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A notable feature of advanced eusocial insect groups is a division of labor within the sterile worker caste. However, the physiological aspects underlying the differentiation of behavioral phenotypes are poorly understood in one of the most successful social taxa, the ants. By starting to understand the foundations on which social

A notable feature of advanced eusocial insect groups is a division of labor within the sterile worker caste. However, the physiological aspects underlying the differentiation of behavioral phenotypes are poorly understood in one of the most successful social taxa, the ants. By starting to understand the foundations on which social behaviors are built, it also becomes possible to better evaluate hypothetical explanations regarding the mechanisms behind the evolution of insect eusociality, such as the argument that the reproductive regulatory infrastructure of solitary ancestors was co-opted and modified to produce distinct castes. This dissertation provides new information regarding the internal factors that could underlie the division of labor observed in both founding queens and workers of Pogonomyrmex californicus ants, and shows that changes in task performance are correlated with differences in reproductive physiology in both castes. In queens and workers, foraging behavior is linked to elevated levels of the reproductively-associated juvenile hormone (JH), and, in workers, this behavioral change is accompanied by depressed levels of ecdysteroid hormones. In both castes, the transition to foraging is also associated with reduced ovarian activity. Further investigation shows that queens remain behaviorally plastic, even after worker emergence, but the association between JH and behavioral bias remains the same, suggesting that this hormone is an important component of behavioral development in these ants. In addition to these reproductive factors, treatment with an inhibitor of the nutrient-sensing pathway Target of Rapamycin (TOR) also causes queens to become biased towards foraging, suggesting an additional sensory component that could play an important role in division of labor. Overall, this work provides novel identification of the possible regulators behind ant division of labor, and suggests how reproductive physiology could play an important role in the evolution and regulation of non-reproductive social behaviors.
ContributorsDolezal, Adam G (Author) / Amdam, Gro V (Thesis advisor) / Brent, Colin S. (Committee member) / Gadau, Juergen (Committee member) / Hoelldobler, Bert (Committee member) / Liebig, Juergen (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Persistent cooperation between unrelated conspecifics rarely occurs in mature eusocial insect societies. In this dissertation, I present evidence of non-kin cooperation in the Nearctic honey ant Myrmecocystus mendax. Using microsatellite markers, I show that mature colonies in the Sierra Ancha Mountain of central Arizona contain multiple unrelated matrilines, an observation

Persistent cooperation between unrelated conspecifics rarely occurs in mature eusocial insect societies. In this dissertation, I present evidence of non-kin cooperation in the Nearctic honey ant Myrmecocystus mendax. Using microsatellite markers, I show that mature colonies in the Sierra Ancha Mountain of central Arizona contain multiple unrelated matrilines, an observation that is consistent with primary polygyny. In contrast, similar analyses suggest that colonies in the Chiricahua Mountains of southeastern Arizona are primarily monogynous. These interpretations are consistent with field and laboratory observations. Whereas cooperative colony founding was observed frequently among groups of Sierra Ancha foundresses, founding in the Chiricahua population was restricted to individual foundresses. Furthermore, Sierra Ancha foundresses successfully established incipient laboratory colonies without undergoing queen culling following emergence of the first workers. Multi-queen laboratory Sierra Ancha colonies also produced more workers and repletes than haplometrotic colonies, and when brood raiding was induced between colonies, queens of those with more workers had a higher survival probability.

Microsatellite analyses of additional locations within the M. mendax range suggest that polygyny is also present in some other populations, especially in central-northern Arizona, albeit at lower frequencies than that in the Sierra Anchas. In addition, analyses of multiple types of genetic data, including microsatellites, the mitochondrial barcoding region, and over 2000 nuclear ultra-conserved elements indicate that M. mendax populations within the southwestern U.S. and northwestern Mexico are geographically structured, with strong support for the existence of two or more divergent clades as well as isolation-by-distance within clades. This structure is further shown to correlate with variation in queen number and hair length, a diagnostic taxonomic feature used to distinguish honey ant species.

Together, these findings suggest that regional ecological pressures (e.g. colony density , climate) may have acted on colony founding and social strategy to select for increasing workforce size and, along with genetic drift, have driven geographically isolated M. mendax populations to differentiate genetically and morphologically. The presence of colony fusion in the laboratory and life history traits in honey ant that are influenced by colony size, including repletism, brood raiding, and tournament, support this evolutionary scenario.
ContributorsEriksson, Ti (Author) / Gadau, Jürgen (Thesis advisor) / Taylor, Jay (Thesis advisor) / Fewell, Jennifer (Committee member) / Hӧlldobler, Bert (Committee member) / Johnson, Robert (Committee member) / Pratt, Stephen (Committee member) / Arizona State University (Publisher)
Created2018
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Description
The most abundantly studied societies, with the exception of humans, are those of the eusocial insects, which include all ants. Eusocial insect societies are typically composed of many dozens to millions of individuals, referred to as nestmates, which require some form of communication to maintain colony cohesion and coordinate the

