Heat stress responses and population genetics of the kelp Laminaria digitata (Phaeophyceae) across latitudes reveal differentiation among North Atlantic populations

To understand the thermal plasticity of a coastal foundation species across its latitudinal distribution, we assess physiological responses to high temperature stress in the kelp Laminaria digitata in combination with population genetic characteristics and relate heat resilience to genetic features and phylogeography. We hypothesize that populations from Arctic and cold-temperate locations are less heat resilient than populations from warm distributional edges. Using meristems of natural L. digitata populations from six locations ranging between Kongsfjorden, Spitsbergen (79°N), and Quiberon, France (47°N), we performed a common-garden heat stress experiment applying 15°C to 23°C over eight days. We assessed growth, photosynthetic quantum yield, carbon and nitrogen storage, and xanthophyll pigment contents as response traits. Population connectivity and genetic diversity were analyzed with microsatellite markers. Results from the heat stress experiment suggest that the upper temperature limit of L. digitata is nearly identical across its distribution range, but subtle differences in growth and stress responses were revealed for three populations from the species' ecological range margins. Two populations at the species' warm distribution limit showed higher temperature tolerance compared to other populations in growth at 19°C and recovery from 21°C (Quiberon, France), and photosynthetic quantum yield and xanthophyll pigment responses at 23°C (Helgoland, Germany). In L. digitata from the northernmost population (Spitsbergen, Norway), quantum yield indicated the highest heat sensitivity. Microsatellite genotyping revealed all sampled populations to be genetically distinct, with a strong hierarchical structure between southern and northern clades. Genetic diversity was lowest in the isolated population of the North Sea island of Helgoland and highest in Roscoff in the English Channel. All together, these results support the hypothesis of moderate local differentiation across L. digitata's European distribution, whereas effects are likely too weak to ameliorate the species' capacity to withstand ocean warming and marine heatwaves at the southern range edge.

Correlation between intermediary metabolism, Hsp gene expression, and oxidative stress-related proteins in long-term thermal-stressed Mytilus galloprovincialis

Long-term exposure of Mytilus galloprovincialis to temperatures beyond 26°C triggers mussel mortality. The present study aimed to integratively illustrate the correlation between intermediary metabolism, hsp gene expression, and oxidative stress-related proteins in long-term thermally stressed Mytilus galloprovincialis and whether they are affected by thermal stress magnitude and duration. We accordingly evaluated the gene expression profiles, in the posterior adductor muscle (PAM) and the mantle, concerning heat shock protein 70 and 90 ( hsp70 and hsp90), and the antioxidant defense indicators Mn-SOD, Cu/Zn-SOD, catalase, glutathione S-transferase, and the metallothioneins mt-10 and mt-20. Moreover, we determined antioxidant enzyme activities, oxidative stress through lipid peroxidation, and activities of intermediary metabolism enzymes. The pattern of changes in relative mRNA expression levels indicate that mussels are able to sense thermal stress even when exposed to 22°C and before mussel mortality is initiated. Data indicate a close correlation between the magnitude and duration of thermal stress with lipid peroxidation levels and changes in the activity of antioxidant enzymes and the enzymes of intermediary metabolism. The gene expression and increase in the activities of antioxidant enzymes support a scenario, according to which exposure to 24°C might trigger reactive oxygen species (ROS) production, which is closely correlated with anaerobic metabolism under hypometabolic conditions. Increase and maintenance of oxidative stress in conjunction with energy balance disturbance seem to trigger mussel mortality after long-term exposure at temperatures beyond 26°C. Eventually, in the context of preparation for oxidative stress, certain hypotheses and models are suggested, integrating the several steps of cellular stress response.

Oceanographic Fronts Shape Phaeocystis Assemblages: A High-Resolution 18S rRNA Gene Survey From the Ice-Edge to the Equator of the South Pacific

The cosmopolitan haptophyte Phaeocystis is recognized as a key contributor to marine biogeochemical cycling and important primary producer within polar marine environments. Yet, little is known about its solitary, non-colonial cell stages or its distribution during the colder, low-productivity seasons. We examined the biogeography of Phaeocystis along a high-resolution (0.5-degree latitudinal interval) transect from the Antarctic ice-edge to the equator of the South Pacific, in the austral autumn-winter. Using high-throughput 18S rRNA gene sequences with single nucleotide variable (zero-radius) operational taxonomic units (zOTUs) allowed us to explore the possibility of strain-level variation. From water samples within the upper water column, we show the presence of an abundant Phaeocystis assemblage that persisted during the colder months, contributing up to 9% of the microbial eukaryote community at high latitudes. The biogeography of Phaeocystis was strongly shaped by oceanographic boundaries, most prominently the polar and subantarctic fronts. Marked changes in dominant Phaeocystis antarctica zOTUs between different frontal zones support the concept that ecotypes may exist within the Phaeocystis assemblage. Our findings also show that the Phaeocystis assemblage did not abide by the classical latitudinal diversity gradient of increasing richness from the poles to the tropics; richness peaked at 30°S and declined to a minimum at 5°S. Another surprise was that P. globosa and P. cordata, previously thought to be restricted to the northern hemisphere, were detected at moderate abundances within the Southern Ocean. Our results emphasize the importance of oceanographic processes in shaping the biogeography of Phaeocystis and highlights the importance of genomics-based exploration of Phaeocystis, which have found the assemblage to be more complex than previously understood. The high winter relative abundance of the Phaeocystis assemblage suggests it could be involved in more complex ecological interactions during the less productive seasons, which should be considered in future studies to better understand the ecological role and strategies of this keystone species.

Thermal displacement by marine heatwaves

Marine heatwaves (MHWs)-discrete but prolonged periods of anomalously warm ocean temperatures-can drastically alter ocean ecosystems, with profound ecological and socioeconomic impacts^1-8. Considerable effort has been directed at understanding the patterns, drivers and trends of MHWs globally^9-11. Typically, MHWs are characterized on the basis of their intensity and persistence at a given location-an approach that is particularly relevant for corals and other sessile organisms that must endure increased temperatures. However, many ecologically and commercially important marine species respond to environmental disruptions by relocating to favourable habitats, and dramatic range shifts of mobile marine species are among the conspicuous impacts of MHWs^1,4,12,13. Whereas spatial temperature shifts have been studied extensively in the context of long-term warming trends^14-18, they are unaccounted for in existing global MHW analyses. Here we introduce thermal displacement as a metric that characterizes MHWs by the spatial shifts of surface temperature contours, instead of by local temperature anomalies, and use an observation-based global sea surface temperature dataset to calculate thermal displacements for all MHWs from 1982 to 2019. We show that thermal displacements during MHWs vary from tens to thousands of kilometres across the world's oceans and do not correlate spatially with MHW intensity. Furthermore, short-term thermal displacements during MHWs are of comparable magnitude to century-scale shifts inferred from warming trends¹⁸, although their global spatial patterns are very different. These results expand our understanding of MHWs and their potential impacts on marine species, revealing which regions are most susceptible to thermal displacement, and how such shifts may change under projected ocean warming. The findings also highlight the need for marine resource management to account for MHW-driven spatial shifts, which are of comparable scale to those associated with long-term climate change and are already happening.

