Biological consequences of global warming: is the signal already apparent?

Marine biodiversity-ecosystem functions under uncertain environmental futures

Anthropogenic activity is currently leading to dramatic transformations of ecosystems and losses of biodiversity. The recognition that these ecosystems provide services that are essential for human well-being has led to a major interest in the forms of the biodiversity-ecosystem functioning relationship. However, there is a lack of studies examining the impact of climate change on these relationships and it remains unclear how multiple climatic drivers may affect levels of ecosystem functioning. Here, we examine the roles of two important climate change variables, temperature and concentration of atmospheric carbon dioxide, on the relationship between invertebrate species richness and nutrient release in a model benthic estuarine system. We found a positive relationship between invertebrate species richness and the levels of release of NH(4)-N into the water column, but no effect of species richness on the release of PO(4)-P. Higher temperatures and greater concentrations of atmospheric carbon dioxide had a negative impact on nutrient release. Importantly, we found significant interactions between the climate variables, indicating that reliably predicting the effects of future climate change will not be straightforward as multiple drivers are unlikely to have purely additive effects, resulting in increased levels of uncertainty.

A multispecies perspective on ecological impacts of climatic forcing

1. In the prevailing context of concerns over climate change and its potential impacts on ecosystems, evaluating ecological consequences of climatic forcing has become a critical issue. 2. Historical data on the abundance of organisms have been extensively used to characterize the ecological effects of climatic forcing through specific weather and/or climatic variables, with most of the studies confined to single population models. 3. However, population responses to environmental fluctuations typically depend upon positive and negative feedbacks induced by interactions with other species. It is therefore important to integrate the insights gained from single population approaches into a multispecies perspective. 4. Here we combine the hierarchical Bayesian modelling approach with the state-space formulation to extend the scope of previously proposed models of population dynamics under climatic forcing to multi-species systems. 5. We use our model to analyse long-term macro-moth (Lepidoptera) community data from the Rothamsted Insect Survey network in the UK, using winter rainfall and winter temperature as environmental covariates. 6. The effects of the two weather variables were consistent across species, being negative for winter rainfall and positive for winter temperature. The two weather variables jointly explained 15-40% of the total environmental variation affecting the dynamics of individual species, and could explain up to 90% of covariances in species dynamics. 7. The contribution of interspecific interactions to community-level variation was found to be weak compared to the contributions of environmental forcing and intraspecific interactions.

Light, time, and the physiology of biotic response to rapid climate change in animals

Examination of temperate and polar regions of Earth shows that the nonbiological world is exquisitely sensitive to the direct effects of temperature, whereas the biological world is largely organized by light. Herein, we discuss the use of day length by animals at physiological and genetic levels, beginning with a comparative experimental study that shows the preeminent role of light in determining fitness in seasonal environments. Typically, at seasonally appropriate times, light initiates a cascade of physiological events mediating the input and interpretation of day length to the output of specific hormones that ultimately determine whether animals prepare to develop, reproduce, hibernate, enter dormancy, or migrate. The mechanisms that form the basis of seasonal time keeping and their adjustment during climate change are reviewed at the physiological and genetic levels. Future avenues for research are proposed that span basic questions from how animals transition from dependency on tropical cues to temperate cues during range expansions, to more applied questions of species survival and conservation biology during periods of climatic stress.

Genetic structure of a recent climate change-driven range extension

The life-history strategies of some species make them strong candidates for rapid exploitation of novel habitat under new climate regimes. Some early-responding species may be considered invasive, and negatively impact on 'naïve' ecosystems. The barrens-forming sea urchin Centrostephanus rodgersii is one such species, having a high dispersal capability and a high-latitude range margin limited only by a developmental temperature threshold. Within this species' range in eastern Australian waters, sea temperatures have increased at greater than double the global average rate. The coinciding poleward range extension of C. rodgersii has caused major ecological changes, threatening reef biodiversity and fisheries productivity. We investigated microsatellite diversity and population structure associated with range expansion by this species. Generalized linear model analyses revealed no reduction in genetic diversity in the newly colonized region. A 'seascape genetics' analysis of genetic distances found no spatial genetic structure associated with the range extension. The distinctive genetic characteristic of the extension zone populations was reduced population-specific F(ST), consistent with very rapid population expansion. Demographic and genetic simulations support our inference of high connectivity between pre- and post-extension zones. Thus, the range shift appears to be a poleward extension of the highly-connected rangewide population of C. rodgersii. This is consistent with advection of larvae by the intensified warm water East Australian current, which has also increased Tasmanian Sea temperatures above the species' lower developmental threshold. Thus, ocean circulation changes have improved the climatic suitability of novel habitat for C. rodgersii and provided the supply of recruits necessary for colonization.

