Future Environmental Change Research Articles

Water-limited environments affect the association between functional diversity and forest productivity.

The link between biodiversity and ecosystem function can depend on environmental conditions. This contingency can impede our ability to predict how biodiversity-ecosystem function (BEF) relationships will respond to future environmental change, causing a clear need to explore the processes underlying shifts in BEF relationships across large spatial scales and broad environmental gradients. We compiled a dataset on five functional traits (maximum height, wood density, specific leaf area [SLA], seed size, and xylem vulnerability to embolism [P50]), covering 78%-90% of the tree species in the National Forest Inventory from Italy, to test (i) how a water limitation gradient shapes the functional composition and diversity of forests, (ii) how functional composition and diversity of trees relate to forest annual increment via mass ratio and complementarity effects, and (iii) how the relationship between functional diversity and annual increment varies between Mediterranean and temperate climate regions. Functional composition varied with water limitation; tree communities tended to have more conservative traits in sites with higher levels of water limitation. The response of functional diversity differed among traits and climatic regions but among temperate forest plots, we found a consistent increase of functional diversity with water limitation. Tree diversity was positively associated with annual increment of Italian forests through a combination of mass ratio and niche complementarity effects, but the relative importance of these effects depended on the trait and range of climate considered. Specifically, niche complementarity effects were more strongly associated with annual increment in the Mediterranean compared to temperate forests. Synthesis: Overall, our results suggest that biodiversity mediates forest annual increment under water-limited conditions by promoting beneficial interactions between species and complementarity in resource use. Our work highlights the importance of conserving functional diversity for future forest management to maintain forest annual increment under the expected increase in intensity and frequency of drought.

Importance of fish biodiversity conservation and management

One of the key concerns for enabling the sustainable use of natural resources is biodiversity and its conservation. Fish make up the most varied group of vertebrates and they are considered to be a reliable indication of water pollution. Humans are causing an increasing loss of biodiversity in aquatic ecosystems, which is likely to have a detrimental impact on ecosystem functioning, services, and resistance to future environmental change. Overfising from different water bodies is one of the major issues which could affect the aquatic ecosystems. These fishing pressures may alter the development and behaviour of fish, alter the life cycles and productivity of fish, and reduce availability of fish stocks. All ecosystems undergo change, and both the existence and number of species will fluctuate with or without human intervention and this should be taken into account for safeguarding biodiversity. In some of the most biodiverse areas in the globe, patterns and causes of aquatic biodiversity loss are poorly understood. This is concerning because a growing number of development projects, like hydropower dams, could have significant effects on the fish fauna of the associated river systems. Many of these areas are also among the most threatened aquatic system on Earth and have human populations that are heavily dependent on the ecosystem services they provide.

Consequences of migratory distance, habitat distribution and season on the migratory process in a short distance migratory shorebird population

BackgroundThe migratory process in birds consists of alternating periods of flight and fueling. Individuals of some populations make few flights and long stopovers, while others make multiple flights between short stopovers. Shorebirds are known for executing marathon flights (jumps), but most populations studied are long distance migrants, often crossing major barriers and thus forced to make long-haul flights. The sub-division of migration in short/medium distance migratory populations, where the total migration distance is shorter than documented non-stop flight capacity and where routes offer more homogenous stopover landscape, is little explored.MethodsHere we combine data based on conventional light level geolocators and miniaturized multi sensor loggers, comprising acceleration and light sensors, to characterize the migratory routes and migration process for a short/medium distance (~ 1300 to 3000 km) migratory population of common ringed plover (Charadrius hiaticula) breeding in southern Sweden. We were specifically interested in the variation in number and duration (total and individual) of flights/stopovers between seasons and in relation to migration distance.ResultsMost stopovers were located along the European Atlantic coast. On average 4.5 flights were made during autumn migration irrespective of migration distance, but in spring the number of flights increased with distance. The equal number of flights in autumn was explained by that most individuals migrating farther performed one longer flight (all but one lasting > 20 h), likely including crossing of the Bay of Biscay. Median duration of single flights was 8.7 h in autumn and 5.5 h in spring, and median stopover duration was ~ 1 day in both seasons. There was a positive relationship between total flight duration and migration distance, but total flight duration was 36% lower in spring compared to autumn.ConclusionsOur results suggest that when suitable stopovers are abundant common ringed plovers prefer making shorter flights even if longer flights are within the capacity of the species. This behaviour is predicted under both time and energy minimizing strategies, although the variable flight distances suggest a policy of time selected migration. Even if populations using several stopovers seem to be more resilient for environmental change along the route, these results are informative for conservation efforts and for predicting responses to future environmental change.

