Strong reduction in diapause survival under warm and humid overwintering conditions in a temperate-zone butterfly

Anthropogenic climate change poses substantial challenges to biodiversity conservation. Effects of climate change on summer conditions and associated heat and desiccation stress have attracted much research interest, while the implications of changing winter conditions on hibernation have hitherto received fairly little attention. This is surprising as the latter may also strongly affect biodiversity. By investigating the effects of overwintering conditions on diapause and postdiapause survival in a temperate-zone butterfly, we found that warmer and moister winter conditions substantially decreased survival rates. However, detrimental effects were restricted to survival during diapause and subsequent development and had no clear effects on butterfly performance. We suggest that overwintering survival is an important driver of vulnerability to climate change. Our study stresses the importance of collating more data on overwintering survival in species with different hibernation strategies to predict the impact of ongoing climate change on biodiversity.     

Effects of changing climate on aquatic habitat and connectivity for remnant populations of a wide‐ranging frog species in an arid landscape

Amphibian species persisting in isolated streams and wetlands in desert environments can be susceptible to low connectivity, genetic isolation, and climate changes. We evaluated the past (1900–1930), recent (1981–2010), and future (2071–2100) climate suitability of the arid Great Basin (USA) for the Columbia spotted frog (Rana luteiventris) and assessed whether changes in surface water may affect connectivity for remaining populations. We developed a predictive model of current climate suitability and used it to predict the historic and future distribution of suitable climates. We then modeled changes in surface water availability at each time period. Finally, we quantified connectivity among existing populations on the basis of hydrology and correlated it with interpopulation genetic distance. We found that the area of the Great Basin with suitable climate conditions has declined by approximately 49% over the last century and will likely continue to decline under future climate scenarios. Climate conditions at currently occupied locations have been relatively stable over the last century, which may explain persistence at these sites. However, future climates at these currently occupied locations are predicted to become warmer throughout the year and drier during the frog's activity period (May – September). Fall and winter precipitation may increase, but as rain instead of snow. Earlier runoff and lower summer base flows may reduce connectivity between neighboring populations, which is already limited. Many of these changes could have negative effects on remaining populations over the next 50–80 years, but milder winters, longer growing seasons, and wetter falls might positively affect survival and dispersal. Collectively, however, seasonal shifts in temperature, precipitation, and stream flow patterns could reduce habitat suitability and connectivity for frogs and possibly other aquatic species inhabiting streams in this arid region.     

Flying in the face of climate change: a review of climate change, past, present and future

The distribution and abundance of birds is known to depend critically upon climate variability at a range of temporal and spatial scales. In this paper we review historical changes in climate in the context of what is known about climate variability over the last millennium, with particular reference to the British Isles. The climate of Britain is now warmer than it has been in at least 340 years, with the 1990s decade 0.5 °C warmer than the 1961–1990 average. In addition, the frequency of cold days (mean temperature below 0 °C), particularly during March and November, has declined and there has been a marked shift in the seasonality of precipitation, with winters becoming substantially wetter and summers becoming slightly drier. Current understanding is that the rate of future warming is likely to accelerate with more frequent and more intense summer heatwaves, milder winters, an increase in winter rainfall, an increased risk of winter river floods, and an increase in mean sea-level and associated coastal flooding. All of these aspects of climate change are likely to impact on coastal birds. A range of potential future climate scenarios for the British Isles are presented derived from recently completed global climate model experiments. For migrant bird species, changes in the British climate have also to be seen within the context of remote climate change in both the breeding and the overwintering grounds.     

Asymmetrical thermal constraints on the parapatric species boundaries of two widespread generalist butterflies

Abstract.  1. The sibling species Papilio glaucus and Papilio canadensis meet in a narrow hybrid zone believed to be maintained by temperature thresholds acting independently on both species. The present study tests if this assertion is true for the cold-adapted species, P. canadensis , which is presumed to be limited by the effect of high temperatures in late summer and/or autumn on pupal survival.
2. Three experiments were conducted examining the effects of: (i) short periods of high temperature stress in autumn, (ii) prolonged warm temperatures in autumn, and (iii) temperatures simulating warmer winters/longer springs upon the survival of P. canadensis and P. glaucus.
3. Results indicated that short periods of high temperatures did not induce the high mortality rates required to be the key factor limiting the range of P. canadensis . However, P. canadensis did exhibit a considerably lower tolerance to high temperature extremes, prolonged warm temperatures in autumn, and conditions simulating shorter/warmer winters than P. glaucus .
4. Differences in temperature tolerance throughout the pupal stage are likely to be a significant factor in maintaining the southern range limit of P. canadensis . Further warming as may occur during climate change, particularly in winter and spring, will likely affect the dynamics of southerly populations of P. canadensis.     