How will species respond to climate change? Examining the effects of temperature and population density on an herbivorous insect

An important challenge facing ecologists is to understand how climate change may affect species performance and species interactions. However, predicting how changes in abiotic variables associated with climate change may affect species performance also depends on the biotic context, which can mediate species responses to climatic change. We conducted a 3-yr field experiment to determine how the herbivorous grasshopper Camnula pellucida (Scudder) responds to manipulations of temperature and population density. Grasshopper survival and fecundity decreased with density, indicating the importance of intraspecific competition. Female fecundity tended to increase with temperature, whereas grasshopper survival exhibited a unimodal response to temperature, with highest survival at intermediate temperatures. Grasshopper performance responses to temperature also depended on density. Peak survival in the low-density treatment occurred in warmer conditions than for the high-density treatment, indicating that the intensity of intraspecific competition varies with temperature. Our data show that changes to the temperature regimen can alter grasshopper performance and determine the intensity of intraspecific competition. However, the effects of temperature on grasshopper performance varied with density. Our data indicate the importance of the biotic context in mediating species responses to climatic factors associated with global change.

Early emergence in a butterfly causally linked to anthropogenic warming

There is strong correlative evidence that human-induced climate warming is contributing to changes in the timing of natural events. Firm attribution, however, requires cause-and-effect links between observed climate change and altered phenology, together with statistical confidence that observed regional climate change is anthropogenic. We provide evidence for phenological shifts in the butterfly Heteronympha merope in response to regional warming in the southeast Australian city of Melbourne. The mean emergence date for H. merope has shifted -1.5 days per decade over a 65-year period with a concurrent increase in local air temperatures of approximately 0.16°C per decade. We used a physiologically based model of climatic influences on development, together with statistical analyses of climate data and global climate model projections, to attribute the response of H. merope to anthropogenic warming. Such mechanistic analyses of phenological responses to climate improve our ability to forecast future climate change impacts on biodiversity.

Physiological, behavioral, and ecological aspects of migration in reptiles

Seasonal movements between foraging, breeding, and overwintering sites occur in a wide variety of reptile species. Terrestrial snakes, lizards, and turtles migrate short distances (\20 km) between seasonal habitats, whereas fully aquatic marine turtles migrate hundreds to thousands of kilometers between foraging and breeding areas. The purpose of this article is to summarize aspects of migratory physiology and behavior in reptiles, particularly with regards to energetics and sensory mechanisms for navigation and orientation. We discuss the influence of aerobic scope, endurance, and cost of transport on migratory capacity, the effects of temperature and circulating hormones on activity and behavior, and mechanisms of detecting and transducing environmental cues to successfully navigate and orient toward a goal during migration. Topics worthy of further research are highlighted in the text, and we conclude with a discussion of how information on migration patterns of reptiles may be used to manage and conserve threatened populations.

Simulating Species Richness Using Agents with Evolving Niches, with an Example of Galápagos Plants

I sought to evolve plant species richness patterns on 22 Galápagos Islands, Ecuador, as an exploration of the utility of evolutionary computation and an agent-based approach in biogeography research. The simulation was spatially explicit, where agents were plant monocultures defined by three niche dimensions, lava (yes or no), elevation, and slope. Niches were represented as standard normal curves subjected to selection pressure, where neighboring plants bred if their niches overlapped sufficiently, and were considered the same species, otherwise they were different species. Plants that bred produced seeds with mutated niches. Seeds dispersed locally and longer distances, and established if the habitat was appropriate given the seed's niche. From a single species colonizing a random location, hundreds of species evolved to fill the islands. Evolved plant species richness agreed very well with observed plant species richness. I review potential uses of an agent-based representation of evolving niches in biogeography research.

