Seasonal variation in dragonfly assemblage colouration suggests a link between thermal melanism and phenology.

Phenology, the seasonal timing of life events, is an essential component of diversity patterns. However, the mechanisms involved are complex and understudied. Body colour may be an important factor, because dark-bodied species absorb more solar radiation, which is predicted by the Thermal Melanism Hypothesis to enable them to thermoregulate successfully in cooler temperatures. Here we show that colour lightness of dragonfly assemblages varies in response to seasonal changes in solar radiation, with darker early- and late-season assemblages and lighter mid-season assemblages. This finding suggests a link between colour-based thermoregulation and insect phenology. We also show that the phenological pattern of dragonfly colour lightness advanced over the last decades. We suggest that changing seasonal temperature patterns due to global warming together with the static nature of solar radiation may drive dragonfly flight periods to suboptimal seasonal conditions. Our findings open a research avenue for a more mechanistic understanding of phenology and spatio-phenological impacts of climate warming on insects.

Global change impacts on bird biodiversity in South Asia: potential effects of future land-use and climate change on avian species richness in Pakistan.

Evaluating the impact of future changes in land-use and climate on species communities, especially species richness, is one of the most important challenges of current research in ecology and conservation. The impact of environmental changes on species richness depends on its sensitivity (i.e., how strongly a given level of change influences the ecological community) and its exposure (i.e., the amount of change that occurs). To examine the sensitivity, exposure, and potential impact of future environmental conditions on bird communities, we compiled data on bird species richness for Pakistan-a neglected region in macro- or country-scale studies. Since bird species richness strongly varies across seasons due to the seasonal occurrence of migratory species in winter, we compared both wintering (migratory plus resident species) and breeding (resident species only) bird richness. We found breeding and wintering species richness to be sensitive to temperature, precipitation and rainfed cropland by being positively related to these factors. Exposure varied regionally, with projected temperature changes being most profound in northern regions while the strongest projected precipitation changes occurred in central and southern regions. The projected impact of future environmental change were highly heterogeneous across the country and differed between the wintering and breeding communities. Overall, the most negatively impacted region was projected to be the Khyber Pakhtunkha province in the North of Pakistan, due to reductions in precipitation and rainfed cropland, resulting in a projected negative impact, especially on wintering species richness. By highlighting the regional and seasonal bird communities most at risk, our findings provide useful information for policy makers to help devise new policies for mitigating negative impacts of future environmental changes on birds within Pakistan.

The role of thermal tolerance in determining elevational distributions of four arthropod taxa in mountain ranges of southern Asia.

Understanding the role of thermal tolerances in determining species distributions is important for assessing species responses to climate change. Two hypotheses linking physiology with species distributions have been put forward-the climatic variability hypothesis and the climatic extreme hypothesis. The climatic variability hypothesis predicts the selection of individuals with broad thermal tolerance in more variable climatic conditions and the climatic extreme hypothesis predicts the selection of individuals with extreme thermal tolerance values under extreme climatic conditions. However, no study has tested the predictions of these hypotheses simultaneously for several taxonomic groups along elevational gradients. Here, we related experimentally measured critical thermal maxima, critical thermal minima and thermal tolerance breadths for 15,187 individuals belonging to 116 species of ants, beetles, grasshoppers, and spiders from mountain ranges in central and northern Pakistan to the limits and breadths of their geographic and temperature range. Across all species and taxonomic groups, we found strong relationships between thermal traits and elevational distributions both in terms of geography and temperature. The relationships were robust when repeating the analyses for ants, grasshoppers, and spiders but not for beetles. These results indicate a strong role of physiology in determining elevational distributions of arthropods in Southern Asia. Overall, we found strong support for the climatic variability hypothesis and the climatic extreme hypothesis. A close association between species' distributional limits and their thermal tolerances suggest that in case of a failure to adapt or acclimate to novel climatic conditions, species may be under pressure to track their preferred climatic conditions, potentially facing serious consequences under current and future climate change.

Microhabitat conditions remedy heat stress effects on insect activity.

