Estimating long-term survival temperatures at the assemblage level in the marine environment: towards macrophysiology

Defining ecologically relevant upper temperature limits of species is important in the context of environmental change. The approach used in the present paper estimates the relationship between rates of temperature change and upper temperature limits for survival in order to evaluate the maximum long-term survival temperature (Ts). This new approach integrates both the exposure time and the exposure temperature in the evaluation of temperature limits. Using data previously published for different temperate and Antarctic marine environments, we calculated Ts in each environment, which allowed us to calculate a new index: the Warming Allowance (WA). This index is defined as the maximum environmental temperature increase which an ectotherm in a given environment can tolerate, possibly with a decrease in performance but without endangering survival over seasonal or lifetime time-scales. It is calculated as the difference between maximum long-term survival temperature (Ts) and mean maximum habitat temperature. It provides a measure of how close a species, assemblage or fauna are living to their temperature limits for long-term survival and hence their vulnerability to environmental warming. In contrast to data for terrestrial environments showing that warming tolerance increases with latitude, results here for marine environments show a less clear pattern as the smallest WA value was for the Peru upwelling system. The method applied here, relating upper temperature limits to rate of experimental warming, has potential for wide application in the identification of faunas with little capacity to survive environmental warming.     

Occupancy‐derived thermal affinities reflect known physiological thermal limits of marine species

Predicting how species will respond to increased environmental temperatures is key to understanding the ecological consequences of global change. The physiological tolerances of a species define its thermal limits, while its thermal affinity is a summary of the environmental temperatures at the localities at which it actually occurs. Experimentally derived thermal limits are known to be related to observed latitudinal ranges in marine species, but accurate range maps from which to derive latitudinal ranges are lacking for many marine species. An alternative approach is to combine widely available data on global occurrences with gridded global temperature datasets to derive measures of species‐level “thermal affinity”—that is, measures of the central tendency, variation, and upper and lower bounds of the environmental temperatures at the locations at which a species has been recorded to occur. Here, we test the extent to which such occupancy‐derived measures of thermal affinity are related to the known thermal limits of marine species using data on 533 marine species from 24 taxonomic classes and with experimentally derived critical upper temperatures spanning 2–44.5°C. We show that thermal affinity estimates are consistently and positively related to the physiological tolerances of marine species, despite gaps and biases in the source data. Our method allows thermal affinity measures to be rapidly and repeatably estimated for many thousands more marine species, substantially expanding the potential to assess vulnerability of marine communities to warming seas.     

Climate sensitivity across marine domains of life: limits to evolutionary adaptation shape species interactions

Organisms in all domains, Archaea, Bacteria, and Eukarya will respond to climate change with differential vulnerabilities resulting in shifts in species distribution, coexistence, and interactions. The identification of unifying principles of organism functioning across all domains would facilitate a cause and effect understanding of such changes and their implications for ecosystem shifts. For example, the functional specialization of all organisms in limited temperature ranges leads us to ask for unifying functional reasons. Organisms also specialize in either anoxic or various oxygen ranges, with animals and plants depending on high oxygen levels. Here, we identify thermal ranges, heat limits of growth, and critically low (hypoxic) oxygen concentrations as proxies of tolerance in a meta‐analysis of data available for marine organisms, with special reference to domain‐specific limits. For an explanation of the patterns and differences observed, we define and quantify a proxy for organismic complexity across species from all domains. Rising complexity causes heat (and hypoxia) tolerances to decrease from Archaea to Bacteria to uni‐ and then multicellular Eukarya. Within and across domains, taxon‐specific tolerance limits likely reflect ultimate evolutionary limits of its species to acclimatization and adaptation. We hypothesize that rising taxon‐specific complexities in structure and function constrain organisms to narrower environmental ranges. Low complexity as in Archaea and some Bacteria provide life options in extreme environments. In the warmest oceans, temperature maxima reach and will surpass the permanent limits to the existence of multicellular animals, plants and unicellular phytoplankter. Smaller, less complex unicellular Eukarya, Bacteria, and Archaea will thus benefit and predominate even more in a future, warmer, and hypoxic ocean.     