Modeling climate change impacts on overwintering bald eagles

Bald eagles (Haliaeetus leucocephalus) are recovering from severe population declines, and are exerting pressure on food resources in some areas. Thousands of bald eagles overwinter near Puget Sound, primarily to feed on chum salmon (Oncorhynchus keta) carcasses. We used modeling techniques to examine how anticipated climate changes will affect energetic demands of overwintering bald eagles. We applied a regional downscaling method to two global climate change models to obtain hourly temperature, precipitation, wind, and longwave radiation estimates at the mouths of three Puget Sound tributaries (the Skagit, Hamma Hamma, and Nisqually rivers) in two decades, the 1970s and the 2050s. Climate data were used to drive bald eagle bioenergetics models from December to February for each river, year, and decade. Bald eagle bioenergetics were insensitive to climate change: despite warmer winters in the 2050s, particularly near the Nisqually River, bald eagle food requirements declined only slightly (<1%). However, the warming climate caused salmon carcasses to decompose more rapidly, resulting in 11% to 14% less annual carcass biomass available to eagles in the 2050s. That estimate is likely conservative, as it does not account for decreased availability of carcasses due to anticipated increases in winter stream flow. Future climate-driven declines in winter food availability, coupled with a growing bald eagle population, may force eagles to seek alternate prey in the Puget Sound area or in more remote ecosystems.     

A hot summer,cold winters,and the geographical limit of Trochocochlea lineat in Somerset

The common or toothed topshell, Trochocochlea lineata (da Costa, 1778), is at its northeastern geographical limit in the south and west of the British Isles. It is likely that these limits are related to some feature of air or water temperature. Along the Somerset coast, as elsewhere in southern Britain, the summer of 1995 was warmer for longer than most of its predecessors and the 1995–1996 winter was colder for longer than any since 1978. This combination of circumstances prompted an investigation into the relative effects of these two seasons. Recruitment of the 1995 cohort was unusually successful at some sites but the subsequent cold winters have removed much of that advantage on Gore Point, probably the easternmost permanent population in the Bristol Channel. The two most easterly populations, either side of Helwell Bay (Watchet), did not survive the winter of 1996–1997. The conclusion from these observations is that a hot summer can encourage recruitment but that the geographical limit in Somerset may be maintained by cold weather in winter.     

Adaptation to variation in growing season length in arctic populations of Saxifraga oppositifolia L.

Summary

At high latitudes Saxifraga oppositifolia exists with distinct ecotypes adapted to differences in growing season length. In areas with late snow-lie and cold, wet soils increased metabolic rates and rapid shoot production compensate for ultra-short growing seasons but do not conserve carbohydrate or water for adverse periods. An opposing strategy is evident in ecotypes living in sites with an earlier resumption of growth where soils are warmer and drier and the growing season longer. Here metabolic rates are lower and result in a greater ability to conserve both carbohydrate and water. The existence of opposing strategies for survival in warm and cold habitats, suggests that even in the minimal thermal conditions of the high Arctic a high degree of biodiversity gives the species as a whole a wide ecological amplitude. This degree of diversity not only increases the sites in which the species can survive but confers an ability to adapt to climate change by changing ecotype frequencies to accommodate climatic fluctuations. This facility may have contributed to the survival of populations of this and other species in the high Arctic during the Weichselian glaciation.     

