“Individual variation in cooperative behavior: a lifetime perspective”

Thu, Dec 10, 2015, 12:30 pm to 1:30 pm

Eily DuVal - Florida State University Abstract: Understanding the factors that influence the emergence and maintenance of cooperation is a central goal of evolutionary biology. Cooperators act to increase othersÂ’ fitness at an apparent cost to their own, and so it is unclear how cooperation persists in competitive natural environments. This evolutionary puzzle is even more complicated when individuals vary in whether they cooperate. Widespread variation in cooperative behavior in the lance-tailed manakin (Chiroxiphia lanceolata) creates an opportunity to investigate sources of variation in a complex behavioral trait. Males of this lekking species display for females in two-male teams, but with rare exceptions only the alpha male mates with females they jointly attract. Subordinate beta males serve as non-breeding helpers for up to six years, and gain no immediate direct or indirect benefits while betas. Instead, long-delayed direct benefits seem to select for cooperation in this system. Interestingly, nearly half of males are never betas before becoming alpha, and prior beta experience does not affect siring success once males reach alpha status. Here I use behavioral and genetic data from the first 12 years of my long-term study of a marked population to separately quantify the influences of survival, status transitions, and reproductive success on subordinatesÂ’ cooperative behavior. These forces combine to create disruptive selection on pre-breeding cooperation, and allow assessment of the relative influence of components of natural selection (status-specific estimates of survival) and sexual selection (acquisition of a breeding territory and success in attracting mates) in generating the complex fitness surface of cooperation in this system. A parallel investigation of female behavior illustrates that realized mating success of males results from a multi-stage process of mate choice that is itself variable among females. Together, these results emphasize the need for an integrative, lifetime perspective in adaptive analyses of cooperative behavior.

10 Guyot Hall

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