Species better track climate warming in the oceans than on land

There is mounting evidence of species redistribution as climate warms. Yet, our knowledge of the coupling between species range shifts and isotherm shifts remains limited. Here, we introduce BioShifts-a global geo-database of 30,534 range shifts. Despite a spatial imbalance towards the most developed regions of the Northern Hemisphere and a taxonomic bias towards the most charismatic animals and plants of the planet, data show that marine species are better at tracking isotherm shifts, and move towards the pole six times faster than terrestrial species. More specifically, we find that marine species closely track shifting isotherms in warm and relatively undisturbed waters (for example, the Central Pacific Basin) or in cold waters subject to high human pressures (for example, the North Sea). On land, human activities impede the capacity of terrestrial species to track isotherm shifts in latitude, with some species shifting in the opposite direction to isotherms. Along elevational gradients, species follow the direction of isotherm shifts but at a pace that is much slower than expected, especially in areas with warm climates. Our results suggest that terrestrial species are lagging behind shifting isotherms more than marine species, which is probably related to the interplay between the wider thermal safety margin of terrestrial versus marine species and the more constrained physical environment for dispersal in terrestrial versus marine habitats.

A novel index based on planktonic copepod reproductive traits as a tool for marine ecotoxicology studies

Copepods are excellent bioindicators of climate change and ecosystem pollution in anthropized coastal waters. This work reviewed the results of previous studies examining changes in egg production rate (EPR), hatching success (HS), and nauplius survival rate (NSR) in natural conditions and in the presence of pollutants, including heavy metals and organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) and persistent organic pollutants (POPs). At high concentrations, cadmium and silver induce an increase in EPR in the copepods Acartia tonsa and Acartia hudsonica, while exposure to mercury decreases EPR in adults by 50%. All three metals affect HS, with mercury inducing a stronger effect than cadmium and silver. Cadmium affects reproductive traits in Centropages ponticus, decreasing EPR and particularly HS. Furthermore, copper and chromium at high concentrations induce significant decreases in eggs per female in Notodiaptomus conifer. In terms of organic contaminant and Polycyclic Aromatic Hydrocarbons (PAHs), Eurytemora affinis is reported to be affected by naphthalene, 2-methylnaphthalene, 2,6-dimethylnaphthalene, and 2,3,5-trimethylnaphthalene and can thus be used in ecotoxicity studies, but only if the exposure time is high. Acartia tonsa shows significant reductions in EPR and HS at high concentrations of fluoranthene, phenanthrene, and pyrene. However, the response to Persistent Organic Pollutants (POPs) such as pentachlorophenol (PCP) and 1,2-dichlorobenzene (DCB) differs. In E. affinis, EPR increases with DCB, but HS falls to <1%. EPR increases when the species is exposed overnight, but HS remains low in the presence of DCB. Based on these results, we developed a novel copepod reproductive trait index (CRT-Index) for use in marine ecotoxicology surveys and tested in some simple cases. We show that copepods are good candidates as models for ecotoxicology studies, in particular using reproductive traits (EPR, HS and NSR) because of their sensitivity to a wide range or pollutants.

One hundred years of climate change in Mexico

Spatial assessments of historical climate change provide information that can be used by scientists to analyze climate variation over time and evaluate, for example, its effects on biodiversity, in order to focus their research and conservation efforts. Despite the fact that there are global climatic databases available at high spatial resolution, they represent a short temporal window that impedes evaluating historical changes of climate and their impacts on biodiversity. To fill this gap, we developed climate gridded surfaces for Mexico for three periods that cover most of the 20^th and early 21^st centuries: t₁-1940 (1910–1949), t₂-1970 (1950–1979) and t₃-2000 (1980–2009), and used these interpolated surfaces to describe how climate has changed over time, both countrywide and in its 19 biogeographic provinces. Results from our characterization of climate change indicate that the mean annual temperature has increased by nearly 0.2°C on average across the whole country from t₂-1970 to t₃-2000. However, changes have not been spatially uniform: Nearctic provinces in the north have suffered higher temperature increases than southern tropical regions. Central and southern provinces cooled at the beginning of the 20^th century but warmed consistently since the 1970s. Precipitation increased between t₁-1940 and t₂-1970 across the country, more notably in the northern provinces, and it decreased between t₂-1970 and t₃-2000 in most of the country. Results on the historical climate conditions in Mexico may be useful for climate change analyses for both environmental and social sciences. Nonetheless, our climatology was based on information from climate stations for which 9.4–36.2% presented inhomogeneities over time probably owing to non-climatic factors, and climate station density changed over time. Therefore, the estimated changes observed in our analysis need to be interpreted cautiously.

Ocean warming is the key filter for successful colonization of the migrant octocoral Melithaea erythraea (Ehrenberg, 1834) in the Eastern Mediterranean Sea

Climate, which sets broad limits for migrating species, is considered a key filter to species migration between contrasting marine environments. The Southeast Mediterranean Sea (SEMS) is one of the regions where ocean temperatures are rising the fastest under recent climate change. Also, it is the most vulnerable marine region to species introductions. Here, we explore the factors which enabled the colonization of the endemic Red Sea octocoral Melithaea erythraea (Ehrenberg, 1834) along the SEMS coast, using sclerite oxygen and carbon stable isotope composition (δ ¹⁸O_SC and δ ¹³C_SC), morphology, and crystallography. The unique conditions presented by the SEMS include a greater temperature range (∼15 °C) and ultra-oligotrophy, and these are reflected by the lower δ ¹³C_SCvalues. This is indicative of a larger metabolic carbon intake during calcification, as well as an increase in crystal size, a decrease of octocoral wart density and thickness of the migrating octocoral sclerites compared to the Red Sea samples. This suggests increased stress conditions, affecting sclerite deposition of the SEMS migrating octocoral. The δ ¹⁸Osc range of the migrating M. erythraea indicates a preference for warm water sclerite deposition, similar to the native depositional temperature range of 21-28 °C. These findings are associated with the observed increase of minimum temperatures in winter for this region, at a rate of 0.35 ± 0.27 °C decade^-1 over the last 30 years, and thus the region is becoming more hospitable to the Indo-Pacific M. erythraea. This study shows a clear case study of "tropicalization" of the Mediterranean Sea due to recent warming.