Global analysis of thermal tolerance and latitude in ectotherms

A tenet of macroecology is that physiological processes of organisms are linked to large-scale geographical patterns in environmental conditions. Species at higher latitudes experience greater seasonal temperature variation and are consequently predicted to withstand greater temperature extremes. We tested for relationships between breadths of thermal tolerance in ectothermic animals and the latitude of specimen location using all available data, while accounting for habitat, hemisphere, methodological differences and taxonomic affinity. We found that thermal tolerance breadths generally increase with latitude, and do so at a greater rate in the Northern Hemisphere. In terrestrial ectotherms, upper thermal limits vary little while lower thermal limits decrease with latitude. By contrast, marine species display a coherent poleward decrease in both upper and lower thermal limits. Our findings provide comprehensive global support for hypotheses generated from studies at smaller taxonomic subsets and geographical scales. Our results further indicate differences between terrestrial and marine ectotherms in how thermal physiology varies with latitude that may relate to the degree of temperature variability experienced on land and in the ocean.     

Are there adequate data to assess how well theories of rarity apply to marine invertebrates?

Understanding the biology of rare species is a very important part of conservation biology. Most of our current understanding of rarity has, however, come from studies of terrestrial plants, birds, mammals and some insects. Freshwater and marine habitats are underrepresented in published studies of rare species or conservation biology. We therefore have little knowledge about how well our understanding of what makes particular species rare and how rare species persist applies to marine invertebrates which form a major component of coastal biodiversity. In this review, I examine some theories about rarity with respect to intertidal and shallow subtidal invertebrates to identify whether there are adequate data to apply these theories to marine invertebrates and how well such theories apply. The general conclusions are that the lack of quantitative data on abundances, ranges, habitat-requirements, dispersal and connectedness among populations for marine invertebrates means that their status as rare species cannot really be assessed appropriately. It is also unlikely that, without extensive sampling programmes and considerable expense, adequate data could be obtained for these small, cryptic animals, which typically have very patchy, variable and unpredictable patterns of distribution and abundance. Intertidal and subtidal assemblages are diverse, including species with many different life-histories from many phyla, occupying the same suite of habitats. It is therefore suggested that future research on rare organisms in marine habitats should build upon the long and successful history of experimental marine studies to test specific hypotheses about processes influencing rarity in the field. Such studies would not only add a new dimension to our current understanding of rarity, but would also provide badly-needed data on the status of rare marine invertebrates. abundances, invertebrates, marine, range, rarity     

Plant distribution and the temperature coefficient of metabolism

The spatial distribution of a plant species is limited by the range of climatic conditions to which the species can adapt. Temperature is one of the most significant determinants of plant distribution, but except for the effects of lethal limits, little is known about physiological changes in responses to differences in environmental temperature. In this study, temperature coefficients of non-photosynthetic metabolism have been determined in the normal environmental temperature range for selected annual and perennial plants. Distinct differences were found in the temperature coefficient of metabolism of woody perennial plants from high latitudes and high elevations and closely related low-latitude and low-elevation plants. Low-latitude and low-elevation woody perennials have Arrhenius temperature coefficients for metabolism that are larger than those for congeneric high-latitude and high-elevation plants. The Arrhenius temperature coefficient is not rapidly adapted to new environments. A simple function was developed relating Arrhenius temperature coefficient to latitude and elevation for accessions of three, woody, perennial species complexes of plants collected from a wide geographic range but grown in common gardens. Within these taxa, plants that experience broader ranges of temperature during growth in their native habitat have smaller temperature coefficients. Temperature coefficients also varied with growth stage or season. No similar relationship was found for annuals and herbaceous perennials. For the plants tested, Arrhenius temperature coefficients are high during early spring growth, but shift to lower values later in the season. The shift in Arrhenius temperature coefficients occurs early in the season for southern and low-elevation plants and progressively later for plants from further north or higher elevation. The changes in Arrhenius temperature coefficients result largely from increases in plant metabolic rates at lower temperatures while little change occurs in the rates at higher temperatures. Altering the temperature dependence of the control of metabolic rate is apparently an important means of response to climate change.     

