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- All Subjects: Evolution & development
- Creators: Schwartz, Gary T
- Creators: Gadau, Jürgen
Description
Speciation is the fundamental process that has generated the vast diversity of life on earth. The hallmark of speciation is the evolution of barriers to gene flow. These barriers may reduce gene flow either by keeping incipient species from hybridizing at all (pre-zygotic), or by reducing the fitness of hybrids (post-zygotic). To understand the genetic architecture of these barriers and how they evolve, I studied a genus of wasps that exhibits barriers to gene flow that act both pre- and post-zygotically. Nasonia is a genus of four species of parasitoid wasps that can be hybridized in the laboratory. When two of these species, N. vitripennis and N. giraulti are mated, their offspring suffer, depending on the generation and cross examined, up to 80% mortality during larval development due to incompatible genic interactions between their nuclear and mitochondrial genomes. These species also exhibit pre-zygotic isolation, meaning they are more likely to mate with their own species when given the choice. I examined these two species and their hybrids to determine the genetic and physiological bases of both speciation mechanisms and to understand the evolutionary forces leading to them. I present results that indicate that the oxidative phosphorylation (OXPHOS) pathway, an essential pathway that is responsible for mitochondrial energy generation, is impaired in hybrids of these two species. These results indicate that this impairment is due to the unique evolutionary dynamics of the combined nuclear and mitochondrial origin of this pathway. I also present results showing that, as larvae, these hybrids experience retarded growth linked to the previously observed mortality and I explore possible physiological mechanisms for this. Finally, I show that the pre-mating isolation is due to a change in a single pheromone component in N. vitripennis males, that this change is under simple genetic control, and that it evolved neutrally before being co-opted as a species recognition signal. These results are an important addition to our overall understanding of the mechanisms of speciation and showcase Nasonia as an emerging model for the study of the genetics of speciation.
ContributorsGibson, Joshua D (Author) / Gadau, Jürgen (Thesis advisor) / Harrison, Jon (Committee member) / Pratt, Stephen (Committee member) / Verrelli, Brian (Committee member) / Willis, Wayne (Committee member) / Arizona State University (Publisher)
Created2013
Description
Extremely thick cranial vaults have been noted as a diagnostic characteristic of Homo erectus since the first fossil of the species was identified, but potential mechanisms underlying this seemingly unique trait have not been rigorously investigated. Cranial vault thickness (CVT) is not a monolithic trait, and the responsiveness of its layers to environmental stimuli is unknown. Identifying factors that affect CVT would be exceedingly valuable in teasing apart potential contributors to thick vaults in the Pleistocene. Four hypotheses were tested using CT scans of skulls of more than 1100 human and non-human primates. Data on total frontal, parietal, and occipital bone thickness and bone composition were collected to test the hypotheses: H1. CVT is an allometric consequence of brain or body size. H2. Thick cranial vaults are a response to long, low cranial vault shape. H3. High masticatory stress causes localized thickening of cranial vaults. H4. Activity-mediated systemic hormone levels affect CVT. Traditional comparative methods were used to identify features that covary with CVT across primates to establish behavior patterns that might correlate with thick cranial vaults. Secondly, novel experimental manipulation of a model organism, Mus musculus, was used to evaluate the relative plasticity of CVT. Finally, measures of CVT in fossil hominins were described and discussed in light of the extant comparative and experimental results. This dissertation reveals previously unknown variation among extant primates and humans and illustrates that Homo erectus is not entirely unique among primates in its CVT. The research suggests that it is very difficult to make a mouse grow a thick head, although it can be genetically programmed to have one. The project also identifies a possible hominin synapomorphy: high diploë ratios compared to non-human primates. It also found that extant humans differ from non-human primates in overall pattern of which cranial vault bones are thickest. What this project was unable to do was definitively provide an explanation for why and how Homo erectus grew thick skulls. Caution is required when using CVT as a diagnostic trait for Homo erectus, as the results presented here underscore the complexity inherent in its evolution and development.