How pathogens affect the marine habitat use and migration of sea trout (Salmo trutta) in two Norwegian fjord systems

Wild fish are confronting changing pathogen dynamics arising from anthropogenic disturbance and climate change. Pathogens can influence animal behaviour and life histories, yet there are little such data from fish in the high north where pathogen dynamics may differ from comparatively southern regions. We aimed to compare the pathogen communities of 160 wild anadromous brown trout in two fjords in northern Norway and to determine whether pathogens influenced area use or return to spawn. Application of high-throughput qPCR detected 11 of the 46 pathogens screened for; most frequently encountered were Ichthyobodo spp., Flavobacterium psychrophilum and Candidatus Branchiomonas cysticola. The rate of returning to freshwater during the spawning season was significantly lower for the Skjerstadfjord fish. Piscichlamydia salmonis and F. psychrophilum were indicator species for the Skjerstadfjord and pathogen communities in the two fjords differed according to perMANOVA. Individual length, Fulton's condition factor and the time between first and last detection of the fish were not related to the presence of pathogens ordinated using non-metric multidimensional scaling (NMDS). However, there was evidence that pathogen load was correlated with the expression of smoltification genes, which are upregulated by salmonids in freshwater. Correspondingly, percentage of time in freshwater after release was longer for fish with greater pathogen burdens.

Is subarctic forest advance able to keep pace with climate change?

Recent climate warming and scenarios for further warming have led to expectations of rapid movement of ecological boundaries. Here we focus on the circumarctic forest-tundra ecotone (FTE), which represents an important bioclimatic zone with feedbacks from forest advance and corresponding tundra disappearance (up to 50% loss predicted this century) driving widespread ecological and climatic changes. We address FTE advance and climate history relations over the 20th century, using FTE response data from 151 sites across the circumarctic area and site-specific climate data. Specifically, we investigate spatial uniformity of FTE advance, statistical associations with 20th century climate trends, and whether advance rates match climate change velocities (CCVs). Study sites diverged into four regions (Eastern Canada; Central and Western Canada and Alaska; Siberia; and Western Eurasia) based on their climate history, although all were characterized by similar qualitative patterns of behaviour (with about half of the sites showing advancing behaviour). The main associations between climate trend variables and behaviour indicate the importance of precipitation rather than temperature for both qualitative and quantitative behaviours, and the importance of non-growing season as well as growing season months. Poleward latitudinal advance rates differed significantly among regions, being smallest in Eastern Canada (~10 m/year) and largest in Western Eurasia (~100 m/year). These rates were 1-2 orders of magnitude smaller than expected if vegetation distribution remained in equilibrium with climate. The many biotic and abiotic factors influencing FTE behaviour make poleward advance rates matching predicted 21st century CCVs (~10³ -10⁴  m/year) unlikely. The lack of empirical evidence for swift forest relocation and the discrepancy between CCV and FTE response contradict equilibrium model-based assumptions and warrant caution when assessing global-change-related biotic and abiotic implications, including land-atmosphere feedbacks and carbon sequestration.

Biodiversity policy beyond economic growth

Increasing evidence-synthesized in this paper-shows that economic growth contributes to biodiversity loss via greater resource consumption and higher emissions. Nonetheless, a review of international biodiversity and sustainability policies shows that the majority advocate economic growth. Since improvements in resource use efficiency have so far not allowed for absolute global reductions in resource use and pollution, we question the support for economic growth in these policies, where inadequate attention is paid to the question of how growth can be decoupled from biodiversity loss. Drawing on the literature about alternatives to economic growth, we explore this contradiction and suggest ways forward to halt global biodiversity decline. These include policy proposals to move beyond the growth paradigm while enhancing overall prosperity, which can be implemented by combining top-down and bottom-up governance across scales. Finally, we call the attention of researchers and policy makers to two immediate steps: acknowledge the conflict between economic growth and biodiversity conservation in future policies; and explore socioeconomic trajectories beyond economic growth in the next generation of biodiversity scenarios.

Effect of geographic variation on the proteome of sea cucumber (Stichopus japonicus)

Sea cucumber is a sensitive organism that is easily challenged by environmental change. The aim of this study was to characterize the proteome of sea cucumbers from 5 main Chinese origins, including Xiamen (XM), Dalian (DL), Weihai (WH), Yantai (YT) and Qingdao (QD). In this work, a tandem mass tag (TMT) labeling proteomic approach was applied to identify and quantify the proteome of sea cucumber. A total of 5051 proteins were identified in the body wall; among those proteins, 1594 proteins (31.6%) were identified as enzyme proteins, and 33 proteins belonged to collagen. In addition, the 10 most highly abundant proteins were further discussed. Among all quantified proteins, 2266 were significantly differentially expressed proteins (SDEPs) across the 5 origins. These SDEPs were related to pigmentation (5 proteins), antioxidant activity (13 proteins), and immune system processes (29 proteins). Based on SDEPs, DL differed the most from QD and XM, as well as WH and YT, as shown in principal component analysis (PCA) and hierarchical clustering. In conclusion, one-fourth of the significantly different proteins found in the sea cucumber body wall among the 5 main Chinese locations indicated the sensitivity of sea cucumber to variations in temperature, environment, and feeding.

Species better track climate warming in the oceans than on land

There is mounting evidence of species redistribution as climate warms. Yet, our knowledge of the coupling between species range shifts and isotherm shifts remains limited. Here, we introduce BioShifts-a global geo-database of 30,534 range shifts. Despite a spatial imbalance towards the most developed regions of the Northern Hemisphere and a taxonomic bias towards the most charismatic animals and plants of the planet, data show that marine species are better at tracking isotherm shifts, and move towards the pole six times faster than terrestrial species. More specifically, we find that marine species closely track shifting isotherms in warm and relatively undisturbed waters (for example, the Central Pacific Basin) or in cold waters subject to high human pressures (for example, the North Sea). On land, human activities impede the capacity of terrestrial species to track isotherm shifts in latitude, with some species shifting in the opposite direction to isotherms. Along elevational gradients, species follow the direction of isotherm shifts but at a pace that is much slower than expected, especially in areas with warm climates. Our results suggest that terrestrial species are lagging behind shifting isotherms more than marine species, which is probably related to the interplay between the wider thermal safety margin of terrestrial versus marine species and the more constrained physical environment for dispersal in terrestrial versus marine habitats.

