High voltinism, late-emerging butterflies are sensitive to interannual variation in spring temperature in North Carolina.

Climate change has been repeatedly linked to phenological shifts in many taxa, but the factors that drive variation in phenological sensitivity remain unclear. For example, relatively little is known about phenological responses in areas that have not exhibited a consistent warming trend, making it difficult to project phenological responses in response to future climate scenarios for these regions. We used an extensive community science dataset to examine changes in the adult flight onset dates of 38 butterfly species with interannual variation in spring temperatures in the Piedmont region of North Carolina, a region that did not experience a significant overall warming trend in the second half of the 20th century.

Heat stress and host-parasitoid interactions: lessons and opportunities in a changing climate.

Ongoing climate change is increasing the frequency and magnitude of high-temperature events (HTEs), causing heat stress in parasitoids and their hosts. We argue that HTEs and heat stress should be viewed in terms of the intersecting life cycles of host and parasitoid. Recent studies illustrate how the biological consequences of a given HTE may vary dramatically depending on its timing within these lifecycles.

Population divergence in nutrient-temperature interactions in .

The interaction between larval host plant quality and temperature can influence the short-term physiological rates and life-history traits of insect herbivores. These factors can vary locally, resulting in local adaptation in responses to diet and temperature, but the comparison of these interactions between populations is infrequently carried out. In this study, we examine how the macronutrient ratio of an artificial diet determines the larval growth, development, and survival of larval (Lepidoptera: Pieridae) at different temperatures between two invasive North American populations from different climatic regions.

Host species differences in the thermal mismatch of host-parasitoid interactions.

Extreme high temperatures associated with climate change can affect species directly, and indirectly through temperature-mediated species interactions. In most host-parasitoid systems, parasitization inevitably kills the host, but differences in heat tolerance between host and parasitoid, and between different hosts, may alter their interactions. Here, we explored the effects of extreme high temperatures on the ecological outcomes - including, in some rare cases, escape from the developmental disruption of parasitism - of the parasitoid wasp, Cotesia congregata, and two co-occurring congeneric larval hosts, Manduca sexta and M.

Predicting age and mass at maturity from feeding behavior and diet in : An empirical test of a life history model.

Feeding for most animals involves bouts of active ingestion alternating with bouts of no ingestion. In insects, the temporal patterning of bouts varies widely with resource quality and is known to affect growth, development time, and fitness. However, the precise impacts of resource quality and feeding behavior on insect life history traits are poorly understood.

Developmental timing of extreme temperature events (heat waves) disrupts host-parasitoid interactions.

When thermal tolerances differ between interacting species, extreme temperature events (heat waves) will alter the ecological outcomes. The parasitoid wasp suffers high mortality when reared throughout development at temperatures that are nonstressful for its host, . However, the effects of short-term heat stress during parasitoid development are unknown in this host-parasitoid system.

Responses of Manduca sexta larvae to heat waves.

Climate change is increasing the frequency of heat waves and other extreme weather events experienced by organisms. How does the number and developmental timing of heat waves affect survival, growth and development of insects? Do heat waves early in development alter performance later in development? We addressed these questions using experimental heat waves with larvae of the tobacco hornworm, Manduca sexta. The experiments used diurnally fluctuating temperature treatments differing in the number (0-3) and developmental timing (early, middle and/or late in larval development) of heat waves, in which a single heat wave involved three consecutive days with a daily maximum temperature of 42°C.

Responses of larvae to heat waves.

Climate change is increasing the frequency of heat waves and other extreme weather events experienced by organisms. How does the number and developmental timing of heat waves affect survival, growth and development of insects? Do heat waves early in development alter performance later in development? We addressed these questions using experimental heat waves with larvae of the tobacco hornworm, The experiments used diurnally fluctuating temperature treatments differing in the number (0-3) and developmental timing (early, middle and/or late in larval development) of heat waves, in which a single heat wave involved three consecutive days with a daily maximum temperature of 42°C. Survival to pupation declined with increasing number of heat waves.

Growth, stress, and acclimation responses to fluctuating temperatures in field and domesticated populations of .

Diurnal fluctuations in temperature are ubiquitous in terrestrial environments, and insects and other ectotherms have evolved to tolerate or acclimate to such fluctuations. Few studies have examined whether ectotherms acclimate to diurnal temperature fluctuations, or how natural and domesticated populations differ in their responses to diurnal fluctuations. We examine how diurnally fluctuating temperatures during development affect growth, acclimation, and stress responses for two populations of : a field population that typically experiences wide variation in mean and fluctuations in temperature, and a laboratory population that has been domesticated in nearly constant temperatures for more than 300 generations.

A Stochastic Model for Predicting Age and Mass at Maturity of Insects.

Variation in age and mass at maturity is commonly observed in populations, even among individuals with the same genetic and environmental backgrounds. Accounting for such individual variation with a stochastic model is important for estimating optimal evolutionary strategies and for understanding potential trade-offs among life-history traits. However, most studies employ stochastic models that are either phenomenological or account for variation in only one life-history trait.

Ontogenetic variation in thermal sensitivity shapes insect ecological responses to climate change.

Insects have distinct life stages that can differ in their responses to environmental factors. We discuss empirical evidence and theoretical models for ontogenetic variation in thermal sensitivity and performance curves (TPCs). Data on lower thermal limits for development (T) demonstrate variation between stages within a species that is of comparable magnitude to variation among species; we illustrate the consequences of such ontogenetic variation for developmental responses to changing temperature.