Spring vegetation phenology is a robust predictor of breeding date across broad landscapes: a multi-site approach using the Corsican blue tit (Cyanistes caeruleus)

The regulation of reproductive schedules is an important determinant of avian breeding success. In heterogeneous environments, the optimal breeding period may fluctuate temporally across habitats, often on a spatial scale much shorter than the average dispersal range of individuals. The synchronisation of reproductive events with the most favourable period at a given site therefore involves the integration of a suite of fine-scale environmental signals which contain information about future breeding conditions. In this study, we monitored clutch initiation date of blue tits (Cyanistes caeruleus) breeding in a wide range of environmental conditions (altitude, temperature regimes, habitat type) in Corsica (France) to understand the role of spring temperature and leafing phenology on the precise fine-tuning of egg laying on a local scale. Timing of breeding in blue tits was strongly correlated with phenology of the dominant vegetation (r(2) = 0.87). In contrast, spring temperature was not as robust a predictor of the timing of breeding, because a large part of the residual variation in egg-laying date was accounted by differences (ca. 2 weeks) in the development of the vegetation between habitat types (evergreen vs. deciduous oak forests). Female blue tits therefore appear to use the environmental variable (vegetation phenology) that is most closely linked to the future production of insect prey in order to accurately time laying over the entire spatio-temporal breeding landscape.

Shifts in phenology due to global climate change: the need for a yardstick

Climate change has led to shifts in phenology in many species distributed widely across taxonomic groups. It is, however, unclear how we should interpret these shifts without some sort of a yardstick: a measure that will reflect how much a species should be shifting to match the change in its environment caused by climate change. Here, we assume that the shift in the phenology of a species' food abundance is, by a first approximation, an appropriate yardstick. We review the few examples that are available, ranging from birds to marine plankton. In almost all of these examples, the phenology of the focal species shifts either too little (five out of 11) or too much (three out of 11) compared to the yardstick. Thus, many species are becoming mistimed due to climate change. We urge researchers with long-term datasets on phenology to link their data with those that may serve as a yardstick, because documentation of the incidence of climate change-induced mistiming is crucial in assessing the impact of global climate change on the natural world.

Mitochondrial DNA indicates late pleistocene divergence of populations of Heteronympha merope, an emerging model in environmental change biology

Knowledge of historical changes in species range distribution provides context for investigating adaptive potential and dispersal ability. This is valuable for predicting the potential impact of environmental change on species of interest. Butterflies are one of the most important taxa for studying such impacts, and Heteronympha merope has the potential to provide a particularly valuable model, in part due to the existence of historical data on morphological traits and glycolytic enzyme variation. This study investigates the population genetic structure and phylogeography of H. merope, comparing the relative resolution achieved through partial DNA sequences of two mitochondrial loci, COI and ND5. These data are used to define the relationship between subspecies, showing that the subspecies are reciprocally monophyletic. On this basis, the Western Australian subspecies H. m. duboulayi is genetically distinct from the two eastern subspecies. Throughout the eastern part of the range, levels of migration and the timing of key population splits of potential relevance to climatic adaptation are estimated and indicate Late Pleistocene divergence both of the Tasmanian subspecies and of an isolated northern population from the eastern mainland subspecies H. m. merope. This information is then used to revisit historical data and provides support for the importance of clinal variation in wing characters, as well as evidence for selective pressure acting on allozyme loci phosphoglucose isomerase and phosphoglucomutase in H. merope. The study has thus confirmed the value of H. merope as a model organism for measuring responses to environmental change, offering the opportunity to focus on isolated populations, as well as a latitudinal gradient, and to use historical changes to test the accuracy of predictions for the future.