30 years revisit survey for long-term changes in the Antarctic subtidal algal assemblage

A long-term change of a subtidal macroalgal assemblage has been investigated in Maxwell Bay, King George Island (KGI) of the Antarctic coast by a revisit survey after 30 years. Field surveys were done by SCUBA diving at six sites in 2016–2018 to directly compare with the previous survey conducted in 1988–1993 at the same sites. The total number of macroalgal species was similar between the previous and the present survey, 25 and 27 species respectively. However, the macroalgal assemblage changed substantially with the average similarity of 48.2% between the two surveys. Also, the species-level abundance showed a high variability between surveys. On the other hand, over the 30 years interval there was little overall change at the between-site level hierarchical structure in the subtidal communities of Maxwell Bay. The sites near the penguin rookery consistently showed the highest biodiversity, indicating the importance of land-based nutrients input in Antarctic coastal habitats. A noticeable pattern change over 30 years was the increase of Desmarestia complex and Plocamium cartilagineum and the decrease of Himantothallus grandifolius. Both groups are still dominant, but the shift from Himantothallus to Desmarestia-Plocamium may reflects temperature rise on the Maxwell Bay coast compared to the past.

Forest microclimate dynamics drive plant responses to warming

Climate warming is causing a shift in biological communities in favor of warm-affinity species (i.e., thermophilization). Species responses often lag behind climate warming, but the reasons for such lags remain largely unknown. Here, we analyzed multidecadal understory microclimate dynamics in European forests and show that thermophilization and the climatic lag in forest plant communities are primarily controlled by microclimate. Increasing tree canopy cover reduces warming rates inside forests, but loss of canopy cover leads to increased local heat that exacerbates the disequilibrium between community responses and climate change. Reciprocal effects between plants and microclimates are key to understanding the response of forest biodiversity and functioning to climate and land-use changes.

Quantifying biodiversity trade-offs in the face of widespread renewable and unconventional energy development

The challenge of balancing biodiversity protection with economic growth is epitomized by the development of renewable and unconventional energy, whose adoption is aimed at stemming the impacts of global climate change, yet has outpaced our understanding of biodiversity impacts. We evaluated the potential conflict between biodiversity protection and future electricity generation from renewable (wind farms, run-of-river hydro) and non-renewable (shale gas) sources in British Columbia (BC), Canada using three metrics: greenhouse gas (GHG) emissions, electricity cost, and overlap between future development and conservation priorities for several fish and wildlife groups - small-bodied vertebrates, large mammals, freshwater fish - and undisturbed landscapes. Sharp trade-offs in global versus regional biodiversity conservation exist for all energy technologies, and in BC they are currently smallest for wind energy: low GHG emissions, low-moderate overlap with top conservation priorities, and competitive energy cost. GHG emissions from shale gas are 1000 times higher than those from renewable sources, and run-of-river hydro has high overlap with conservation priorities for small-bodied vertebrates. When all species groups were considered simultaneously, run-of-river hydro had moderate overlap (0.56), while shale gas and onshore wind had low overlap with top conservation priorities (0.23 and 0.24, respectively). The unintended cost of distributed energy sources for regional biodiversity suggest that trade-offs based on more diverse metrics must be incorporated into energy planning.

Temperature-related biodiversity change across temperate marine and terrestrial systems

Climate change is reshaping global biodiversity as species respond to changing temperatures. However, the net effects of climate-driven species redistribution on local assemblage diversity remain unknown. Here, we relate trends in species richness and abundance from 21,500 terrestrial and marine assemblage time series across temperate regions (23.5-60.0° latitude) to changes in air or sea surface temperature. We find a strong coupling between biodiversity and temperature changes in the marine realm, where species richness mostly increases with warming. However, biodiversity responses are conditional on the baseline climate, such that in initially warmer locations richness increase is more pronounced while abundance declines with warming. In contrast, we do not detect systematic temperature-related richness or abundance trends on land, despite a greater magnitude of warming. As the world is committed to further warming, substantial challenges remain in maintaining local biodiversity amongst the non-uniform inflow and outflow of 'climate migrants'. Temperature-driven community restructuring is especially evident in the ocean, whereas climatic debt may be accumulating on land.

Cold range edges of marine fishes track climate change better than warm edges

Species around the world are shifting their ranges in response to climate change. To make robust predictions about climate-related colonizations and extinctions, it is vital to understand the dynamics of range edges. This study is among the first to examine annual dynamics of cold and warm range edges, as most global change studies average observational data over space or over time. We analyzed annual range edge dynamics of marine fishes-both at the individual species level and pooled into cold- and warm-edge assemblages-in a multi-decade time-series of trawl surveys conducted on the Northeast US Shelf during a period of rapid warming. We tested whether cold edges show stronger evidence of climate tracking than warm edges (due to non-climate processes or time lags at the warm edge; the biogeography hypothesis or extinction debt hypothesis), or whether they tracked temperature change equally (due to the influence of habitat suitability; the ecophysiology hypothesis). In addition to exploring correlations with regional temperature change, we calculated species- and assemblage-specific sea bottom and sea surface temperature isotherms and used them to predict range edge position. Cold edges shifted further and tracked sea surface and bottom temperature isotherms to a greater degree than warm edges. Mixed-effects models revealed that for a one-degree latitude shift in isotherm position, cold edges shifted 0.47 degrees of latitude, and warm edges shifted only 0.28 degrees. Our results suggest that cold range edges are tracking climate change better than warm range edges, invalidating the ecophysiology hypothesis. We also found that even among highly mobile marine ectotherms in a global warming hotspot, few species are fully keeping pace with climate.

The Impact of Climate Change on Cholera: A Review on the Global Status and Future Challenges

Water ecosystems can be rather sensitive to evolving or sudden changes in weather parameters. These changes can result in alterations in the natural habitat of pathogens, vectors, and human hosts, as well as in the transmission dynamics and geographic distribution of infectious agents. However, the interaction between climate change and infectious disease is rather complicated and not deeply understood. In this narrative review, we discuss climate-driven changes in the epidemiology of Vibrio species-associated diseases with an emphasis on cholera. Changes in environmental parameters do shape the epidemiology of Vibrio cholerae. Outbreaks of cholera cause significant disease burden, especially in developing countries. Improved sanitation systems, access to clean water, educational strategies, and vaccination campaigns can help control vibriosis. In addition, real-time assessment of climatic parameters with remote-sensing technologies in combination with robust surveillance systems could help detect environmental changes in high-risk areas and result in early public health interventions that can mitigate potential outbreaks.