Anthropogenic global warming has major implications for mobile terrestrial insects, including long-term effects from constant warming, for example, on species distribution patterns, and short-term effects from heat extremes that induce immediate physiological responses. To cope with heat extremes, they either have to reduce their activity or move to preferable microhabitats. The availability of favorable microhabitat conditions is strongly promoted by the spatial heterogeneity of habitats, which is often reduced by anthropogenic land transformation. Thus, it is decisive to understand the combined effects of these global change drivers on insect activity. Here, we assessed the movement activity of six insect species (from three orders) in response to heat stress using a unique tracking approach via radio frequency identification. We tracked 465 individuals at the iDiv Ecotron across a temperature gradient up to 38.7°C. In addition, we varied microhabitat conditions by adding leaf litter from four different tree species to the experimental units, either spatially separated or well mixed. Our results show opposing effects of heat extremes on insect activity depending on the microhabitat conditions. The insect community significantly decreased its activity in the mixed litter scenario, while we found a strong positive effect on activity in the separated litter scenario. We hypothesize that the simultaneous availability of thermal refugia as well as resources provided by the mixed litter scenario allows animals to reduce their activity and save energy in response to heat stress. Contrary, the spatial separation of beneficial microclimatic conditions and resources forces animals to increase their activity to fulfill their energetic needs. Thus, our study highlights the importance of habitat heterogeneity on smaller scales, because it may buffer the consequences of extreme temperatures of insect performance and survival under global change.

Effective or predatory funding? Evaluating the hidden costs of grant applications.

Researchers are spending an increasing fraction of their time on applying for funding; however, the current funding system has considerable deficiencies in reliably evaluating the merit of research proposals, despite extensive efforts on the sides of applicants, grant reviewers and decision committees. For some funding schemes, the systemic costs of the application process as a whole can even outweigh the granted resources-a phenomenon that could be considered as predatory funding. We present five recommendations to remedy this unsatisfactory situation.

Projected climate change impacts on the phylogenetic diversity of the world's terrestrial birds: more than species numbers.

Ongoing climate change is a major threat to biodiversity. As abiotic tolerances and dispersal abilities vary, species-specific responses have the potential to further amplify or ameliorate the ensuing impacts on species assemblages. Here, we investigate the effects of climate change on species distributions across non-marine birds, quantifying its projected impact on species richness (SR) as well as on different aspects of phylogenetic diversity globally. Going beyond previous work, we disentangle the potential impacts of species gains versus losses on assemblage-level phylogenetic diversity under climate change and compare the projected impacts to randomized assemblage changes. We show that beyond its effects on SR, climate change could have profound impacts on assemblage-level phylogenetic diversity and composition, which differ significantly from random changes and among regions. Though marked species losses are most frequent in tropical and subtropical areas in our projections, phylogenetic restructuring of species communities is likely to occur all across the globe. Furthermore, our results indicate that the most severe changes to the phylogenetic diversity of local assemblages are likely to be caused by species range shifts and local species gains rather than range reductions and extinctions. Our findings highlight the importance of considering diverse measures in climate impact assessments.

Consistent signals of a warming climate in occupancy changes of three insect taxa over 40 years in central Europe.

Recent climate and land-use changes are having substantial impacts on biodiversity, including population declines, range shifts, and changes in community composition. However, few studies have compared these impacts among multiple taxa, particularly because of a lack of standardized time series data over long periods. Existing data sets are typically of low resolution or poor coverage, both spatially and temporally, thereby limiting the inferences that can be drawn from such studies. Here, we compare climate and land-use driven occupancy changes in butterflies, grasshoppers, and dragonflies using an extensive data set of highly heterogeneous observation data collected in the central European region of Bavaria (Germany) over a 40-year period. Using occupancy models, we find occupancies (the proportion of sites occupied by a species in each year) of 37% of species have decreased, 30% have increased and 33% showed no significant trend. Butterflies and grasshoppers show strongest declines with 41% of species each. By contrast, 52% of dragonfly species increased. Temperature preference and habitat specificity appear as significant drivers of species trends. We show that cold-adapted species across all taxa have declined, whereas warm-adapted species have increased. In butterflies, habitat specialists have decreased, while generalists increased or remained stable. The trends of habitat generalists and specialists both in grasshoppers and semi-aquatic dragonflies, however did not differ. Our findings indicate strong and consistent effects of climate warming across insect taxa. The decrease of butterfly specialists could hint towards a threat from land-use change, as especially butterfly specialists' occurrence depends mostly on habitat quality and area. Our study not only illustrates how these taxa showed differing trends in the past but also provides hints on how we might mitigate the detrimental effects of human development on their diversity in the future.

Global impacts of climate change on avian functional diversity.