Biological collections and ecological/environmental research: a review, some observations and a look to the future

Housed worldwide, mostly in museums and herbaria, is a vast collection of biological specimens developed over centuries. These biological collections, and associated taxonomic and systematic research, have received considerable long-term public support. The work remaining in systematics has been expanding as the estimated total number of species of organisms on Earth has risen over recent decades, as have estimated numbers of undescribed species. Despite this increasing task, support for taxonomic and systematic research, and biological collections upon which such research is based, has declined over the last 30-40 years, while other areas of biological research have grown considerably, especially those that focus on environmental issues. Reflecting increases in research that deals with ecological questions (e.g. what determines species distribution and abundance) or environmental issues (e.g. toxic pollution), the level of research attempting to use biological collections in museums or herbaria in an ecological/environmental context has risen dramatically during about the last 20 years. The perceived relevance of biological collections, and hence the support they receive, should be enhanced if this trend continues and they are used prominently regarding such environmental issues as anthropogenic loss of biodiversity and associated ecosystem function, global climate change, and decay of the epidemiological environment. It is unclear, however, how best to use biological collections in the context of such ecological/environmental issues or how best to manage collections to facilitate such use. We demonstrate considerable and increasingly realized potential for research based on biological collections to contribute to ecological/environmental understanding. However, because biological collections were not originally intended for use regarding such issues and have inherent biases and limitations, they are proving more useful in some contexts than in others. Biological collections have, for example, been particularly useful as sources of information regarding variation in attributes of individuals (e.g. morphology, chemical composition) in relation to environmental variables, and provided important information in relation to species' distributions, but less useful in the contexts of habitat associations and population sizes. Changes to policies, strategies and procedures associated with biological collections could mitigate these biases and limitations, and hence make such collections more useful in the context of ecological/environmental issues. Haphazard and opportunistic collecting could be replaced with strategies for adding to existing collections that prioritize projects that use biological collections and include, besides taxonomy and systematics, a focus on significant environmental/ecological issues. Other potential changes include increased recording of the nature and extent of collecting effort and information associated with each specimen such as nearby habitat and other individuals observed but not collected. Such changes have begun to occur within some institutions. Institutions that house biological collections should, we think, pursue a mission of 'understanding the life of the planet to inform its stewardship' (Krishtalka & Humphrey, 2000), as such a mission would facilitate increased use of biological collections in an ecological/environmental context and hence lead to increased appreciation, encouragement and support from the public for these collections, their associated research, and the institutions that house them.

Impact of three global change drivers on a Mediterranean shrub

Global change is not restricted to climate change, and plant species generally face multiple human-driven disturbances constraining their viability. Most importantly, interactions among these drivers frequently generate nonadditive effects that cannot be predicted based on single-factor studies. Our goal was to assess the joint effects of three global change drivers that are especially relevant in Mediterranean ecosystems, namely, fragmentation, reduced habitat quality, and climate change on Centaurea hyssopifolia, a gypsum specialist plant. We carried out a two-year study (2005-2006) in natural populations of this plant in large (>11 ha) and small (< 1.5 ha) fragments. Within each fragment, we identified areas of contrasting habitat quality as revealed by plant cover and nutrient content, and within each combination of habitat quality and fragment size we performed a rainfall manipulation experiment simulating the most likely future climate scenario for the region. Survival, growth, phenology, and reproductive success of selected plants were monitored. The three drivers profoundly affected responses of Centaurea hyssopifolia in both study years, phenology being mainly affected by changes in habitat quality and reductions in rainfall and reproductive traits being mainly affected by fragmentation. Plants in sites of poor habitat quality and plants in the dry treatment advanced most of their phenophases (flowering and dispersing earlier) and showed reduced growth rate and increased fraction of senescent leaves. Plants growing in small fragments had lower survival, lower number of viable seeds, and a reduced seed set compared to those from large fragments. We found significant synergistic interactions among drivers. For example, the interaction between fragmentation and habitat quality led to lower survival and lower relative growth in plants from small and poor-quality habitat sites. Our results highlight the importance of studies addressing simultaneously all relevant drivers of global change potentially affecting plant performance under natural conditions. In addition, the complex responses of phenology and reproductive traits of C. hyssopifolia emphasize the need for studies integrating traits from vegetative to reproductive and from the organ to the whole-plant level.

