1. Mating Systems Laksmis Cornejo, Sara Nishikawa, Shannon Oki Emlen, S.T., Oring, L.W. (1977). Ecology, Sexual Selection, and the Evolution of Mating Systems. Science, 197, 215-223

2. Hypotheses Certain ecological factors determine the degree to which mates can be defended or monopolized Emlen, S.T., Oring, L.W. (1977). Ecology, Sexual Selection, and the Evolution of Mating Systems. Science, 197, 215-223

3. Polygamy Prerequisite: economic monopoly of several mates OSR: the average ratio of fertilizable females to sexually active males at any given time an imbalance in the OSR skewed toward males then there is a greater chance of polygamy Emlen, S.T., Oring, L.W. (1977). Ecology, Sexual Selection, and the Evolution of Mating Systems. Science, 197, 215-223

4. Monogamy Neither sex has the opportunity of monopolizing additional members of the opposite sex Considerable parental care by both parents is required for successful rearing of the young Emlen, S.T., Oring, L.W. (1977). Ecology, Sexual Selection, and the Evolution of Mating Systems. Science, 197, 215-223

5. Polygyny Individual males frequently control or gain access to multiple females Resource defense polygyny occurs when males defend resources essential to females such that they can monopolize the resources and therefore the females. Female defense polygyny usually occurs with resource defense polygyny where the females are forcibly herded by a male such that other males are excluded from the group. Male dominance polygyny occurs when the environment does not allow for monopoly of resources or females therefore the males establish dominance amongst themselves. Emlen, S.T., Oring, L.W. (1977). Ecology, Sexual Selection, and the Evolution of Mating Systems. Science, 197, 215-223

6. Male Incubation / Female Emancipation Female viewpoint: lessens her metabolic burden and allows her to devote more time and energy to replenish nutrient and mineral reserves Male viewpoint: insurance strategy- cost of his incubation is beneficial in that she is able to prepare to have more kids Rapid multiple clutch polygamy Emlen, S.T., Oring, L.W. (1977). Ecology, Sexual Selection, and the Evolution of Mating Systems. Science, 197, 215-223

7. Polyandry Individual females frequently control or gain access to multiple mates Resource Defense Polyandry: females compete and defend resources essential to males Male defense polyandry: females control access to males directly Female access polyandry: Through interactions among themselves, females may limit access to males Emlen, S.T., Oring, L.W. (1977). Ecology, Sexual Selection, and the Evolution of Mating Systems. Science, 197, 215-223