Integrative and Comparative Biology最新文献

Rising environmental temperatures and extreme climatic events are negatively affecting ectothermic animals, especially those with limited opportunities for behavioral thermoregulation (i.e., passive thermoregulators). Rather than rely on behavioral buffering, thermally passive ectotherms may instead adjust their thermal preferences (either lowering or increasing them) to perform their biological activities at warmer temperatures. Nevertheless, temporal comparisons of preferred temperatures in wild populations of passive thermoregulators remain scant, limiting our capacity to broadly anticipate their responses to rising temperatures. Here, we compared laboratory thermal preferences across years (2003-2004 vs. 2016-2018) in 3 thermally passive lizard species from Central Mexico: the anguimorphs Gerrhonotus liocephalus, Xenosaurus rectocollaris, and X. tzacualtipantecus. These species exhibit different habitat use and live in places where heat wave events have increased over time, allowing temporal comparisons of thermal preferences in warming habitats. We discovered that the 3 species increased their thermal preferences by ∼1°C in 12-15 years. Our results indicate that these, and likely other passive thermoregulators must adjust their thermal preferences in response to global warming, rising a profound concern about their long-term viability as they approach intrinsic limits in their thermal physiology.

Global temperatures are shifting in complex ways due to climate change. While early research focused on rising mean temperatures and its effect on biological outcomes, recent work has emphasized understanding the influence of temperature variability. In particular, many studies investigate temperature variation by symmetrically expanding daily temperature ranges around a fixed mean or by increasing daytime maximums. Although these approaches isolate specific aspects of temperature change, they often fail to capture how climate change is actually reshaping daily temperature cycles. In this perspective paper, we use climate data across three geographic scales to illustrate a striking and consistent pattern: daily minimum temperatures are rising faster than daily maximums, effectively reducing daily temperature range. A global analysis reveals that nighttime minimum temperatures are increasing more rapidly than daytime maximums across most land areas worldwide, especially at higher latitudes and elevations. At the continental scale, North American climate data show that asymmetric warming occurs year-round, with the strongest effects in winter. Regional patterns reveal especially strong nighttime warming in mountainous regions like the Rocky and Pacific Mountain systems. Locally, hourly data from Paradise, Nevada show nighttime temperatures have risen by over 4°C since the 1950s, while daytime highs remained stable, reducing daily temperature range by more than 4°C. We then synthesize findings from 84 studies that directly investigated biological responses to nighttime warming. Nearly half (47%) of the orders studied were plants, highlighting major taxonomic gaps in animal and microbial systems. Most studies (57%) were in organismal biology, yet few were hypothesis driven. Across taxa, asymmetric warming alters energetics, increases metabolic costs, and affects both thermal performance traits (e.g., metabolism, activity) and threshold-dependent traits (e.g., phenology, sex determination). We highlight evidence that nighttime warming may enhance or inhibit cellular recovery from heat stress (Heat Stress Recovery Hypotheses), shift species interactions, disrupt pollination networks, and reshape community structure. We conclude with a call for broader research across taxa, life stages, and ecological contexts, and recommend experimental, field-based, and modeling approaches tailored to disentangle the unique effects of asymmetric warming. Understanding asymmetric warming is not just a research gap-it's a pressing ecological imperative essential for predicting and mitigating climate change impacts on biodiversity.