Environmental determinants correlated to Vibrio harveyi-mediated death of marine gastropods

Vibrio harveyi is an emerging pathogen that causes mass mortality in a wide variety of marine animal species; however, it is still unclear which environmental determinants correlate V. harveyi dynamics and the bacterium-mediated death of marine animal life. We conducted a correlation analysis over a 5-year period (2003-2007) analysing the following data: V. harveyi abundance, marine animal mortality and environmental variables (seawater temperature, salinity, pH, chlorophyll a, rainfall and total viable bacterial counts). The samples were collected from a coastal area in northern Japan, where deaths of a marine gastropod species (Haliotis discus hannai) have been reported. Our analysis revealed significant positive correlations between average seawater temperature and average V. harveyi abundance (R = 0.955; P < 0.05), and between average seawater temperature and V. harveyi-mediated abalone death (R = 0.931; P < 0.05). Based on the regression model, n degrees C rise in seawater temperature gave rise to a 21(n)-fold increase in the risk of mortality caused by V. harveyi infection. This is the first report providing evidence of the strong positive correlation between seawater temperature and V. harveyi-mediated death of marine species.

Re-shuffling of species with climate disruption: a no-analog future for California birds?

By facilitating independent shifts in species' distributions, climate disruption may result in the rapid development of novel species assemblages that challenge the capacity of species to co-exist and adapt. We used a multivariate approach borrowed from paleoecology to quantify the potential change in California terrestrial breeding bird communities based on current and future species-distribution models for 60 focal species. Projections of future no-analog communities based on two climate models and two species-distribution-model algorithms indicate that by 2070 over half of California could be occupied by novel assemblages of bird species, implying the potential for dramatic community reshuffling and altered patterns of species interactions. The expected percentage of no-analog bird communities was dependent on the community scale examined, but consistent geographic patterns indicated several locations that are particularly likely to host novel bird communities in the future. These no-analog areas did not always coincide with areas of greatest projected species turnover. Efforts to conserve and manage biodiversity could be substantially improved by considering not just future changes in the distribution of individual species, but including the potential for unprecedented changes in community composition and unanticipated consequences of novel species assemblages.

Global warming and Bergmann's rule: do central European passerines adjust their body size to rising temperatures?

Recent climate change has caused diverse ecological responses in plants and animals. However, relatively little is known about homeothermic animals’ ability to adapt to changing temperature regimes through changes in body size, in accordance with Bergmann’s rule. We used fluctuations in mean annual temperatures in south-west Germany since 1972 in order to look for direct links between temperature and two aspects of body size: body mass and flight feather length. Data from regionally born juveniles of 12 passerine bird species were analysed. Body mass and feather length varied significantly among years in eight and nine species, respectively. Typically the inter-annual changes in morphology were complexly non-linear, as was inter-annual variation in temperature. For six (body mass) and seven species (feather length), these inter-annual fluctuations were significantly correlated with temperature fluctuations. However, negative correlations consistent with Bergmann’s rule were only found for five species, either for body mass or feather length. In several of the species for which body mass and feather length was significantly associated with temperature, morphological responses were better predicted by temperature data that were smoothed across multiple years than by the actual mean breeding season temperatures of the year of birth. This was found in five species for body mass and three species for feather length. These results suggest that changes in body size may not merely be the result of phenotypic plasticity but may hint at genetically based microevolutionary adaptations.