Environmental constraints on life histories in Antarctic ecosystems: tempos, timings and predictability

Knowledge of Antarctic biotas and environments has increased dramatically in recent years. There has also been a rapid increase in the use of novel technologies. Despite this, some fundamental aspects of environmental control that structure physiological, ecological and life-history traits in Antarctic organisms have received little attention. Possibly the most important of these is the timing and availability of resources, and the way in which this dictates the tempo or pace of life. The clearest view of this effect comes from comparisons of species living in different habitats. Here, we (i) show that the timing and extent of resource availability, from nutrients to colonisable space, differ across Antarctic marine, intertidal and terrestrial habitats, and (ii) illustrate that these differences affect the rate at which organisms function. Consequently, there are many dramatic biological differences between organisms that live as little as 10 m apart, but have gaping voids between them ecologically.Identifying the effects of environmental timing and predictability requires detailed analysis in a wide context, where Antarctic terrestrial and marine ecosystems are at one extreme of the continuum of available environments for many characteristics including temperature, ice cover and seasonality. Anthropocentrically, Antarctica is harsh and as might be expected terrestrial animal and plant diversity and biomass are restricted. By contrast, Antarctic marine biotas are rich and diverse, and several phyla are represented at levels greater than global averages. There has been much debate on the relative importance of various physical factors that structure the characteristics of Antarctic biotas. This is especially so for temperature and seasonality, and their effects on physiology, life history and biodiversity. More recently, habitat age and persistence through previous ice maxima have been identified as key factors dictating biodiversity and endemism. Modern molecular methods have also recently been incorporated into many traditional areas of polar biology. Environmental predictability dictates many of the biological characters seen in all of these areas of Antarctic research.     

Environmental marginality and geographic range limits: a case study with Arabidopsis lyrata ssp. lyrata

Understanding the factors that govern the distribution of species is a central goal of evolutionary ecology. It is commonly assumed that geographic range limits reflect ecological niche limits and that species experience increasingly marginal conditions towards the edge of their ranges. Using spatial data and ecological niche models we tested these hypotheses in Arabidopsis lyrata. Specifically, we asked whether range limits coincide with predicted niche limits in this system and whether the suitability of sites declines towards the edge of the species’ range in North America. We further explored patterns of environmental change towards the edge of the range and asked whether genome‐wide patterns of genetic diversity decline with increasing peripherality and environmental marginality. Our results suggest that latitudinal range limits coincide with niche limits. Populations experienced increasingly marginal environments towards these limits – though patterns of environmental change were more complex than most theoretical models for range limits assume. Genomic diversity declined towards the edge of the species’ range and with increasing distance from the estimated centre of the species’ niche in environmental space, but not with the suitability of sites based on niche model predictions. Thus while latitudinal range limits in this system are broadly associated with niche limits, the link between environmental conditions and genetic diversity (and thus the adaptive potential of populations) is less clear.     

Temperature effects on gametophyte life-history traits and geographic distribution of two cryptic kelp species