Understanding the mechanisms by which organisms adapt to variation in temperature is key to explaining their distribution across environments and to predicting their persistence to changing climate. The cellular response to heat shock, heat shock response (HSR), is a highly conserved mechanism for coping with elevated temperatures which functions through the upregulation of molecular chaperones like heat shock proteins (HSPs). Recent studies have also shown cellular response to heat shock can be quantitative (changing the magnitude of expression) or qualitative (differential usage of exons originating from the same gene). However, few studies have explored the time course of these two mechanisms in response to heat shock. We conducted a time-course experiment to examine the gene expression and exon usage changes in response to heat shock at four post-stress timepoints (30 min, 1 h, 2 h, 24 h) in a splash pool copepod, Tigriopus californicus. We detected signatures of both gene expression and exon usage changes across all timepoints. The magnitude of this response was higher at timepoints closer to heat shock and decreased with time post-heat shock. We observed that heat shock predominantly induced changes in gene expression in genes coding for chitin, HSPs, cellular growth, and differentiation. In contrast, we found that genes coding for peptidases showed both altered expression levels and exon usage. Genes associated with cellular metabolism and cytoskeletal elements primarily showed changes in exon usage. These ontology-specific response mechanisms provide new insights into the temporal landscape of HSR in Tigriopus and highlight the need to integrate qualitative and quantitative changes in gene expression to fully understand organismal responses to heat shock.

The majority of flowering plants depend on insect pollination for reproduction and declining pollinator populations pose a threat to biodiversity as well as critical crop pollination services globally. Widespread insecticide use negatively impacts pollinator physiology and behavior even at environmentally realistic concentrations below lethal toxicity, leading to reduced fitness and long-term population declines. However, significant gaps remain in our understanding of how insecticides affect diverse aspects of behavior and ultimately influence pollinator populations and pollination services. These gaps partly stem from the challenge of quantifying sublethal effects of pesticides on the complex behavioral repertoires of insects. Current methods often focus on a narrow set of behaviors at a time, limiting our ability to capture the comprehensive range of impacts within management-relevant timescales. The emergence of low-cost techniques for high-throughput behavioral quantification, or "ethomics," holds enormous potential to address this knowledge gap. Here, we used automated, computer vision-based tracking implemented on open-source hardware (Raspberry Pis) to investigate the sublethal effects of an emerging "bee-safe" butenolide insecticide (flupyradifurone), as well as a neonicotinoid insecticide (imidacloprid), on bumble bee (Bombus impatiens) behavior. We simultaneously quantified the behavior of uniquely tagged individual workers both within the nest, and during foraging in a semi-field environment, to assess the holistic effects of insecticides under naturalistic conditions. Both insecticides increased mortality risk and altered behavior, but in distinct ways across behavioral contexts. Imidacloprid modified nest behavior by decreasing activity, while flupyradifurone altered spatial behavior within the nest (shifting bees toward the brood). Imidacloprid-but not flupyradifurone-reduced overall foraging activity, while both affected floral preference. Overall, our results highlight the complex potential mechanistic links between sublethal insecticide exposure, behavior, and pollinator health. This work emphasizes the need-and possibility-for rapid and holistic pesticide risk assessment under realistic environmental conditions using high-throughput ethomics, and could inform the development of sustainable agricultural practices and conservation strategies.

Climate change will continue to increase mean global temperatures, with daily minima increasing more than daily maxima temperatures on average. In addition, altered rainfall patterns due to climate change will disrupt water availability. Such changes are likely to influence thermo-hydroregulation and reproduction strategies in terrestrial ectotherms. We manipulated access to preferred diurnal temperature (9 h vs. 4 h at preferred temperature), nocturnal temperature at rest (22 vs. 17°C) as well as water availability during gestation (± ad libitum access to water) in female common lizards (Zootoca vivipara), a cold- and wet-adapted species. We previously reported that hot conditions (day and night) accelerated gestation but high nighttime temperatures increased the burden on females already constrained by heavy resource and water investment during gestation. We expanded the understanding of this relationship by examining the effects of maternal hydration and temperature on offspring (neonates and juveniles; N = 625) physiology (water loss rates and respiratory activity), morphology, performance (endurance capacity and growth), and survival. On average, longer access to preferred temperature during the day conferred benefits on offspring growth and survival, despite a negative effect on body condition at birth. High nighttime temperatures during gestation reduced offspring postnatal growth during early life and, together with high daytime temperatures, reduced tail width and endurance capacity at birth as well as offspring survival. Additionally, water deprivation poses a challenge to homeostasis, but offspring demonstrate resilience in coping with this potential stressor and these effects were not stronger in hot climates. Notably, the benefits of hotter environments are not always additive, highlighting the complexity of temperature-mediated effects on maternal and offspring outcomes.