The most abundantly studied societies, with the exception of humans, are those of the eusocial insects, which include all ants. Eusocial insect societies are typically composed of many dozens to millions of individuals, referred to as nestmates, which require some form of communication to maintain colony cohesion and coordinate the activities within them. Nestmate recognition is the process of distinguishing between nestmates and non-nestmates, and embodies the first line of defense for social insect colonies. In ants, nestmate recognition is widely thought to occur through olfactory cues found on the exterior surfaces of individuals. These cues, called cuticular hydrocarbons (CHCs), comprise the overwhelming majority of ant nestmate profiles and help maintain colony identity. In this dissertation, I investigate how nestmate recognition is influenced by evolutionary, ontogenetic, and environmental factors. First, I contributed to the sequencing and description of three ant genomes including the red harvester ant, Pogonomyrmex barbatus, presented in detail here. Next, I studied how variation in nestmate cues may be shaped through evolution by comparatively studying a family of genes involved in fatty acid and hydrocarbon biosynthesis, i.e., the acyl-CoA desaturases, across seven ant species in comparison with other social and solitary insects. Then, I tested how genetic, developmental, and social factors influence CHC profile variation in P. barbatus, through a three-part study. (1) I conducted a descriptive, correlative study of desaturase gene expression and CHC variation in P. barbatus workers and queens; (2) I explored how larger-scale genetic variation in the P. barbatus species complex influences CHC variation across two genetically isolated lineages (J1/J2 genetic caste determining lineages); and (3) I experimentally examined how CHC development is influenced by an individual’s social environment. In the final part of my work, I resolved discrepancies between previous findings of nestmate recognition behavior in P. barbatus by studying how factors of territorial experience, i.e., spatiotemporal relationships, affect aggressive behaviors among red harvester ant colonies. Through this research, I was able to identify promising methodological approaches and candidate genes, which both broadens our understanding of P. barbatus nestmate recognition systems and supports future functional genetic studies of CHCs in ants.
ContributorsCash, Elizabeth I (Author) / Gadau, Jürgen (Thesis advisor) / Liebig, Jürgen (Thesis advisor) / Fewell, Jennifer (Committee member) / Hölldobler, Berthold (Committee member) / Kusumi, Kenro (Committee member) / Arizona State University (Publisher)
Created2016
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Description
Transgenic experiments in Drosophila have proven to be a useful tool aiding in the

determination of mammalian protein function. A CNS specific protein, dCORL is a

member of the Sno/Ski family. Sno acts as a switch between Dpp/dActivin signaling.

dCORL is involved in Dpp and dActivin signaling, but the two homologous mCORL

protein functions

Transgenic experiments in Drosophila have proven to be a useful tool aiding in the

determination of mammalian protein function. A CNS specific protein, dCORL is a

member of the Sno/Ski family. Sno acts as a switch between Dpp/dActivin signaling.

dCORL is involved in Dpp and dActivin signaling, but the two homologous mCORL

protein functions are unknown. Conducting transgenic experiments in the adult wings,

and third instar larval brains using mCORL1, mCORL2 and dCORL are used to provide

insight into the function of these proteins. These experiments show mCORL1 has a

different function from mCORL2 and dCORL when expressed in Drosophila. mCORL2

and dCORL have functional similarities that are likely conserved. Six amino acid

substitutions between mCORL1 and mCORL2/dCORL may be the reason for the

functional difference. The evolutionary implications of this research suggest the

conservation of a switch between Dpp/dActivin signaling that predates the divergence of

arthropods and vertebrates.
ContributorsStinchfield, Michael J (Author) / Newfeld, Stuart J (Thesis advisor) / Capco, David (Committee member) / Laubichler, Manfred (Committee member) / Arizona State University (Publisher)
Created2019
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Description
In many social groups, reproduction is shared between group members, whocompete for position in the social hierarchy for reproductive dominance. This reproductive conflict can lead to different means of enforcing reproductive differences, such as dominance displays or limited control of social hierarchy through antagonistic encounters. In eusocial insects, archetypal colonies contain a single,

In many social groups, reproduction is shared between group members, whocompete for position in the social hierarchy for reproductive dominance. This reproductive conflict can lead to different means of enforcing reproductive differences, such as dominance displays or limited control of social hierarchy through antagonistic encounters. In eusocial insects, archetypal colonies contain a single, singly-mated fertile queen, such that no reproductive conflict exists within a colony. However, many eusocial insects deviate from this archetype and have multiply-mated queens (polyandry), multiple queens in a single colony (polygyny), or both. In these cases, reproductive conflict exists between the matrilines and patrilines represented in a colony, specifically over the production of sexual offspring. A possible outcome of reproductive conflict may be the emergence of cheating lineages, which favor the production of sexual offspring, taking advantage of the worker force produced by nestmate queens and/or patrilines. In extreme examples, inquiline social parasites may be an evolutionary consequence of reproductive conflict between nestmate queens. Inquiline social parasitism is a type of social parasitism that is usually defined by a partial or total loss of the worker caste, and the “infiltration” of host colonies to take advantage of the host worker force for reproduction. It has been hypothesized that these inquiline social parasites evolve through the speciation of cheating queen lineages from within their incipient host species. This “intra- specific” origin model involves a foundational hypothesis that the common ancestor of host and parasite (and thus, putatively, the host at the time of speciation) should be functionally polygynous, and that parasitism evolves as a “resolution” of reproductive conflict in colonies. In this dissertation, I investigate the hypothesized role of polygyny in the evolution of inquiline social parasites. I use molecular ecology and statistical approaches to validate the role of polygyny in the evolution of some inquiline social parasites. I further discuss potential mechanisms for the evolution and speciation of social parasites, and discuss future directions to elucidate these mechanisms.
ContributorsDahan, Romain Arvid (Author) / Rabeling, Christian (Thesis advisor) / Amdam, Gro V (Committee member) / Fewell, Jennifer H (Committee member) / Pratt, Stephen C (Committee member) / Rüppell, Olav (Committee member) / Arizona State University (Publisher)
Created2021