A major determinant of the geographic distribution of a species is expected to be its physiological response to changing abiotic variables over its range. The range of a species often corresponds to the geographic extent of temperature regimes the organism can physiologically tolerate. Many species have very distinct life history stages that may exhibit different responses to environmental factors. In this study we emphasized the critical role of the haploid microscopic stage (gametophyte) of the life cycle to explain the difference of edge distribution of two related kelp species. Lessonia nigrescens was recently identified as two cryptic species occurring in parapatry along the Chilean coast: one located north and the other south of a biogeographic boundary at latitude 29-30°S. Six life history traits from microscopic stages were identified and estimated under five treatments of temperature in eight locations distributed along the Chilean coast in order to (1) estimate the role of temperature in the present distribution of the two cryptic L. nigrescens species, (2) compare marginal populations to central populations of the two cryptic species. In addition, we created a periodic matrix model to estimate the population growth rate (λ) at the five temperature treatments. Differential tolerance to temperature was demonstrated between the two species, with the gametophytes of the Northern species being more tolerant to higher temperatures than gametophytes from the south. Second, the two species exhibited different life history strategies with a shorter haploid phase in the Northern species contrasted with considerable vegetative growth in the Southern species haploid stage. These results provide strong ecological evidence for the differentiation process of the two cryptic species and show local adaptation of the life cycle at the range limits of the distribution. Ecological and evolutionary implications of these findings are discussed.     

Consistent abundance distributions of marine fishes in an old,climatically buffered,infertile seascape

Aim Macroecological theory predicts that along direct physiological gradients there will be unimodal abundance distributions of species and consistent rates of assemblage turnover. However, the majority of marine studies that have investigated the realized distribution of species along latitudinal or temperature gradients have generally found unimodal distributions to be rare. We assess fish distributions along a temperature gradient in a stable oligotrophic seascape and suggest that unimodal distributions will be more common. Location Nearshore demersal fish habitat extending 1500 km along the coast of south‐western Australia. Methods The relative abundances of demersal fish species were sampled off the coast of south‐western Australia along a temperature gradient. The confounding influence of other environmental variables was tested, and the assemblage was found to be highly correlated with temperature. For the 20 most abundant species, quantile regression spline models were used to construct a model within which 95% of their abundance was expected to fall. We compared the results from this study with the proportion of unimodal species abundance distributions observed in other studies. Results Of the 20 most abundant species, 19 displayed patterns that indicated temperature was an important factor influencing their range and relative abundance; with 15 species exhibiting unimodal abundance distributions, four having ramped distribution to one end of the sampled range and one showing no consistent pattern. Main conclusions The high diversity and percentage of endemic species in terrestrial and marine habitats of south‐western Australia is likely to be due to the stable geological and oceanographic history of the region. In comparison, studies of abundance distribution in other marine systems have been conducted in relatively heterogeneous and productive environments. The old, climatically buffered, oligotrophic seascape of south‐western Australia has provided a simple system in which the consistent influence of physiological gradients on the abundance distribution of fish species can be observed.     

Comparative physiological studies on the growth of cryptic species of Bostrychia intricata (Rhodomelaceae,Rhodophyta) in various salinity and temperature conditions

Inter‐ and intra‐specific physiological variations of intertidal macroalgae have been well investigated. However, studies on physiological responses of cryptic algal species have been poorly documented. Bostrychia intricata is a widespread marine red alga in the Southern Hemisphere, and has many cryptic species. We investigated the effect of different salinities and temperatures on the specific growth rate of three cryptic species (N2, N4 and N5) of B. intricata from New Zealand. Our data indicated that all cryptic species grew at the full range of salinities and temperatures tested, but exhibited a significant difference in their specific growth rates. Cryptic species N4 had a higher growth rate than the other two cryptic species under all experimental conditions, whereas cryptic species N2 occasionally showed a higher growth rate than cryptic species N5 at high salinities and lower temperatures. The distinct physiological properties of these cryptic species may explain their distribution pattern (a wider distribution of cryptic species N4 than N2 and N5) in New Zealand. The physiological divergence between the cryptic species could be related to their levels of evolutionary divergence, with more similar physiology between cryptic species, which share a more recent common ancestor (N2 and N5). Our findings underline that morphologically indistinguishable cryptic algal species are different in many other aspects and are truly independent entities.     