Climate change is predicted to drive geographical range shifts, leading to fluctuations in species richness (SR) worldwide. However, the effect of these changes on functional diversity (FD) remains unclear, in part because comprehensive species-level trait data are generally lacking at global scales. Here, we use morphometric and ecological traits for 8268 bird species to estimate the impact of climate change on avian FD. We show that future bird assemblages are likely to undergo substantial shifts in trait structure, with a magnitude of change greater than predicted from SR alone, and a direction of change varying according to geographical location and trophic guild. For example, our models predict that FD of insect predators will increase at higher latitudes with concurrent losses at mid-latitudes, whereas FD of seed dispersing birds will fluctuate across the tropics. Our findings highlight the potential for climate change to drive continental-scale shifts in avian FD with implications for ecosystem function and resilience.

Representation of the world's biophysical conditions by the global protected area network.

Protected areas (PAs) are often implemented without consideration of already existing PAs, which is likely to cause an overrepresentation of certain biophysical conditions. We assessed the representativeness of the current PA network with regard to the world's biophysical conditions to highlight which conditions are underprotected and where these conditions are located. We overlaid terrestrial and marine PAs with information on biophysical conditions (e.g., temperature, precipitation, and elevation) and then quantified the percentage of area covered by the PA network. For 1 variable at a time in the terrestrial realm, high temperature, low precipitation, and medium and very high elevation were underrepresented. For the marine realm, low and medium sea surface temperature (SST), medium and high sea surface salinity (SSS), and the deep sea were underrepresented. Overall, protection was evenly distributed for elevation across the terrestrial realm and SST across the marine realm. For 2 variables at a time, cold and very dry terrestrial environments had mostly low protection, which was also the case for low SST and low and medium SSS across most depths for marine environments. Low protection occurred mostly in the Sahara and the Arabian Peninsula for the terrestrial realm and along the Tropic of Capricorn and toward the poles for the marine realm. Although biodiversity measures are of prime importance for the design of PA networks, highlighting biophysical gaps in current PAs adds a frequently overlooked perspective. These gaps may weaken the potential of PAs to conserve biodiversity. Thus, our results may provide useful insights for researchers, practitioners, and policy makers to establish a more comprehensive global PA network.

Las áreas protegidas (AP) son frecuentemente implementadas sin considerar las ya existentes, lo que probablemente ocasiona una sobrerrepresentación de ciertas condiciones biofísicas. Analizamos la representatividad de la red actual de AP con respecto a las condiciones biofísicas del mundo para resaltar que condiciones están subprotegidas y en dónde se encuentran localizadas. Superpusimos las AP terrestres y marinas con la información sobre las condiciones biofísicas (p. ej.: temperatura, precipitación y elevación) y luego cuantificamos el porcentaje de área cubierta por la red de AP. Para el análisis de una variable a la vez, en el ambito terrestre, la alta temperatura, baja precipitación y las elevaciones media y muy alta estuvieron subrepresentadas. Para el ambito marino, la baja y media temperatura de la superficie marina (TSM), la media y alta salinidad de la superficie marina (SSM) y el mar profundo estuvieron subrepresentados. En general, la protección para la elevación en el ambito terrestre y para la TSM en el ambito marino se distribuyó uniformemente. Para el análisis de dos variables a la vez, los ambientes terrestres fríos y muy secos tuvieron en su mayoría una baja protección, lo que también ocurrió para la baia TSM y la baja y media SSM en casi todas las profundidades de los entornos marinos. La baja protección para el ambito terrestre estuvo presente en su mayoría en el Sahara y en la Península Arábiga, y en el ambito marino, a lo largo del Trópico de Cáncer y hacia los polos. Aunque las medidas de biodiversidad son de suma importancia para el diseño de las redes de AP, resaltar los vacíos de información biofísica en las actuales AP añade una perspectiva que con frecuencia se ignora. Estos vacíos pueden debilitar el potencial que tienen las AP para conservar la biodiversidad. Por lo tanto, nuestros resultados pueden proporcionar información útil para que investigadores, profesionales y tomadores de decisiones establezcan una red mundial de AP más completa.

Towards more integration of physiology, dispersal and land-use change to understand the responses of species to climate change.