Floral color plays a critical role in shaping plant-pollinator interactions, yet the extent to which lepidopteran flower visitation is color-dependent remains underexplored. Using over 8000 community-science observations from the southwestern Ozarks, central USA, from 2002 to 2024, we assessed whether butterflies and moths visit flowers randomly or according to color preferences, and how these preferences vary across taxa. Our results reveal that flower visitation by Lepidoptera is both flower color-dependent and Lepidoptera taxon-specific. Magenta flowers stood out as the most distinct in terms of their visitors. Although broad color preferences emerged at the family level, species-level analyses uncovered even greater complexity, with unique, non-random combinations of preferred flower colors. Lycaenidae exhibited the narrowest color spans, frequently visiting white and beige flowers. In contrast, monarchs and fritillaries (both from Nymphalidae), swallowtails (Papilionidae), and many skippers (Hesperiidae) visited flowers of nearly all available hues at similar rates. Some observed patterns were consistent with findings from other geographic regions, such as a strong preference for magenta and lavender in diurnal hawkmoths (Sphingidae). However, others were not, as many butterfly lineages associated with yellow flowers in other geographic regions instead showed a pronounced preference for red, crimson, and blush flowers in our study area. Our findings highlight the potential of community-science data for studying pollinator behavior at an unprecedented spatial and temporal scale, while also demonstrating diversity in Lepidoptera floral preferences and the potential for geographic variation in floral preferences within species.

Plant-pollinator interactions are frequently affected by microbes that grow on flowers. Bacteria and yeast commonly grow within floral nectar, which is a sugar-rich floral reward often sought out by pollinators. Nectar is also commonly contaminated with protein-rich pollen. Microbes can induce this pollen to germinate or burst within the nectar, which potentially results in pollen nutrients being made available to nectar foraging pollinators. Yet whether pollen-microbe interactions in nectar impact pollinator behavior remains unknown. We therefore investigated how a common nectar yeast (Metschnikowia reukaufii) and bacteria (Acinetobacter nectaris) affected pollen germination and bursting within artificial nectar and effects on bumble bee (Bombus impatiens) foraging behavior. We found that both bacteria and yeast reduced the proportion of intact pollen in nectar, with bacteria inducing the most germination and bursting. Although microbes may thus potentially increase the quality of the nectar reward via increased access to pollen nutrients, we did not observe effects on bee flower preference. Similarly, bees did not show increased constancy (i.e., fidelity to one flower type across flower visits) to nectar contaminated with pollen and microbes. In contrast, bees were much more likely to reject flowers with nectar contaminated with pollen and yeast alone or together, relative to flowers that offered uncontaminated nectar. Altogether, our work suggests pollen-microbe interactions within nectar may have relatively minor influences on pollinator foraging behavior. We discuss possible explanations and implications of these results for plant and pollinator ecology.

The Damage-Fitness model describes how stress is linked to damage and repair pathways that drive health and fitness outcomes across taxa. However, we lack an understanding of how variation in hypothalamic-pituitary-adrenal (HPA) responses (i.e., endocrine flexibility) affects damage, especially after recovery from stressors. In this study, adult female zebra finches were exposed to a normal photoperiod or constant light for 23 days followed by a recovery period. Using path analysis, we combined a suite of morphological and physiological traits to examine the mechanisms related to cellular damage outcomes. In control individuals, HPA axis reactivity was condition-dependent, such that birds with higher body mass had stronger HPA axis reactivity. HPA axis reactivity was associated with two specific relationships: a strong, positive, relationship with glucose reactivity and a slightly negative relationship with liver 4-hydroxynonaneal that covaried. Interestingly, this condition dependency disappeared in birds recovering from constant light. While HPA axis reactivity was positively associated with glucose reactivity, this path relationship was not associated with any damage marker in birds recovering from constant light. Liver glucocorticoid receptor abundance was negatively associated with liver protein carbonyl damage in control birds, but this relationship was lost in birds recovering from light. These patterns indicate that long-term exposure to a stressor such as constant light can alter biologically linked relationships, even after cessation and recovery from that stressor. Yet, whether rewiring of physiological network connectivity is related to adaptive physiological outcomes, fitness-related traits, or performance remains unclear.

