Biology subjects

Baucom, R.

Publications and source records attributed to Baucom, R..

11 recordsLinked to original sources

bioRxiv2026

A fast neutron mutant resource for Ipomoea purpurea reveals dose-dependent genomic and phenotypic variation

A central goal in evolutionary biology is to understand the genomic basis of phenotypic traits, yet this pursuit is often constrained by a lack of accessible phenotypic and genetic variation, particularly in non-model organisms. Fast neutron irradiation offers a powerful approach for generating such variation, as it does not require prior genomic resources, established transformation systems, or reference mutant collections. Here, we describe the development and characterization of the first fast neutron mutant library in Ipomoea purpurea (common morning glory), a noxious agricultural weed and established model system in evolutionary ecology. We exposed an I. purpurea reference genotype to three levels of irradiation and developed 1,043 lines third generation lines and characterized the phenotypic and genetic variation in a subset of 200. Phenotypic screens identified seven mutant lines exhibiting eleven distinct phenotypes, and revealed higher phenotypic variance for anther-stigma distance, flower number, and pollen count relative to a non-irradiated control line. We further identified genetic variation across eight phenotypic traits among the mutant lines. Together, these results show that fast neutron mutagenesis generates novel phenotypic and genetic variation in ecologically relevant traits, offering the research community a new genomic resource for an established model in evolutionary ecology.

plant biology↗

bioRxiv2026

Tolerance to herbicide drift in "weedy" species is context-dependent and driven by early vegetative growth

While plant communities that exist at the edges of agricultural fields are typically composed of 'weedy' species, they provide essential resources for insect pollinators and other wildlife. However, little is known about how sublethal exposures to herbicides via drift (off-target chemical movement by air) affects the fitness of weedy plant species across varying agro-ecological environments. If weed species vary in sensitivity to herbicide drift, then this could result in plant community shifts in favor of more tolerant species. Consequently, these changes in species composition could alter resource availability in agroecosystems. Here, we replicated a common garden experiment in three US states where agriculture is a major form of land use (Michigan, Pennsylvania, and Tennessee). We exposed nine weed species to a sublethal, drift-level rate of the herbicide dicamba and examined plant fitness. We found that fitness in the presence of dicamba drift depended on both the weed species and the environmental context. For some species, dicamba drift significantly reduced fitness. For others, it had no effect, indicating greater tolerance to the herbicide. However, more variation in tolerance to dicamba drift among species was observed in Michigan compared to Pennsylvania or Tennessee, a result that was partially explained by the severity of damage from insect herbivory that occurred at each location. In a follow-up study, we explored the relationships between plant developmental traits and fitness to determine the functional pathways that underlie tolerance to dicamba drift using structural equation modeling. This approach revealed that weedy plants that are better able to buffer the effects of dicamba drift on short-term growth are then better equipped to minimize effects on flower production and ultimately fitness (seed set). Overall, our work advances knowledge about how wild plant populations in different contexts are responding to unintentional, yet increasingly common occurrences of anthropogenic stress in the form of off-target herbicide exposures.

ecology↗

bioRxiv2026

The Dynamics of Long Terminal Repeat Proliferation in the Hesperis matronalis Genome

