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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