Climate change effects on trematodiases, with emphasis on zoonotic fascioliasis and schistosomiasis

The capacity of climatic conditions to modulate the extent and intensity of parasitism is well known since long ago. Concerning helminths, among the numerous environmental modifications giving rise to changes in infections, climate variables appear as those showing a greater influence, so that climate change may be expected to have an important impact on the diseases they cause. However, the confirmation of the impact of climate change on helminthiases has been reached very recently. Only shortly before, helminthiases were still noted as infectious diseases scarcely affected by climate change, when compared to diseases caused by microorganisms in general (viruses, bacteriae, protozoans). The aim of the present paper is to review the impact of climate change on helminthiases transmitted by snails, invertebrates which are pronouncedly affected by meteorological factors, by focusing on trematodiases. First, the knowledge on the effects of climate change on trematodiases in general is reviewed, including aspects such as influence of temperature on cercarial output, cercarial production variability in trematode species, influences of magnitude of cercarial production and snail host size, cercarial quality, duration of cercarial production increase and host mortality, influence of latitude, and global-warming-induced impact of trematodes. Secondly, important zoonotic diseases such as fascioliasis, schistosomiasis and cercarial dermatitis are analysed from the point of view of their relationships with meteorological factors. Emphasis is given to data which indicate that climate change influences the characteristics of these trematodiases in concrete areas where these diseases are emerging in recent years. The present review shows that trematodes, similarly as other helminths presenting larval stages living freely in the environment and/or larval stages parasitic in invertebrates easily affected by climate change as arthropods and molluscs as intermediate hosts, may be largely more susceptible to climate change impact than those helminths in whose life cycle such phases are absent or reduced to a minimum. Although helminths also appear to be affected by climate change, their main difference with microparasites lies on the usually longer life cycles of helminths, with longer generation times, slower population growth rates and longer time period needed for the response in the definitive host to become evident. Consequently, after a pronounced climate change in a local area, modifications in helminth populations need more time to be obvious or detectable than modifications in microparasite populations. Similarly, the relation of changes in a helminthiasis with climatic factor changes, as extreme events elapsed relatively long time ago, may be overlooked if not concretely searched for. All indicates that this phenomenon has been the reason for previous analyses to conclude that helminthiases do not constitute priority targets in climate change impact studies.

Shifting latitudinal clines in avian body size correlate with global warming in Australian passerines

Intraspecific latitudinal clines in the body size of terrestrial vertebrates, where members of the same species are larger at higher latitudes, are widely interpreted as evidence for natural selection and adaptation to local climate. These clines are predicted to shift in response to climate change. We used museum specimens to measure changes in the body size of eight passerine bird species from south-eastern Australia over approximately the last 100 years. Four species showed significant decreases in body size (1.8-3.6% of wing length) and a shift in latitudinal cline over that period, and a meta-analysis demonstrated a consistent trend across all eight species. Southern high-latitude populations now display the body sizes typical of more northern populations pre-1950, equivalent to a 7 degrees shift in latitude. Using ptilochronology, we found no evidence that these morphological changes were a plastic response to changes in nutrition, a likely non-genetic mechanism for the pattern observed. Our results demonstrate a generalized response by eight avian species to some major environmental change over the last 100 years or so, probably global warming.

Major conservation policy issues for biodiversity in Oceania

Oceania is a diverse region encompassing Australia, Melanesia, Micronesia, New Zealand, and Polynesia, and it contains six of the world's 39 hotspots of diversity. It has a poor record for extinctions, particularly for birds on islands and mammals. Major causes include habitat loss and degradation, invasive species, and overexploitation. We identified six major threatening processes (habitat loss and degradation, invasive species, climate change, overexploitation, pollution, and disease) based on a comprehensive review of the literature and for each developed a set of conservation policies. Many policies reflect the urgent need to deal with the effects of burgeoning human populations (expected to increase significantly in the region) on biodiversity. There is considerable difference in resources for conservation, including people and available scientific information, which are heavily biased toward more developed countries in Oceania. Most scientific publications analyzed for four threats (habitat loss, invasive species, overexploitation, and pollution) are from developed countries: 88.6% of Web of Science publications were from Australia (53.7%), New Zealand (24.3%), and Hawaiian Islands (10.5%). Many island states have limited resources or expertise. Even countries that do (e.g., Australia, New Zealand) have ongoing and emerging significant challenges, particularly with the interactive effects of climate change. Oceania will require the implementation of effective policies for conservation if the region's poor record on extinctions is not to continue.