Prospects for surviving climate change in Antarctic aquatic species

Maritime Antarctic freshwater habitats are amongst the fastest changing environments on Earth. Temperatures have risen around 1°C and ice cover has dramatically decreased in 15 years. Few animal species inhabit these sites, but the fairy shrimp Branchinecta gaini typifies those that do. This species survives up to 25°C daily temperature fluctuations in summer and passes winter as eggs at temperatures down to -25°C. Its annual temperature envelope is, therefore around 50°C. This is typical of Antarctic terrestrial species, which exhibit great physiological flexibility in coping with temperature fluctuations. The rapidly changing conditions in the Maritime Antarctic are enhancing fitness in these species by increasing the time available for feeding, growth and reproduction, as well as increasing productivity in lakes. The future problem these animals face is via displacement by alien species from lower latitudes. Such invasions are now well documented from sub-Antarctic sites. In contrast the marine Antarctic environment has very stable temperatures. However, seasonality is intense with very short summers and long winter periods of low to no algal productivity. Marine animals grow slowly, have long generation times, low metabolic rates and low levels of activity. They also die at temperatures between +5°C and +10°C. Failure of oxygen supply mechanisms and loss of aerobic scope defines upper temperature limits. As temperature rises, their ability to perform work declines rapidly before lethal limits are reached, such that 50% of populations of clams and limpets cannot perform essential activities at 2–3°C, and all scallops are incapable of swimming at 2°C. Currently there is little evidence of temperature change in Antarctic marine sites. Models predict average global sea temperatures will rise by around 2°C by 2100. Such a rise would take many Antarctic marine animals beyond their survival limits. Animals have 3 mechanisms for coping with change: they can 1) use physiological flexibility, 2) evolve new adaptations, 3) migrate to better sites. Antarctic marine species have poor physiological scopes, long generation times and live on a continent whose coastline covers fewer degrees of latitude than all others. On all 3 counts Antarctic marine species have poorer prospects than most large faunal groups elsewhere.     

Sphingomonads from marine environments

Sphingomonas species play an important role in the ecology of a range of marine habitats. Isolates and 16S-rRNA clones have been obtained from corals, natural and artificial sources of marine hydrocarbons and eutrophic and oligotrophic waters, and have been isolated as hosts for marine phages. In addition they are found in oceans spanning temperature ranges from polar to temperate waters. While less is known about marine sphingomonads in comparison to their terrestrial counterparts, their importance in microbial ecology is evident. This is illustrated by, for example, the numerical dominance of strain RB2256 in oligotrophic waters. Furthermore, the known marine sphingomonads represent a phylogenetic cross-section of the Sphingomonas genus. This review focuses on our present knowledge of cultured isolates and 16S-rDNA clones from marine environments. Received 01 May 1999/ Accepted in revised form 13 July 1999     

Evolution and biodiversity of Antarctic organisms: a molecular perspective

The Antarctic biota is highly endemic, and the diversity and abundance of taxonomic groups differ from elsewhere in the world. Such characteristics have resulted from evolution in isolation in an increasingly extreme environment over the last 100 Myr. Studies on Antarctic species represent some of the best examples of natural selection at the molecular, structural and physiological levels. Analyses of molecular genetics data are consistent with the diversity and distribution of marine and terrestrial taxa having been strongly influenced by geological and climatic cooling events over the last 70 Myr. Such events have resulted in vicariance driven by continental drift and thermal isolation of the Antarctic, and in pulses of species range contraction into refugia and subsequent expansion and secondary contact of genetically distinct populations or sister species during cycles of glaciation. Limited habitat availability has played a major role in structuring populations of species both in the past and in the present day. For these reasons, despite the apparent simplicity or homogeneity of Antarctic terrestrial and marine environments, populations of species are often geographically structured into genetically distinct lineages. In some cases, genetic studies have revealed that species defined by morphological characters are complexes of cryptic or sibling species. Climate change will cause changes in the distribution of many Antarctic and sub-Antarctic species through affecting population-level processes such as life history and dispersal.     