Geomorphology and Species Interactions Control Facilitation Cascades in a Salt Marsh Ecosystem

Facilitation cascades are chains of positive interactions that occur as frequently as trophic cascades and are equally important drivers of ecosystem function, where they involve the overlap of primary and secondary, or dependent, habitat-forming foundation species [1]. Although it is well recognized that the size and configuration of secondary foundation species' patches are critical features modulating the ecological effects of facilitation cascades [2], the mechanisms governing their spatial distribution are often challenging to discern given that they operate across multiple spatial and temporal scales [1, 3]. We therefore combined regional surveys of southeastern US salt marsh geomorphology and invertebrate communities with a predator exclusion experiment to elucidate the drivers, both geomorphic and biotic, controlling the establishment, persistence, and ecosystem functioning impacts of a regionally abundant facilitation cascade involving habitat-forming marsh cordgrass and aggregations of ribbed mussels. We discovered a hierarchy of physical and biological factors predictably controlling the strength and self-organization of this facilitation cascade across creekshed, landscape, and patch scales. These results significantly enhance our capacity to spatially predict coastal ecosystem function across scales based on easily identifiable metrics of geomorphology that are mechanistically linked to ecological processes. Replication of this approach across vegetated coastal ecosystems has the potential to support management efforts by elucidating the multi-scale linkages between geomorphology and ecology that, in turn, define spatially explicit patterns in community assembly and ecosystem functioning.

Climate change effects on Black Sigatoka disease of banana

Climate change has significantly altered species distributions in the wild and has the potential to affect the interactions between pests and diseases and their human, animal and plant hosts. While several studies have projected changes in disease distributions in the future, responses to historical climate change are poorly understood. Such analyses are required to dissect the relative contributions of climate change, host availability and dispersal to the emergence of pests and diseases. Here, we model the influence of climate change on the most damaging disease of a major tropical food plant, Black Sigatoka disease of banana. Black Sigatoka emerged from Asia in the late twentieth Century and has recently completed its invasion of Latin American and Caribbean banana-growing areas. We parametrize an infection model with published experimental data and drive the model with hourly microclimate data from a global climate reanalysis dataset. We define infection risk as the sum of the number of modelled hourly spore cohorts that infect a leaf over a time interval. The model shows that infection risk has increased by a median of 44.2% across banana-growing areas of Latin America and the Caribbean since the 1960s, due to increasing canopy wetness and improving temperature conditions for the pathogen. Thus, while increasing banana production and global trade have probably facilitated Black Sigatoka establishment and spread, climate change has made the region increasingly conducive for plant infection.

This article is part of the theme issue ‘Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes’. This issue is linked with the subsequent theme issue ‘Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control’.

Global-scale species distributions predict temperature-related changes in species composition of rocky shore communities in Britain

Changes in rocky shore community composition as responses to climatic fluctuations and anthropogenic warming can be shown by changes in average species thermal affinities. In this study, we derived thermal affinities for European Atlantic rocky intertidal species by matching their known distributions to patterns in average annual sea surface temperature. Average thermal affinities (the Community Temperature Index, CTI) tracked patterns in sea surface temperature from Portugal to Norway, but CTI for communities of macroalgae and plant species changed less than those composed of animal species. This reduced response was in line with the expectation that communities with a smaller range of thermal affinities among species would change less in composition along thermal gradients and over time. Local-scale patterns in CTI over wave exposure gradients suggested that canopy macroalgae allow species with ranges centred in cooler than local temperatures ('cold-affinity') to persist in otherwise too-warm conditions. In annual surveys of rocky shores, communities of animal species in Shetland showed a shift in dominance towards warm-affinity species ('thermophilization') with local warming from 1980 to 2018 but the community of plant and macroalgal species did not. From 2002 to 2018, communities in southwest Britain showed the reverse trend in CTI: declining average thermal affinities over a period of modest temperature decline. Despite the cooling, trends in species abundance were in line with the general mechanism of direction and magnitude of long-term trends depending on the difference between species thermal affinities and local temperatures. Cold-affinity species increased during cooling and warm-affinity ones decreased. The consistency of responses across different communities and with general expectations based on species thermal characteristics suggests strong predictive accuracy of responses of community composition to anthropogenic warming.

The changing physical and ecological meanings of North Pacific Ocean climate indices

Climate change is likely to change the relationships between commonly used climate indices and underlying patterns of climate variability, but this complexity is rarely considered in studies using climate indices. Here, we show that the physical and ecological conditions mapping onto the Pacific Decadal Oscillation (PDO) index and North Pacific Gyre Oscillation (NPGO) index have changed over multidecadal timescales. These changes apparently began around a 1988/1989 North Pacific climate shift that was marked by abrupt northeast Pacific warming, declining temporal variance in the Aleutian Low (a leading atmospheric driver of the PDO), and increasing correlation between the PDO and NPGO patterns. Sea level pressure and surface temperature patterns associated with each climate index changed after 1988/1989, indicating that identical index values reflect different states of basin-scale climate over time. The PDO and NPGO also show time-dependent skill as indices of regional northeast Pacific ecosystem variability. Since the late 1980s, both indices have become less relevant to physical-ecological variability in regional ecosystems from the Bering Sea to the southern California Current. Users of these climate indices should be aware of nonstationary relationships with underlying climate variability within the historical record, and the potential for further nonstationarity with ongoing climate change.

Contemporary climate change hinders hybrid performance of ecologically dominant marine invertebrates

Human activities alter patterns of biodiversity, particularly through species extinctions and range shifts. Two of these activities are human mediated transfer of species and contemporary climate change, and both allow previously isolated genotypes to come into contact and hybridize, potentially altering speciation rates. Hybrids have been shown to survive environmental conditions not tolerated by either parent, suggesting that, under some circumstances, hybrids may be able to expand their ranges and perform well under rapidly changing conditions. However, studies assessing how hybridization influences contemporary range shifts are scarce. We performed crosses on Pyura herdmani and Pyura stolonifera (Chordata, Tunicata), two closely related marine invertebrate species that are ecologically dominant and can hybridize. These sister species live in sympatry along the coasts of southern Africa, but one has a disjunct distribution that includes northern hemisphere sites. We experimentally assessed the performance of hybrid and parental crosses using different temperature regimes, including temperatures predicted under future climate change scenarios. We found that hybrids showed lower performance than parental crosses at the experimental temperatures, suggesting that hybrids are unlikely to expand their ranges to new environments. In turn, we found that the more widespread species performed better at a wide array of temperatures, indicating that this parental species may cope better with future conditions. This study illustrates how offspring fitness may provide key insights to predict range expansions and how contemporary climate change may mediate both the ability of hybrids to expand their ranges and the occurrence of speciation as a result of hybridization.

Climate adaptation by crop migration

Many studies have estimated the adverse effects of climate change on crop yields, however, this literature almost universally assumes a constant geographic distribution of crops in the future. Movement of growing areas to limit exposure to adverse climate conditions has been discussed as a theoretical adaptive response but has not previously been quantified or demonstrated at a global scale. Here, we assess how changes in rainfed crop area have already mediated growing season temperature trends for rainfed maize, wheat, rice, and soybean using spatially-explicit climate and crop area data from 1973 to 2012. Our results suggest that the most damaging impacts of warming on rainfed maize, wheat, and rice have been substantially moderated by the migration of these crops over time and the expansion of irrigation. However, continued migration may incur substantial environmental costs and will depend on socio-economic and political factors in addition to land suitability and climate.

