[Paleopsych] SW: On Social Selection for Eccentricity

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Evolution: On Social Selection for Eccentricity

    The following points are made by Michel Chapuisat (Current Biology
    2004 14:1003):
    1) In nature, colorful patterns usually constitute a signal; they may
    deter competitors, frighten predators, or attract mates. The standard
    view on animal signaling is that variation in ornamentation carries
    information about the condition and quality of the signaler [1,2]. For
    example, the black-and-yellow stripes of wasps are a signal of danger
    to other species. But there is more to it than that. Recently,
    Tibbetts [3] reported an experimental study showing that paper wasps
    use intraspecific variation in facial and abdominal markings to
    recognize individuals. A new comparative analysis by the same author
    [4] has revealed that species with a flexible nest-founding strategy
    have more variable markings than those with obligate single or
    multiple foundresses. This new work suggests that complex social
    interactions may select for individual distinctiveness and raises
    interesting questions about the costs and benefits of revealing
    individuality in social groups.
    2) Polistes paper wasps form a widespread, species-rich group of
    social insects [5]. They build small, open paper nests in protected
    places. All paper wasps are eusocial: one or a few individuals
    monopolize reproduction, while other individuals defend the colony,
    forage, and care for the brood. After overwintering, mated females --
    the queens -- found new nests. The species differ in their
    nest-founding habits, following one of three possible strategies: they
    may have an obligate single foundress, where only one queen starts a
    nest; they may have obligate multiple foundresses, where two or more
    queens start a nest together; or they may show flexible nest-founding,
    where either a single queen or multiple queens start a nest.
    3) Paper wasp colonies are well known for having a dominance hierarchy
    [5]. In species with an obligate single foundress or obligate multiple
    foundresses, dominant queens usually monopolize all reproduction, and
    other females behave as workers. In species with a flexible
    nest-founding strategy, the social interactions tend to be more
    complex. There are even some theoretical and empirical indications
    that queens engage in reproductive transactions whereby they yield
    part of the reproductive potential to other females in order to make
    them stay and cooperate peacefully. Complex alliances of this kind
    require that wasps are able to accurately recognize individuals.
    4) Polistes fuscatus individuals have highly variable markings on
    their face and abdomen, such as the presence or absence of conspicuous
    yellow eyebrows [3]. Together, these markings yield dozens of unique
    patterns, suggesting they may serve for visual recognition of
    individuals. Indeed, wasps that had experimentally altered markings
    were found to receive more aggression than control wasps that had been
    painted without altering their markings [3]. Importantly, the
    aggression was transient and declined with time as wasps became
    familiar with the new markings. This elegant study showed that wasps
    use visual cues to distinguish individuals. Further, it suggested that
    variable markings might undergo selection for improved individual
    recognition in species with complex social interactions.
    References (abridged):
    1. Maynard Smith, J. and Harper, D. (2003). Animal signals. (Oxford:
    Oxford University Press)
    2. In Animal signals: signalling and signal design in animal
    communication. (2000). Espmark, Y., Amundsen, T. and Rosenqvist, G.
    eds. (Trondheim, Norway: Tapir, Academic Press)
    3. Tibbetts, E.A. (2002). Visual signals of individual identity in the
    wasp Polistes fuscatus. Proc. R. Soc. Lond. B 269, 1423-1428
    4. Tibbetts, E.A. (2004). Complex social behavior can select for
    variability in visual features: a case study in Polistes wasps. Proc.
    R. Soc. Lond. B 271, 1955-1960
    5. In Natural history and evolution of paper-wasps. (1996).
    Turillazzi, S. and West-Eberhard, M.J. eds. (Oxford: Oxford University
    Current Biology http://www.current-biology.com
    Related Material:
    Notes by ScienceWeek:
    The so-called social insects live in societies that rival human
    societies in complexity and internal cohesion. Honey bees, for
    example, apparently always follow 3 rules: a) they live in colonies
    with overlapping generations; b) they care cooperatively for offspring
    other than their own; and, c) they maintain a reproductive division of
    The following points are made by Gene E. Robinson (American Scientist
    1998 86:456):
    1) Genes do not play an exclusive role in regulating behavior:
