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Chapter 13 Opener: Weaver ants form superbly cooperative societies This chapter is about the evolution of social behavior.
13.1 The energy budget of “helpers” in Neolamprologus pulcher (Part 2) This species of fish is a type of cichlid (not the variety discussed earlier, but very similar), and will display a wide range of biparental care behaviors. In the above scenario, we are seeing an even more complex grouping whereby some non-reproductive fish become “helpers” at the nest site.
13.1 The energy budget of “helpers” in Neolamprologus pulcher (Part 1) The role of the helper is primarily to perform “submissive” behaviors around the nesting site.
13.2 Effect of removal of the top-ranked subordinate helper in a cooperatively breeding group In this, another cichlid species, the change in patterns seen in helper fish where the head subordinate (HS) is removed is shown. The HS removal changes dramatically the boundaries traveled by the other five “helper” fish.
13.3 Reproductive interference in a social animal The acorn woodpecker is a bird species that lives in a communal nesting site. Here we have REPRODUCTIVE INTERFERENCE being shown where the bird removes a nestmate’s egg.
13.5 Effect of parasites on cliff swallow nestlings From a nest treated with insecticide. From a nest infested with swallow bugs… note small size.
13.6 Social living with defensive benefits? Schooling of fish (these are striped catfish) can reduce predation pressures and increase survivability of individuals.
13.8 The different categories of helping behavior Fitness consequences of different helping behaviors.
13.10 Cooperative courtship of the long-tailed manakin Alpha male mates with all females. Beta male mates with none. Other subordninates mate with none.
13.12 A meerkat sentinel on the alert for approaching predators Reciprocity hypothesis – the idea that there is reciprocal altruism in which a helpful action is repaid at a later date by the recipient of the assistance.
13.13 Reciprocity in a social primate Grooming is one example of a relatively low cost form of reciprocity.
13.14 Experimental demonstration of reciprocity in cotton-top tamarins (Part 1) Tamarin helper (right) can drag food to its partner. Or the Tamarin helper may be non-responsive.
13.15 The prisoner’s dilemma Aka: Game Theory
Direct fitness – fitness gained through reproduction Indirect fitness – fitness gained by helping “kin” Inclusive fitness – the combination of direct and indirect fittness Hamilton’s rule – a rare altruistic allele can become more common in a population only if the indirect fitness gained by the altruist is greater than the direct fitness it loses as a result of the self-sacrificing actions.
13.18 Altruism and relatedness in pied kingfishers Primary helpers are related to the breeders whereas the secondary helpers are not.
13.24 Conflict within ant colonies over reproduction The center ant is covered with the sting scent of the queen to identify her as becoming reproductive. The three worker ants hold her in position to prevent reproduction. A single ant iimpobolizes another ant whose ovaries have begun to mature.
13.27 Eusocial insects have sterile castes Many social insects like honeybees and ants have a sterile caste.
13.30 Haplodiploidy and the evolution of eusociality in the Hymenoptera (Part 1)
13.30 Haplodiploidy and the evolution of eusociality in the Hymenoptera (Part 2)
13.31 A sterile thrips soldier (right) next to a reproductive foundress female (left) Note the larger forelimbs on the sterile worker.