The accelerating biodiversity crisis, for which climate change has become an important driver, urges the scientific community for answers to the question of whether and how species are capable of responding successfully to rapidly changing climatic conditions. For a better understanding and more realistic predictions of species' and biodiversity responses, the consideration of extrinsic (i.e. environment-related) and intrinsic (i.e. organism-related) factors is important, among which four appear to be particularly crucial: climate change and land-use change, as extrinsic factors, as well as physiology and dispersal capacity, as intrinsic factors. Here, I argue that these four factors should be considered in an integrative way, but that the scientific community has not yet been very successful in doing so. A quantitative literature review revealed a generally low level of integration within global change biology, with a pronounced gap especially between the field of physiology and other (sub)disciplines. After a discussion of potential reasons for this unfortunate lack of integration, some of which may relate to key deficits e.g. in the reward and incentive systems of academia, I suggest a few ideas that might help to overcome some of the barriers between separated research communities. Furthermore, I list several examples for promising research along the integration frontier, after which I outline some research questions that could become relevant if one is to push the boundary of integration among disciplines, of data and methods, and across scales even further - for a better understanding and more reliable predictions of species and biodiversity in a world of global change.

Trait-Based Assessments of Climate-Change Impacts on Interacting Species.

Plant-animal interactions are fundamentally important in ecosystems, but have often been ignored by studies of climate-change impacts on biodiversity. Here, we present a trait-based framework for predicting the responses of interacting plants and animals to climate change. We distinguish three pathways along which climate change can impact interacting species in ecological communities: (i) spatial and temporal mismatches in the occurrence and abundance of species, (ii) the formation of novel interactions and secondary extinctions, and (iii) alterations of the dispersal ability of plants. These pathways are mediated by three kinds of functional traits: response traits, matching traits, and dispersal traits. We propose that incorporating these traits into predictive models will improve assessments of the responses of interacting species to climate change.

Bioenergy cropland expansion may offset positive effects of climate change mitigation for global vertebrate diversity.

Climate and land-use change interactively affect biodiversity. Large-scale expansions of bioenergy have been suggested as an important component for climate change mitigation. Here we use harmonized climate and land-use projections to investigate their potential combined impacts on global vertebrate diversity under a low- and a high-level emission scenario. We combine climate-based species distribution models for the world's amphibians, birds, and mammals with land-use change simulations and identify areas threatened by both climate and land-use change in the future. The combined projected effects of climate and land-use change on vertebrate diversity are similar under the two scenarios, with land-use change effects being stronger under the low- and climate change effects under the high-emission scenario. Under the low-emission scenario, increases in bioenergy cropland may cause severe impacts in biodiversity that are not compensated by lower climate change impacts. Under this low-emission scenario, larger proportions of species distributions and a higher number of small-range species may become impacted by the combination of land-use and climate change than under the high-emission scenario, largely a result of bioenergy cropland expansion. Our findings highlight the need to carefully consider both climate and land-use change when projecting biodiversity impacts. We show that biodiversity is likely to suffer severely if bioenergy cropland expansion remains a major component of climate change mitigation strategies. Our study calls for an immediate and significant reduction in energy consumption for the benefit of both biodiversity and to achieve the goals of the Paris Agreement.

Testing the heat dissipation limitation hypothesis: basal metabolic rates of endotherms decrease with increasing upper and lower critical temperatures.

Metabolic critical temperatures define the range of ambient temperatures where endotherms are able to minimize energy allocation to thermogenesis. Examining the relationship between metabolic critical temperatures and basal metabolic rates (BMR) provides a unique opportunity to gain a better understanding of how animals respond to varying ambient climatic conditions, especially in times of ongoing and projected future climate change. We make use of this opportunity by testing the heat dissipation limit (HDL) theory, which hypothesizes that the maximum amount of heat a species can dissipate constrains its energetics. Specifically, we test the theory's implicit prediction that BMR should be lower under higher metabolic critical temperatures. We analysed the relationship of BMR with upper and lower critical temperatures for a large dataset of 146 endotherm species using regression analyses, carefully accounting for phylogenetic relationships and body mass. We show that metabolic critical temperatures are negatively related with BMR in both birds and mammals. Our results confirm the predictions of the HDL theory, suggesting that metabolic critical temperatures and basal metabolic rates respond in concert to ambient climatic conditions. This implies that heat dissipation capacities of endotherms may be an important factor to take into account in assessments of species' vulnerability to climate change.

Moving in the Anthropocene: Global reductions in terrestrial mammalian movements.

Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission.

