
--> aim for
quantity
,
Females
--> aim for
quality
Formation of arms race due to sexual conflict
"scarcity" of females present
Leads to increased value of females for males
Leads to increased competition for females
Females= greater choice to choose who to mate with
Maximising reproductive success
:
Males:
Mate often with more females
Ex Guppies
:
-
Males
: max. reproductive success --> courtship/show off colors to multiple females
-
Females
: max. reproductive success --> choose males based on how brightly colored they are (high genetic fitness)
good genetic fitness = passing genes down future generations --> offspring have most advantageous traits
Types of mating systems
Monogamy
:
Each sex has 1 partner
Favoured when
:
both parents needed to raise offspring
(ex. birds)
male has to guard his mate to ensure he's the father of offspring
low chance of meeting many females
Polygyny
:
Males have more than 1 partner, females have 1 partner
Favoured when
:
1 sex is operationally rare
males can control resources of females
females can exert free choice
Polyandry
(rare):
Females have more than 1 partner, males have 1 partner
Favoured when:
females can escape parental duties
females require resources provided by more than 1 male
male biased sex ratio
Polygynandry
:
both sexes have more than 1 partner
Favored when
: males can't control females + females gain from multiple matings (genetic benefits)
Why should females carefully choose?**
Direct benefits of choosing
:
-female gains
direct benefit
from choosing a good mate
territory
protection
parental care
reduced harassment from other males
Indirect benefits of choosing
:
female's
offspring gain benefit
have more advantageous traits --> survive longer or produce more offspring
Males can signal benefits through their behavioural repertoire or physical features
Females should
:
pay attention to signals showing benefits
prefer males w/exaggerated signals/traits
prefer signals that are legit and not "fake"
maximise their benefits by choosing best male
Runaway selection (Fisherian runaway
): -
daughters of successful matings will have same mate preference as mother
sons will have same features as father
trait= fixed in population when all females choose it + males possess it