Temperature dependence of germination and growth in Anthurium (Araceae)

By the year 2100, temperatures are predicted to increase by about 6 °C at higher latitudes and about 3 °C in the tropics. In spite of the smaller increase in the tropics, consequences may be more severe because the climatic niches of tropical species are generally assumed to be rather narrow due to a high degree of climate stability and higher niche specialisation. However, rigorous data to back up this notion are rare. We chose the megadiverse genus Anthurium (Araceae) for study. Considering that the regeneration niche of a species is crucial for overall niche breadth, we focused on the response of germination and early growth through a temperature range of 24 °C of 15 Anthurium species, and compared the thermal niche breadth (TNB) with the temperature conditions in their current range, modelled from occurrence records. Surprisingly, an increase of 3 °C would lead to a larger overlap of TNB of germination and modelled in situ temperature conditions, while the overlap of TNB of growth with in situ conditions under current and future conditions is statistically indistinguishable. We conclude that future temperatures tend to be closer to the thermal optima of most species. Whether this really leads to an increase in performance depends on other abiotic and biotic factors, most prominently potentially changing precipitation patterns.

Range-extending coral reef fishes trade-off growth for maintenance of body condition in cooler waters

As ocean waters warm due to climate change, tropical species are shifting their ranges poleward to remain within their preferred thermal niches. As a result, novel communities are emerging in which tropical species interact with local temperate species, competing for similar resources, such as food and habitat. To understand how range-extending coral reef fish species perform along their leading edges when invading temperate ecosystems, we studied proxies of their fitness, including somatic growth (length increase), feeding rates, and body condition, along a 730-km latitudinal gradient situated in one of the global warming hotspots. We also studied co-occurring temperate species to assess how their fitness is affected along their trailing edges under ocean warming. We predicted that tropical fishes would experience reduced performance as they enter novel communities with suboptimal environmental conditions. Our study shows that although tropical fish maintain their body condition (based on three proxies) and stomach fullness across all invaded temperate latitudes, they exhibit decreased in situ growth rates, activity levels, and feeding rates in their novel temperate environment, likely a result of lower metabolic rates in cooler waters. We posit that tropical fishes face a growth-maintenance trade-off under the initial phases of ocean warming (i.e. at their leading edges), allowing them to maintain their body condition in cooler temperate waters but at the cost of slower growth. Temperate fish exhibited no distinct patterns in body condition and performance along the natural temperature gradient studied. However, in the face of future climate change, when metabolism is no longer stymied by low water temperatures, tropical range-extending species are likely to approach their native-range growth rates along their leading edges, ultimately leading to increased competitive interactions with local species in temperate ecosystems.

Assessment of the vulnerability of alpine grasslands on the Qinghai-Tibetan Plateau

Assessing ecosystem vulnerability to climate change is critical for sustainable and adaptive ecosystem management. Alpine grasslands on the Qinghai-Tibetan Plateau are considered to be vulnerable to climate change, yet the ecosystem tends to maintain stability by increasing resilience and decreasing sensitivity. To date, the spatial pattern of grassland vulnerability to climate change and the mechanisms that vegetation applies to mitigate the impacts of climate change on grasslands by altering relevant ecosystem characteristics, especially sensitivity and resilience, remain unknown. In this study, we first assessed the spatial pattern of grassland vulnerability to climate change by integrating exposure, sensitivity, and resilience simultaneously, and then identified its driving forces. The results show that grasslands with high vulnerability were mainly located on the edges of the plateau, whereas alpine grasslands in the hinterlands of the plateau showed a low vulnerability. This spatial pattern of alpine grassland vulnerability was controlled by climatic exposure, and grassland sensitivity and resilience to climate change might also exacerbate or alleviate the degree of vulnerability. Climate change had variable impacts on different grassland types. Desert steppes were more vulnerable to climate change than alpine meadows and alpine steppes because of the high variability in environmental factors and their low ability to recover from perturbations. Our findings also confirm that grazing intensity, a quantitative index of the most important human disturbance on alpine grasslands in this plateau, was significantly correlated with ecosystem vulnerability. Moderate grazing intensity was of benefit for increasing grassland resilience and then subsequently reducing grassland vulnerability. Thus, this study suggests that future assessments of ecosystem vulnerability should not ignore anthropogenic disturbances, which might benefit environmental protection and sustainable management of grasslands on the Qinghai-Tibetan Plateau.

Fine-grained climate velocities reveal vulnerability of protected areas to climate change

Climate change velocity is an increasingly used metric to assess the broad-scale climatic exposure and climate change induced risks to terrestrial and marine ecosystems. However, the utility of this metric in conservation planning can be enhanced by determining the velocities of multiple climatic drivers in real protected area (PA) networks on ecologically relevant scales. Here we investigate the velocities of three key bioclimatic variables across a nation-wide reserve network, and the consequences of including fine-grained topoclimatic data in velocity assessments. Using 50-m resolution data describing present-day and future topoclimates, we assessed the velocities of growing degree days, the mean January temperature and climatic water balance in the Natura 2000 PA network in Finland. The high-velocity areas for the three climate variables differed drastically, indicating contrasting exposure risks in different PAs. The 50-m resolution climate data revealed more realistic estimates of climate velocities and more overlap between the present-day and future climate spaces in the PAs than the 1-km resolution data. Even so, the current temperature conditions were projected to disappear from almost all the studied PAs by the end of this century. Thus, in PA networks with only moderate topographic variation, far-reaching climate change induced ecological changes may be inevitable.

Trophic niche segregation allows range-extending coral reef fishes to co-exist with temperate species under climate change

Changing climate is forcing many terrestrial and marine species to extend their ranges poleward to stay within the bounds of their thermal tolerances. However, when such species enter higher latitude ecosystems, they engage in novel interactions with local species, such as altered predator-prey dynamics and competition for food. Here, we evaluate the trophic overlap between range-extending and local fish species along the east coast of temperate Australia, a hotspot for ocean warming and species range extensions. Stable isotope ratios (δ¹⁵ N and δ¹³ C) of muscle tissue and stomach content analysis were used to quantify overlap of trophic niche space between vagrant tropical and local temperate fish communities along a 730 km (6°) latitudinal gradient. Our study shows that in recipient temperate ecosystems, sympatric tropical and temperate species do not overlap significantly in their diet-even though they forage on broadly similar prey groups-and are therefore unlikely to compete for trophic niche space. The tropical and temperate species we studied, which are commonly found in shallow-water coastal environments, exhibited moderately broad niche breadths and local-scale dietary plasticity, indicating trophic generalism. We posit that because these species are generalists, they can co-exist under current climate change, facilitating the existence of novel community structures.