The Effects of Age and Sex on the Energy Intake of Captive Sea Otters (Enhydra lutris): Implications for Captive Management and Species Conservation

Sea otters (Enhydra lutris) are known ecosystem engineers that have significant impacts on their kelp forest and rocky intertidal communities due to their high levels of food intake. Quantifying sea otter food biomass and energy intake is a valuable way to understand potential ecological impacts of sea otter populations on ecosystems and for predicting future population trends and potential for expansion. While detailed, fine-scale, age-specific food intake is difficult to quantify in wild sea otters, there is a wealth of potential information available from otters under human care. This study used food and energy intake data from husbandry records of 10 sea otters collected over three decades at the Vancouver Aquarium. Within these husbandry records, daily food biomass intake and body mass measurements were recorded and converted to annual average food mass and gross energy intake (GEI). Age-, sex-, and mass-specific trends were also observed. Young sea otters had the highest relative ingested food mass, equivalent to ~26% of body mass, which decreased to ~20% in adult otters. Young otters similarly had the highest mass-specific GEI, where measures from near birth to year 1 were ~40% higher than at year 3, the age of sexual and physical maturity. There were also key differences in trends between sexes. Captive adult male sea otters were 25 to 42% larger than females and their GEI was 23 to 58% higher, although mass-specific GEI was almost identical for male and non-reproductive female otters at all ages, plateauing at ~650 kJ kg-1 d-1. Despite high levels of ingested food mass, GEI was only 5 to 15% higher than for other captive marine mammals and was comparable to previous estimates for wild sea otters. These estimates of ingested food mass and energy intake requirements are valuable when modelling the ecological impact of sea otter populations and for considering the potential effects of future environmental changes.

Long-term satellite observations show continuous increase of vegetation growth enhancement in urban environment

Urbanization shows continuous expansion and development, ushering in the co-evolution of urban environments and vegetation over time. Recent remote sensing-based studies have discovered prevalent vegetation growth enhancement in urban environments. However, whether there is a temporal evolution of the growth enhancement remains unknown and unexplored. Here we expanded the existing framework for assessing the long-term impact of urbanization on vegetation greenness (enhanced vegetation index, EVI) using long time series of remote sensing images and applied it in Changsha, the capital city of Hunan province in China. Results showed that vegetation growth experienced widespread enhancement from 2000 to 2017, and increased 1.8 times from 2000 to 2017, suggesting strong continuous adaptive capability of vegetation to urban conditions. Although the overall impact of urbanization was negative due to the replacement of vegetated surfaces, the growth enhancement nevertheless offset or compensated the direct loss of vegetated cover during urbanization in the magnitude of 28 % in 2000 to 44 % in 2017. Our study also revealed large spatial heterogeneity in vegetation growth response among various districts at different urbanization levels and found an emergent trend under the observed spatial heterogeneity toward an asymptotic maximum with urbanization, showing EVI converges to 0.22 in highly urbanized areas. We further found that the positive effect of urbanization on vegetation growth is a function of urbanization intensity and time, which implies that the effect of the urban environment on vegetation can be simulated and predicted, and can be verified in more cities in the future. Our study is the first to successfully quantify long-term spatial patterns on the co-evolution of urbanization and vegetation, providing a new understanding of the continuous adaptive responses of vegetation growth to urbanization and shedding light on predicting biological responses to future environmental change.