Genome sizes vary across four orders of magnitude in flowering plants, with consequences for evolution. Much of this variation is due to differences in transposable element content, particularly in long terminal repeat (LTR) retrotransposons. Despite their importance in plant genome evolution, LTRs have long been challenging to characterize because of their repetitive nature, but recent advances in sequencing allow more detailed explorations of their behavior. They are now known to occupy distinct genomic niches, and to evolve and proliferate over time as they escape host controls. In this study, we present a new genome sequence of the largest Brassicaceae genome, Hesperis matronalis, and describe its transposable element complement and how LTRs contributed to its genome expansion. We find evidence for both early proliferation of Ty3 elements and rapid recent expansion of Ty1-copia elements. In addition, we place the H. matronalis LTRs in a broader context of LTR evolution in the Brassicaceae, showing that the dominant copia families are part of an evolutionary radiation endemic to Hesperis. Finally, we describe differences in LTR age, proximity to genes, and apparent removal rate which suggest consistent genomic niches over the lifespan of a TE family. These results shed light on how LTRs evolve dynamically with host genomes, and have contributed to the expansion of the largest genome in the Brassicaceae. Significance StatementOrganisms differ in many ways, including the size of their genomes. Genome size, in turn, can affect many aspects of evolution, such as what kinds of mutations are available to natural selection and how effectively natural selection can act. The "complexity" of an organism does not predict its genome size; rather, much of this variation is explained by the amount of transposable elements, or "jumping genes," that inhabit a genome. This study describes the evolutionary history of the transposable elements in dames rocket (Hesperis matronalis), which has the largest genome of any plant in the mustard family (Brassicaceae). We find that the genome inflation in Hesperis is due to transposable elements that are not found elsewhere in the Brassicaceae, and likely diversified within Hesperis. Characterizing the evolution and behavior of transposable elements in this genome offers a better understanding of the forces that determine genome size and ultimately affect the evolution of life on earth.

genomics↗

bioRxiv2026

Hormesis without evolution: plastic compensatory responses to herbicide drift in Oxalis stricta, a common weed of agriculture

O_LIHerbicide drift exposes non-target plants to sublethal doses of agrochemicals, yet its ecological and evolutionary consequences remain poorly understood. Although hormesis--defined as stimulatory responses to low doses of otherwise toxic compounds--has been documented following herbicide exposure, it has rarely been evaluated within an evolutionary ecology framework. Here, we integrate concepts of tolerance and overcompensation to examine herbicide-induced hormesis in the common agricultural weed Oxalis stricta across two field experiments. C_LIO_LIWe exposed replicated maternal lines to a drift-relevant dose of dicamba and quantified growth, reproductive traits, floral allocation, and pollinator visitation. Dicamba drift consistently increased flower production in both years, revealing a robust plastic shift toward reproductive allocation. However, the fitness consequences of increased flowering differed between years: in 2022, increased flowering was associated with higher seed production through indirect, trait-mediated pathways, whereas in 2023 increased flowering did not translate into detectable differences in reproductive output. Structural equation modelling indicated that dicamba effects on reproduction were largely indirect, mediated through correlated trait responses rather than direct stimulation of fitness. C_LIO_LIDespite consistent plastic responses, we detected little genetic variation in the magnitude of hormesis, suggesting limited potential for adaptive evolution of overcompensation. Dicamba drift also reduced individual flower size, indicating a shift toward larger floral displays composed of smaller flowers. These allocation shifts altered pollinator visitation patterns, primarily through changes in flower number, linking herbicide exposure to trait-mediated changes in plant-pollinator interactions. C_LIO_LITogether, our results demonstrate that low-dose herbicide exposure can generate repeatable compensatory responses that reshape ecological interactions, even when evolutionary responses are constrained. C_LI

evolutionary biology↗

bioRxiv2025

Context dependence shapes the evolution of glyphosate and herbivory resistance in Ipomoea purpurea

The evolution of plant resistance naturally occurs in complex, multifaceted environments that consist of multiple simultaneous stressors. Understanding how shifting environmental contexts may shape resistance evolution requires empirical studies that consider the combined effects of interacting stressors on fitness and selection. Here, we examined how exposure to an insecticide impacts the evolution of resistance to the herbicide glyphosate in Ipomoea purpurea (common morning glory). Through a factorial field experiment, we manipulated glyphosate and an insecticide to estimate selection on glyphosate and herbivory resistance. We found that glyphosate, not herbivory, acted as the primary agent of selection, favoring higher levels of glyphosate resistance. In the presence of glyphosate alone, positive correlational selection favored a combination of higher glyphosate and herbivory resistance, supporting prior work that suggested these traits may be linked. Importantly, insecticide exposure modified both glyphosate resistance and the strength of selection acting upon the trait by increasing resistance and weakening selection. Together, our results indicate that the evolution of herbicide resistance is context-dependent and that additional chemicals like insecticide can alter the evolutionary trajectories of plant defense.

