John H. Willis

Summary: Temperatures are rising globally and threatening the persistence of natural plant populations. Elevated temperatures disrupt gametogenesis, fertilization, and seed filling, often at lower thresholds than those affecting photosynthesis, growth, or survival. While crop scientists have found that key reproductive stages are particularly vulnerable to heat stress across plant systems, ecological and evolutionary studies have largely focused on other fitness metrics to estimate populations' resilience to warming. We advocate for integrating pollen, ovule, and seed filling developmental metrics into ecological and evolutionary studies to improve predictions of plant population dynamics under future climates. Such studies will offer not only a better understanding of how natural populations will respond to increasing temperature stress but also are likely to reveal novel mechanistic insights that can be utilized to improve crop resilience in a warming world.

When students answer test questions incorrectly, we often assume they don't understand the content; instead, they may struggle with certain cognitive skills or with how questions are asked. Our goal was to look beyond content to understand what makes assessment questions most challenging. On the basis of more than 76,000 answers to multiple-choice questions in a large, introductory biology course, we examined three question components—cognitive skills, procedural knowledge, and question forms—and their interactions. We found that the most challenging questions require the students to organize information and make meaning from it—skills that are essential in science. For example, some of the most challenging questions are presented as unstructured word problems and require interpretation; to answer correctly, the students must identify and extract the important information and construct their understanding from it. Our results highlight the importance of teaching students to organize and make meaning from the content we teach.

Fluctuating selection in nature: Natural environmental variation can lead to individuals within a species experiencing different selective parameters. Seep monkeyflower ( Mimulus guttatus ) populations are constrained by local moisture availability and the onset of summer drought. This results in a selective tradeoff between the amount of seed set, which is determined by plant size, and the timing of reproduction. Troth et al. sequenced and phenotyped 187 M. guttatus plants and identified genetic variants associated with plant and flower size and rapid flowering. In wild populations surveyed over 3 years, the magnitude of selection changed depending on the rainfall patterns. Thus, fluctuating selection may maintain genetic variation in this species. Science , this issue p. 475