Assessing carbon storage capacity and saturation across six central US grasslands using data–model integration

Abstract. Future global changes will impact carbon (C) fluxes and pools in most terrestrial ecosystems and the feedback of terrestrial carbon cycling to atmospheric CO2. Determining the vulnerability of C in ecosystems to future environmental change is thus vital for targeted land management and policy. The C capacity of an ecosystem is a function of its C inputs (e.g., net primary productivity – NPP) and how long C remains in the system before being respired back to the atmosphere. The proportion of C capacity currently stored by an ecosystem (i.e., its C saturation) provides information about the potential for long-term C pools to be altered by environmental and land management regimes. We estimated C capacity, C saturation, NPP, and ecosystem C residence time in six US grasslands spanning temperature and precipitation gradients by integrating high temporal resolution C pool and flux data with a process-based C model. As expected, NPP across grasslands was strongly correlated with mean annual precipitation (MAP), yet C residence time was not related to MAP or mean annual temperature (MAT). We link soil temperature, soil moisture, and inherent C turnover rates (potentially due to microbial function and tissue quality) as determinants of carbon residence time. Overall, we found that intermediates between extremes in moisture and temperature had low C saturation, indicating that C in these grasslands may trend upwards and be buffered against global change impacts. Hot and dry grasslands had greatest C saturation due to both small C inputs through NPP and high C turnover rates during soil moisture conditions favorable for microbial activity. Additionally, leaching of soil C during monsoon events may lead to C loss. C saturation was also high in tallgrass prairie due to frequent fire that reduced inputs of aboveground plant material. Accordingly, we suggest that both hot, dry ecosystems and those frequently disturbed should be subject to careful land management and policy decisions to prevent losses of C stored in these systems.

Phosphorus availability shapes size structure, co-occurrence patterns and network stability of surface microeukaryotic plankton communities in an urbanized estuarine ecosystem

The size structure of microeukaryotic plankton communities exerts a fundamental control on marine ecosystem functions, such as food web dynamics and element flows. The global expansion of nitrogen (N) and phosphorus (P) nutrient pollutants into estuaries and coastal waters is causing public health and environmental concerns associated with microeukaryotic plankton activities. In the context of eutrophication, understanding how size structure and biotic activities of microeukaryotic plankton communities responds to anthropogenic nutrient inputs is vital to evaluate the future fate of coastal ecosystems. Here, we conducted onboard incubation experiments to provide the first investigation of how size structure and co-occurrence network of microeukaryotic plankton communities change under the dynamic nutrient conditions in the Pearl River Estuary. Our study revealed (1) a transition from P limitation to N limitation or potential NP co-limitation for the growth of pigmented protists along the Pearl River-South China Sea continuum, and isohaline ∼ 31.5 being the geographic boundary; (2) P availability drove the microeukaryotic plankton community size structure that the increased P inputs favored the dominance of nano-sized (3–20 μm) protists due to the increased relative abundance of Chlorophyta; (3) increased P inputs enhanced the species competition among phototrophic protists and improved the network stability of microeukaryotic plankton communities. In the future, if there is an increase in anthropogenic input of P in the Pearl River Estuary during summer, which would alleviate the pressure of P-deficiency, it is expected to increase the biomass of microeukaryotic plankton, with a dominance of nano-sized Chlorophyta. Altogether, this study advances our understanding of the geographic nutrient limitation pattern for pigmented protist plankton in the Pearl River Estuary, an urbanized estuarine ecosystem. Moreover, it enhances our knowledge regarding the response of marine microeukaryotic plankton communities to future environmental changes.

A new framework for identifying ecological conservation and restoration areas to enhance carbon storage

Limited attention has been given to improving carbon storage by identifying ecological conservation and restoration areas (ECRAs). In this research, we proposed a new framework for identifying ECRAs by incorporating future carbon storage changes into ecological security patterns (ESPs), including several models of the Patch-generating Land Use Simulation (PLUS), Integrated Valuation of Ecosystem Service and Tradeoffs (InVEST), Minimum Cumulative Resistance (MCR) and circuit theory. This new framework was applied in Jiangsu Yangtze River Economic Belt, East China. To evaluate the effectiveness of this new framework, we compared two scenarios: an ecological priority scenario (EPS) where future carbon storage change was not considered and an ecosystem carbon sequestration scenario (ECSS) where future carbon storage change was explicitly incorporated. Under the EPS, ecological conservation areas and ecological restoration areas were 11169.87 km2 and 221.11 km2, respectively. Under the ECSS, the ecological conservation areas and ecological restoration areas were 14768.76 km2 and 244.89 km2, respectively. Carbon storage will be most likely to increase around lakes and the Yangtze River, and the identified key areas under the ECSS will be more adaptable to future environmental changes than the EPS. This new framework can effectively enhance both ecological function and carbon sequestration, providing effective support for policymakers in landscape management and low-carbon development in other regions facing similar challenges. In the meantime, more caution is needed for the possible limitations, such as without adequate consideration of uncertainties of changes in population, land use, and economy in the future.