Exploring the Effect of Asymmetric Mitochondrial DNA Introgression on Estimating Niche Divergence in Morphologically Cryptic Species

If potential morphologically cryptic species, identified based on differentiated mitochondrial DNA, express ecological divergence, this increases support for their treatment as distinct species. However, mitochondrial DNA introgression hampers the correct estimation of ecological divergence. We test the hypothesis that estimated niche divergence differs when considering nuclear DNA composition or mitochondrial DNA type as representing the true species range. We use empirical data of two crested newt species (Amphibia: Triturus) which possess introgressed mitochondrial DNA from a third species in part of their ranges. We analyze the data in environmental space by determining Fisher distances in a principal component analysis and in geographical space by determining geographical overlap of species distribution models. We find that under mtDNA guidance in one of the two study cases niche divergence is overestimated, whereas in the other it is underestimated. In the light of our results we discuss the role of estimated niche divergence in species delineation.     

Wintering space use and site fidelity in a nomadic species,the snowy owl

Migratory species can exploit many habitats over vast geographic areas and adopt various patterns of space and habitat use throughout their annual cycle. In nomadic species, determinants of habitat use during the non‐breeding season are poorly known due to the unpredictability of their movement patterns. Here, we analysed variability in wintering space and habitat use by a highly nomadic species, the snowy owl, in eastern North America. Using 21 females tracked by satellite telemetry between 2007 and 2016, we 1) assessed how space use patterns in winter varied according to the type of environment (marine vs terrestrial), latitudinal zone (Arctic vs temperate), local snow conditions and lemming densities and 2) investigated winter habitat and site fidelity. Our results confirmed a high inter‐individual variation in patterns of habitat use by wintering snowy owls. Highly‐used areas were concentrated in the Arctic and in the marine and coastal environments. Owls wintering in the marine environment travelled over longer distances during the winter, had larger home ranges and these were divided in more smaller zones than individuals in terrestrial environments. Wintering home range sizes decreased with high winter lemming densities, use of the marine environment increased following high summer lemming densities, and a thick snow cover in autumn led to later settlement on the wintering ground. Contrary to expectations, snowy owls tended to make greater use of the marine environment when snow cover was thin. Snowy owls were highly consistent in their use of a given wintering environment and a specific latitudinal zone between years, but demonstrated flexibility in their space use and a modest site fidelity. The snowy owls’ consistency in wintering habitat use may provide them with advantages in terms of experience but their mobility and flexibility may help them to cope with changing environmental conditions at fine spatial scale.     

Combining physiological threshold knowledge to species distribution models is key to improving forecasts of the future niche for macroalgae

Species distribution models (SDM) are a useful tool for predicting species range shifts in response to global warming. However, they do not explore the mechanisms underlying biological processes, making it difficult to predict shifts outside the environmental gradient where the model was trained. In this study, we combine correlative SDMs and knowledge on physiological limits to provide more robust predictions. The thermal thresholds obtained in growth and survival experiments were used as proxies of the fundamental niches of two foundational marine macrophytes. The geographic projections of these species’ distributions obtained using these thresholds and existing SDMs were similar in areas where the species are either absent‐rare or frequent and where their potential and realized niches match, reaching consensus predictions. The cold‐temperate foundational seaweed Himanthalia elongata was predicted to become extinct at its southern limit in northern Spain in response to global warming, whereas the occupancy of southern‐lusitanic Bifurcaria bifurcata was expected to increase. Combined approaches such as this one may also highlight geographic areas where models disagree potentially due to biotic factors. Physiological thresholds alone tended to over‐predict species prevalence, as they cannot identify absences in climatic conditions within the species’ range of physiological tolerance or at the optima. Although SDMs tended to have higher sensitivity than threshold models, they may include regressions that do not reflect causal mechanisms, constraining their predictive power. We present a simple example of how combining correlative and mechanistic knowledge provides a rapid way to gain insight into a species’ niche resulting in consistent predictions and highlighting potential sources of uncertainty in forecasted responses to climate change.     

