Browsing by Subject "Phenotypic plasticity"
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Item Developmental Plasticity of Cochliomyia macellaria Fabricius (Diptera: Calliphoridae) from Three Distinct Ecoregions in Texas(2012-12-11) Owings, Charity Grace 1987-Forensic entomology is a well-established science linking arthropod biology and ecology to legal investigations. Specifically, immature development on a decomposing corpse may give insight into the minimum time elapsed since death. Until recently, biological variation within a single species has been overlooked when estimating colonization events. Variation in the form of phenotypic plasticity, or the ability of a single genotype to produce multiple phenotypes under alternative stresses, has been documented in genetic and ecological literature and spans across all phyla. Taking this into account, different subpopulations of forensically pertinent insect species should also possess the ability to adapt to changing environments as geographic distribution increases. Thus, plastic responses of a species to alternative stresses may be measured in biological parameters, such as development time. In this research, three geographically distinct strains of the blow fly Cochliomyia macellaria Fabricius (Diptera Calliphoridae) were reared in two distinct environments in order to measure development time, as well as pupal and adult masses. Strains exhibited genetic variance when compared to each other, and each strain exhibited variable responses across environments (phenotypic plasticity). Plasticity in the form of genotype by environment (GxE) interactions was also exhibited by C. macellaria, although consistent adherence to any single rule explaining ontogenetic trends was not apparent. This research supports the existence of intraspecific variation in a common blow fly of forensic importance. Results of this study will impact the forensic entomology community by encouraging the generation of either strain;specific developmental datasets or statistical models to minimize variation caused by genetic, environment, or GxE effects in order to compare developmental data across strains.Item Evolutionary genetics and ecology of water use efficiency ([delta]¹³C) in Ipomopsis agregata and Arabidopsis thaliana(2011-12) Kenney, Amanda Marie; Juenger, Thomas; Bolnick, Daniel I.; Linder, C. Randal; Roux, Stanley J.; McKay, John K.My dissertation research investigates the genetic architecture and evolutionary significance of physiological variation in two wildflower species, Ipomopsis aggregata and Arabidopsis thaliana. In particular, my work focuses on water use efficiency (WUE), a critical physiological trait that dictates plant growth and performance in resource-limited environments. I used a combination of quantitative trait loci (QTL) mapping, field selection experiments, and classic quantitative genetics to investigate 1) the genetic architecture of water use efficiency and flowering time, 2) patterns of natural selection on water use efficiency, flowering time, and other ecological traits in I. aggregata, and 3) additive genetic variation, genetic correlations, and selection on water use efficiency, flowering time, and plasticity to drought in Arabidopsis thaliana. Using an Ipomopsis aggregata genetic mapping population, I identified four QTL underlying WUE, three QTL-QTL epistatic interactions, and evidence for a possible QTL x cytoplasmic interaction affecting WUE. I found a similar genetic architecture underlying flowering time, with four main effect QTLs that all adjacently localized to the same linkage groups as WUE, and three QTL-QTL epistatic interactions, which occur between the same chromosome pairs as the WUE interactions. The combined main and interactive effects explain 35% and 40% of the phenotypic variation in WUE and flowering time, respectively. The adjacent localization suggests a possible role for the evolution of co-inheritance or, if the true QTL positions actually overlap, a possible role for pleiotropy underlying the phenotypic correlation between WUE and flowering time. Additionally, these results suggest epistasis is a significant factor affecting phenotypic variation in nature. In a reciprocal transplant and water addition experiment, I demonstrated variable natural selection on WUE, flowering time, and nectar production in I. aggregata across elevation/habitat and differential water availability. At low elevation in the water addition treatment, natural selection favors early flowering and greater nectar sugar concentration, while dry conditions favor high WUE and early flowering time. At high elevation, where the growing season is shorter and drier, selection favors early flowering regardless of water addition. These results suggest natural selection on ecophysiological and floral traits varies with resource availability (e.g. water availability and pollinator visitation). Using data from a glasshouse experiment involving a global panel of accessions of Arabidopsis thaliana, I demonstrated strong positive genetic correlation between WUE and flowering time, as well as selection for low WUE and early flowering under experimental season-ending drought. Finally, I found significant genetic variation in plasticity as well as selection favoring greater WUE plasticity under drought, indicating plasticity to drought is adaptive in A. thaliana.Item Geographic variation in male nuptial color across multiple scales in threespine stickleback, Gasterosteus aculeatus(2015-12) Brock, Chad Daniel; Bolnick, Daniel; Cummings, Molly E.; Hofmann, Johann A; Kirkpatrick, MarkMost species exhibit geographic variation in phenotypic traits, and this variation can occur across a broad range of spatial scales. Consistent phenotype-environment correlations are often invoked as evidence for adaptation in response to spatially varying natural selection. Both theoretical and empirical work suggests that local adaptation can occur most readily when the strength of selection exceeds the homogenizing effect of gene flow. Consequently, adaptive phenotype-environment correlations are typically studied at broad spatial scales at which gene flow is weak and environmental variation is pronounced. Despite this, a number of species show adaptive phenotypic divergence across microspatial scales. Signal detectability in animal communication is frequently contingent on the local environment. Consequently, to maintain optimal detectability, signal design should covary with the signaling environment, resulting in predictable phenotype-environment correlations. We investigated whether spatial variation in nuptial color of male threespine stickleback, Gasterosteus aculeatus, varies predictably with optical environment at two spatial scales: 1) between lakes 2) within lakes. We demonstrate that male nuptial color varies significantly between 15 lakes on Vancouver Island, BC. Male orange/red reflectance negatively covaries with the amount of orange/red in the optical background, suggesting that nuptial color tracks the local optical environment to maintain signal contrast. However, visual model results indicate that male signal contrast varies between lakes. Some lakes showed evidence of local adaptation, while others did not. A number of ecological characteristics also covary with male color and contrast, and we suggest these factors may constrain males’ ability to track local signaling optima. Within lakes, we found ’microclines’ across a small spatial gradient: male nuptial color changes across a 2-meter vertical range of nest depths. The color microcline is repeatably associated with depth gradients in ambient light, suggesting that these microclines reflect adaptation to local optical environments. Visual modeling demonstrates that these signals vary in contrast with background, depending on a male’s nest depth. Deeper-nesting males reflected more UV/blue and were more conspicuous than shallow-nesting males. Experimental manipulation of male nesting depth induced plastic changes in nuptial color that replicated the natural gradients in color and conspicuousness, implicating plasticity as the primary mechanism driving microcline formation.