Browsing by Subject "Ipomopsis aggregata"
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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 The genetic architecture of quantitative traits in locally adapted plant ecotypes(2015-08) Milano, Elizabeth Rose; Juenger, Thomas; Kirkpatrick, Mark; Linder, Craig R; Lloyd, Alan; Martin, NolandLocally adapted ecotypes are a common phenomenon generating plant diversity within species, yet we know surprisingly little about the genetic mechanisms that lead to locally adapted traits. The genetic architecture underlying traits can indicate evolutionary history and predict response to selection, with applications in evolutionary ecology, conservation, and crop development. This research broadly investigates the genetic architecture of quantitative traits in paired ecotypes from different plant species. I used multivariate comparative methods and quantitative trait loci (QTL) mapping to quantify genetic correlations and population divergence, between ecologically relevant traits, both at the phenotypic and genotypic level. I tested for adaptive floral trait evolution in a perennial wildflower by comparing differentiation at neutral loci to differentiation in a suite of quantitative floral traits in an Ipomopsis aggregata hybrid zone. I used multivariate comparisons to incorporate the genetic covariance architecture underlying floral display and reward traits, and found a strong signal for divergent selection. Non-neutral divergence for multivariate quantitative traits suggests that selection by pollinators is maintaining a correlation between floral display and reward. In Panicum virgatum, a native perennial grass, I used a genetic mapping population, segregating ecotypic variation, to construct a linkage map, and map QTL for nine ecological traits. Most QTL had intermediate to small effects and clustered on a limited number of linkage groups. I also found over half of the functional allelic effects displayed patterns associated with fixed differences between ecotypes. These results suggest there is considerable standing genetic variation within local populations, as well as between ecotypes for ecologically relevant traits. Lastly, I explored the genetics of plant tissue quality in Panicum hallii, a model lignocellulosic grass system. Cell wall components compose the bulk of lignocellulosic biomass and contribute to the recalcitrance of plant tissue. I characterized the divergence of four major cell wall components between ecotypes, identified 14 QTL, and found half of the QTL localized to a single linkage group. Exploring the genetic architecture of tissue traits in a tractable system will lead to a better understanding of cell wall structure and function as well as provide genomic resources for bioenergy crop improvement.