This thesis examines whether juvenile feral pigeons, Columba livia, form sibling alliances when competing for access to a defensible food source. When tested as a flock at a non-depletable column feeder, with room for either one or two birds to feed, siblings associated with each other more often than expected by chance. Frequency of aggression between siblings at these feeders tended to be lower than expected on the basis of their association. Removal experiments showed that sibling presence had a positive effect on relative feeding success at the single column feeder: a juvenile who lost to another juvenile on a one-to-one basis tended, in the presence of its sibling, to lose less badly to, or even beat, that same juvenile. In contrast, presence of the winner's sibling tended not to affect the relative feeding success of competitors. These results support the hypothesis that pigeon siblings form aggressive alliances when competing for food that is defensible.

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Thesis (Ph. D.)--State University of New York at Binghamton, Department of Biological Sciences, 2009. / Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Biological Sciences, 2008. / Includes bibliographical references.

Within social insect colonies, sterile workers are responsible for brood care, while queens are the primary egg-layers. These reproductive caste differences are often accompanied by pronounced morphological distinctions. Queen and worker phenotypic differences are particularly remarkable considering caste is environmentally, rather than genetically, determined. Environmental caste determination can produce intralocus genetic conflict between castes, particularly when homologous traits are highly dimorphic. Therefore, when studying the evolution of social insect caste dimorphism, one must consider the genetic architecture underlying phenotypic expression as well as the selective pressures that have shaped caste morphology. This dissertation presents the results of four studies that investigated factors affecting caste morphology in the social wasp Vespula maculifrons. The first two studies focused on identifying queen morphological traits that were positively associated with queen fitness and would therefore be subject to selection. Queen length, specifically gaster length, was positively associated with overwintering survival and was consistently associated with mating success. Both of these findings suggest that queen gaster length is under selection during two life-history events, mating and overwintering, in which workers do not participate. These findings provide empirical support for the adaptive evolution of a caste dimorphic trait. The third and fourth studies used classical quantitative genetic and morphological analyses to examine the genetic architecture underlying caste dimorphism in V. maculifrons. I determined which traits were under caste-specific selection by analyzing trait allometries and the levels of genetic control, variation, and dimorphism of traits between castes. Little genetic variation for morphological trait size was detected for most worker and queen traits, suggesting a strong influence of environment on phenotypic variation. Additionally, analyses of trait allometries indicated that several queen traits (mass, thorax width and length) were under queen-specific selection. The relationship between thorax length, gaster length, and overall body size is further evidence of selection on length in queens. Overall, these studies provide evidence for the importance of queen-specific selection in the evolution of caste dimorphism. When placed in the broader context of caste evolution, they point to the importance of life-history in shaping the genetic architecture underlying caste dimorphism.