Does metabolism constrain bird and mammal ranges and predict shifts in response to climate change?

Mechanistic approaches for predicting the ranges of endotherms are needed to forecast their responses to environmental change. We test whether physiological constraints on maximum metabolic rate and the factor by which endotherms can elevate their metabolism (metabolic expansibility) influence cold range limits for mammal and bird species. We examine metabolic expansibility at the cold range boundary (MECRB) and whether species' traits can predict variability in MECRB and then use MECRB as an initial approach to project range shifts for 210 mammal and 61 bird species. We find evidence for metabolic constraints: the distributions of metabolic expansibility at the cold range boundary peak at similar values for birds (2.7) and mammals (3.2). The right skewed distributions suggest some species have adapted to elevate or evade metabolic constraints. Mammals exhibit greater skew than birds, consistent with their diverse thermoregulatory adaptations and behaviors. Mammal and bird species that are small and occupy low trophic levels exhibit high levels of MECRB. Mammals with high MECRB tend to hibernate or use torpor. Predicted metabolic rates at the cold range boundaries represent large energetic expenditures (>50% of maximum metabolic rates). We project species to shift their cold range boundaries poleward by an average of 3.9° latitude by 2070 if metabolic constraints remain constant. Our analysis suggests that metabolic constraints provide a viable mechanism for initial projections of the cold range boundaries for endotherms. However, errors and approximations in estimating metabolic constraints (e.g., acclimation responses) and evasion of these constraints (e.g., torpor/hibernation, microclimate selection) highlight the need for more detailed, taxa-specific mechanistic models. Even coarse considerations of metabolism will likely lead to improved predictions over exclusively considering thermal tolerance for endotherms.

Cross-taxa generalities in the relationship between population abundance and ambient temperatures.

Identifying patterns in the effects of temperature on species' population abundances could help develop a general framework for predicting the consequences of climate change across different communities and realms. We used long-term population time series data from terrestrial, freshwater, and marine species communities within central Europe to compare the effects of temperature on abundance across a broad range of taxonomic groups. We asked whether there was an average relationship between temperatures in different seasons and annual abundances of species in a community, and whether species attributes (temperature range of distribution, range size, habitat breadth, dispersal ability, body size, and lifespan) explained interspecific variation in the relationship between temperature and abundance. We found that, on average, warmer winter temperatures were associated with greater abundances in terrestrial communities (ground beetles, spiders, and birds) but not always in aquatic communities (freshwater and marine invertebrates and fish). The abundances of species with large geographical ranges, larger body sizes, and longer lifespans tended to be less related to temperature. Our results suggest that climate change may have, in general, positive effects on species' abundances within many terrestrial communities in central Europe while the effects are less predictable in aquatic communities.

Cross-realm assessment of climate change impacts on species' abundance trends.

Climate change, land-use change, pollution and exploitation are among the main drivers of species' population trends; however, their relative importance is much debated. We used a unique collection of over 1,000 local population time series in 22 communities across terrestrial, freshwater and marine realms within central Europe to compare the impacts of long-term temperature change and other environmental drivers from 1980 onwards. To disentangle different drivers, we related species' population trends to species- and driver-specific attributes, such as temperature and habitat preference or pollution tolerance. We found a consistent impact of temperature change on the local abundances of terrestrial species. Populations of warm-dwelling species increased more than those of cold-dwelling species. In contrast, impacts of temperature change on aquatic species' abundances were variable. Effects of temperature preference were more consistent in terrestrial communities than effects of habitat preference, suggesting that the impacts of temperature change have become widespread for recent changes in abundance within many terrestrial communities of central Europe.

Ecological networks are more sensitive to plant than to animal extinction under climate change.

Impacts of climate change on individual species are increasingly well documented, but we lack understanding of how these effects propagate through ecological communities. Here we combine species distribution models with ecological network analyses to test potential impacts of climate change on >700 plant and animal species in pollination and seed-dispersal networks from central Europe. We discover that animal species that interact with a low diversity of plant species have narrow climatic niches and are most vulnerable to climate change. In contrast, biotic specialization of plants is not related to climatic niche breadth and vulnerability. A simulation model incorporating different scenarios of species coextinction and capacities for partner switches shows that projected plant extinctions under climate change are more likely to trigger animal coextinctions than vice versa. This result demonstrates that impacts of climate change on biodiversity can be amplified via extinction cascades from plants to animals in ecological networks.