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

Polygyny Lekking Systems High Variance in Male Mating Success Females Prefer “Central” Males Lekking Common: Birds, Mammals Found in Some Insects

Polygyny Lekking Systems Male Dominance Obtain Central Position Direct/Intrasexual Competition Female Choice: Indirect Male Competition

White-bearded Manakin Shorey, L Behavioral Ecology and Sociobiology 52: Northern Trinidad

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 Manakin Correlates Male Mating Success Size (Tarsus Length, +) Condition (Extra Mass, +) Distance from Lek Center (-) Large Males at Lek Center ?

White-bearded Manakin

Males Compete for Central Positions Larger Males More Likely Dominant, More Likely Central Lek Centrality: Cue for Female Choice

Polyandry Female PI < Male PI Dichromatism: Female Brighter Females Larger, More Aggressive

Polyandry Polyandry Relatively Rare “Test” of General Concepts

Jacana spinosa Jacana: Polyandry Some Females: Large Territories, Contain 2 – 10 Male Nesting Territories Females Provide Eggs; Males Care for Brood

Jacana spinosa

Polyandry Females More Aggressive, Slightly Larger Than Males Younger Females: Excluded from Breeding New Female Territory Holder: Infanticide, Free Males for New Clutch

Polyandry PI Pattern, Intrasexual Selection Follows Conceptual Construct Female Variance in Reproductive Success > Male Variance

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 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

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

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 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 Shrimp Mate-Guarding by Males Females Molt, Release Eggs, Brood Cycle Repeated Male May Stay with Female Through Multiple Episodes of Reproduction

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 Shrimp Mathews, L.M Behavioral Ecology and Sociobiology 51: Field: Population Density Fort Pierce, FL Lab: Sex Ratio

Monogamy: Snapping Shrimp Proportion of Males Paired with (Guarding) Females Independent of Shrimp Population Density Social Monogamy Unresponsive to Population Density

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