Comparing niche- and process-based models to reduce prediction uncertainty in species range shifts under climate change

Obtaining reliable predictions of species range shifts under climate change is a crucial challenge for ecologists and stakeholders. At the continental scale, niche-based models have been widely used in the last 10 years to predict the potential impacts of climate change on species distributions all over the world, although these models do not include any mechanistic relationships. In contrast, species-specific, process-based predictions remain scarce at the continental scale. This is regrettable because to secure relevant and accurate predictions it is always desirable to compare predictions derived from different kinds of models applied independently to the same set of species and using the same raw data. Here we compare predictions of range shifts under climate change scenarios for 2100 derived from niche-based models with those of a process-based model for 15 North American boreal and temperate tree species. A general pattern emerged from our comparisons: niche-based models tend to predict a stronger level of extinction and a greater proportion of colonization than the process-based model. This result likely arises because niche-based models do not take phenotypic plasticity and local adaptation into account. Nevertheless, as the two kinds of models rely on different assumptions, their complementarity is revealed by common findings. Both modeling approaches highlight a major potential limitation on species tracking their climatic niche because of migration constraints and identify similar zones where species extirpation is likely. Such convergent predictions from models built on very different principles provide a useful way to offset uncertainties at the continental scale. This study shows that the use in concert of both approaches with their own caveats and advantages is crucial to obtain more robust results and that comparisons among models are needed in the near future to gain accuracy regarding predictions of range shifts under climate change.

Climate change: is the dark Soay sheep endangered?

It was recently reported that the proportion of dark-coloured Soay sheep (Ovis aries) in the Hebrides has decreased, despite the fact that dark sheep tend to be larger than lighter sheep, and there exists a selective advantage to large body size. It was concluded that an apparent genetic linkage between loci for the coat colour polymorphism and loci with antagonistic effects on body size explained the decrease. Those results explain why the proportion of dark animals is not increasing, but not why it is decreasing. Between 1985 and 2005 there was a significant increase in mean ambient temperature near the islands. We suggest that, while in the past a dark coat has offset the metabolic costs of thermoregulation by absorbing solar radiation, the selective advantage of a dark coat may be waning as the climate warms in the North Atlantic. In parallel, Bergman's rule may be operating, reducing the selective advantage of large body size in the cold. Either or both of these mechanisms can explain the decrease in the proportion of dark-coloured larger sheep in this population in which smaller (and light-coloured) sheep should be favoured by their lower gross energy demand. If environmental effects are the cause of the decline, then we can expect the proportion of dark-coloured Soay sheep to decrease further.

Respective impact of climate and fisheries on the growth of an albatross population

Climate and human activities such as fisheries impact many animal species. However, the demographic processes through which the population vital rates are affected, and the sensitivity of their growth rates, are poorly understood. The Black-browed Albatross, Thalassarche melanophrys, is a long-lived threatened seabird species. Previous studies have shown that the adult survival and breeding success of the population breeding at Kerguelen are affected by sea surface temperature anomalies (SSTA) during both the breeding and the nonbreeding season, and by tuna long-lining in Tasmanian waters through bycatch mortality. Here, using long-term demographic data from a Black-browed Albatross colony monitored for 26 years at Kerguelen, we estimate all demographic parameters from early to adult stages of the life cycle in order to build a fully parameterized population model and predict population growth rates under several scenarios of climate and fishing effort. The observed population growth rate (1.003) indicates that the population was stable or slightly increasing, and our population model gives a close estimate of 1.008. Population growth rate is more sensitive to survival of experienced breeders and accordingly to a change in SSTA during incubation and to tuna long-lining effort (both affecting survival of experienced breeders) than to other demographic parameters/environmental covariates. The population stability results from multiple factors and complex relationships between demographic parameters and environmental conditions, and therefore population equilibrium is precarious. If fishing effort remains stable at its current level and positive SSTA increase, or inversely if fishing effort decreases and SSTA remain similar to present values, then the population would increase. However, if fishing effort increases by 20% (i.e., to 40 million hooks) on the wintering grounds, without any change in SSTA, then the population would decrease at 0.9% per year. If fishing effort stops, the population would increase at 3.5% per year, suggesting that bycatch mortality probably currently limits the Black-browed Albatross population at Kerguelen. Our study shows how this type of model could be useful to predict trajectories of top predator populations, and eventually lower trophic web levels, in relation to climatic projections and future human activities. We highlight the need to reinforce mitigation measures.