Differentiation for flowering time and phenotypic integration in Arabidopsis thaliana in response to season length and vernalization

The response of plants or animals to different environmental regimes may take the form of specialization of their life history patterns to match the prevailing conditions in a geographical area. In turn, the evolution of different life histories implies that there are trade-offs between distinct components of the life cycle. We investigate some of the possible explanations for the existence of distinct types of populations in the weed Arabidopsis thaliana (Brassicaceae), differentiated by flowering schedule. The so-called early flowering and late flowering "ecotypes" are hypothesized to result from adaptation to harsh winters or short seasons as opposed to mild winters or long seasons, respectively. We carried out two experiments in which we studied the reaction of natural populations to an increase in season length and to conditions simulating mild winter or spring. Unfortunately, only one of our accessions turned out to be a late flowering population; however, it did have a fitness disadvantage when the season was too short, although it had a higher reproductive output at the end of longer growing seasons. Most populations reacted to the simulation of a mild winter by extending their vegetative phase and increasing their reproductive output; however, this could be offset by increased winter mortality under harsh conditions. Character correlations (phenotypic integration) showed contrasting patterns of change in response to the two environmental factors: at the shortest season's length many correlations were negative, displaying a trade-off between vegetative and reproductive traits; during longer seasons, all correlations were positive and there was no evidence of vegetative-reproductive trade-offs. Exposure to cold did not trigger any major change in the pattern of character correlations.     

Survival of Svalbard pink-footed geese Anser brachyrhynchus in relation to winter climate, density and land-use

1. Global change may strongly affect population dynamics, but mechanisms remain elusive. Several Arctic goose species have increased considerably during the last decades. Climate, and land-use changes outside the breeding area have been invoked as causes but have not been tested. We analysed the relationships between conditions on wintering and migration staging areas, and survival in Svalbard pink-footed geese Anser brachyrhynchus. Using mark-recapture data from 14 winters (1989-2002) we estimated survival rates and tested for time trends, and effects of climate, goose density and land-use. 2. Resighting rates differed for males and females, were higher for birds recorded during the previous winter and changed smoothly over time. Survival rates did not differ between sexes, varied over time with a nonsignificant negative trend, and were higher for the first interval after marking (0.88-0.97) than afterwards (0.74-0.93). Average survival estimates were 0.967 (SE 0.026) for the first and 0.861 (SE 0.023) for all later survival intervals. 3. We combined 16 winter and spring climate covariates into two principal components axes. F1 was related to warm/wet winters and an early spring on the Norwegian staging areas and F2 to dry/cold winters. We expected that F1 would be positively related to survival and F2 negatively. F1 explained 23% of survival variation (F1,10=3.24; one-sided P=0.051) when alone in a model and 28% (F1,9=4.50; one-sided P=0.031) in a model that assumed a trend for survival. In contrast, neither F2 nor density, land-use, or scaring practices on important Norwegian spring staging areas had discernible effects on survival. 4. Climate change may thus affect goose population dynamics, with warmer winters and earlier springs enhancing survival and fecundity. A possible mechanism is increased food availability on Danish wintering and Norwegian staging areas. As geese are among the main herbivores in Arctic ecosystems, climate change, by increasing goose populations, may have important indirect effects on Arctic vegetation. Our study also highlights the importance of events outside the breeding area for the population dynamics of migrant species.     

Divergent carbon cycle response of forest and grass‐dominated northern temperate ecosystems to record winter warming

Northern temperate ecosystems are experiencing warmer and more variable winters, trends that are expected to continue into the foreseeable future. Despite this, most studies have focused on climate change impacts during the growing season, particularly when comparing responses across different vegetation cover types. Here we examined how a perennial grassland and adjacent mixed forest ecosystem in New Hampshire, United States, responded to a period of highly variable winters from 2014 through 2017 that included the warmest winter on record to date. In the grassland, record‐breaking temperatures in the winter of 2015/2016 led to a February onset of plant growth and the ecosystem became a sustained carbon sink well before winter ended, taking up roughly 90 g/m² more carbon during the winter to spring transition than in other recorded years. The forest was an unusually large carbon source during the same period. While forest photosynthesis was restricted by leaf‐out phenology, warm winter temperatures caused large pulses of ecosystem respiration that released nearly 230 g C/m² from February through April, more than double the carbon losses during that period in cooler years. These findings suggest that, as winters continue to warm, increases in ecosystem respiration outside the growing season could outpace increases in carbon uptake during a longer growing season, particularly in forests that depend on leaf‐out timing to initiate carbon uptake. In ecosystems with a perennial leaf habit, warming winter temperatures are more likely to increase ecosystem carbon uptake through extension of the active growing season. Our results highlight the importance of understanding relationships among antecedent winter conditions and carbon exchange across land‐cover types to understand how landscape carbon exchange will change under projected climate warming.     