Trait modularity is a defining feature of complex life. However, the drivers of modularity across different scales of biological organization remain opaque. Studies have shown that a combination of developmental and functional interactions can structure patterns of trait covariation at the developmental, population, and even macroevolutionary level. However, it remains unclear how developmental and functional interactions may translate or influence macroevolutionary patterns of trait covariance and diversification. Pharyngognathy is a striking evolutionary innovation that has evolved multiple times in acanthomorph fishes and has resulted in the evolution of robust pharyngeal jaws that are used to process hard prey. Recent studies have found strong patterns of evolutionary integration among the jaw systems in pharyngognathous fishes suggesting that this innovation was brought about by the evolutionary coupling of two otherwise distinct trait complexes. Furthermore, the pharyngeal jaws have been hypothesized to act as a constraining force on the evolution of the oral jaws potentially due to their developmental origins in the more conserved hox-positive region of the skull. While multiple studies have recovered strong evolutionary integration between the jaw systems, patterns of modularity at the population (variational) level appear to differ, where a high degree of modularity has been found between the oral and pharyngeal jaws suggesting a disconnect between patterns of evolutionary modularity and patterns of variational modularity. Here, we are using three-dimensional geometric morphometrics to test for modularity between the oral and pharyngeal jaws at the variational level in a population of Lunar wrasse collected from Kagoshima, Japan and additionally test for differences in morphological disparity between the oral and pharyngeal jaws. We find strong support for a developmental hypothesis of modularity that separates the jaw systems into distinct modules. We additionally find mixed support for the constraint hypothesis of the pharyngeal jaws, where some elements of the pharyngeal jaws were found to exhibit less morphological disparity than the oral jaws while others exhibited more morphological disparity. Our findings suggest that developmental and functional interactions at the variational level may impart patterns of covariation that are distinct from evolutionary patterns of modularity that are found between species.

Symbiotic host-associated microbial communities are nearly ubiquitous and are often essential to host growth and development. The assembly of these communities on hosts is the result of a combination of the processes of selection, dispersal, and drift. For some species, essential symbionts are quickly acquired from the environment during embryonic development, while others may vertically acquire symbionts from parents. For amphibians with complex life cycles that undergo metamorphosis, an additional physiological transition from larval to adult forms may represent another distinct developmental window for bacterial colonization. Prior research has demonstrated that metamorphosis impacts the composition of amphibian-associated bacterial communities; however, we do not know whether similar shifts occur during metamorphosis across different amphibian species. To more clearly understand patterns in microbiome development across host species within a given area, we assessed the bacterial communities associated with eggs from five locally occurring amphibian species and tadpoles and juveniles from four of the species. Additionally, to determine if stochasticity result in varied microbiome composition among conspecifics, we raised one species, spring peepers (Pseudacris crucifer), in outdoor 1000 L mesocosms. Through 16S rRNA gene amplicon sequencing, we detected distinct bacterial communities across amphibian species and development. Additionally, we found that tadpoles harbored different communities of bacteria in the different mesocosms, suggesting that stochasticity may play a large role in bacterial assembly on tadpoles. Our results serve to deepen our understanding of natural shifts in amphibian-associated bacterial communities and how these shifts are host-species dependent. Additionally, this study provides support for the idea that stochasticity in the form of drift or priority effects can drive individual variation in microbiome composition among hosts.