Richness and Elevation Patterns of a Stonefly (Insecta, Plecoptera) Community of a Southern Appalachian Mountains Watershed, USA

Protected areas are relatively free of human disturbance, are especially common in montane regions, and provide opportunities to study native fauna and flora. Stoneflies are model organisms to assess present and future environmental changes. While stoneflies inhabit cold lakes and a wide size range of lotic systems, diversity is greatest in streams draining mountain landscapes. This study addressed seasonal and elevation patterns of a stonefly fauna inhabiting a protected landscape draining the eastern flank of Mount Mitchell, the highest point of the Appalachian Mountains, USA. In total, 58 species were collected with estimated richness values ranging from 63 to 65. Species determinations were assisted with an integrative molecular approach using the mitochondrial barcode gene. Sampling during spring yielded the most species seasonally. Although certain species were only found at lower or higher sites, several were collected from across a broad range of elevations. Roughly 1/3 (21 = 36%) of the fauna present is known only from the southern Appalachian Highlands region, including one species described as new during this study. The assemblage reported here, however, did not closely align with other Appalachian fauna. Overall, well-structured faunal research continues to be important in light of continuing habitat modifications and climate change.

Looking Ahead: Predicting the Possible Ecological and Physiological Response of Galago Moholi to Environmental Change

AbstractLarge scale changes to the natural environment, due to both climate change and direct human activities (e.g., urbanization), pose a great risk to biodiversity. As this realization has set in, the number of studies modelling and monitoring the effect of environmental change on species response and survival has increased significantly; however, these studies focus on flagship species, often neglecting the lesser-known, cryptic species, which include the nocturnal primates. This is especially true for the 20 species of galago who, despite their large distribution throughout Africa, have had little to no research conducted on the effect of environmental change on population fitness and long-term survival. With urbanization set to increase throughout their distribution range, along with an increase in climate change parameters (e.g., increased temperature and a decrease in annual rainfall), the most studied species of the family, namely the African lesser bushbaby Galago moholi, provides an ideal model to assess the impact of future environmental change on galago species. In this review, we discuss the possible impact of environmental change on G. moholi and specifically focus on the effect of environmental change on feeding ecology, genetics, thermal biology, and reproduction, all of which contribute to the fitness and survival of the species. We also highlight the need for specific, long-term research to be conducted on the effect of environmental change on the survival likelihood of G. moholi and other galago species.

Reduced genetic diversity and restricted gene flow of broadcast-spawning coral Galaxea fascicularis in the South China Sea reveals potential degradation under environmental change

Under the dual effects of climate change and anthropogenic activities, coral reefs in the South China Sea (SCS) are at serious risk of degradation. Galaxea fascicularis is a widely distributed species in the SCS, and the study of its genetics, survival, and adaptability is conducive to further understanding the future characteristics of coral reefs in the SCS. In this study, 146 G. fascicularis samples were selected from 9 survey stations across 12 latitudes in the SCS, and 8 pairs of microsatellite markers were used to characterize their genetic diversity and structure. The results showed moderate genetic diversity index values (Ar = 3.444–4.147, He = 0.634–0.782, Ho = 0.367–0.586). The AMOVA results and pairwise FST values showed a moderate level of genetic differentiation (ΦST = 0.119, P < 0.05) among G. fascicularis populations in the SCS, whereas its genetic structure showed high genetic differentiation (FST = 0.062–0.225) among relatively high-latitude populations (n = 3) and low genetic differentiation (FST = 0.012–0.064) in low-latitude populations (n = 6). The living environment of relatively high-latitude populations is disturbed by high-intensity human activities, leading to the specialization of local populations. Mantel test results showed a significant positive correlation between genetic differentiation among G. fascicularis populations and sea surface temperature (SST) variance (R2 = 0.4885; Mantel test, p = 0.010 < 0.05) in addition to geographical distance (R2 = 0.1134; Mantel, test p = 0.040 < 0.05), indicating that SST and geographical isolation were primary factors affecting the genetic structure of this species in the SCS. The lower genetic diversity and limited gene flow of G. fascicularis indicate limited genetic adaptation, and corresponding vulnerability may be more pronounced under future environmental changes. These findings provide a theoretical basis for the conservation and restoration of coral reefs in the SCS.