Shorter migration distances associated with higher winter temperatures suggest a mechanism for advancing nesting phenology of American kestrels Falco sparverius

Global climate change has affected avian migration patterns and nesting phenology. Changes in one phase of a bird's cycle will most likely affect other stages, but few studies focus simultaneously on multiple life‐history events. We used western North American ringing records and Christmas Bird Counts to examine whether changes in migration patterns were concordant with advancing American kestrel Falco sparverius nesting phenology. Consistent with previous findings, male kestrels migrated shorter distances than female kestrels, and kestrels nesting in southern latitudes migrated shorter distances than kestrels nesting in more northern areas. In addition, kestrel migration distance decreased significantly from 1960 to 2009 and was negatively associated with winter minimum temperatures. Christmas Birds Counts from the same time period showed increasing indices of overwintering kestrel abundance in northern states (Washington, Idaho, and Utah), where winter minimum temperatures have increased significantly, and concomitant decreases in southern states (California and Arizona). Finally, changes in nesting phenology of kestrels in southwestern Idaho were best explained by warmer winters, not springs. Warmer winters may decrease energetic demands on migrants by allowing for shorter migration distances, decreasing thermoregulatory costs, or both. Decreased energy demands during winter may allow birds to gain resources necessary for reproduction earlier in the nesting season. Higher winter temperatures that decrease (former) constraints on early nesting may be a particularly important mechanism leading to advancing nesting phenology for species with strong seasonal declines in fecundity or intense early season competition for high‐quality nesting areas.     

Large-scale effect of climate change on breeding parameters of pied flycatchers in Western Europe

Variations in laying date and clutch size of pied flycatchers Ficedula hypoleuca across populations throughout western Europe are examined in relation to climatic fluctuations, measured by the winter North Atlantic Oscillation (NAO) index. Across breeding sites, the winter-NAO index affected laying date such that females lay earlier after warmer and moister winters (positive values of winter NAO-index). Female pied flycatchers breed progressively earlier because presumably the whole breeding season is being shifted, as a direct result of the positive values of winter NAO-index. Moreover, clutch size of pied flycatchers across populations was negatively related to winter NAO-index during the last 50 yr. These analyses controlled for potentially confounding variables such as latitude, longitude, elevation and habitat of each study site. The present study conclude that pied flycatchers across western Europe are breeding earlier and laying smaller clutch sizes and that the most likely cause is a long-term increase in spring temperature. On the other hand, this study shows that climate change may not act uniformly between breeding populations in Western Europe. From those results, this study concludes that northern pied flycatcher populations are more sensitive to climate change than southern populations breeding in montane habitats.     

Climate change,phenology, and habitat degradation: drivers of gosling body condition and juvenile survival in lesser snow geese

Nesting migratory geese are among the dominant herbivores in (sub) arctic environments, which have undergone unprecedented increases in temperatures and plant growing days over the last three decades. Within these regions, the Hudson Bay Lowlands are home to an overabundant breeding population of lesser snow geese that has dramatically damaged the ecosystem, with cascading effects at multiple trophic levels. In some areas the overabundance of geese has led to a drastic reduction in available forage. In addition, warming of this region has widened the gap between goose migration timing and plant green‐up, and this ‘mismatch’ between goose and plant phenologies could in turn affect gosling development. The dual effects of climate change and habitat quality on gosling body condition and juvenile survival are not known, but are critical for predicting population growth and related degradation of (sub) arctic ecosystems. To address these issues, we used information on female goslings marked and measured between 1978 and 2005 (4125 individuals). Goslings that developed within and near the traditional center of the breeding colony experienced the effects of long‐term habitat degradation: body condition and juvenile survival declined over time. In newly colonized areas, however, we observed the opposite pattern (increase in body condition and juvenile survival). In addition, warmer than average winters and summers resulted in lower gosling body condition and first‐year survival. Too few plant ‘growing days’ in the spring relative to hatch led to similar results. Our assessment indicates that geese are recovering from habitat degradation by moving to newly colonized locales. However, a warmer climate could negatively affect snow goose populations in the long‐run, but it will depend on which seasons warm the fastest. These antagonistic mechanisms will require further study to help predict snow goose population dynamics and manage the trophic cascade they induce.     

