The effects of early-season herbivory and subsequent induced plant responses have the potential to affect the diversity of herbivorous insect communities. We investigated the seasonal development of the herbivore fauna on common milkweed (Asclepias syriaca) to understand the effect of early-season herbivory by different species on insect growth, natural colonization, and community composition. First, we showed that damage by an early-season stem-feeding weevil (Rhyssomatus lineaticollis) reduced growth of monarch larvae (Danaus plexippus) and leaf beetle larvae (Labidomera clivicollis), suggesting that plant quality is reduced by weevil damage. To better understand the potential for initial herbivore damage to affect subsequent colonization by herbivores in the field, we compared undamaged controls to plants experimentally damaged with one of three herbivores: weevils, monarchs, or leaf beetles. We counted seven species of naturally colonizing herbivores on all plants for the next two months to assess colonization, damage, and insect community richness. Our results showed that initial herbivory by different species altered host plant use by herbivores in two years of experiments. Similarly, induced resistance and susceptibility occurred in both years, but due to different initial damaging species on individual plants. Treatment effects also scaled up to alter herbivore community richness. Initial treatments varied in their persistence through the season. For example, in 2001, the influence of initial monarch damage dissipated due to subsequent damage by colonizing herbivores, but the impacts of initial weevil treatment were unaffected. This result suggests that, although induced responses to weevil feeding persisted through the season, monarch herbivory was more likely to affect the herbivore community via a cascade of indirect effects. In 2002, plant and insect responses were more specific, depending on the identity of both initial and colonizing herbivore species. Despite year-to-year variation, considerable consistency in many responses to our treatments indicates that the identity of the initially colonizing herbivore can affect subsequent plant use and community structure. Given the preponderance of influential early-season herbivores, the effects of induced plant responses similar to those presented here may be widespread and may strongly contribute to the structure of phytophagous insect communities.

2004. Specificity of induced plant responses to specialist herbiores of the common milkweed, Asclepias syriaca . Á/ Oikos 104: 401 Á/409.Induced plant responses to herbivory appear to be universal, yet the degree to which they are specific to sets of herbivores is poorly understood. The generalist/specialist hypothesis predicts that generalist herbivores are more often negatively affected by host plant defenses, wheras specialists may be either unaffected by or attracted to these same ''plant defenses''. Therefore, specialists should be less predictable than generalists in their responses to induced plant resistance traits. To better understand the variation in plant responses to herbivore attack, and the impacts these responses have on specialist herbivores, we conducted a series of experiments examining pairwise interactinos between two specialaist herbivores of the common milkweed (Asclepias syriaca ). We damaged plants mechnically, with swamp milkweed beetles (Labidomera clivicollis ), or with monarchs (Danaus plexippus ), and then asessed specificity of elicitation, both by measuring a putative defensive trait (latex volume) and by challenging plants with insects of both species in bioasays. Latex production increased by 34% and 13% following beetle and monarch herbivory, respectively, but only beetles significantly elevated latex production compared to undamaged controls. While beetle growth was negatively affected by latex across all experiments, beetles were not affected by previous damage caused by conspecifies or by monarchs. In contrast, monarchs feeding on previously damaged plants were 20% smaller, and their response was the same on plants damaged mechnically or by either herbivore. Therefore, these specialist herbivores exhibit both specificity of elicitation in plant responses and specificity of effects in response to prior damage.

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Extinction of populations occurs naturally, but global extinction rates are accelerating, making understanding extinction a high priority for conservation. Extinction in experimental populations of brine shrimp (Artemia franciscana) was measured to assess hypothesized extinction processes. Greater initial population size, greater maximum population size supported by the environment, and lower variation in environmental conditions reduced the likelihood of extinction, as hypothesized. However, initial population size was less important, and maximum population size and environmental variation were more important than often hypothesized. Unexpectedly, deterministic oscillations in population size due to inherent nonlinear dynamics and overcrowding were as important or more important than hypothesized processes.

Although development of critical thinking skills has emerged as an important issue in undergraduate education, implementation of pedagogies targeting these skills across different science, technology, engineering, and mathematics disciplines has proved challenging. Our goal was to assess the impact of targeted interventions in 1) an introductory cell and molecular biology course, 2) an intermediate-level evolutionary ecology course, and 3) an upper-level biochemistry course. Each instructor used Web-based videos to flip some aspect of the course in order to implement active-learning exercises during class meetings. Activities included process-oriented guided-inquiry learning, model building, case studies, clicker-based think–pair–share strategies, and targeted critical thinking exercises. The proportion of time spent in active-learning activities relative to lecture varied among the courses, with increased active learning in intermediate/upper-level courses. Critical thinking was assessed via a pre/posttest design using the Critical Thinking Assessment Test. Students also assessed their own learning through a self-reported survey. Students in flipped courses exhibited gains in critical thinking, with the largest objective gains in intermediate and upper-level courses. Results from this study suggest that implementing active-learning strategies in the flipped classroom may benefit critical thinking and provide initial evidence suggesting that underrepresented and first-year students may experience a greater benefit.