An Analysis of Runoff Variation in a Small Basin in the Loess Plateau: Identifying the Variation Causes and Implications for Sustainable Water Management

Analyzing the characteristics and causes of runoff variation in a typical small basin is beneficial for ecological restoration in the Loess Plateau. This study employed a series of statistical methodologies to examine the characteristics of meteorological changes and underlying surface evolution in the Qishui River Basin (QRB). To differentiate the impacts of climate change and human activities on runoff variation, we applied the Choudhury–Yang formula and the Double Mass Curve (DMC) method. Subsequently, by incorporating future watershed protection strategies and various SSP scenarios, we utilized the Soil and Water Assessment Tool to simulate future runoff while employing the DMC to identify underlying causes of runoff variation. The results suggested that human activity has a slightly greater impact than climate change on reducing runoff during the historical period, with only a 1% difference. However, this will change in the future as human impact becomes increasingly significant. Human activities such as afforestation have dual effects, encompassing positive effects such as improving water quality and mitigating soil erosion, as well as negative consequences such as diminishing local water availability and exacerbating drought. Effective policies should be implemented, involving the use of appropriate tree species and planting methods, finding an appropriate value of forest area, monitoring and evaluation, etc., in order to ensure that the policies are aligned with the broader social, economic, and environmental goals of the QRB. These findings provide valuable guidance for policy-makers in developing management strategies for future environmental changes.

Countering ecological misconceptions with strategic translocation and assessment of microhabitat use

Wildlife translocations to human-modified and inferred formerly occupied habitats can be controversial when they involve a high degree of perceived risk of failure, often stemming from a large number of unknowns or misconceptions regarding the focal species' ecology. However, it is increasingly recognised that such translocations are necessary to guide effective conservation strategies, particularly for species that persist in a subset of the habitats they formerly occupied. As a step towards alleviating some of the perceived risks around these translocations, we suggest the focal species' microhabitat use in the recipient locality of a trial translocation be compared with that where they still persist. Using a case study of a threatened Australian rodent, the pookila (Pseudomys novaehollandiae, New Holland mouse), we demonstrate how such an assessment can shed light on ecological misconceptions that may need to be addressed, and bring about the revision of species-specific recommendations for restoration works and release tactics. Feeding this knowledge back into the decision-making process, practitioners may more confidently direct future conservation activities (including further trial translocations) across a broader diversity of habitats within the species' indigenous range. Widespread and systematic implementation of this approach may help to reverse the impacts of shifting baseline syndrome, and should ultimately aid the resilience of species to future environmental change.

Quantitative constraints on flood variability in the rock record

Floods determine river behaviour in time and space. Yet quantitative measures of discharge variability from geological stratigraphy are sparse, even though they are critical to understand landscape sensitivity to past and future environmental change. Here we show how storm-driven river floods in the geologic past can be quantified, using Carboniferous stratigraphy as an exemplar. The geometries of dune cross-sets demonstrate that discharge-driven disequilibrium dynamics dominated fluvial deposition in the Pennant Formation of South Wales. Based on bedform preservation theory, we quantify dune turnover timescales and hence the magnitude and duration of flow variability, showing that rivers were perennial but prone to flashy floods lasting 4–16 h. This disequilibrium bedform preservation is consistent across 4 Ma of stratigraphy, and coincides with facies-based markers of flooding, such as mass-preservation of woody debris. We suggest that it is now possible to quantify climate-driven sedimentation events in the geologic past, and reconstruct discharge variability from the rock record on a uniquely short (daily) timescale, revealing a formation dominated by flashy floods in perennial rivers.

