Mating Systems

Mating System Species typical pattern of mate-finding, reproduction and parenting of offspring

Kinds of mating systems Number of females Number of males Monogamy Polygyny Polygamous Polygynandry Polyandry

Kinds of mating systems Monogamous Mating Systems -a mating system in which one male and one female for and mate with only each other during a given breeding season To put it another way -neither sex is able to monopolize more than one member of the opposite sex

Kinds of mating systems Monogamous Mating Systems First question - why should a male be monogamous? If the particular niche dictates that a male will do better reproductively staying with one mate - will do so. mates are scarce resources are scarce or non-defendable

Kinds of mating systems Monogamous Mating Systems 1. Mate assistance hypothesis -male stays with one female because it is to his advantage to help raise offspring Hippocampus whitei -male carries offspring -brood pouch contains 1 clutch -no point to new matings

Kinds of mating systems Monogamous Mating Systems 2. Mate guarding hypothesis -male spends time with mate to ensure fertilization Assumes Females are scarce (highly male-biased OSR) Females will mate multiply Hymenocera elegans male stays with female for weeks female receptive every 3 weeks

Kinds of mating systems Monogamous Mating Systems 3. Female-enforced monogamy -female blocks polygamous moves by mate Icteria virens (yellow-breasted chat) - aggression by females More aggressive Less aggressive Toward Toward Toward males females wrens

Kinds of mating systems Monogamous Mating Systems 3. Female-enforced monogamy -female blocks polygamous moves by mate Burying beetle – Nicophorus defodiens

Kinds of mating systems Polygamous Mating Systems 1. Polygyny - males mate with several females a. Female Defense Polygyny -females live in permanent groups that males defend Male

Kinds of mating systems Polygamous Mating Systems 1. Polygyny - males mate with several females a. Female Defense Polygyny -females live in permanent groups that males defend Yellow-bellied marmot

Kinds of mating systems Polygamous Mating Systems 1. Polygyny - male mate with several females b. Resource Defence Polygyny - males defend resource females need Lamprologus -males gather and defend oviposition sites - mollusc shells

Kinds of mating systems Polygamous Mating Systems 1. Polygyny - male mate with several females c. Lek Polygyny - males compete for high rank

Kinds of mating systems Polygamous Mating Systems 1. Polygyny - male mate with several females c. Lek Polygyny - males compete for high rank Upper limit on lek effectiveness Mating rate 10 Lek size

Kinds of mating systems Polygamous Mating Systems 1. Polygyny - male mate with several females c. Lek Polygyny Hypotheses for the formation of leks 1. Hotspot Hypothesis 2. Hotshot Hypothesis 3. Female Preference Hypothesis

Kinds of mating systems Polygamous Mating Systems 1. Polygyny - male mate with several females d. Scramble competition -females are available for a short period -males mate with as many as possible

Kinds of mating systems Polygamous Mating Systems Polygamous Polygyny a. Female Defence Polygyny Male controls access to resources b. Resource Defence Polygyny c. Lek Polygyny Male can’t control access to resources d. Scramble Competition

Kinds of mating systems Polygamous Mating Systems 2. Polyandry - one female mates with several males Jacana Male territories Female territory

Kinds of mating systems Polygamous Mating Systems 2. Polyandry - one female mates with several males Kinds of Polyandry 1. Sperm replenishment -females mate multiply to get extra sperm e.g. Drosophila 1 mate Multiple mates # of eggs Time

Kinds of mating systems Polygamous Mating Systems 2. Polyandry - one female mates with several males Kinds of Polyandry 1. Sperm replenishment 2. Prostitution - females mate with males to get access to resources 3. Resource Defense - females control access to resources 4. Lek Polyandry - females compete for dominance - some primate troops

Kinds of mating systems Polygamous Mating Systems 2. Polyandry - one female mates with several males Genetic Benefits of Polyandry 1. Egg fertilization insurance via acquisition of sufficient numbers of competent sperm. 2. Better sperm with genes acquired from preferred sexual partners. 3. Genetic variety gained via acquisition of genetically diverse sperm. Material Benefits of Polyandry 1. Acquisition of resources controlled by mating partners. 2. Acquisition of parental care from mating partners. 3. Improved foraging success via distraction of a male foraging competitor. 4. Reduced risk of sexual harassment form non-partners.

Polyandry – do the data support the hypothesized benefits? Egg fertilization insurance via acquisition of sufficient numbers of competent sperm. Prairie dogs

Polyandry – do the data support the hypothesized benefits? 3. Genetic variety gained via acquisition of genetically diverse sperm. Yellow-toothed cavy

Kinds of mating systems Are mating systems ‘fixed’? - do all members of a species conform to one mating system How monogamous is monogamy? Indigo bunting Within pair Extra-pair 12 Days before egglaying

Kinds of mating systems Are mating systems ‘fixed’? - do all members of a species conform to one mating system How monogamous is monogamy? Indigo bunting Rate of extra pair copulation - 27 - 76%

Kinds of mating systems What are females gaining in extra-pair copulations? Agelaius phoeniceus 100 50 % of broods with EPC nestlings 1990 1991 1992

Kinds of mating systems Are mating systems ‘fixed’? - do all members of a species conform to one mating system How monogamous is monogamy? Humans U.S.-10 - 18% Yanomama - 9% !Kung - 2 - 3%

Summary Mating Systems Monogamous 1. Mate assistance hypothesis Polygamous Polygyny 2. Mate guarding hypothesis a. Female Defence Polygyny 3. Female-enforced monogamy b. Resource Defence Polygyny c. Lek Polygyny d. Scramble Competition 2. Polyandry a. Sperm replenishment b. Prostitution c. Resource Defence d. Lek