AIM: Correlative models that forecast extinction risk from climate change and invasion risks following species introductions, depend on the assumption that species' current distributions reflect ...their climate tolerances (‘climatic equilibrium’). This assumption has rarely been tested with independent distribution data, and studies that have done so have focused on species that are widespread or weedy in their native range. We use independent data to test climatic equilibrium for a broadly representative group of species, and ask whether there are any general indicators that can be used to identify when equilibrium occurs. LOCATION: Europe and contiguous USA. METHODS: We contrasted the climate conditions occupied by 51 plant species in their native (European) and naturalized (USA) distributions by applying kernel smoothers to species' occurrence densities. We asked whether species had naturalized in climate conditions that differ from their native ranges, suggesting climatic disequilibrium in the native range, and whether characteristics of species' native distributions correspond with climatic equilibrium. RESULTS: A large proportion of species' naturalized distributions occurred outside the climatic conditions occupied in their native ranges: for 22 species, the majority of their naturalized ranges fell outside their native climate conditions. Our analyses revealed large areas in Europe that species do not occupy, but which match climatic conditions occupied in the USA, suggesting a high degree of climatic disequilibrium in the native range. Disequilibrium was most severe for species with native ranges that are small and occupy a narrow range of climatic conditions. MAIN CONCLUSIONS: Our results demonstrate that the direct effects of climate on species distributions have been widely overestimated, and that previous large‐scale validations of the equilibrium assumption using species' native and naturalized distributions are not generally applicable. Non‐climatic range limitations are likely to be the norm, rather than the exception, and pose added risks for species under climate change.
Information on the ecological traits of species might improve predictions of climate-driven range shifts. However, the usefulness of traits is usually assumed rather than quantified. Here, we present ...a framework to identify the most informative traits, based on four key range-shift processes: emigration of individuals or propagules away from the natal location; the distance a species can move; establishment of self-sustaining populations; and proliferation following establishment. We propose a framework that categorises traits according to their contribution to range-shift processes. We demonstrate how the framework enables the predictive value of traits to be evaluated empirically and how this categorisation can be used to better understand range-shift processes; we also illustrate how range-shift estimates can be improved.
The ecological traits of species are increasingly used to inform predictions of climate-driven range shifts.
Traits utilised should correspond to range-shift processes: emigration, movement, establishment, and proliferation. We categorise traits according to the information that they offer for each process.
The most informative traits can be informed by biogeographical and demographic evidence bases: species range sizes, range filling, recent range shifts, population fluctuations, and success following naturalisation.
Movement traits are often used in range-shift studies, although their importance is not universally supported. Ecological generalisation, persistence in unfavourable conditions, reproductive strategy, and intraspecific competitive ability should be considered for inclusion in range-shift evaluations.
Many analyses of biological responses to climate rely on gridded climate data derived from weather stations, which differ from the conditions experienced by organisms in at least two respects. First, ...the microclimate recorded by a weather station is often quite different to that near the ground surface, where many organisms live. Second, the temporal and spatial resolutions of gridded climate datasets derived from weather stations are often too coarse to capture the conditions experienced by organisms. Temporally and spatially coarse data have clear benefits in terms of reduced model size and complexity, but here we argue that coarse‐grained data introduce errors that, in biological studies, are too often ignored. However, in contrast to common perception, these errors are not necessarily caused directly by a spatial mismatch between the size of organisms and the scale at which climate data are collected. Rather, errors and biases are primarily due to (a) systematic discrepancies between the climate used in analysis and that experienced by organisms under study; and (b) the non‐linearity of most biological responses in combination with differences in climate variance between locations and time periods for which models are fitted and those for which projections are made. We discuss when exactly problems of scale can be expected to arise and highlight the potential to circumvent these by spatially and temporally down‐scaling climate. We also suggest ways in which adjustments to deal with issues of scale could be made without the need to run high‐resolution models over wide extents.
Many analyses of biological responses to climate rely on coarse spatial and temporal resolution climate data. The use of such data are likely to cause errors, but these errors are not caused directly by spatial mismatch between the size of organisms and the scale of climate data. Rather, errors arise because of the non‐linearity of most biological responses in combination with differences in climate variance between locations and time periods for which models are fitted and those for which predictions are made.
