Individual differences in fighting ability between animals often determine the outcome of agonistic contests, but how animals assess their relative fighting abilities is not obvious. Morphological differences in the color patterns of bird plumage and wasp facial-spots signal fighting abilities, i.e., they are badge of status. However, laboratory experimental tests on the badges of status of wasps have been contradictory, suggesting that badges of status may vary geographically within a species. We analysed the facial patterns in three geographically-separated populations of the paper wasp Polistes biglumis. In these populations, nest-foundresses are often attacked by conspecific females who try to displace foundresses and take over their nest. Both foundresses and usurpers have very variable facial patterns. We tested whether facial patterns predicted the outcome of nest-usurpation contests by taking shoots of foundresses and usurpers in the wild. Fighting abilities, as measured by body size, were reliable predictors of who wins in nest-usurpation contests across populations - usurpers were significantly larger than foundresses. As for badges of status, facial patterns, as measured by blackness and brokenness of clipei, were not reliable predictors of dominance across populations. Indeed, in some population usurpers had significantly less blackness and more brokenness than the foundresses they displaced, whereas in others they had not. Understanding how signals evolve is a central focus in animal behavior study. Geographic variations in signals offers important clues to identify the selective forces that act on communication signals.
Geographic variations in badges of status in paper wasps
LORENZI, Maria Cristina
2012-01-01
Abstract
Individual differences in fighting ability between animals often determine the outcome of agonistic contests, but how animals assess their relative fighting abilities is not obvious. Morphological differences in the color patterns of bird plumage and wasp facial-spots signal fighting abilities, i.e., they are badge of status. However, laboratory experimental tests on the badges of status of wasps have been contradictory, suggesting that badges of status may vary geographically within a species. We analysed the facial patterns in three geographically-separated populations of the paper wasp Polistes biglumis. In these populations, nest-foundresses are often attacked by conspecific females who try to displace foundresses and take over their nest. Both foundresses and usurpers have very variable facial patterns. We tested whether facial patterns predicted the outcome of nest-usurpation contests by taking shoots of foundresses and usurpers in the wild. Fighting abilities, as measured by body size, were reliable predictors of who wins in nest-usurpation contests across populations - usurpers were significantly larger than foundresses. As for badges of status, facial patterns, as measured by blackness and brokenness of clipei, were not reliable predictors of dominance across populations. Indeed, in some population usurpers had significantly less blackness and more brokenness than the foundresses they displaced, whereas in others they had not. Understanding how signals evolve is a central focus in animal behavior study. Geographic variations in signals offers important clues to identify the selective forces that act on communication signals.
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