Terrestrial gastropods and experimental climate change: A field study in a calcareous grassland

The impact of field manipulations of local climate on terrestrial gastropod populations and how they may affect the dynamics of the plant community were studied in a calcareous grassland. The experimental site was located in a grassland at the Wytham estate, Oxfordshire, UK. Manipulations representing two climate change scenarios in a factorial combination were used, these were warmer winters with increased summer rainfall, and warmer winters with summer drought. The climate manipulations had a significant effect on the relative abundance of molluscs. However, no important changes in species composition were found. Distribution and densities of snails and slugs were affected because of changes in the physical environment and the vegetation in the grassland. The responses of different species to the climate manipulations were strongly influenced by their phenological traits and food preferences. Potential responses of mollusc populations to a changing climate are discussed.     

Palms tracking climate change

Aim  Many species are currently expanding their ranges in response to climate change, but the mechanisms underlying these range expansions are in many cases poorly understood. In this paper we explore potential climatic factors governing the recent establishment of new palm populations far to the north of any other viable palm population in the world.
Location  Southern Switzerland, Europe, Asia and the world.
Methods  We identified ecological threshold values for the target species, Trachycarpus fortunei , based on gridded climate data, altitude and distributional records from the native range and applied them to the introduced range using local field monitoring and measured meteorological data as well as a bioclimatic model.
Results  We identified a strong relationship between minimum winter temperatures, influenced by growing season length and the distribution of the palm in its native range. Recent climate change strongly coincides with the palm's recent spread into southern Switzerland, which is in concert with the expansion of the global range of palms across various continents.
Main conclusions  Our results strongly suggest that the expansion of palms into (semi-)natural forests is driven by changes in winter temperature and growing season length and not by delayed population expansion. This implies that this rapid expansion is likely to continue in the future under a warming climate. Palms in general, and T. fortunei in particular, are significant bioindicators across continents for present-day climate change and reflect a global signal towards warmer conditions.     

Differential response to climatic variation of free‐floating and submerged macrophytes in ditches

1. Experimental studies have indicated in freshwater ecosystems that a shift in dominance from submerged to free‐floating macrophytes may occur with climate change because of increased water surface temperatures and eutrophication. Field evidence is, however, rare. 2. Here, we analysed long‐term (26 years) dynamics of macrophyte cover in Dutch ditches in relation to Dutch weather variables and the North Atlantic Oscillation (NAO) winter index. The latter appears to be a good proxy for Dutch weather conditions. 3. Cover of both free‐floating macrophytes and evergreen overwintering submerged macrophytes was positively related to mild winters (positive NAO winter index). On the other hand, high cover of submerged macrophytes that die back in winter coincided with cold winters (negative NAO winter index). Our results therefore suggest that the effect of weather on macrophyte species depends strongly on their overwintering strategy. 4. The positive relation of free‐floating macrophytes with the NAO winter index was significantly stronger in ditches in organic soil than in those in inorganic soil. This may be because of increased nutrient loading associated with increased decomposition of organic matter and increased run‐off to these ditches during mild wet winters. 5. Our results suggest that mild winters in a changing climate may cause submerged macrophytes with an evergreen overwintering strategy and free‐floating macrophytes to outcompete submerged macrophytes that die back in winter.     

Seasonal climate effects on the survival of a hibernating mammal

Global climate change and associated regional climate variability is impacting the phenology of many species, ultimately altering individual fitness and population dynamics. Yet, few studies have considered the effects of pertinent seasonal climate variability on phenology and fitness. Hibernators may be particularly susceptible to changes in seasonal climate since they have a relatively short active season in which to reproduce and gain enough mass to survive the following winter. To understand whether and how seasonal climate variability may be affecting hibernator fitness, we estimated survival from historical (1964–1968) and contemporary (2014–2017) mark–recapture data collected from the same population of Uinta ground squirrels (UGS, Urocitellus armatus), a hibernator endemic to the western United States. Despite a locally warming climate, the phenology of UGS did not change over time, yet season‐specific climate variables were important in regulating survival rates. Specifically, older age classes experienced lower survival when winters or the following springs were warm, while juveniles benefited from warmer winter temperatures. Although metabolic costs decrease with decreasing temperature in the hibernacula, arousal costs increase with decreasing temperature. Our results suggest that this trade‐off is experienced differently by immature and mature individuals. We also observed an increase in population density during that time period, suggesting resources are less limited today than they used to be. Cheatgrass is now dominating the study site and may provide a better food source to UGS than native plants did historically.     