ContributorsCopes, Lynn (Author) / Kimbel, William H. (Thesis advisor) / Schwartz, Gary T (Committee member) / Spencer, Mark A. (Committee member) / Ravosa, Matthew J. (Committee member) / Arizona State University (Publisher)
Created2012
Description
Fundamental hypotheses about the life history, complex cognition and social dynamics of humans are rooted in feeding ecology - particularly in the experiences of young animals as they grow. However, the few existing primate developmental data are limited to only a handful of species of monkeys and apes. Without comparative data from more basal primates, such as lemurs, we are limited in the scope of our understanding of how feeding has shaped the evolution of these extraordinary aspects of primate biology. I present a developmental view of feeding ecology in the ring-tailed lemur (Lemur catta) using a mixed longitudinal sample (infant through adult) collected at the Beza Mahafaly Special Reserve in southwestern Madagascar from May 2009 to March 2010. I document the development of feeding, including weaning, the transition to solid food, and how foods are included in infant diets. Early in juvenility ring-tailed lemurs efficiently process most foods, but that hard ripe fruits and insects require more time to master. Infants and juveniles do not use many of the social learning behaviors that are common in monkeys and apes, and instead likely rely both on their own trial and error and simple local enhancement to learn appropriate foods. Juvenile ring-tailed lemurs are competent and efficient foragers, and that mitigating ecological risks may not best predict the lemur juvenile period, and that increases in social complexity and brain size may be at the root of primate juvenility. Finally, from juvenility through adulthood, females have more diverse diets than males. The early emergence of sex differences in dietary diversity in juvenility that are maintained throughout adulthood indicate that, in addition to reproductive costs incurred by females, niche partitioning is an important aspect of sex differential feeding ecology, and that ontogenetic studies of feeding are particularly valuable to understanding how selection shapes adult, species-typical diets. Overall, lemur juvenility is a time to play, build social relationships, learn about food, and where the kernels of sex-typical feeding develop. This study of the ontogeny of feeding ecology contributes an important phylogenetic perspective on the relationship between juvenility and the emergent foraging behaviors of developing animals
ContributorsO'Mara, Michael Teague (Author) / Nash, Leanne T. (Thesis advisor) / Reed, Kaye E (Committee member) / Schwartz, Gary T (Committee member) / Sauther, Michelle L (Committee member) / Arizona State University (Publisher)
Created2012
Description
The pattern and strength of genetic covariation is shaped by selection so that it is strong among functionally related characters and weak among functionally unrelated characters. Genetic covariation is expressed as phenotypic covariation within species and acts as a constraint on evolution by limiting the ability of linked characters to evolve independently of one another. Such linked characters are "constrained" and are expected to express covariation both within and among species. In this study, the pattern and magnitude of covariation among aspects of dental size and shape are investigated in anthropoid primates. Pleiotropy has been hypothesized to play a significant role in derivation of derived hominin morphologies. This study tests a series of hypotheses; including 1) that negative within- and among-species covariation exists between the anterior (incisors and canines) and postcanine teeth, 2) that covariation is strong and positive between the canines and incisors, 3) that there is a dimorphic pattern of within-species covariation and coevolution for characters of the canine honing complex, 4) that patterns of covariation are stable among anthropoids, and 5) that genetic constraints have been a strong bias on the diversification of anthropoid dental morphology. The study finds that patterns of variance-covariance are conserved among species. Despite these shared patterns of variance-covariance, dental diversification has frequently occurred along dimensions not aligned with the vector of genetic constraint. As regards the canine honing complex, there is no evidence for a difference in the pleiotropic organization or the coevolution of characters of the complex in males and females, which undermines arguments that the complex is selectively important only in males. Finally, there is no evidence for strong or negative pleiotropy between any dental characters, which falsifies hypotheses that predict such relationships between incisors and postcanine teeth or between the canines and the postcanine teeth.
ContributorsDelezene, Lucas (Author) / Kimbel, William H. (Thesis advisor) / Schwartz, Gary T (Committee member) / Spencer, Mark (Committee member) / Verrelli, Brian C (Committee member) / Arizona State University (Publisher)
Created2011
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 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.
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
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 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
Description
Across primates, molar-emergence age is strongly correlated to life-history variables, such as age-at-first-reproduction and longevity. This relationship allows for the reconstruction of life-history parameters in fossil primates. The mechanism responsible for modulating molar-emergence age is unknown, however. This dissertation uses a biomechanical model that accurately predicts the position of molars in adults to determine whether molar emergence is constrained by chewing biomechanics throughout ontogeny. A key aspect of chewing system configuration in adults is the position of molars: the distal-most molar is constrained to avoid tensile forces at the temporomandibular joint (TMJ). Using three-dimensional data from growth samples of 1258 skulls, representing 21 primate species, this research tested the hypothesis that the location and timing of molar emergence is constrained to avoid high and potentially dangerous tensile forces at the TMJ throughout growth. Results indicate that molars emerge in a predictable position to safeguard the TMJ during chewing. Factors related to the size of the buffer zone, a safety feature that creates greater stability at the TMJ during biting, account for a large portion of both ontogenetic and interspecific variation in the position of emergence. Furthermore, the rate at which space is made available in the jaws and the duration of jaw growth both determine the timing of molar emergence. Overall, this dissertation provides a mechanical and developmental model for explaining temporal and spatial variation in molar emergence and a framework for understanding how variation in the timing of molar emergence has evolved among primates. The findings suggest that life history is related to ages at molar emergence through its influence on the rate and duration of jaw growth. This dissertation provides support for the functionally integrated nature of craniofacial growth and has implications for the study of primate life history evolution and masticatory morphology in the fossil record.
