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  1. Abstract

    Whole‐genome duplication has long been appreciated for its role in driving phenotypic novelty in plants, often altering the way organisms interface with the abiotic environment. Only recently, however, have we begun to investigate how polyploidy influences interactions of plants with other species, despite the biotic niche being predicted as one of the main determinants of polyploid establishment. Nevertheless, we lack information about how polyploidy affects the diversity and composition of the microbial taxa that colonize plants, and whether this is genotype‐dependent and repeatable across natural environments. This information is a first step towards understanding whether the microbiome contributes to polyploid establishment. We, thus, tested the immediate effect of polyploidy on the diversity and composition of the bacterial microbiome of the aquatic plantSpirodela polyrhizausing four pairs of diploids and synthetic autotetraploids. Under controlled conditions, axenic plants were inoculated with pond waters collected from 10 field sites across a broad environmental gradient. Autotetraploids hosted 4%–11% greater bacterial taxonomic and phylogenetic diversity than their diploid progenitors. Polyploidy, along with its interactions with the inoculum source and genetic lineage, collectively explained 7% of the total variation in microbiome composition. Furthermore, polyploidy broadened the core microbiome, with autotetraploids having 15 unique bacterial taxa in addition to the 55 they shared with diploids. Our results show that whole‐genome duplication directly leads to novelty in the plant microbiome and importantly that the effect is dependent on the genetic ancestry of the polyploid and generalizable over many environmental contexts.

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  2. Abstract Background and Aims When plant communities are exposed to herbicide ‘drift’, wherein particles containing the active ingredient travel off-target, interspecific variation in resistance or tolerance may scale up to affect community dynamics. In turn, these alterations could threaten the diversity and stability of agro-ecosystems. We investigated the effects of herbicide drift on the growth and reproduction of 25 wild plant species to make predictions about the consequences of drift exposure on plant-plant interactions and the broader ecological community. Methods We exposed potted plants from species that commonly occur in agricultural areas to a drift-level dose of the widely used herbicide dicamba or a control solution in the glasshouse. We evaluated species-level variation in resistance and tolerance for vegetative and floral traits. We assessed community-level impacts of drift by comparing species evenness and flowering networks of glasshouse synthetic communities comprised of drift-exposed and control plants. Key Results Species varied significantly in resistance and tolerance to dicamba drift: some were negatively impacted while others showed overcompensatory responses. Species also differed in the way they deployed flowers over time following drift exposure. While drift had negligeable effects on community evenness based on vegetative biomass, it caused salient differences in the structure of coflowering networks within communities. Drift reduced the degree and intensity of flowering overlap among species, altered the composition of groups of species that were more likely to coflower with each other than with others, and shifted species roles (e.g., from dominant to inferior floral producers and vice versa). Conclusions These results demonstrate that even low levels of herbicide exposure can significantly alter plant growth and reproduction, particularly flowering phenology. If field-grown plants respond similarly, then these changes would likely impact plant-plant competitive dynamics and potentially plant-pollinator interactions occurring within plant communities at the agro-ecological interface. 
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    Free, publicly-accessible full text available November 23, 2023
  3. Free, publicly-accessible full text available October 1, 2023
  4. Summary

    Ecological theory predicts that early generation polyploids (‘neopolyploids’) should quickly go extinct owing to the disadvantages of rarity and competition with their diploid progenitors. However, polyploids persist in natural habitats globally. This paradox has been addressed theoretically by recognizing that reproductive assurance of neopolyploids and niche differentiation can promote establishment. Despite this, the direct effects of polyploidy at the population level remain largely untested despite establishment being an intrinsically population‐level process.

    We conducted population‐level experiments where life‐history investment in current and future growth was tracked in four lineage pairs of diploids and synthetic autotetraploids of the aquatic plantSpirodela polyrhiza. Population growth was evaluated with and without competition between diploids and neopolyploids across a range of nutrient treatments.

    Although neopolyploid populations produce more biomass, they reach lower population sizes and have reduced carrying capacities when growing alone or in competition across all nutrient treatments. Thus, contrary to individual‐level studies, our population‐level data suggest that neopolyploids are competitively inferior to diploids. Conversely, neopolyploid populations have greater investment in dormant propagule production than diploids.

    Our results show that neopolyploid populations should not persist based on current growth dynamics, but high potential future growth may allow polyploids to establish in subsequent seasons.

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  5. Abstract

    When sex chromosomes stop recombining, they start to accumulate differences. The sex-limited chromosome (Y or W) especially is expected to degenerate via the loss of nucleotide sequence and the accumulation of repetitive sequences. However, how early signs of degeneration can be detected in a new sex chromosome is still unclear. The sex-determining region of the octoploid strawberries is young, small, and dynamic. Using PacBio HiFi reads, we obtained a chromosome-scale assembly of a female (ZW) Fragaria chiloensis plant carrying the youngest and largest of the known sex-determining region on the W in strawberries. We fully characterized the previously incomplete sex-determining region, confirming its gene content, genomic location, and evolutionary history. Resolution of gaps in the previous characterization of the sex-determining region added 10 kb of sequence including a noncanonical long terminal repeat-retrotransposon; whereas the Z sequence revealed a Harbinger transposable element adjoining the sex-determining region insertion site. Limited genetic differentiation of the sex chromosomes coupled with structural variation may indicate an early stage of W degeneration. The sex chromosomes have a similar percentage of repeats but differ in their repeat distribution. Differences in the pattern of repeats (transposable element polymorphism) apparently precede sex chromosome differentiation, thus potentially contributing to recombination cessation as opposed to being a consequence of it.