Mitogenome evidence for the existence of cryptic species in Coelomactra antiquata

Cryptic species which improve our understanding of species diversity and evolutionary histories within marine animals have been increasingly revealed in the marine realm. Coelomactra antiquate is an important commercial bivalve species, but has been suffering from severe population decline due to over-exploitation and deterioration of environmental conditions. To test the hypothesis that cryptic species might exist in C. antiquate presented in previous study, four complete mitogenomes of C. antiquate from northern and southern China were determined here. Comprehensive comparative analysis of the mitochondrial genomes of C. antiquate between northern and southern population reveals significant differences in genome composition, protein coding genes, tRNA genes, non-coding regions, genetic divergence and phylogenetic analysis. The results provide strong mitogenome evidence for the existence of cryptic species in C. antiquate. Besides, our results also support that comprehensive comparative analysis of mtDNA represents an accessible and powerful tool to identify cryptic species.     

Differential response to abiotic stress controls species distributions at biogeographic transition zones

Understanding range limits is critical to predicting species responses to climate change. Subtropical environments, where many species overlap at their range margins, are cooler, more light‐limited and variable than tropical environments. It is thus likely that species respond variably to these multi‐stressor regimes and that factors other than mean climatic conditions drive biodiversity patterns. Here, we tested these hypotheses for scleractinian corals at their high‐latitude range limits in eastern Australia and investigated the role of mean climatic conditions and of parameters linked to abiotic stress in explaining the distribution and abundance of different groups of species. We found that environmental drivers varied among taxa and were predominantly linked to abiotic stress. The distribution and abundance of tropical species and gradients in species richness (alpha diversity) and turnover (beta diversity) were best explained by light limitation, whereas minimum temperatures and temperature fluctuations best explained gradients in subtropical species, species nestedness and functional diversity. Variation in community structure (considering species composition and abundance) was most closely linked to the combined thermal and light regime. Our study demonstrates the role of abiotic stress in controlling the distribution of species towards their high‐latitude range limits and suggests that, at biogeographic transition zones, robust predictions of the impacts of climate change require approaches that account for various aspects of physiological stress and for species abundances and characteristics. These findings support the hypothesis that abiotic stress controls high‐latitude range limits and caution that projections solely based on mean temperature could underestimate species’ vulnerabilities to climate change.     

Marine range shifts and species introductions: comparative spread rates and community impacts

Aim Shifts in species ranges are a predicted and realized effect of global climate change; however, few studies have addressed the rates and consequence of such shifts, particularly in marine systems. Given ecological similarities between shifting and introduced species, we examined how our understanding of range shifts may be informed by the more established study of non‐native species introductions. Location Marine systems world‐wide. Methods Database and citation searches were used to identify 129 marine species experiencing range shifts and to determine spread rates and impacts on recipient communities. Analyses of spread rates were based on studies for which post‐establishment spread was reported in linear distance. The sizes of the effects of community impacts of shifting species were compared with those of functionally similar introduced species having ecologically similar impacts. Results Our review and meta‐analyses revealed that: (1) 75% of the range shifts found through the database search were in the poleward direction, consistent with climate change scenarios, (2) spread rates of range shifts were lower than those of introductions, (3) shifting species spread over an order of magnitude faster in marine than in terrestrial systems, and (4) directions of community effects were largely negative and magnitudes were often similar for shifters and introduced species; however, this comparison was limited by few data for range‐shifting species. Main conclusions Although marine range shifts are likely to proceed more slowly than marine introductions, the community‐level effects could be as great, and in the same direction, as those of introduced species. Because it is well‐established that introduced species are a primary threat to global biodiversity, it follows that, just like introductions, range shifts have the potential to seriously affect biological systems. In addition, given that ranges shift faster in marine than terrestrial environments, marine communities might be affected faster than terrestrial ones as species shift with climate change. Regardless of habitat, consideration of range shifts in the context of invasion biology can improve our understanding of what to expect from climate change‐driven shifts as well as provide tools for formal assessment of risks to community structure and function.