Diatom evidence for late Holocene environmental change in a permafrost peatland in the northern Greater Khingan Mountains, Northeast China

High-latitude permafrost peatlands are sensitive to global warming, and understanding their paleohydrological evolution is critical for assessing future hydrological and environmental changes. This paper presents a diatom record from a peat deposit covering the past 3300 years to reconstruct the moisture and acidity conditions in the Tuqiang permafrost peatland in the northern Greater Khingan Mountains of northeast China. Our findings are integrated with previously published records of plant macrofossils, palynology, and geochemistry from the same profile. From 3300 to 2800 cal yr BP, planktonic and benthic diatoms were equally abundant, indicating relatively high moisture conditions, while the low abundance of acidophilous diatoms reflects relatively high pH during this interval. Pollen data show dominance by sedges with input from the surrounding Pinus forest, while LOI data and lithology suggest that the site was a non-peat accumulating wetland. During the period 2800–1100 cal yr BP, the dominance of planktonic diatoms indicates a wetter local environment, concurrent with the dominance of peat-forming sedges (Eriophorum), indicating the development of a peatland. Between 1100 and 500 cal yr BP, a short-lived increase in acidophilous diatoms (Eunotia) marks a decrease in pH. Since 500 cal yr BP, the dominance of benthic diatoms reflects a drier environment, while a vegetation shift from an Eriophorum-dominated rich fen to a Sphagnum- and Ericaceae-dominated poor fen. An increase in Eunotia diatoms prior to the Sphagnum peak may indicate that diatoms are more sensitive to local acidified habitats than moss. Peatland development in the northern Greater Khingan Mountains was likely induced by the onset of a cooler and wetter climate starting at approximately 2800 cal yr BP, a scenario supported by regional paleoclimate records. Since 700 cal yr BP, the peatland has been affected by both anthropogenic activities and climatic changes, as a drying climate and intensified human activities around the study area reduced diatom species diversity and peat accumulation. Under the background of future global warming and enhanced human activities, the decreasing species diversity and carbon accumulation rate of peatlands in high-latitude permafrost regions need more attention.

A secure future? Human urban and agricultural land use benefits a flightless island-endemic rail despite climate change

Identifying environmental characteristics that limit species' distributions is important for contemporary conservation and inferring responses to future environmental change. The Tasmanian native hen is an island endemic flightless rail and a survivor of a prehistoric extirpation event. Little is known about the regional-scale environmental characteristics influencing the distribution of native hens, or how their future distribution might be impacted by environmental shifts (e.g. climate change). Using a combination of local fieldwork and species distribution modelling, we assess environmental factors shaping the contemporary distribution of the native hen, and project future distribution changes under predicted climate change. We find 37% of Tasmania is currently suitable for the native hens, owing to low summer precipitation, low elevation, human-modified vegetation and urban areas. Moreover, in unsuitable regions, urban areas can create ‘oases’ of habitat, able to support populations with high breeding activity by providing resources and buffering against environmental constraints. Under climate change predictions, native hens were predicted to lose only 5% of their occupied range by 2055. We conclude that the species is resilient to climate change and benefits overall from anthropogenic landscape modifications. As such, this constitutes a rare example of a flightless rail to have adapted to human activity.

Breeding season management is unlikely to improve population viability of a data-deficient migratory species in decline

A major challenge in conservation is developing effective approaches to mitigate population declines in the face of ongoing environmental change. For migratory species, it is often more feasible to implement management during periods of stationarity, like the breeding season, when populations are less mobile. However, such management strategies are only successful if the demographic rates targeted (e.g., reproductive rates) contribute substantively to population growth. Thus, evaluation of population growth rate sensitivity to variation in demographic parameters is needed to determine the most effective conservation strategies. This is especially true for small and declining populations that require targeted and urgent action to mitigate declines under current and future environmental change. Here, we used a coupled integrated population model-Bayesian population viability analysis (IPM-BPVA) to estimate demographic rates and population viability within the context of climatic and management-related changes for a data-deficient, declining population of black terns in the Upper Midwestern United States. We found that current conservation efforts during the breeding season are unlikely to reverse the declines observed within the last decade (from an average of 307 breeding pairs in 2013 to 53 in 2022). Rather, interventions aimed at increasing adult survival are projected to reduce local extinction probability by 30–46 % compared to no additional management or management targeting other rates, depending on the climate scenario. Our results highlight the importance of enhancing management efforts for migratory species during migration and nonbreeding periods, which constitute a much larger, and generally riskier, proportion of the annual cycle compared to the breeding season.

