Chapter 10: Mating systems

Mating system

Collection of behaviors and adaptations that dictate what an individual does to mate in a set of circumstances

2 main factors determining a mating system

1: Limiting sex

2: Degree to which the other sex can monopolize resources

4 hypotheses for monogamy

Mate limitation: Can only find one hoe

Mate guarding hypothesis: Restricted by partner to not mate with others

Mate assistance hypothesis: Need help parenting b/c resources are critical to reproduction

Infanticide reduction: Form bond to protect from infanticide

Mate limitation hypothesis case study

Clown shrimp - females both spatially and temporally limited (short receptive period)

Density relation to monogamy in mammals

Increased density → Lower chance of monogamy

How Bushveld sengi (desert mouse) do monogamy

Mate guarding hypothesis

• Males guard females but spend little time together outside of estrus

2 animals that demonstrate mate guarding monogamy

Rhinos, Bushveld sengi (Desert Mouse)

2 monogamy hypotheses demonstrated in some crickets

Mate guarding and mate assistance

• When paired male death skyrockets, female drops, he dies for her aww

In ideal circumstances what dictates (lack of) parental care?

Whoever can leave first to multiple mate does

European starling case study and what it demonstrates (hint: monogamy)

mate assistance hypothesis to explain monogamy

• Egg temperatures higher and more stable when male helps incubate)

• Led to more fledged young

From net benefit perspective why paternal care would exist

Additional offspring as a result of paternal care is more than what would be produced by multiple mating

Issue for males with polyandry

Already uncertain paternity increased a lot

4 species and ways males “counter” polyandry issues

Red-necked phalarope: Sequential polyandry

Spotted sandpiper: Ask Jorja tmrw

Red Jungle Fowl: Use more sperm according to amount of mates female has

Chinook Salmon: Subordinate sperm swims far slower when in presence of dominant seminal fluid and vice versa

Sequential polyandry

Polyandry method in which the first clutch is of the sperm with the male she mated with first. If that fails the second clutch is with the second male, etc. Males high certainty of paternity (swap taking care when their nest fails)

4 hypotheses for indirect benefits of polyandry

Good genes: Duh

Genetic compatibility: Increase odds of receiving genetically complementary sperm

Genetic diversity: Increase heterozygosity

Inbreeding avoidance: Avoid accidental inbreeding

Tree frog case study and what it demonstrates

Offspring of polyandrous tree frog females have better survival than single mating females

• Good genes hypothesis for indirect benefits of polyandry

Yellow-toothed cavy case study and what it demonstrates (hint: polyandry)

Survival of offspring goes up with number of mates

• Good genes hypothesis for indirect benefits of polyandry

Superb starlings case study and what it demonstrates (hint: polyandry)

More mates correlated with more heterozygosity

• Genetic diversity hypothesis for indirect benefits of polyandry

Bluethroat bird case study and what it demonstrates

Better immune responses of offspring of multiple mating bluethroats

• Genetic diversity and good genes hypothesis for indirect benefits of polyandry

Honey bees case study and what it demonstrates (hint: polyandry)

More diverse colonies have larger combs

• Genetic diversity hypothesis for indirect benefits of polyandry

3 hypotheses for direct benefits of polyandry

Additional resources: gain access to more resources from partner

Additional care: Gain access to more caregivers

Infanticide reduction: Uncertainty about paternity reduces risk of infanticide

Red wing blackbird demonstrates this hypothesis (hint: polyandry)

Additional resources hypothesis for direct benefits of polyandry

Pierid butterfly case study and what it demonstrates

Females with more mates have higher reproductive output and receive more nuptial gifts

• Additional resources hypothesis for direct benefit of polyandry

dunnock case study and what it demonstrates

Females target males she spent less time with for copulation, they help raise offspring

• Additional care hypothesis for direct benefits of polyandry

4 kinds / hypotheses of polygyny

Female defense polygyny

Resource defense polygyny

Lek polygyny

Scramble polygyny

Female defense polygyny: Resource distribution, female distribution, male behavior

Resources: scattered

Females: grouped (avoid predation, better access to resources, or any other reason)

Males: Follow and guard females

Resource defense polygyny: Resource distribution, female distribution, male behavior

Resources: Clumped

Females: Scattered

Males: Guard clumped resource, females need resource so are attracted to them

Lek polygyny: Resource distribution, female distribution, male behavior

Resources: scattered randomly

Females: scattered

males: Set up leks - not resource-based (usually, Sage Grouse exception), wait for females

Scramble polygyny: Resource distribution, female distribution

Resources: Scattered randomly

Females: scattered

Males: Race to seek out females

3 examples of female defense polygyny

Impalas

Gorillas

spear-nosed bat

African cichlid case study and what it demonstrates

Males guard shells they collect and monopolize females that are attracted

• Resource defense polygyny

Pied flycatchers mating type and unique trait

Resource defense polygyny

Females mated with a territorial male compete with each other for the resources

3 hypotheses for lek polygyny

Hotshot model

Hotspot model

Female preference model

Hotspot model

Hypothesis for development of leks: Males gather at sites where females most likely go

Hotshot model

Hypothesis for lek polygyny: Males gather around dominant / attractive males to get a chance at interacting with a female (lowkey guys do this)

Female preference model

Hypothesis for lek polygyny: Females prefer clusters of males to compare quality / have options

Greater sage grouse and what it demonstrates

Distribution of leks correlates to density of nesting females

• Supports hotspot hypothesis

Greater snipe case study and what it demonstrates

Removed successful lek males, subordinate males left

• Supports hotshot hypothesis

Uganda Kob (impala - type animal) case study and what it demonstrates

Females aggregate proportionately to lek size

• Support against female preference hypothesis

Richardson’s ground squirrels and what it demonstrates (hint: mating systems")

Plastic mating system

in low elevation they are highly territorial of good burrows

In high elevation females wake asynchronously and later than males - becomes overlapping ranges with dominance hierarchy

Case study of female distribution in relation to food intake

Food supplementation of swamp sparrow reduced home range - males began to monopolize females

Cape ground squirrel case study about distribution range

Talk to Jorja: Isn’t this inverse of previous table?

Common form of scramble polygyny in frogs

Explosive breeding assemblage

• Very compressed breeding seasons, lots of eggs and sperm mix

Polygynandry vs promiscuity

In polygynandry multiple males and females form pair bonds, not just mating

When polygynandry evolves (3 conditions)

Neither sex can gain advantage of the other

Live together

Resources not needed for breeding

Parental care of promiscuity

Mixed, sometimes none, but since promiscuity infiltrates many mating systems it can be present