Contributions of winter foraging to the annual growth of thermally dissimilar fish species

The seasonal energy dynamics of temperate fishes will likely be affected by climate change, especially during the winter. Few studies, however, have focused on winter. Fishes are more active in winter than previously thought, thus, an inquiry into the energetic contributions of winter foraging to the annual growth of fishes is needed given expected changes in winter conditions. We used stomach content data, total lipid analyses, and bioenergetics modeling to assess the effects of winter foraging on three species in Lake Champlain, Vermont, USA. We compared species in two thermal guilds, the cool-water species yellow perch (Perca flavescens) and two warm-water species, pumpkinseed (Lepomis gibbosus) and bluegill (Lepomis macrochirus). Our results indicate that winter energy dynamics likely depend on the thermal preference of individual fish species – the cool-water species foraged in all seasons whereas the two warm-water species foraged only in the open-water seasons. In addition, winter foraging provided sufficient energy for overwinter growth in cool-water species but not in warm-water species. Climate change will affect the seasonal energy dynamics that these species have evolved to survive winter conditions in temperate lakes. Thus, we expect climate change to affect individual survival and reproductive success.

     

Contrasting bottom-up effects of warming ocean on two king penguin populations

Breeding success is often correlated with climate, but the underlying bottom-up mechanisms remain elusive—particularly in marine environments. Consequently, conservation plans of many species often consider climate change as a unilateral threat, ignoring that even nearby populations can show contradicting trends with climate. Better understanding the relationship between climate and environment at different scales can help us interpret local differences in population trends, ultimately providing better tools to evaluate the global response of a species to threats such as global warming. We studied a growing king penguin population nesting at Kerguelen island (Southern Indian Ocean), hosting one of the largest colonies in the world. We used a unique dataset of foraging, breeding success, and climate data spanning over 25 years to examine the links between climate, marine environment, and breeding success at this colony. The results were then compared to the neighboring population of Crozet, which experienced the steepest decline for this species over the past few decades. At Crozet, penguins experienced lower breeding success in warmer years due to productive currents shifting away from the colony, affecting foraging behavior during chick rearing. At Kerguelen, while chick mass and survival experienced extreme variation from year to year, the annual variation was not associated with the position of the currents, which varied very little compared to the situation in Crozet. Rather than being affected by prey distribution shifts, we found evidence that chick provisioning in Kerguelen might be influenced by prey abundance, which seem to rather increase in warmer conditions. Furthermore, warmer air temperature in winter increased chick survival rate, likely due to reduced thermoregulation cost. Investigating the mechanisms between climate and fitness allowed us to predict two different fates for these populations regarding ongoing global warming.     

Gray wolves as climate change buffers in Yellowstone

Understanding the mechanisms by which climate and predation patterns by top predators co-vary to affect community structure accrues added importance as humans exert growing influence over both climate and regional predator assemblages. In Yellowstone National Park, winter conditions and reintroduced gray wolves (Canis lupus) together determine the availability of winter carrion on which numerous scavenger species depend for survival and reproduction. As climate changes in Yellowstone, therefore, scavenger species may experience a dramatic reshuffling of food resources. As such, we analyzed 55 y of weather data from Yellowstone in order to determine trends in winter conditions. We found that winters are getting shorter, as measured by the number of days with snow on the ground, due to decreased snowfall and increased number of days with temperatures above freezing. To investigate synergistic effects of human and climatic alterations of species interactions, we used an empirically derived model to show that in the absence of wolves, early snow thaw leads to a substantial reduction in late-winter carrion, causing potential food bottlenecks for scavengers. In addition, by narrowing the window of time over which carrion is available and thereby creating a resource pulse, climate change likely favors scavengers that can quickly track food sources over great distances. Wolves, however, largely mitigate late-winter reduction in carrion due to earlier snow thaws. By buffering the effects of climate change on carrion availability, wolves allow scavengers to adapt to a changing environment over a longer time scale more commensurate with natural processes. This study illustrates the importance of restoring and maintaining intact food chains in the face of large-scale environmental perturbations such as climate change.