Embryonic Temperature Programs Phenotype in Reptiles

Reptiles are critically affected by temperature throughout their lifespan, but especially so during early development. Temperature-induced changes in phenotype are a specific example of a broader phenomenon called phenotypic plasticity in which a single individual is able to develop different phenotypes when exposed to different environments. With climate change occurring at an unprecedented rate, it is important to study temperature effects on reptiles. For example, the potential impact of global warming is especially pronounced in species with temperature-dependent sex determination (TSD) because temperature has a direct effect on a key phenotypic (sex) and demographic (population sex ratios) trait. Reptiles with TSD also serve as models for studying temperature effects on the development of other traits that display continuous variation. Temperature directly influences metabolic and developmental rate of embryos and can have permanent effects on phenotype that last beyond the embryonic period. For instance, incubation temperature programs post-hatching hormone production and growth physiology, which can profoundly influence fitness. Here, we review current knowledge of temperature effects on phenotypic and developmental plasticity in reptiles. First, we examine the direct effect of temperature on biophysical processes, the concept of thermal performance curves, and the process of thermal acclimation. After discussing these reversible temperature effects, we focus the bulk of the review on developmental programming of phenotype by temperature during embryogenesis (i.e., permanent developmental effects). We focus on oviparous species because eggs are especially susceptible to changes in ambient temperature. We then discuss recent work probing the role of epigenetic mechanisms in mediating temperature effects on phenotype. Based on phenotypic effects of temperature, we return to the potential impact of global warming on reptiles. Finally, we highlight key areas for future research, including the identification of temperature sensors and assessment of genetic variation for thermosensitivity.

Benthic-based contributions to climate change mitigation and adaptation

Innovative solutions to improve the condition and resilience of ecosystems are needed to address societal challenges and pave the way towards a climate-resilient future. Nature-based solutions offer the potential to protect, sustainably manage and restore natural or modified ecosystems while providing multiple other benefits for health, the economy, society and the environment. However, the implementation of nature-based solutions stems from a discourse that is almost exclusively derived from a terrestrial and urban context and assumes that risk reduction is resolved locally. We argue that this position ignores the importance of complex ecological interactions across a range of temporal and spatial scales and misses the substantive contribution from marine ecosystems, which are notably absent from most climate mitigation and adaptation strategies that extend beyond coastal disaster management. Here, we consider the potential of sediment-dwelling fauna and flora to inform and support nature-based solutions, and how the ecology of benthic environments can enhance adaptation plans. We illustrate our thesis with examples of practice that are generating, or have the potential to deliver, transformative change and discuss where further innovation might be applied. Finally, we take a reflective look at the realized and potential capacity of benthic-based solutions to contribute to adaptation plans and offer our perspectives on the suitability and shortcomings of past achievements and the prospective rewards from sensible prioritization of future research. This article is part of the theme issue 'Climate change and ecosystems: threats, opportunities and solutions'.

Climate-Driven Shifts in Marine Species Ranges: Scaling from Organisms to Communities

The geographic distributions of marine species are changing rapidly, with leading range edges following climate poleward, deeper, and in other directions and trailing range edges often contracting in similar directions. These shifts have their roots in fine-scale interactions between organisms and their environment-including mosaics and gradients of temperature and oxygen-mediated by physiology, behavior, evolution, dispersal, and species interactions. These shifts reassemble food webs and can have dramatic consequences. Compared with species on land, marine species are more sensitive to changing climate but have a greater capacity for colonization. These differences suggest that species cope with climate change at different spatial scales in the two realms and that range shifts across wide spatial scales are a key mechanism at sea. Additional research is needed to understand how processes interact to promote or constrain range shifts, how the dominant responses vary among species, and how the emergent communities of the future ocean will function.

The Role of Symbioses in the Adaptation and Stress Responses of Marine Organisms

Ocean ecosystems are experiencing unprecedented rates of climate and anthropogenic change, which can often initiate stress in marine organisms. Symbioses, or associations between different organisms, are plentiful in the ocean and could play a significant role in facilitating organismal adaptations to stressful ocean conditions. This article reviews current knowledge about the role of symbiosis in marine organismal acclimation and adaptation. It discusses stress and adaptations in symbioses from coral reef ecosystems, which are among the most affected environments in the ocean, including the relationships between corals and microalgae, corals and bacteria, anemones and clownfish, and cleaner fish and client fish. Despite the importance of this subject, knowledge of how marine organisms adapt to stress is still limited, and there are vast opportunities for research and technological development in this area. Attention to this subject will enhance our understanding of the capacity of symbioses to alleviate organismal stress in the oceans.

A framework for experimental scenarios of global change in marine systems using coral reefs as a case study

Understanding the consequences of rising CO₂ and warming on marine ecosystems is a pressing issue in ecology. Manipulative experiments that assess responses of biota to future ocean warming and acidification conditions form a necessary basis for expectations on how marine taxa may respond. Although designing experiments in the context of local variability is most appropriate, local temperature and CO₂ characteristics are often unknown as such measures necessitate significant resources, and even less is known about local future scenarios. To help address these issues, we summarize current uncertainties in CO₂ emission trajectories and climate sensitivity, examine region-specific changes in the ocean, and present a straightforward global framework to guide experimental designs. We advocate for the inclusion of multiple plausible future scenarios of predicted levels of ocean warming and acidification in forthcoming experimental research. Growing a robust experimental base is crucial to understanding the prospect form and function of marine ecosystems in the Anthropocene.

Ocean warming compresses the three-dimensional habitat of marine life

Vertical migration to reach cooler waters is a suitable strategy for some marine organisms to adapt to ocean warming. Here, we calculate that realized vertical isotherm migration rates averaged -6.6 + 18.8 m dec^-1 across the global ocean between 1980 and 2015. Throughout this century (2006-2100), surface isotherms are projected to deepen at an increasing rate across the globe, averaging -32.3 m dec^-1 under the representative concentration pathway (RCP)8.5 'business as usual' emissions scenario, and -18.7 m dec^-1 under the more moderate RCP4.5 scenario. The vertical redistribution required by organisms to follow surface isotherms over this century is three to four orders of magnitude less than the equivalent horizontal redistribution distance. However, the seafloor depth and the depth of the photic layer pose ultimate limits to the vertical migration possible by species. Both limits will be reached by the end of this century across much of the ocean, leading to a rapid global compression of the three-dimensional (3D) habitat of many marine organisms. Phytoplankton diversity may be maintained but displaced toward the base of the photic layer, whereas highly productive benthic habitats, especially corals, will have their suitable 3D habitat rapidly reduced.

