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Abstract The ability to cope with heat is likely to influence species success amidst climate change. However, heat coping mechanisms are poorly understood in wild endotherms, which are increasingly pushed to their thermoregulatory limits.We take an organismal approach to this problem, unveiling how behavioural and physiological responses may allow success in the face of sublethal heat. We experimentally elevated nest temperatures for 4 h to mimic a future climate scenario (+4.5°C) during a critical period of post‐natal development in tree swallows (Tachycineta bicolor).Heat‐exposed nestlings exhibited marked changes in behaviour, including movement to cooler microclimates in the nest. They panted more and weighed less than controls at the end of the four‐hour heat challenge, suggesting panting‐induced water loss. Physiologically, heat induced high levels of heat shock protein (HSP) gene expression in the blood, alongside widespread transcriptional differences related to antioxidant defences, inflammation and apoptosis.Critically, all nestlings survived the heat challenge, and those exposed to milder heat weremorelikely to recruit into the breeding population. Early life but sub‐lethal heat may therefore act as a selective event, with the potential to shape population trajectories.Within the population, individuals varied in their physiological response to heat, namely in HSP gene expression, which exhibited higher mean and higher variance in heat‐exposed nestlings than in controls. Heat‐induced HSP levels were unrelated to individual body mass, or among‐nest differences in brood size, temperature, and behavioural thermoregulation. Nest identity explained a significant amount of HSP variation, yet siblings in the same nest differed by an average of ~4‐fold and individuals in the population differed by as much as ~100‐fold in their HSP response. This massive variation extends previous laboratory work in model organisms showing that heat shock proteins may harbour cryptic phenotypic variation.These results shed light on oft‐ignored elements of thermotolerance in wild birds at a critical stage of post‐natal development. By highlighting the scope of heat‐induced HSP gene expression and coupling it with a suite of organismal traits, we provide a framework for future testing of the mechanisms that shape species success in the face of change. Read the freePlain Language Summaryfor this article on the Journal blog. 

Abstract We study the minimum number of maximum matchings in a bipartite multigraph with parts and under various conditions, refining the well‐known lower bound due to M. Hall. When , every vertex in has degree at least , and every vertex in has at least distinct neighbors, the minimum is when and is when . When every vertex has at least two neighbors and , the minimum is , where . We also determine the minimum number of maximum matchings in several other situations. We provide a variety of sharpness constructions. 

Abstract The American lobster (Homarus americanusMilne Edwards, 1837) is an ecologically and economically valuable invertebrate in the Northwest Atlantic. Its geographic range is shifting northward due to ocean warming. While extensive research on the thermal tolerance of this species has been performed on adults and postlarvae, there have been few studies focused on its multiple early developmental stages. We applied transcriptomics to investigate transcriptional changes in laboratory-reared American lobster developmental stages I through V. Changes in gene expression were contextualized in the ontogenetic shifts in distribution that these different life history stages experience, with highly active stage IV exhibiting increased cellular metabolism and shell-building processes. We identified differential expression of transcripts related to thermal and UV stress in planktonic stages I-IV compared to benthic stage V, which suggests innate molecular defenses against these stressors. Together, these findings further our understanding of crustacean development in the context of climate change and can be used to inform population distribution modeling efforts. They also provide evidence for the need to investigate the potential trade-offs associated with responding to a changing environment on a stage-by-stage basis. 

Ecological traits have flourished in insect-based studies, resulting in a substantial and growing list of measurable traits. One trait that will likely become more attractive as data quality and curation improve is the diel patterns of insect activities. Diel patterns in ants can help better understand vital ecological processes such as competition and invasion biology. Because diel activity has the potential to be an informative trait in ants, we assessed the diel designations of foraging ants across the literature to quantify and assess the variation and sampling extent of this particular trait. We collected diel designations from 104 peer-reviewed scientific articles and quantified these data across important and documented ecological traits. We found that a disproportionate amount of solitary foraging ants were primarily diurnal foragers relative to ants that cooperatively forage. Our data show that diel patterns in foraging vary widely within and across ant genera. Importantly, we highlight the undersampling of this crucial ecological trait, which currently limits its utility. Our efforts highlight the importance of assessing an ecologically important trait’s landscape of reported data. 

The composition of air-exposed surfaces can have a strong impact on air quality and chemical exposure in the indoor environment. Third hand smoke (THS), which includes surface-deposited cigarette smoke residue along with the collection of gases evolved from such residues, is becoming increasingly recognized as an important source of long-term tobacco smoke exposure. While studies have described gas/surface partitioning behaviour and some multiphase reaction systems involving THS, the possibility of time-dependent changes in chemical composition due to chemical reactivity that is endogenous to the deposited film has yet to be investigated. In this study, sidestream cigarette smoke was allowed to deposit on glass surfaces that were either clean or pre-coated with chemicals that may be oxidized by reactive oxygen species found in the smoke. Surface films included a low volatility antioxidant, tris(2-carboxyethyl)phosphine (TCEP), and two compounds relevant to surface films found within buildings, oleic acid (OA) and squalene (SQ). Upon deposition, oxidation products of nicotine, TCEP, OA, and SQ were formed over time periods of hours to weeks. The inherent oxidative potential of cigarette smoke deposited as a THS film can therefore initiate and sustain oxidation chemistry, transforming the chemical composition of surface films over long periods of time after initial smoke deposition. An interpretation of the THS oxidation results is provided in the context of other types of deposited particulate air pollutants with known oxidative potential that may be introduced to indoor environments. Continued study of THS and deposited surface films found indoors should consider the concept that chemical reservoirs found on surfaces may be reactive, that the chemical composition of indoor surface films may be time-dependent, and that the deposition of aerosol particles can act as a mechanism to initiate oxidation in surface films. 

Abstract External factors such as exposure to a chemical, drug, or toxicant (CDT), or conversely, the lack of certain chemicals can cause many diseases. The ability to identify such causal CDTs based on changes in the gene expression profile is extremely important in many studies. Furthermore, the ability to correctly infer CDTs that can revert the gene expression changes induced by a given disease phenotype is a crucial step in drug repurposing. We present an approach for Predicting Upstream REgulators (PURE) designed to tackle this challenge. PURE can correctly infer a CDT from the measured expression changes in a given phenotype, as well as correctly identify drugs that could revert disease-induced gene expression changes. We compared the proposed approach with four classical approaches as well as with the causal analysis used in Ingenuity Pathway Analysis (IPA) on 16 data sets (1 rat, 5 mouse, and 10 human data sets), involving 8 chemicals or drugs. We assessed the results based on the ability to correctly identify the CDT as indicated by its rank. We also considered the number of false positives, i.e. CDTs other than the correct CDT that were reported to be significant by each method. The proposed approach performed best in 11 out of the 16 experiments, reporting the correct CDT at the very top 7 times. IPA was the second best, reporting the correct CDT at the top 5 times, but was unable to identify the correct CDT at all in 5 out of the 16 experiments. The validation results showed that our approach, PURE, outperformed some of the most popular methods in the field. PURE could effectively infer the true CDTs responsible for the observed gene expression changes and could also be useful in drug repurposing applications.