Polygyny Males: Lower PI and Greater Variance Reproductive Success Male-Male Competition Female...

PolygynyPolygyny

MalesMales: Lower PI: Lower PI

andand

Greater Variance Reproductive SuccessGreater Variance Reproductive Success

Male-Male CompetitionMale-Male Competition

Female ChoiceFemale Choice

PolygynyPolygyny

White-bearded ManakinWhite-bearded Manakin

((Manacus manacus)Manacus manacus)

Male-dominance polygynyMale-dominance polygyny

LekLek

Males Display, Interact AggressivelyMales Display, Interact Aggressively

Females Choose MatesFemales Choose Mates

White-bearded Manakin MaleWhite-bearded Manakin Male

PolygynyPolygyny

Lekking SystemsLekking Systems

High High VarianceVariance in Male Mating Success in Male Mating Success

Females Prefer “Central” MalesFemales Prefer “Central” Males

Lekking Common: Birds, MammalsLekking Common: Birds, Mammals

Found in Some InsectsFound in Some Insects

PolygynyPolygyny

Lekking SystemsLekking Systems

Male DominanceMale Dominance

Obtain Central PositionObtain Central Position

Direct/Intrasexual CompetitionDirect/Intrasexual Competition

Female Choice: Indirect Male CompetitionFemale Choice: Indirect Male Competition

White-bearded ManakinWhite-bearded Manakin

Shorey, L. 2002. Shorey, L. 2002. Behavioral Ecology and Behavioral Ecology and SociobiologySociobiology 5252:451-457.:451-457.

Northern TrinidadNorthern Trinidad

White-bearded ManakinWhite-bearded Manakin

Concentrated LekConcentrated Lek

Each Male Displays on “Court”Each Male Displays on “Court”

Clears Court of LeavesClears Court of Leaves

Emergent Saplings: AcrobaticsEmergent Saplings: Acrobatics

Males Fight: Dominance, PositionMales Fight: Dominance, Position

Males Display: Attract FemalesMales Display: Attract Females

White-bearded ManakinWhite-bearded Manakin

Correlates Male Mating SuccessCorrelates Male Mating Success

Size (Tarsus Length, +)Size (Tarsus Length, +)

Condition (Extra Mass, +)Condition (Extra Mass, +)

Distance from Lek Center (-)Distance from Lek Center (-)

Large Males at Lek Center ?Large Males at Lek Center ?

White-bearded ManakinWhite-bearded Manakin

White-bearded ManakinWhite-bearded Manakin

Males Compete for Central PositionsMales Compete for Central Positions

Larger Males More Likely Larger Males More Likely

Dominant, More Likely CentralDominant, More Likely Central

Lek Centrality: Cue for Female ChoiceLek Centrality: Cue for Female Choice

PolyandryPolyandry

Female PI < Male PIFemale PI < Male PI

Dichromatism: Female BrighterDichromatism: Female Brighter

Females Larger, More AggressiveFemales Larger, More Aggressive

PolyandryPolyandry

Polyandry Relatively RarePolyandry Relatively Rare

““Test” of General ConceptsTest” of General Concepts

Jacana spinosaJacana spinosa

Jacana: PolyandryJacana: Polyandry

Some Females: Large Territories,Some Females: Large Territories,

Contain 2 – 10 Male Nesting TerritoriesContain 2 – 10 Male Nesting Territories

Females Provide Eggs;Females Provide Eggs;

Males Care for BroodMales Care for Brood

Jacana spinosaJacana spinosa

PolyandryPolyandry

Females More Aggressive, Slightly Larger Females More Aggressive, Slightly Larger Than MalesThan Males

Younger Females: Excluded from BreedingYounger Females: Excluded from Breeding

New Female Territory Holder:New Female Territory Holder:

Infanticide, Free Males for New ClutchInfanticide, Free Males for New Clutch

PolyandryPolyandry

PI Pattern, Intrasexual SelectionPI Pattern, Intrasexual Selection

Follows Conceptual ConstructFollows Conceptual Construct

Female Variance in Reproductive SuccessFemale Variance in Reproductive Success

> Male Variance> Male Variance

PolyandryPolyandry

Jacana: Many Clutches Lost to PredationJacana: Many Clutches Lost to Predation

Abundant, Year-Round FoodAbundant, Year-Round Food

Females Free of Caring for YoungFemales Free of Caring for Young

Replace Lost Clutch QuicklyReplace Lost Clutch Quickly

Males Take Brood CareMales Take Brood Care

MonogamyMonogamy

Common in Birds, Rare OtherwiseCommon in Birds, Rare Otherwise

ObligateObligate Monogamy: Offspring Very Low Monogamy: Offspring Very Low Survival in Absence of Biparenal CareSurvival in Absence of Biparenal Care

Facultative Facultative Monogamy: Females AvoidMonogamy: Females Avoid

Already-Mated MalesAlready-Mated Males

SocialSocial Monogamy: Mated Pairs, Monogamy: Mated Pairs, PromiscuityPromiscuity

MonogamyMonogamy

ObligateObligate Monogamy: Offspring Very Low Monogamy: Offspring Very Low Survival in Absence of Biparenal CareSurvival in Absence of Biparenal Care

Common in RaptorsCommon in Raptors

Found in Rodents, CanidsFound in Rodents, Canids

Foraging Demands of Reproduction,Foraging Demands of Reproduction,

Protection of YoungProtection of Young

MonogamyMonogamy

Social Monogamy:Social Monogamy:

Snapping Shrimp (Snapping Shrimp (Alpheus Alpheus angulatus)angulatus)

Females Brood Eggs Until Larvae DisperseFemales Brood Eggs Until Larvae Disperse

No Parental Care by MalesNo Parental Care by Males

Male PI Lower (?)Male PI Lower (?)

How Does Social Monogamy Evolve?How Does Social Monogamy Evolve?

Monogamy: Snapping ShrimpMonogamy: Snapping Shrimp

Territorial MutualismTerritorial Mutualism: Both Sexes Benefit : Both Sexes Benefit by Sharing a Territoryby Sharing a Territory

Females Invest In Burrow Construction;Females Invest In Burrow Construction;

Both OccupyBoth Occupy

Males Aggressively Defend Territory;Males Aggressively Defend Territory;

Both Sexes Avoid EvictionBoth Sexes Avoid Eviction

Monogamy: Snapping ShrimpMonogamy: Snapping Shrimp

Mate-Guarding by MalesMate-Guarding by Males

Females Molt, Release Eggs, BroodFemales Molt, Release Eggs, Brood

Cycle RepeatedCycle Repeated

Male May Stay with Female Through Male May Stay with Female Through Multiple Episodes of ReproductionMultiple Episodes of Reproduction

Monogamy: Snapping ShrimpMonogamy: Snapping Shrimp

Economics Monogamous Mate-GuardingEconomics Monogamous Mate-Guarding

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

Sex Ratio: Male-Biased, Stay & Guard;Sex Ratio: Male-Biased, Stay & Guard;

Female-Biased, Desert?Female-Biased, Desert?

Monogamy: Snapping ShrimpMonogamy: Snapping Shrimp

Mathews, L.M. 2002. Mathews, L.M. 2002. Behavioral Ecology Behavioral Ecology and Sociobiologyand Sociobiology 5151:426-432.:426-432.

Field: Population DensityField: Population Density

Fort Pierce, FLFort Pierce, FL

Lab: Sex RatioLab: Sex Ratio

Monogamy: Snapping ShrimpMonogamy: Snapping Shrimp

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

Social Monogamy Unresponsive to Social Monogamy Unresponsive to Population DensityPopulation Density

Monogamy: Snapping ShrimpMonogamy: Snapping Shrimp

Sex Ratios Lab: 1, 0.2Sex Ratios Lab: 1, 0.2

Equal Frequency Sexes: Males Stayed Equal Frequency Sexes: Males Stayed with Femalewith Female

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

Reduced Tendency for MongamyReduced Tendency for Mongamy