The effect of genome duplication on the reproductive ecology of plants

Whole genome duplication, or polyploidy, is the largest genomic alteration observed in nature. Polyploidy occurs in many different taxa, but is a widely tolerated and recurrent evolutionary phenomenon in plants. Although the importance of polyploidy in plants has been touted for approximately 100 years, we have yet to fully understand the ecological consequences of whole genome duplication on plant reproductive biology. Here I investigated how whole genome duplication impacts plant reproductive ecology. Specifically, I studied the effects of whole genome duplication on flowering phenotypes and the contributions of whole genome duplication to three premating barriers. I used a combination of genomic modifications of plants to induce polyploidy in experimental populations, manipulative field experiments to test ecological hypotheses, and literature surveys to examine evolutionary trends. In the first chapter, I used meta-analytical approaches based on published studies to explore the effect of whole genome duplication on several aspects of floral morphology, phenology, and reproductive output in plants. The results suggested that across a wide variety of plant species, morphological traits increase in size (e.g., flower diameter increases), reproductive output decreases, and there were no general trends in the effect of whole genome duplication on flowering phenology. I also observed that variation in reproductive output increases after whole genome duplication, whereas variation does not increase or decrease in phenology or morphology traits. In the second chapter, I build on existing knowledge of the mechanisms involved in premating reproductive isolation of polyploid lineages by investigating the factors that are important in driving assortative mating in the generations immediately following whole genome duplication. I accomplished this by using synthetic polyploids which provide the opportunity to study polyploidy in the generations immediately following formation when reproductive isolation will be critical to establishment. Trifolium pratense, or red clover, was used in an experimental study of diploids and newly formed polyploids to determine if the phenotypic differences caused by whole genome duplication facilitated premating isolation. The premating barriers examined included flowering phenology, self-fertilization rates, flower visitor community, and flower visitor behavior. I found that whole genome duplication increases flower size, but there were no cascading effects that facilitated premating isolation of newly formed polyploids. Together, my results suggest that polyploidy puts plants at a reproductive disadvantage and that if newly formed polyploids are found in sympatry with their diploid progenitors, rapid adaptation is likely necessary to establish and avoid extinction

Diversity and complexity of arthropod references in haiku.

Haiku are short poems, each composed of about 10 words, that typically describe moments in nature. People have written haiku since at least the 17th century, and the medium continues to be popular with poets, amateurs, educators, and students. Collectively, these poems represent an opportunity to understand which aspects of nature-e.g., which taxa and biological traits-resonate with humans and whether there are temporal trends in their representation or the emotions associated with these moments. We tested this potential using a mix of linguistic and biological methods, in analyses of nearly 4,000 haiku that reference arthropods. We documented the taxa and the life history traits represented in these poems and how they changed over time. We also analyzed the poems for emotion and tone. Our results reveal a mix of predictable trends and compelling surprises, each of which stand to potentially inform engagement strategies. At least 99 families of arthropods, in 28 orders, are represented in these haiku. The eight most commonly referenced taxa, from highest to lowest number of references, include: Lepidoptera, Hymenoptera, Diptera, Coleoptera, Araneae, Orthoptera, Hemiptera, and Odonata. Several common, conspicuous orders were never referenced, including Trichoptera, Plecoptera, and Megaloptera. The most commonly referenced traits relate to ecology (especially habitat, phenology, time of day), behavior (especially sound production), phenotype (especially color), and locomotion (especially flight). The least common traits in haiku relate to arthropod reproduction and physiology. Our analyses revealed few obvious temporal trends in the representations of taxa, biological traits, or emotion and tone. The broader implications of these results and possible future directions are discussed

Data from: Herbivore impacts on marsh production depend upon a compensatory continuum mediated by salinity stress

