Size‐number trade‐offs in reproduction are commonly observed in nature. Bumblebee (Bombus spp.) colonies produce workers that vary considerably in size. This variation suggests that colonies face potential size‐number trade‐offs when producing workers. Here, we estimated size‐based vital rates of Bombus vosnesenskii workers using colonies reared from wild‐caught queens. We conducted a mark–recapture study to estimate worker survival as a function of body size. We also collected data on pollen and nectar loads as well as foraging trips using a radiofrequency identification system to estimate daily resource return as a function of body size. We integrated survival and daily resource return to estimate lifetime resource collection and offset these estimates by the size‐based worker production costs. We found size‐based trade‐offs among workers of different sizes. Smaller workers had higher survival, but larger workers returned with more resources per day. The largest workers made slightly fewer foraging trips per day. Overall, larger workers made the greatest lifetime contribution to both nectar and pollen collection. However, once the benefits of larger workers are offset by their higher production costs, intermediate‐sized workers were the optimal for net resource contribution according to our models. Many previous studies have found that larger workers outperformed smaller workers with foraging and in‐nest tasks, yet these studies have not integrated multiple fitness components or worker production costs to quantify net resource contribution towards colony growth. Accounting for trade‐offs between costs and performance changed our conclusions about optimal body size from being large to being near the observed average.  Similar approaches of integrating multiple vital rates may resolve apparently suboptimal life histories in other taxa. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13251/suppinfo is available for this article.

A rapidly changing climate has the potential to interfere with the timing of environmental cues that ectothermic organisms rely on to initiate and regulate life history events. Short‐lived ectotherms that exhibit plasticity in their life history could increase the number of generations per year under warming climate. If many individuals successfully complete an additional generation, the population experiences an additional opportunity to grow, and a warming climate could lead to a demographic bonanza. However, these plastic responses could become maladaptive in temperate regions, where a warmer climate could trigger a developmental pathway that cannot be completed within the growing season, referred to as a developmental trap. Here we incorporated detailed demography into commonly used photothermal models to evaluate these demographic consequences of phenological shifts due to a warming climate on the formerly widespread, multivoltine butterfly (Pieris oleracea). Using species‐specific temperature‐ and photoperiod‐sensitive vital rates, we estimated the number of generations per year and population growth rate over the set of climate conditions experienced during the past 38 years. We predicted that populations in the southern portion of its range have added a fourth generation in recent years, resulting in higher annual population growth rates (demographic bonanzas). We predicted that populations in the Northeast United States have experienced developmental traps, where increases in the thermal window initially caused mortality of the final generation and reduced growth rates. These populations may recover if more growing degree days are added to the year. Our framework for incorporating detailed demography into commonly used photothermal models demonstrates the importance of using both demography and phenology to predict consequences of phenological shifts.

Summary Management of invasive populations is typically investigated case‐by‐case. Comparative approaches have been applied to single aspects of management, such as demography, with cost or efficacy rarely incorporated.We present an analysis of the ranks of management actions for 14 species in five countries that extends beyond the use of demography alone to include multiple metrics for ranking management actions, which integrate cost, efficacy and demography (cost‐effectiveness) and managers’ expert opinion of ranks. We use content analysis of manager surveys to assess the multiple criteria managers use to rank management strategies.Analysis of the matrix models for managed populations showed that all management actions led to reductions in population growth rate (λ), with a median 48% reduction in λ across all management units; however, only 66% of the actions led to declining populations (λ < 1).Each management action ranked by cost‐effectiveness and cost had a unique rank; however, elasticity ranks were often tied, providing less discrimination among management actions. Ranking management actions by cost alone aligned well with cost‐effectiveness ranks and demographic elasticity ranks were also well aligned with cost‐effectiveness. In contrast, efficacy ranks were aligned with managers’ ranks and managers identified efficacy and demography as important. 80% of managers identified off‐target effects of management as important, which was not captured using any of the other metrics. Synthesis and applications. A multidimensional view of the benefits and costs of management options provides a range of single and integrated metrics. These rankings, and the relationships between them, can be used to assess management actions for invasive plants. The integrated cost‐effectiveness approach goes well ‘beyond demography’ and provides additional information for managers; however, cost‐effectiveness needs to be augmented with information on off‐target effects and social impacts of management in order to provide greater benefits for on‐the‐ground management.