Why hibernate? Tests of four hypotheses to explain intraspecific variation in hibernation phenology

Abstract Hibernation is a remarkable behaviour deployed by a diverse array of endotherms within many clades that greatly reduces metabolic need, but also has somatic costs. Hibernation in modern endotherms is often assumed to be an adaptation allowing animals to avoid extreme thermal conditions or food shortages in seasonal environments. However, many animals hibernate when foraging conditions are energetically profitable, suggesting other causal factors influence hibernation behaviour. Understanding the selection pressures responsible for intraspecific variation in the timing and duration of hibernation can help elucidate the relative evolutionary influences of the ultimate ecological causes of hibernation. We tested four previously proposed mechanistic hypotheses to explain intraspecific variation in hibernation phenology in the federally threatened northern Idaho ground squirrel (Urocitellus brunneus): (1) thermal tolerance, (2) food limitation, (3) predation avoidance and (4) sexual selection. The predation avoidance and sexual selection hypotheses received the most support, although we also found some support for the thermal tolerance and food limitation hypotheses. Heavy squirrels increased hibernation duration regardless of environmental conditions, as predicted solely by the predation avoidance hypothesis. Reproductive males emerged from hibernation earlier in spring than other sex–age classes, a pattern predicted by the sexual selection hypothesis. Temperature and food availability explained a much smaller amount of the variation in hibernation behaviour, only partially supporting predictions of the thermal tolerance and food limitation hypotheses. Our results indicate that animals navigate life‐history trade‐offs between energetic allocation to survival and reproduction via state‐dependent optimization of hibernation phenology. Consequently, any future environmental changes that influence body condition will have implications for population ecology and life‐history evolution of hibernating animals due to stark differences in daily survival probability between hibernation and the active season. Read the free Plain Language Summary for this article on the Journal blog.

Genetic history, structure and gene flow among populations of Belgica antarctica, the only free-living insect in the western Antarctic Peninsula

Changes in climate and environment can impact the sustainability of populations and biodiversity. Understanding population genetic diversity in the past and present can help us better predict species' responses to future environmental change. Antarctica has experienced drastic environmental change which threatens its biodiversity. In this study, we characterized the phylogeography and population genetic structure of Belgica antarctica, a wingless midge that is endemic to the western Antarctic Peninsula. This insect has adaptive features to withstand extremes in temperature, salinity, humidity, anoxia and pH. Belgica antarctica is widespread on widely dispersed islands of ice-free habitat, but questions remain regarding its genetic history, diversity and gene flow. We created nuclear-based, single nucleotide polymorphism (SNP) markers and genotyped 229 individuals from 11 populations to examine historical and current population genetic patterns. Our results support recent divergence among populations on different islands within the last 1 Mya. Furthermore, despite a lack of wings, B. antarctica exhibited frequent migration among islands, perhaps via ocean currents or phoresy with Antarctic vertebrates (e.g. seabirds). The close link between the evolutionary history of B. antarctica and the region's environment and ecology emphasize the importance of understanding its population dynamics to predict its persistence under environmental change.

Otterly delicious: Spatiotemporal variation in the diet of a recovering population of Eurasian otters (Lutra lutra) revealed through DNA metabarcoding and morphological analysis of prey remains.

Eurasian otters are apex predators of freshwater ecosystems and a recovering species across much of their European range; investigating the dietary variation of this predator over time and space, therefore, provides opportunities to identify changes in freshwater trophic interactions and factors influencing the conservation of otter populations. Here we sampled feces from 300 dead otters across England and Wales between 2007 and 2016, conducting both morphological analyses of prey remains and dietary DNA metabarcoding. Comparison of these methods showed that greater taxonomic resolution and breadth could be achieved using DNA metabarcoding but combining data from both methodologies gave the most comprehensive dietary description. All otter demographics exploited a broad range of taxa and variation likely reflected changes in prey distributions and availability across the landscape. This study provides novel insights into the trophic generalism and adaptability of otters across Britain, which is likely to have aided their recent population recovery, and may increase their resilience to future environmental changes.