Diverging phenological responses of Arctic seabirds to an earlier spring

The timing of annual events such as reproduction is a critical component of how free-living organisms respond to ongoing climate change. This may be especially true in the Arctic, which is disproportionally impacted by climate warming. Here, we show that Arctic seabirds responded to climate change by moving the start of their reproduction earlier, coincident with an advancing onset of spring and that their response is phylogenetically and spatially structured. The phylogenetic signal is likely driven by seabird foraging behavior. Surface-feeding species advanced their reproduction in the last 35 years while diving species showed remarkably stable breeding timing. The earlier reproduction for Arctic surface-feeding birds was significant in the Pacific only, where spring advancement was most pronounced. In both the Atlantic and Pacific, seabirds with a long breeding season showed a greater response to the advancement of spring than seabirds with a short breeding season. Our results emphasize that spatial variation, phylogeny, and life history are important considerations in seabird phenological response to climate change and highlight the key role played by the species' foraging behavior.

Climate-human interaction associated with southeast Australian megafauna extinction patterns

The mechanisms leading to megafauna (>44 kg) extinctions in Late Pleistocene (126,000—12,000 years ago) Australia are highly contested because standard chronological analyses rely on scarce data of varying quality and ignore spatial complexity. Relevant archaeological and palaeontological records are most often also biased by differential preservation resulting in under-representated older events. Chronological analyses have attributed megafaunal extinctions to climate change, humans, or a combination of the two, but rarely consider spatial variation in extinction patterns, initial human appearance trajectories, and palaeoclimate change together. Here we develop a statistical approach to infer spatio-temporal trajectories of megafauna extirpations (local extinctions) and initial human appearance in south-eastern Australia. We identify a combined climate-human effect on regional extirpation patterns suggesting that small, mobile Aboriginal populations potentially needed access to drinkable water to survive arid ecosystems, but were simultaneously constrained by climate-dependent net landscape primary productivity. Thus, the co-drivers of megafauna extirpations were themselves constrained by the spatial distribution of climate-dependent water sources.

Whether Australia’s Pleistocene megafauna extinctions were caused by climate change, humans, or both is debated. Here, the authors infer the spatio-temporal trajectories of regional extinctions and find that water availability mediates the relationship among climate, human migration and megafauna extinctions.

Thermal performance responses in free-ranging elasmobranchs depend on habitat use and body size

Temperature is one of the most influential drivers of physiological performance and behaviour in ectotherms, determining how these animals relate to their ecosystems and their ability to succeed in particular habitats. Here, we analysed the largest set of acceleration data compiled to date for elasmobranchs to examine the relationship between volitional activity and temperature in 252 individuals from 8 species. We calculated activation energies for the thermal performance response in each species and estimated optimum temperatures using an Arrhenius breakpoint analysis, subsequently fitting thermal performance curves to the activity data. Juveniles living in confined nursery habitats not only spent substantially more time above their optimum temperature and at the upper limits of their performance breadths compared to larger, less site-restricted animals, but also showed lower activation energies and broader performance curves. Species or life stages occupying confined habitats featured more generalist behavioural responses to temperature change, whereas wider ranging elasmobranchs were characterised by more specialist behavioural responses. The relationships between the estimated performance regimes and environmental temperature limits suggest that animals in confined habitats, including many juvenile elasmobranchs within nursery habitats, are likely to experience a reduction of performance under a warming climate, although their flatter thermal response will likely dampen this impact. The effect of warming on less site-restricted species is difficult to forecast since three of four species studied here did not reach their optimum temperature in the wild, although their specialist performance characteristics may indicate a more rapid decline should optimum temperatures be exceeded.

Differing climatic mechanisms control transient and accumulated vegetation novelty in Europe and eastern North America

Understanding the mechanisms of climate that produce novel ecosystems is of joint interest to conservation biologists and palaeoecologists. Here, we define and differentiate transient from accumulated novelty and evaluate four climatic mechanisms proposed to cause species to reshuffle into novel assemblages: high climatic novelty, high spatial rates of change (displacement), high variance among displacement rates for individual climate variables, and divergence among displacement vector bearings. We use climate simulations to quantify climate novelty, displacement and divergence across Europe and eastern North America from the last glacial maximum to the present, and fossil pollen records to quantify vegetation novelty. Transient climate novelty is consistently the strongest predictor of transient vegetation novelty, while displacement rates (mean and variance) are equally important in Europe. However, transient vegetation novelty is lower in Europe and its relationship to climatic predictors is the opposite of expectation. For both continents, accumulated novelty is greater than transient novelty, and climate novelty is the strongest predictor of accumulated ecological novelty. These results suggest that controls on novel ecosystems vary with timescale and among continents, and that the twenty-first century emergence of novelty will be driven by both rapid rates of climate change and the emergence of novel climate states. This article is part of a discussion meeting issue 'The past is a foreign country: how much can the fossil record actually inform conservation?'

Thermal stress causes nuclear and cellular abnormalities of peripheral erythrocytes in Indian major carp, rohu Labeo rohita

Rise of water temperature as a consequence of global warming is anticipated to affect the physiological activities of fish, especially in tropical regions. In the present experiment, we exposed the Indian major carp, rohu Labeo rohita to three different temperature regimes (30 °C as control and 33 °C and 36 °C) for 60 days and observed the effects of these temperature on: major hemato-biochemical indices (Hemoglobin; Hb, Red blood cell; RBC, White blood cell; WBC and blood glucose levels), erythrocytic nuclear abnormalities (ENA), and erythrocytic cellular abnormalities (ECA) of peripheral erythrocytes along with the formation of differential leucocytes in the blood. Fish were sacrificed at day 7, 15, 30 and 60 after the start of exposure to the temperature regimes. Hb decreased significantly on days 7 and 15 at 36 °C. Throughout the study period, the decrease of RBC and increase of WBC were significant at 36 °C. Blood glucose level increased significantly initially at day 7 but decreased significantly at day 60 at 36 °C. Frequencies of ENA (binucleated, nuclear bud, nuclear bridge, karyopyknosis and notched nuclei) and ECA (twin, fusion, echinocytic, spindle, tear drop and elongated shaped) were significantly increased at the highest temperature (36 °C) at almost all of the sampling days. In the case of differential leucocyte count, high temperature caused a significant increase in the number of neutrophils and a significant decrease in the number of lymphocytes. Overall, these results indicate that chronic exposure to high temperature (36 °C) induces a number of stress responses in rohu and that temperature should be kept below 36 °C in the aquaculture setting to avoid damage to the fish.