ContributorsGlowacka, Halszka (Author) / Schwartz, Gary T (Thesis advisor) / Kimbel, William H. (Committee member) / Reed, Kaye E (Committee member) / Wright, Barth W (Committee member) / Arizona State University (Publisher)
Created2017
Description
I studied the evolution and cell biology of Paramecium tetraurelia—a model ciliate with over 40,000 distinct protein-coding genes resulting from as many as three ancient whole-genome duplication events. I was interested in the functional diversification of these gene duplicates at the level of protein localization, but the commonly used tools to study this were tedious. I instead applied a protein-correlation profiling approach to this system by way of generating a dozen sub-cellular fractions with different protein constituents due to the density of their resident organelle and then assayed these fractions using quantitative mass spectrometry. Each protein’s unique abundance profile provided evidence for its subcellular localization, and I used both supervised and unsupervised classification algorithms to cluster proteins together based on the similarity of these profiles to several hundred “marker proteins” which I manually curated. After expanding the protein inventory for numerous organelles by as many as a thousand proteins, I determined many features not previously understood or appreciated such as mosaic biochemical pathways, evidence for differential sorting mechanisms, and the abnormal evolutionary patterns of the mitochondrial proteome of ciliates. I developed a simple bioinformatic tool to probe spatial proteomics datasets more easily for proteins of interest. I demonstrate its applicability using a handful of well-characterized proteins in the budding yeast Saccharomyces cerevisiae as well as interesting proteins in less well-studied model systems like P. tetraurelia and the apicomplexan Toxoplasma gondii to both recapitulate known interactions and discover new ones. Finally, I look for large-scale evidence of gene duplicates relocalizing to new cellular compartments in P. tetraurelia and S. cerevisiae using this new dataset and a previously generated one, respectively. I find thousands of pairs of duplicates which are differentially identified and display evidence for subcellular divergence, and this seems to be largely decoupled from large changes in protein sequence but are instead associated with indels in their N-terminal peptide. These findings support the use of high-throughput proteomic techniques to determine evidence of functional divergence of gene duplicates. Taken together, this works provides a deep characterization of one of the largest unicellular proteomes in nature.
ContributorsLicknack, Timothy James (Author) / Lynch, Michael (Thesis advisor) / Wideman, Jeremy (Committee member) / Chen, Julian (Committee member) / Taylor, Jay (Committee member) / Arizona State University (Publisher)
Created2022
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 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.
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
Description
Differences in the postcanine dentition of primates likely represent dietary adaptations given that the teeth interact directly with foods during mastication. Among early hominins, changes to both molar and premolar morphology are purported to indicate consumption of foods differing in their material properties. Some early hominins, such as the robust australopiths, possess premolars that resemble molars with enhancements to the distal part of the tooth (i.e., the talonid), including additional cusps and/or expanded basins. Such molarized premolars are thought to indicate that these hominins were processing mechanically challenging foods; that is, food items that were either hard or tough. Hypotheses tested in this study evaluated the link between the degree of premolar molarization and consumption of mechanically challenging foods in extant primates. Surface anatomy of the distal-most mandibular premolar (the P4) was quantified using a combination of 3D scans of postcanine dental casts and craniodental landmark data collected from 541 individuals, representing 22 extant primate taxa with well-studied diets and known food material properties. Taxa with more mechanically challenging diets were expected to have premolars with expanded talonids and enlarged P4s (and/or molar rows) relative to several mechanically-relevant size proxies. Taxa consuming high proportions of structural carbohydrates were also expected to have postcanine teeth with high occlusal relief (RFI), sharpness (DNE), and complexity (OPCR). Taxa consuming harder food items were expected to have lower relief and higher complexity, with sharpness determined by the proportion of structural carbohydrates included in their diet. The work presented in this dissertation supports most of these expectations, though talonid expansion per se was not clearly linked to the consumption of any particular diet. Overall, taxa with more mechanically challenging diets generally had relatively enlarged premolars when compared to taxa with softer diets and also differed predictably in their occlusal topography. The results of this dissertation support the functional significance of P4 crown size and measures of dental topography as they relate to diet and have implications for improving dietary inferences from the fossil record.
ContributorsDaly, Elizabeth Susanne (Author) / Schwartz, Gary T (Thesis advisor) / Delezene, Lucas K (Committee member) / Kimbel, William H (Committee member) / Arizona State University (Publisher)
Created2021