    biologists have long realized that behavior is influenced by genes,
    the environment, and interactions between the two.
    2) Genes never act alone. They must operate in an environment where
    they code for proteins that participate in many systems in an
    organism, with these systems in turn influencing the expression of
    genes. Consequently, biologists must take a broad approach in
    assessing the impact of any gene.
    3) The research group of the author uses the Western honey bee, Apis
    mellifera. Honey bees pass through different life stages as they age,
    and their behavioral responses to environmental and social stimuli
    change in predictable ways. Although worker bees go through a
    consistent path of behavioral development, this path is not rigidly
    determined. Bees can accelerate, retard, or even reverse their
    behavioral development in response to changing environmental and
    colony conditions.
    4) Experimental evidence indicates that juvenile hormone, one of the
    most important hormones influencing insect development, helps time the
    pace of behavioral maturation in honey bees. The rate of
    endocrine-mediated behavioral development is influenced by inhibitory
    social interactions. Older bees inhibit the behavioral development of
    younger bees: the rate of behavioral development is negatively
    correlated with the proportion of older bees in a colony. Inhibitory
    social interactions that influence the rate of behavioral development
    involve chemical communication between colony members.
    5) Evidence from the laboratory of the author in 1993 indicated the
    so-called mushroom bodies in the bee brain are involved in the
    behavioral changes occurring during maturation, the volume of the
    bodies increasing, and the volume increase associated with an increase
    in synapses with neurons from brain regions devoted to sensory input.
    The author suggests this was the first report of brain plasticity in
    an invertebrate.
    6) The author suggests that, in general, two-way interactions between
    the nervous system and the genome contribute fundamentally to the
    control of social behavior. Information about social conditions that
    is acquired by the nervous system is likely to induce changes in
    genomic function that in turn produce adaptive modifications of the
    structure and function of the nervous system.
    7) The author proposes a new research initiative called
    "sociogenomics", defined as a "wide-ranging approach to identify genes
    that influence social behavior, determining the influence of these
    genes on underlying neural and endocrine mechanisms, and exploring the
    effects of the environment -- particularly the social environment --
    on gene action."
    American Scientist http://www.americanscientist.org
    Related Material:
    The following points are made by M.J. Krieger and K.G. Ross (Science
    2002 295:328):
    1) The evolution of complex social behavior is among the most
    important events in the history of life. Interest in the genes
    underlying the expression of key social traits is strong because
    knowledge of the genetic architecture will lead to increasingly
    realistic models of social evolution, while identification of the
    products of major genes can elucidate the molecular bases of social
    behavior. Few studies have succeeded in showing that complex social
    behaviors have a heritable basis, and fewer still have suggested that
    variation in these behaviors is attributable to the action of one or
    few genes of major effect. No candidate genes with major effects on
    key social polymorphisms have been identified previously.
    2) The fire ant Solenopsis invicta displays a fundamental social
    polymorphism that appears to be under simple genetic control. A basic
    feature of fire ant colony social organization, the number of
    egg-laying queens, is associated with variation at the gene Gp-9. In
    the US, where this species has been introduced, colonies composed of
    workers bearing only the (B) allele at Gp-9 invariably have a single
    queen (monogyne social form), whereas colonies with workers bearing
    the alternate (b) allele have multiple queens (polygyne social form).
    The two social forms differ in many key reproductive and life history
    3) The authors report they sequenced the gene Gp-9 and found that it
    encodes a pheromone-binding protein, a crucial molecular component in
    same-species (conspecific) chemical recognition. The authors suggest
    this indicates that differences in worker Gp-9 genotypes between
    social forms may cause differences in the abilities of workers to
    recognize queens and regulate their numbers. The authors conclude:
    "This study demonstrates that single genes of major effect can
    underlie the expression of complex behaviors important in social

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