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Polygyny. Males : Lower PI and Greater Variance Reproductive Success Male-Male Competition Female Choice. Polygyny. White-bearded Manakin ( Manacus manacus) Male-dominance polygyny Lek Males Display, Interact Aggressively Females Choose Mates. White-bearded Manakin Male.

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Polygyny

Polygyny

Males: Lower PI

and

Greater Variance Reproductive Success

Male-Male Competition

Female Choice


Polygyny1

Polygyny

White-bearded Manakin

(Manacus manacus)

Male-dominance polygyny

Lek

Males Display, Interact Aggressively

Females Choose Mates



Polygyny2
Polygyny

Lekking Systems

High Variance in Male Mating Success

Females Prefer “Central” Males

Lekking Common: Birds, Mammals

Found in Some Insects


Polygyny3
Polygyny

Lekking Systems

Male Dominance

Obtain Central Position

Direct/Intrasexual Competition

Female Choice: Indirect Male Competition


White bearded manakin
White-bearded Manakin

Shorey, L. 2002. Behavioral Ecology and Sociobiology52:451-457.

Northern Trinidad


White bearded manakin1
White-bearded Manakin

Concentrated Lek

Each Male Displays on “Court”

Clears Court of Leaves

Emergent Saplings: Acrobatics

Males Fight: Dominance, Position

Males Display: Attract Females


White bearded manakin2
White-bearded Manakin

Correlates Male Mating Success

Size (Tarsus Length, +)

Condition (Extra Mass, +)

Distance from Lek Center (-)

Large Males at Lek Center ?



White bearded manakin4
White-bearded Manakin

Males Compete for Central Positions

Larger Males More Likely

Dominant, More Likely Central

Lek Centrality: Cue for Female Choice


Polyandry
Polyandry

Female PI < Male PI

Dichromatism: Female Brighter

Females Larger, More Aggressive


Polyandry1
Polyandry

Polyandry Relatively Rare

“Test” of General Concepts


Jacana spinosa
Jacana spinosa

Jacana: Polyandry

Some Females: Large Territories,

Contain 2 – 10 Male Nesting Territories

Females Provide Eggs;

Males Care for Brood



Polyandry2
Polyandry

Females More Aggressive, Slightly Larger Than Males

Younger Females: Excluded from Breeding

New Female Territory Holder:

Infanticide, Free Males for New Clutch


Polyandry3
Polyandry

PI Pattern, Intrasexual Selection

Follows Conceptual Construct

Female Variance in Reproductive Success

> Male Variance


Polyandry4
Polyandry

Jacana: Many Clutches Lost to Predation

Abundant, Year-Round Food

Females Free of Caring for Young

Replace Lost Clutch Quickly

Males Take Brood Care


Monogamy
Monogamy

Common in Birds, Rare Otherwise

Obligate Monogamy: Offspring Very Low Survival in Absence of Biparenal Care

Facultative Monogamy: Females Avoid

Already-Mated Males

Social Monogamy: Mated Pairs, Promiscuity


Monogamy1
Monogamy

Obligate Monogamy: Offspring Very Low Survival in Absence of Biparenal Care

Common in Raptors

Found in Rodents, Canids

Foraging Demands of Reproduction,

Protection of Young


Monogamy2
Monogamy

Social Monogamy:

Snapping Shrimp (Alpheus angulatus)

Females Brood Eggs Until Larvae Disperse

No Parental Care by Males

Male PI Lower (?)

How Does Social Monogamy Evolve?


Monogamy snapping shrimp
Monogamy: Snapping Shrimp

Territorial Mutualism: Both Sexes Benefit by Sharing a Territory

Females Invest In Burrow Construction;

Both Occupy

Males Aggressively Defend Territory;

Both Sexes Avoid Eviction


Monogamy snapping shrimp1
Monogamy: Snapping Shrimp

Mate-Guarding by Males

Females Molt, Release Eggs, Brood

Cycle Repeated

Male May Stay with Female Through Multiple Episodes of Reproduction


Monogamy snapping shrimp2
Monogamy: Snapping Shrimp

Economics Monogamous Mate-Guarding

Population Density: Low Density, Search Time for Mate Extended, Stay & Guard

Sex Ratio: Male-Biased, Stay & Guard;

Female-Biased, Desert?


Monogamy snapping shrimp3
Monogamy: Snapping Shrimp

Mathews, L.M. 2002. Behavioral Ecology and Sociobiology51:426-432.

Field: Population Density

Fort Pierce, FL

Lab: Sex Ratio


Monogamy snapping shrimp4
Monogamy: Snapping Shrimp

Proportion of Males Paired with (Guarding) Females Independent of Shrimp Population Density

Social Monogamy Unresponsive to Population Density


Monogamy snapping shrimp5
Monogamy: Snapping Shrimp

Sex Ratios Lab: 1, 0.2

Equal Frequency Sexes: Males Stayed with Female

1 Male/5 Females: Males More Likely to Leave Recently Mated Female;

Reduced Tendency for Mongamy