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AbstractBet hedging consists of life history strategies that buffer against environmental variability by trading off immediate and long-term fitness. Delayed germination in annual plants is a classic example of bet hedging and is often invoked to explain low germination fractions. We examined whether bet hedging explains low and variable germination fractions among 20 populations of the winter annual plant Clarkia xantiana ssp. xantiana that experience substantial variation in reproductive success among years. Leveraging 15 years of demographic monitoring and 3 years of field germination experiments, we assessed the fitness consequences of seed banks and compared optimal germination fractions from a density-independent bet-hedging model to observed germination fractions. We did not find consistent evidence of bet hedging or the expected trade-off between arithmetic and geometric mean fitness, although delayed germination increased long-term fitness in 7 of 20 populations. Optimal germination fractions were two to five times higher than observed germination fractions, and among-population variation in germination fractions was not correlated with risks across the life cycle. Our comprehensive test suggests that bet hedging is not sufficient to explain the observed germination patterns. Understanding variation in germination strategies will likely require integrating bet hedging with complementary forces shaping the evolution of delayed germination.

Plant population ecologists regularly study soil seed banks with seed bag burial and seed addition experiments. These experiments contribute crucial data to demographic models, but we lack standard methods to analyze them. Here, we propose statistical models to estimate seed mortality and germination with observations from these experiments. We develop these models following the principles of event history analysis, and analyze their identifiability and statistical properties by algebraic methods and simulation. We demonstrate that seed bag burial, but not seed addition experiments, can be used to make inferences about age-dependent mortality and germination. When mortality and germination do not change with seed age, both experiments produce unbiased estimates but seed bag burial experiments are more precise. However, seed mortality and germination estimates may be inaccurate when the statistical model that is fit makes incorrect assumptions about the age dependence of mortality and germination. The statistical models and simulations that we present here can be adopted and modified by plant population ecologists to strengthen inferences about seed mortality and germination in the soil seed bank., (© 2022 The Ecological Society of America.)

Overwhelming evidence demonstrating the benefits of active-learning pedagogy has led to a shift in teaching that requires students to interact more in the classroom. To date, few studies have assessed whether there are gender-specific differences in participation in active-learning science, technology, engineering, and mathematics (STEM) courses, and fewer have looked across different types of classroom participation. Over two semesters, we observed an introductory biology course at a large research-intensive university and categorized student participation into seven distinct categories to identify gender gaps in participation. Additionally, we collected student grades and administered a postcourse survey that gauged student scientific self-efficacy and salience of gender identity. We found that men participated more than expected based on the class composition in most participation categories. In particular, men were strongly overrepresented in voluntary responses after small-group discussions across both semesters. Women in the course reported lower scientific self-efficacy and greater salience of gender identity. Our results suggest that active learning in itself is not a panacea for STEM equity; rather, to maximize the benefits of active-learning pedagogy, instructors should make a concerted effort to use teaching strategies that are inclusive and encourage equitable participation by all students.

Understanding how environmental changes influence the pathogenicity and virulence of infectious agents is critical for predicting epidemiological patterns of disease. Thraustochytrids, part of the larger taxonomic class Labyrinthulomycetes, contain several highly pathogenic species, including the hard clam pathogen quahog parasite unknown (QPX). QPX has been associated with large-scale mortality events along the northeastern coast of North America. Growth and physiology of QPX is temperature-dependent, and changes in local temperature profiles influence pathogenicity. In this study we characterize the partial genome of QPX and examine the influence of temperature on gene expression. Genes involved in several biological processes are differentially expressed upon temperature change, including those associated with altered growth and metabolism and virulence. The genomic and transcriptomic resources developed in this study provide a foundation for better understanding virulence, pathogenicity and life history of thraustochytrid pathogens.