In the Light of Evolution Volume I: Adaptation and Complex Design (2007) / Chapter Skim
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Pages 145-164
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From page 145... ...
. Although kin selection explains the extensive cooperation and common pur pose of social insect colonies, it also predicts a certain amount of cross-purpose and conflict behavior.
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From page 146... ...
Queller selection analysis of cooperation and conflict in social insects is one of the outstanding achievements of evolutionary theory. THE ROCK, THE CLOCK, AND ORGANISMAL COMPLEXITY D arwin built his theory of descent with modifications from many quarters.
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We will argue that social insect colonies are much like organisms, and we will show how their unity of purpose can arise through kin selection. We will also show that some cross-purpose remains, that colonies are not perfectly coherent.
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. This scene summarizes what is special about social insects: complex communication and integration of behavior, and individuals caring for the offspring of another.
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if social insect colonies lack this unity of genotype, what gives them the unity of purpose that makes them an organism rather than a contentious flock?
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each caste or cell type specializes in certain tasks, with the division of labor aiding the whole. All social insects have functional reproductive and worker roles, but only some are morphologically differentiated into queen and worker castes.
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From page 151... ...
of course, this logic does not apply to just any social community, so the social insects force the question of how some entities become organ ismal while others do not. Although social insect colonies may not have physiologies that closely match those of multicellular organisms, they do have their own systems for
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From page 152... ...
similar kinds of coordination are found wherever they are looked for in social insects, for example, in nest construction in Polybia wasps (Jeanne, 1986) , in nest-finding in honey bees (seeley and visscher, 2004)
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With respect to superorganisms, there also seems to be an inordinate fondness for kinship ties among cooperators. Darwin had at least an inkling of this: ‘‘As with the varieties of the stock, so with social insects, selection has been applied to the family, and not to the individual, for the sake of gaining a serviceable end'' (Darwin, 1872, p.
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, favoring daughters who remain with their mothers to rear additional sisters. hamilton noted that this observation could potentially explain at a stroke at least two salient feature of social insects (hamilton, 1964b)
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. KIN SELECTION AND SYNERGISM: LIFE INSURANCE AND FORTRESS DEFENSE Kin selection has been so closely identified with the haplodiploid hypothesis that concerns with the latter have caused some to question kin selection in general.
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life insurance. here we assume that dispersal carries no cost but that a parent survives the period of parental care with probability sc.
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still provides the framework for understanding altru ism, even if the altruism is not driven by extra-high relatedness. As noted above, the fact that social insect colonies consist of families, and that they exclude outsiders, shows that relatedness matters.
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From page 158... ...
. This means that these workers should rear more males than those in singly mated colonies, and the frequency-dependent nature of sex ratio selection should cause the two kinds of colonies to increasingly specialize (Boomsma and Grafen, 1990, 1991)
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The success of predictions of sex ratio conflict led researchers to ask how much conflict over reproduction remains in highly eusocial insects, those with morphologically distinct queen and worker castes. Are these colonies subject to the complexities of cross-purpose?
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This limitation is extremely common in social insects with queen and worker castes. Queens generally require more food, offering the opportunity to control queen production (Wilson, 1971)
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From page 161... ...
The nest has chambers a person could stand in, gardens tended by a suite of worker castes, including leaf processors who use microbial fungicides and have specialized organs to carry these symbionts (Currie et al., 2006)
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From page 162... ...
. in other social insects, workers have wider opportunities to lay eggs when the queen is absent.
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From page 163... ...
Although social insect colonies have clock-like design in many respects, kin selection theory predicts who is throwing sand into the clock works, as well as which gears might be slipped and which springs sprung. Many of the predicted findings, such as sex ratio conflict and policing, were otherwise completely unexpected.
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