Plant communities are disturbed by several stressors and they are expected to be further impacted by increasing anthropogenic stress. The consequences of these stressors will depend, in part, upon the ability of plants to compensate for herbivory. Previous studies found that herbivore impacts on plants can vary from negative to positive because of environmental control of plant compensatory responses, a.k.a. the Compensatory Continuum Hypothesis. While these influential studies enhanced our appreciation of the dynamic nature of plant-herbivore interactions, they largely focused on the impact of resource limitation. This bias limits our ability to predict how other environmental factors will shape the impact of herbivory. We examined the role of salinity stress on herbivory of salt marsh cordgrass, Spartina foliosa, by an herbivore previously hypothesized to influence the success of restoration projects (the scale insect, Haliaspis spartinae). Using a combination of field and mesocosm manipulations of scales and salinity, we measured how these factors affected Spartina growth and timing of senescence. In mesocosm studies, Spartina overcompensated for herbivory by growing taller shoots at low salinities but the impact of scales on plants switched from positive to neutral with increasing salinity stress. In field studies of intermediate salinities, scales reduced Spartina growth and increased the rate of senescence. Experimental salinity additions at this field site returned the impact of scales to neutral. Because salinity decreased scale densities, the switch in impact of scales on Spartina with increasing salinity was not simply a linear function of scale abundance. Thus, the impact of scales on primary production depended strongly upon environmental context because intermediate salinity stress prevented plant compensatory responses to herbivory. Understanding this context-dependency will be required if we are going to successfully predict the success of restoration efforts and the ecological consequences of anthropogenic disturbances

Trait category representation through time.

This figure illustrates the proportion of haiku that reference the major trait categories in each decade. (TIF)</p

Secondary corpus with results.

This spreadsheet contains all the haiku analyzed as the secondary corpus, with results from the trait scoring and the LIWC-22 analysis. (XLSX)</p

Data from: Herbivore impacts on marsh production depend upon a compensatory continuum mediated by salinity stress

Plant communities are disturbed by several stressors and they are expected to be further impacted by increasing anthropogenic stress. The consequences of these stressors will depend, in part, upon the ability of plants to compensate for herbivory. Previous studies found that herbivore impacts on plants can vary from negative to positive because of environmental control of plant compensatory responses, a.k.a. the Compensatory Continuum Hypothesis. While these influential studies enhanced our appreciation of the dynamic nature of plant-herbivore interactions, they largely focused on the impact of resource limitation. This bias limits our ability to predict how other environmental factors will shape the impact of herbivory. We examined the role of salinity stress on herbivory of salt marsh cordgrass, Spartina foliosa, by an herbivore previously hypothesized to influence the success of restoration projects (the scale insect, Haliaspis spartinae). Using a combination of field and mesocosm manipulations of scales and salinity, we measured how these factors affected Spartina growth and timing of senescence. In mesocosm studies, Spartina overcompensated for herbivory by growing taller shoots at low salinities but the impact of scales on plants switched from positive to neutral with increasing salinity stress. In field studies of intermediate salinities, scales reduced Spartina growth and increased the rate of senescence. Experimental salinity additions at this field site returned the impact of scales to neutral. Because salinity decreased scale densities, the switch in impact of scales on Spartina with increasing salinity was not simply a linear function of scale abundance. Thus, the impact of scales on primary production depended strongly upon environmental context because intermediate salinity stress prevented plant compensatory responses to herbivory. Understanding this context-dependency will be required if we are going to successfully predict the success of restoration efforts and the ecological consequences of anthropogenic disturbances

Relative arthropod representation.

Bar size represents proportion in each category, relative to other categories. Blue = alpha diversity (number of species); red = representation on iNaturalist; yellow = representation in haiku. Three bars of equal size for a taxon would indicate that its representation is proportional across all categories (i.e., that the taxon comprises the same percentage in each category). See Discussion for references regarding the diversity of each taxon.</p

Taxonomic representation through time.

This figure illustrates the proportion of haiku that reference any particular taxon at a particular period of time. (TIF)</p

Taxon representation in haiku.

Rectangle sizes are proportional and represent major taxonomic names referenced in haiku. The arrangement is roughly phylogenetic, with blue rectangles representing Holometabola, green rectangles non-holometabolous Hexapoda, and gray representing non-hexapod Arthropoda.</p

Top 20 traits through time.

This figure illustrates the proportion of haiku that reference the top 20 traits in each decade. (TIF)</p