Sequential mate choice strategies predict how females should alter their choosiness based on the availability of attractive males. There are many studies on sequential mate choice within species, but few have asked whether females apply these strategies to interactions between species and how these strategies may affect hybridization. We tested how previous interactions with conspecific and heterospecific males affect mate preference and sexual isolation in two threespine stickleback species (benthics and limnetics:Gasterosteusspp.). Consistent with previous work, we found that within species, stickleback females gauge male attractiveness relative to previously encountered males. If females extend these decision rules between species, we predicted that previous interactions with conspecifics should make heterospecifics less attractive, whereas interactions with heterospecifics should make conspecifics more attractive. However, females found heterospecifics less attractive after prior experience, largely independent of the species of male first encountered. Thus, sequential mate choice strategies are used within but not between species in sticklebacks. Further, learning from prior courtship interactions acts to enhance existing sexual isolation between species.

One approach to understand the importance of reproductive barriers to the speciation process is to study the breakdown of barriers between formerly distinct species. One reproductive barrier, sexual isolation, reduces gene flow between species through differences in mate preferences and mating signals and is likely important for species formation and maintenance. We measure sexual isolation in two limnetic-benthic threespine stickleback species pairs (Gasterosteus spp.). One species pair maintains strong reproductive isolation while the other species pair has recently collapsed into a hybrid swarm. We compare the strength of sexual isolation in the hybridizing pair to the currently isolated pair. We provide the first evidence that sexual isolation has been lost in the hybridizing pair and show furthermore that preferences females have for conspecific mates and the traits they use to distinguish conspecific and heterospecific males contribute to this loss. This work highlights the fragility of reproductive isolation between young species pairs and considers the role of sexual isolation in speciation.

Global change is causing major declines in biodiversity, especially of insects. Scientific interest in global change impacts on insects has increased in recent years, resulting in many different meta‐analyses examining questions within this topic. We performed a comprehensive review of meta‐analyses examining the effects of global change stressors on insects to identify well‐studied questions and gaps in our knowledge and synthesise the responses of insects to those stressors. We identified 75 meta‐analyses that fit our scope, accounting for 905 meta‐results and spanning 18 global change stressors. Our synthesis identified several global change stressors that are relatively well‐studied across insect groups, such as agriculture, habitat degradation, and pesticide use. Moreover, other global change stressors were found to be relatively less studied, highlighting areas that need more attention; for example, very few meta‐analyses considered the impacts of global warming, ozone, light pollution, and interactive effects of multiple stressors on insects. Most stressors are more associated with negative than positive effects on insects, except for nutrient addition, ozone, and air pollution. Negative effects accounted for the large majority of consequences on reproductive responses, which may help explain recent insect declines. Additionally, we found evidence for higher trophic levels being more negatively affected by global change and insects in aquatic habitats experiencing fewer negative responses to stressors. Given these largely negative impacts of global change on insects, we argue for the need for national and local policy actions to monitor and actively conserve insect communities.