Geographically distinct reproductive schedules in a changing world: Costly implications in captive Stonechats

With progressively faster global change, shifts in phenology, and distributional ranges are reported for an increasing number of species. The success of organisms at coping with novel seasonal conditions depends on the mechanisms that determine their schedules. Species that rely on fixed schedules and those that time their activities by predictive cues may be particularly constrained in their ability to accommodate changes. The present study examines rigid scheduling and its implications for breeding in captivity in an avian model taxon, the Stonechat (Saxicola torquata). Within their extensive breeding range, Stonechats differ geographically in migratory behavior and reproduce and molt under a wide range of daylengths (10-17 h). Stonechats time their activities by programs that involve circannual rhythms and photoperiodism. The study reports reproductive timing of four taxa (central European, Irish, Siberian, and Kenyan), relates it to laydates in the field, and investigates modifying influences of housing conditions and of social context. Reproductive consequences of timing programs were then tested by crossbreeding of taxa with different schedules. The study revealed persistent, population-specific breeding windows in captivity. Resident Stonechats from equatorial Kenya synchronized their reproductive cycles with the European summer, presumably in response to local photoperiod, and bred at similar times as northern migrants. In all other taxa schedules matched those in the field, but were timed slightly earlier in captivity and advanced by indoor keeping conditions. Influences of social context were negligible. In pairs with clutches, testes regressed slightly later than in pairs without clutches, but presence of a mate per se had no influence on breeding cycles. Accordingly, crossbreeding Stonechats were predicted to have limited capacity to adjust schedules to those of their mates. This prediction was tested by crossbreeding of single-clutched Siberian long-distance migrants with multiple-clutched European short-distance migrants. Males and females of both taxa retained their characteristic breeding schedules, regardless of their mate's activities. This led to dramatic loss of reproductive success in the population with the longer breeding season, European Stonechats. Siberian Stonechats were unable to profit from the presence of a sexually active mate, but they suffered no disadvantage from crossbreeding. In a changing world, inherited timing programs may severely constrain responses to novel conditions, impose schedule-dependent, asymmetric costs of hybridization, and contribute to directional gene flow or to reproductive isolation.

The melting Himalayas: cascading effects of climate change on water, biodiversity, and livelihoods

The Greater Himalayas hold the largest mass of ice outside polar regions and are the source of the 10 largest rivers in Asia. Rapid reduction in the volume of Himalayan glaciers due to climate change is occurring. The cascading effects of rising temperatures and loss of ice and snow in the region are affecting, for example, water availability (amounts, seasonality), biodiversity (endemic species, predator-prey relations), ecosystem boundary shifts (tree-line movements, high-elevation ecosystem changes), and global feedbacks (monsoonal shifts, loss of soil carbon). Climate change will also have environmental and social impacts that will likely increase uncertainty in water supplies and agricultural production for human populations across Asia. A common understanding of climate change needs to be developed through regional and local-scale research so that mitigation and adaptation strategies can be identified and implemented. The challenges brought about by climate change in the Greater Himalayas can only be addressed through increased regional collaboration in scientific research and policy making.

Complications of complexity: integrating environmental, genetic and hormonal control of insect diapause

Understanding gene interaction and pleiotropy are long-standing goals of developmental and evolutionary biology. We examine the genetic control of diapause in insects and show how the failure to recognize the difference between modular and gene pleiotropy has confounded our understanding of the genetic basis of this important phenotype. This has led to complications in understanding the role of the circadian clock in the control of diapause in Drosophila and other insects. We emphasize three successive modules - each containing functionally related genes - that lead to diapause: photoperiodism, hormonal events and diapause itself. Understanding the genetic basis for environmental control of diapause has wider implications for evolutionary response to rapid climate change and for the opportunity to observe evolutionary change in contemporary time.