Compensating for climate change-induced cue-environment mismatches: evidence for contemporary evolution of a photoperiodic reaction norm in Colias butterflies.

Anthropogenic climate change alters seasonal conditions without altering photoperiod and can thus create a cue-environment mismatch for organisms that use photoperiod as a cue for seasonal plasticity. We investigated whether evolution of the photoperiodic reaction norm has compensated for this mismatch in Colias eurytheme. This butterfly's wing melanization has a thermoregulatory function and changes seasonally.

Climate Warming, Resource Availability, and the Metabolic Meltdown of Ectotherms.

Climate warming may lower environmental resource levels, growth, and fitness of many ectotherms. In a classic experiment, Brett and colleagues documented that growth rates of salmon depended strikingly on both temperature and food levels. Here we develop a simple bioenergetic model that explores how fixed temperatures and food jointly alter the thermal sensitivity of net energy gain.

No evidence that warmer temperatures are associated with selection for smaller body sizes.

Reductions in animal body size over recent decades are often interpreted as an adaptive evolutionary response to climate warming. However, for reductions in size to reflect adaptive evolution, directional selection on body size within populations must have become negative, or where already negative, to have become more so, as temperatures increased. To test this hypothesis, we performed traditional and phylogenetic meta-analyses of the association between annual estimates of directional selection on body size from wild populations and annual mean temperatures from 39 longitudinal studies.

Using museum specimens to track morphological shifts through climate change.

Museum specimens offer a largely untapped resource for detecting morphological shifts in response to climate change. However, morphological shifts can be obscured by shifts in phenology or distribution or sampling biases. Additionally, interpreting phenotypic shifts requires distinguishing whether they result from plastic or genetic changes.

How do phenology, plasticity, and evolution determine the fitness consequences of climate change for montane butterflies?

Species have responded to climate change via seasonal (phenological) shifts, morphological plasticity, and evolutionary adaptation, but how these responses contribute to changes and variation in population fitness are poorly understood. We assess the interactions and relative importance of these responses for fitness in a montane butterfly, , along an elevational gradient. Because environmental temperatures affect developmental rates of each life stage, populations along the gradients differ in phenological timing and the number of generations each year.

The analysis and interpretation of critical temperatures.

Critical temperatures are widely used to quantify the upper and lower thermal limits of organisms. But measured critical temperatures often vary with methodological details, leading to spirited discussions about the potential consequences of stress and acclimation during the experiments. We review a model based on the simple assumption that failure rate increases with increasing temperature, independent of previous temperature exposure, water loss or metabolism during the experiment.

Response to Comment on "Precipitation drives global variation in natural selection".

The comment by Myers-Smith and Myers focuses on three main points: (i) the lack of a mechanistic explanation for climate-selection relationships, (ii) the appropriateness of the climate data used in our analysis, and (iii) our focus on estimating climate-selection relationships across (rather than within) taxonomic groups. We address these critiques in our response.

What Are the Environmental Determinants of Phenotypic Selection? A Meta-analysis of Experimental Studies.

Although many selection estimates have been published, the environmental factors that cause selection to vary in space and time have rarely been identified. One way to identify these factors is by experimentally manipulating the environment and measuring selection in each treatment. We compiled and analyzed selection estimates from experimental studies.

Evolution of plasticity and adaptive responses to climate change along climate gradients.

The relative contributions of phenotypic plasticity and adaptive evolution to the responses of species to recent and future climate change are poorly understood. We combine recent (1960-2010) climate and phenotypic data with microclimate, heat balance, demographic and evolutionary models to address this issue for a montane butterfly, , along an elevational gradient. Our focal phenotype, wing solar absorptivity, responds plastically to developmental (pupal) temperatures and plays a central role in thermoregulatory adaptation in adults.

Insect Development, Thermal Plasticity and Fitness Implications in Changing, Seasonal Environments.

Historical data show that recent climate change has caused advances in seasonal timing (phenology) in many animals and plants, particularly in temperate and higher latitude regions. The population and fitness consequences of these phenological shifts for insects and other ectotherms have been heterogeneous: warming can increase development rates and the number of generations per year (increasing fitness), but can also lead to seasonal mismatches between animals and their resources and increase exposure to environmental variability (decreasing fitness). Insect populations exhibit local adaptation in their developmental responses to temperature, including lower developmental thresholds and the thermal requirements to complete development, but climate change can potentially disrupt seasonal timing of juvenile and adult stages and alter population fitness.

Quantifying thermal extremes and biological variation to predict evolutionary responses to changing climate.

Central ideas from thermal biology, including thermal performance curves and tolerances, have been widely used to evaluate how changes in environmental means and variances generate changes in fitness, selection and microevolution in response to climate change. We summarize the opportunities and challenges for extending this approach to understanding the consequences of extreme climatic events. Using statistical tools from extreme value theory, we show how distributions of thermal extremes vary with latitude, time scale and climate change.

Precipitation drives global variation in natural selection.

Climate change has the potential to affect the ecology and evolution of every species on Earth. Although the ecological consequences of climate change are increasingly well documented, the effects of climate on the key evolutionary process driving adaptation-natural selection-are largely unknown. We report that aspects of precipitation and potential evapotranspiration, along with the North Atlantic Oscillation, predicted variation in selection across plant and animal populations throughout many terrestrial biomes, whereas temperature explained little variation.