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  6. Societal Impact Statement

    The practice of writing science blogs benefits both the scientist and society alike by providing professional development opportunities and delivering information in a format that is accessible to large and diverse audiences. By designing a project that introduced upper‐level undergraduate students to science blog writing with a focus on plant biology, we piqued students' interest in science writing and the content of a popular plant science blog website. If adopted more widely, this work could broaden the scope of science education and promote the development of effective science communication skills for the next generation of scientists.


    Successful scientists must communicate their research to broad audiences, including distilling key scientific concepts for the general public. Students pursuing careers in Science, Technology, Engineering, and Mathematics (STEM) fields benefit from developing public communication skills early in their careers, but opportunities are limited in traditional biology curricula.

    We created the “Plant Science Blogging Project” for a Plant Biology undergraduate course at the University of Pittsburgh in Fall 2018 and 2019. Students wrote blog posts merging personal connections with plants with plant biology concepts for the popular science blogsPlant Love StoriesandEvoBites. By weaving biology into their narratives, students learned how to share botanical knowledge with the general public.

    The project had positive impacts on student learning and public engagement. In post‐assignment surveys, the majority of students reported that they enjoyed the assignment, felt it improved their understanding of plant biology, and piqued their interest in reading and writing science blogs in the future. Approximately one‐third of the student‐authored blogs were published, including two that rose to the top 10 most‐read posts on Plant Love Stories. Some dominant themes in student blogs, including medicine and culture, differed from common story themes published on the web, indicating the potential for students to diversify science blog content.

    Overall, the Plant Science Blogging Project allows undergraduate students to engage with plant biology topics in a new way, sharpen their scientific communication skills in accordance with today's world of mass information sharing, and contribute to the spread of scientific knowledge for public benefit.

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  7. Herbicides act as human-mediated novel selective agents and community disruptors, yet their full effects on eco-evolutionary dynamics in natural communities has only begun to be appreciated. Here we synthesize how herbicide exposures can result in dramatic phenotypic and compositional shifts within communities at the agro-ecological interface and how these in turn affect species interactions and drive plant (and plant-associates’) evolution in ways that can feedback to continue to affect the ecology and ecosystem functions of these assemblages. We advocate a holistic approach to understanding these dynamics that includes plastic changes and plant community transformations and also extends beyond this single trophic level targeted by herbicides to the effects on non-target plant-associated organisms and their potential to evolve, thereby embracing the complexity of these real-world systems. We make explicit recommendations for future research to achieve this goal and specifically address impacts of ecology on evolution, evolution on ecology, and their feedbacks so that we can gain a more predictive view of the fates of herbicide-impacted communities. 
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  8. Abstract

    Assembly of microbial communities is the result of neutral and selective processes. However, the relative importance of these processes is still debated. Microbial communities of flowers, in particular, have gained recent attention because of their potential impact to plant fitness and plant‐pollinator interactions. However, the role of selection and dispersal in the assembly of these communities remains poorly understood. Here, we evaluated the role of pollinator‐mediated dispersal on the contribution of neutral and selective processes in the assembly of floral microbiomes of the yellow monkeyflower (Mimulus guttatus). We sampled floral organs from flowers in the presence and absence of pollinators within five different serpentine seeps in CA and obtained 16S amplicon data on the epiphytic bacterial communities. Consistent with strong microenvironment selection within flowers we observed significant differences in community composition across floral organs and only a small effect of geographic distance. Pollinator exposure affected the contribution of environmental selection and depended on the rate and intimacy of interactions with flower visitors. This study provides evidence of the importance of dispersal and within‐flower heterogeneity in shaping epiphytic bacterial communities of flowers, and highlights the complex interplay between pollinator behaviour, environmental selection and additional abiotic factors in shaping the epiphytic bacterial communities of flowers.

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  9. Premise

    Polyploidy is a major genetic driver of ecological and evolutionary processes in plants, yet its effects on plant interactions with mutualistic microbes remain unresolved. The legume–rhizobium symbiosis regulates global nutrient cycles and plays a role in the diversification of legume species. In this mutualism, rhizobia bacteria fix nitrogen in exchange for carbon provided by legume hosts. This exchange occurs inside root nodules, which house bacterial cells and represent the interface of legume–rhizobium interactions. Although polyploidy may directly impact the legume–rhizobium mutualism, no studies have explored how it alters the internal structure of nodules.


    We created synthetic autotetraploids usingMedicago sativasubsp.caerulea. Neotetraploid plants and their diploid progenitors were singly inoculated with two strains of rhizobia,Sinorhizobium melilotiandS. medicae. Confocal microscopy was used to quantify internal traits of nodules produced by diploid and neotetraploid plants.


    Autotetraploid plants produced larger nodules with larger nitrogen fixation zones than diploids for both strains of rhizobia, although the significance of these differences was limited by power. NeotetraploidM. sativasubsp.caeruleaplants also produced symbiosomes that were significantly larger, nearly twice the size, than those present in diploids.


    This study sheds light on how polyploidy directly affects a plant–bacterium mutualism and uncovers novel mechanisms. Changes in plant–microbe interactions that directly result from polyploidy likely contribute to the increased ability of polyploid legumes to establish in diverse environments.

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