Kin-selection theory states that individuals can increase their total fitness both through direct reproduction and through reproduction of relatives. The recently developed social contract theory asserts that dominant females should yield some direct reproduction to the subordinates in order to keep them in the colony. The theory predicts that a dominant will cede more reproduction to an unrelated subordinate than to a related subordinate since it will take more to keep her. I found that the social wasp, Polistes dominulus, is unusual in that foundresses regularly nest with non-relatives, even when relatives are available on other nests. This offers the opportunity to test one of the basic predictions of social contract theory, that reproductive skew increases as relatedness among co-foundresses increases. Subordinates of the collected colonies did get a small fraction of direct reproduction, but there was no difference in skew among colonies with different co-foundress relatednesses, contrary to skew theory predictions. Subordinates's relatedness to the queen does not affect colony efficiency. This study found no sign of either higher cooperation in colonies with more related females or greater conflicts in colonies founded by unrelated females.

Genetic data was obtained from a colony of Parachartergus colobopterus using DNA microsatellites. A colony cycle referred to as cyclical oligogyny is believed to account for the high relatedness in this polygynous species. The genetic data was analyzed to support the presence of cyclical oligogyny and determine some of the specific mechanisms behind it. Specifically, queen reduction, increasing reproductive dominance, sexual specialization by queens, and maternity of males (worker vs. queen) were examined. There was evidence for queen reduction occurring in this colony. To the contrary, no support was found for either increasing reproductive dominance or sexual specialization among the queens. It appears that the queens produced all of the males in this colony. This concurs with a worker preference for queen laying of the males that was seen in relatedness estimates.

Several transitions to higher levels of biological organization have punctuated the history of life. These transitions occur when cooperative alliances lead to the integration of non-identical partners into more complex wholes. Yet there is inevitable conflict within these cooperative alliances. In the following chapters I investigate reproductive conflicts of interest between cooperators within insect societies and chimeric multicellular organisms. In the first chapter I show that in the tropical wasp, Parachartergus colobopterus, workers use aggression toward totipotent, emerging females to influence the reproductive future of the latter. By doing this workers resolve conflict over who reproduces in accord with their collective interests. In the second chapter I show that environmental heterogeneity can affect the outcome of conflict between co-aggregating clonal lineages of Dictyostelium discoideum. This helps account for the coexistence of cheaters and victims in natural populations of D. discoideum.

Invasive species, fire suppression and nutrient deposition, as distinct disturbance factors, have altered Texas prairie communities. Arthropod diversity, abundance, and community composition may be modified by these factors either directly or by changes in plant community structure. Because arthropods provide essential ecosystem services and represent a large proportion of terrestrial biodiversity, understanding the responses of arthropod communities to disturbance is the central theme of this doctoral thesis. Land managers commonly utilize fire to control woody species encroachment into prairies and anthropogenic nutrient deposition increases plant productivity. The responses of arthropods to fire and fertilizer manipulations were examined. Fire maintained arthropod diversity by limiting woody plant cover. Path analysis indicated fertilization decreased arthropod diversity by promoting woody plant invasion. Direct negative effects of fire on the arthropod community were small compared to the indirect, positive effects. Arthropod abundance and species richness on the invasive species Chinese Tallow Tree (Sapium sebiferum) were compared to arthropods on three native tree species: Silver Maple (Acer saccharinum), Sycamore (Platanus occidentalis), and Sweetgum ( Liquidambar styraciflua). Although arthropod community composition differed on Sapium, species richness and abundance were similar to levels on native trees. Sapium experienced less chewing, fungal, and mining damage and supported relatively abundant predators and detritivores whilst there were relatively fewer herbivores. These observations are in accord with the Enemies Release Hypothesis that predicts low herbivore loads may contribute to Sapium's invasive success. When Sapium was compared to native plant dominated habitats, predators and detritivores were again relatively abundant while total arthropod diversity was comparatively low. This implies that Sapium has not acquired an insect fauna comparable to native plants in Texas. Insect assemblages on Sapium were examined along a geographical gradient, representing time since introduction. Sapium trees in Florida and Georgia (present longer) had higher insect loads compared to those in Louisiana and Texas (more recently introduced), but species richness did not differ. Herbivore and omnivore abundance and species richness were higher where Sapium has been present longer. This suggests that time since introduction is an important factor constraining herbivore diversity and abundance. Accumulation of herbivores may limit Sapium populations in the future.

My dissertation encompasses three studies of social behavior. Two explore the reproductive conflicts that occur between cooperating individuals. I examine conflict at two levels: within colonies of the social wasp, Eustenogaster fraterna, and within chimeric multicellular organisms formed by the social amoeba, Dictyostelium discoideum. The third project investigates the occurrence of sexual reproduction in a natural population of D. discoideum. Eustenogaster fraterna belongs to the basal eusocial family of stenogastrine wasps. Colonies are small averaging only 2.7 adult females but only one mated female. I examined the reproductive and genetic structure of 18 colonies by genotyping all within-colony individuals and assessing the ovarian development of females. My results show that 85% of females were potential reproducers. Adult females were not related as full sisters. Some brood could not be assigned to any of the adult females, suggesting that subordinate females could inherit the nest and replace the dominant female. D. discoideum live as free-living, single cells, but when starved they aggregate to form a multicellular fruiting body. Genetically distinct clones of D. discoideum co-aggregate to form genetic chimeras. 20% of cells form the stalk of the fruiting body and die, while others become reproductive spores. One clone can exploit the other by contributing less than its proportional share to the sterile stalk. I investigated whether cheating is a strategy dependent on the relative proportion of the clones aggregating. In a chimera, a rare clone could benefit by avoiding forming the stalk because it is less related to the reproductive part. My results do not support the frequency-dependence strategy. I investigated the occurrence of sexual reproduction in a natural population of D. discoideum, using the approach of estimating linkage disequilibrium in the population at one site. My results show that recombination does occur and is due to sexual reproduction not to parasexuality. In sum, conflicts within societies can be mitigated. E. fraterna workers gain insurance advantages by obtaining indirect genetic benefits or inheritance of work force. D. discoideum clones gain cheating advantages either when rare or common in the aggregation. Recombination yields novel genotypes; this might increase the complexity of interactions between co-aggregating clones.

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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 2742. Adviser: Andrew Belmont. Includes bibliographical references (leaves 42-47) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 2736. Adviser: Andrew Suarez. Includes bibliographical references (leaves 83-99) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6534. Adviser: Wesley M. Jarrell. Includes supplementary digital materials. Includes bibliographical references (leaves 134-152) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2005. / Title from PDF t.p. (viewed Dec. 2, 2008). Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0687. Chair: Thomas C. Kaufman.