evolutionary biology↗

bioRxiv2024

Herbicidal interference: glyphosate drives both the ecology and evolution of plant-herbivore interactions

The coevolution of plants and their insect herbivores reflects eco-evolutionary dynamics at work-- ecological interactions influence adaptive traits, which feed back to shape the broader ecological community. However, novel anthropogenic stressors like herbicide, which are strong selective agents, can disrupt these dynamics. Little is known about how the evolution of herbicide resistance may impact plant-herbivore interactions. We performed a common garden field experiment using Ipomoea purpurea (common morning glory) and the herbicide glyphosate (Roundup) to investigate the ecological effects of herbicide exposure on insect herbivory patterns and assess the potential evolutionary consequences. We find that plants treated with glyphosate experienced higher levels of herbivory and altered chewing herbivory damage patterns. Additionally, we found that glyphosate resistance is positively associated with herbivory resistance, and uncovered positive selection for increased glyphosate resistance, suggesting that selection for increased glyphosate resistance has the potential to lead to increased herbivory resistance. Positive selection for glyphosate resistance, coupled with the detection of genetic variation for this trait, suggests there is potential for glyphosate resistance--and herbivory resistance via hitchhiking-- to further evolve. Our results show that herbicides can not just influence, but potentially drive the eco-evolutionary dynamics of plant-herbivore interactions.

evolutionary biology↗

bioRxiv2023

Building a barrier: investigating the defensive role of induced trichome production in herbicide exposed plants

Functional traits are increasingly recognized as fundamental determinants for mediating ecological resilience. As global change accelerates, phenotypic plasticity in functional traits may provide a modality for fine-tuning responses to atypical or stressful environments. While various studies have explored induced plant trichomes as a response to biotic stress, emerging evidence suggests that trichome induction may also function as a broader tactic for managing a range of environmental stressors, including abiotic chemical stress. Using the annual invasive weed velvetleaf (Abutilon theophrasti), we examine whether herbicide exposure induces changes in trichome traits and whether these responses are associated with herbicide resistance and fitness outcomes. We quantified changes in trichome density and trichome type proportions across control and glyphosate (active ingredient in "Roundup") treated plants. We identified positive correlations between induced total trichome density and herbicide resistance, as well as induced branched trichomes and herbicide resistance. Selection analysis further revealed positive linear selection acting upon induced trichome density in the presence of herbicide, as well as correlative selection favoring induced trichome density and intermediate plant growth. Overall, our study indicates that plastic defenses like trichomes may contribute to plant performance under novel abiotic stress and highlights key constraints shaping the evolution of stress-responsiveness.

evolutionary biology↗

bioRxiv2022

Dicamba drift alters patterns of chewing herbivory in three common agricultural weeds

How agricultural regimes, such as novel herbicide exposure, may influence plant-herbivore interactions and specifically patterns of plant herbivory has come under increased interest in recent years due to rapidly changing herbicide use in agroecosystems. This paper examines patterns of plant herbivory using three common agricultural weeds exposed to low doses of dicamba, a synthetic auxin herbicide that is exponentially increasing in use given the adoption of dicamba tolerant crops. We used a replicated field study to examine how the amount and type of chewing herbivory may be altered in Ipomoea purpurea (common morning glory, Convolvulaceae), Datura stramonium (jimsonweed, Solanaceae), and Abutilon theophrasti (velvetleaf, Malvaceae) exposed to dicamba drift (i.e., 1% of the field dose). We found an increase in chewing herbivory damage when plants were exposed to dicamba and changes in the type of herbivory following exposure. Chewing herbivory differed among species in the presence of dicamba drift: A. theophrasti and D. stramonium showed more total leaf-chewing herbivory than controls, but I. purpurea showed no difference in the overall amount of herbivory. We also found that the type of herbivory was significantly altered in drift. A. theophrasti and I. purpurea both exhibited declines in hole feeding but increases in margin feeding, whereas D. stramonium showed no such changes. Overall, our results show that herbicide drift can induce shifts in plant-herbivore interactions, highlighting the need for mechanistic studies to uncover the cause underlying the shifts and comparative studies on weed communities to understand long-term consequences.

plant biology↗

bioRxiv2020

Adaptive and maladaptive expression plasticity underlying herbicide resistance in an agricultural weed.

Plastic phenotypic responses to environmental change are common, yet we lack a clear understanding of the fitness consequences of these plastic responses. Here, we use the evolution of herbicide resistance in the common morning glory (Ipomoea purpurea) as a model for understanding the relative importance of adaptive and maladaptive gene expression responses to herbicide. Specifically, we compare leaf gene expression changes caused by herbicide to the expression changes that evolve in response to artificial selection for herbicide resistance. We identify a number of genes that show plastic and evolved responses to herbicide and find that for the majority of genes with both plastic and evolved responses, plastic responses appear to be adaptive. We also find that selection for herbicide response increases gene expression plasticity. Overall, these results show the importance of adaptive plasticity for herbicide resistance in a common weed and that expression changes in response to strong environmental change can be adaptive. Impact statementPredicting whether and how organisms will adapt to environmental change is a crucial goal. However, this goal can be complicated because environmental change can alter traits, in a process called plasticity. The extent and fitness consequences of plasticity will have important effects on the adaptive process. In this study, we use adaptation to herbicide in the agricultural weed, the common morning glory, as a model for understanding the extent and fitness consequences of plasticity in gene expression. We find evidence that gene expression plasticity is adaptive in the presence of herbicide, suggesting that understanding plasticity is crucial for understanding how organisms adapt to new environments.

evolutionary biology↗

bioRxiv2020

Variable inbreeding depression may explain associations between the mating system and herbicide resistance

Inbreeding depression is a central parameter underlying mating system variation in nature and one that can be altered by environmental stress. Although a variety of systems show that inbreeding depression tends to increase under stressful conditions, we have very little understanding across most organisms how the level of inbreeding depression may change as a result of adaptation to stressors. In this work we examined the potential that inbreeding depression varied among lineages of Ipomoea purpurea artificially evolved to exhibit divergent levels of herbicide resistance. We examined inbreeding depression in a variety of fitness-related traits in both the growth chamber and in the field. We paired our examination of inbreeding depression in fitness-related traits with an examination of gene expression changes associated with the level of herbicide resistance, breeding history (inbred or outcrossed), and the interaction of the breeding system and the level of herbicide resistance. We found that, while inbreeding depression was present across many of the traits, lineages artificially selected for increased herbicide resistance often showed no evidence of inbreeding depression in the presence of herbicide, and in fact, showed evidence of outbreeding depression in some traits compared to non-selected control lines and lineages selected for increased herbicide susceptibility. Further, at the transcriptome level, the resistant selection lines had differing patterns of gene expression according to breeding type (inbred vs outcrossed) compared to the control and susceptible selection lines. Our data together indicate that inbreeding depression may be lessened in populations that are adapting to regimes of strong selection.

evolutionary biology↗

bioRxiv2020

Belowground competition favors character convergence but not character displacement in root traits

O_LICharacter displacement can play a major role in species ecology and evolution, however, research testing whether character displacement can influence the evolution of root traits in plant systems remains scarce in the literature. Here we investigated the potential that character displacement may influence the evolution of root traits using two closely related morning glory species, Ipomoea purpurea and I. hederacea. C_LIO_LIWe performed a field experiment where we grew the common morning glory, I. purpurea, in the presence and absence of competition from I. hederacea and examined the potential that the process of character displacement could influence the evolution of root traits. C_LIO_LIWe found maternal line variation in root phenotypes and evidence that belowground competition acts as an agent of selection on these traits. Our test of character displacement, however, showed evidence of character convergence on our measure of root architecture rather than displacement. These results suggest that plants may be constrained by their local environments to express a phenotype that enhances fitness. Therefore, the conditions of the competitive environment experienced by a plant may influence the potential for character convergence or displacement to influence the evolution of root traits. C_LI

evolutionary biology↗