The ranges of species are shifting as a consequence of anthropogenic climate change. In the marine realm biogeographic transition zones could form barriers to dispersal and inhibit range-shift, but ...little is known about this potential effect. The hermit crab
Clibanarius erythropus
appeared in the UK in 2016 with the nearest reproducing population being on the northern coast of Brittany. This raises questions of which conditions may have permitted
C. erythropus
to cross the English Channel (7.25°W, 49.00°N) and whether this barrier could be overcome by other intertidal species. Dispersal simulations suggest the larvae of
C. erythropus
arrived in 2014, originated from North Brittany, experienced a mean temperature of around 16 °C, and took longer than 20 days to be transported across the channel. The transportation of larvae from Brittany to the southwest UK appears to be rare and driven by occasional, unusual ocean currents. The English Channel may continue to prevent species with pelagic larvae that settle within 20 days, such as many species of gastropod, annelids, and macroalgae, from successfully range expanding to the UK. North Brittany was the only landmass from which it is feasible the UK population of
C. erythropus
could have originated. Therefore, species with long-lived pelagic larvae but without reproducing populations in North Brittany may not appear in the southwest UK until the species are established in North Brittany. The English Channel could continue to limit the ability of many intertidal species to shift their range with climate change.
Fall armyworm,
Spodopterafrugiperda
, is a crop pest native to the Americas, which has invaded and spread throughout sub-Saharan Africa within two years. Recent estimates of 20–50% maize yield loss ...in Africa suggest severe impact on livelihoods. Fall armyworm is still infilling its potential range in Africa and could spread to other continents. In order to understand fall armyworm’s year-round, global, potential distribution, we used evidence of the effects of temperature and precipitation on fall armyworm life-history, combined with data on native and African distributions to construct Species Distribution Models (SDMs). We also investigated the strength of trade and transportation pathways that could carry fall armyworm beyond Africa. Up till now, fall armyworm has only invaded areas that have a climate similar to the native distribution, validating the use of climatic SDMs. The strongest climatic limits on fall armyworm’s year-round distribution are the coldest annual temperature and the amount of rain in the wet season. Much of sub-Saharan Africa can host year-round fall armyworm populations, but the likelihoods of colonising North Africa and seasonal migrations into Europe are hard to predict. South and Southeast Asia and Australia have climate conditions that would permit fall armyworm to invade. Current trade and transportation routes reveal Australia, China, India, Indonesia, Malaysia, Philippines and Thailand face high threat of fall armyworm invasions originating from Africa.
Invasive alien species (IAS) threaten human livelihoods and biodiversity globally. Increasing globalization facilitates IAS arrival, and environmental changes, including climate change, facilitate ...IAS establishment. Here we provide the first global, spatial analysis of the terrestrial threat from IAS in light of twenty-first century globalization and environmental change, and evaluate national capacities to prevent and manage species invasions. We find that one-sixth of the global land surface is highly vulnerable to invasion, including substantial areas in developing economies and biodiversity hotspots. The dominant invasion vectors differ between high-income countries (imports, particularly of plants and pets) and low-income countries (air travel). Uniting data on the causes of introduction and establishment can improve early-warning and eradication schemes. Most countries have limited capacity to act against invasions. In particular, we reveal a clear need for proactive invasion strategies in areas with high poverty levels, high biodiversity and low historical levels of invasion.
More species live outside their native range than at any point in human history. Yet, there is little understanding of the geographic regions that will be threatened if these species continue to ...spread, nor of whether they will spread. We predict the world’s terrestrial regions to which 833 naturalised plants, birds, and mammals are most imminently likely to spread, and investigate what factors have hastened or slowed their spread to date. There is huge potential for further spread of naturalised birds in North America, mammals in Eastern Europe, and plants in North America, Eastern Europe, and Australia. Introduction history, dispersal, and the spatial distribution of suitable areas are more important predictors of species spread than traits corresponding to habitat usage or biotic interactions. Natural dispersal has driven spread in birds more than in plants. Whether these taxa continue to spread more widely depends partially on connectivity of suitable environments. Plants show the clearest invasion lag, and the putative importance of human transportation indicates opportunities to slow their spread. Despite strong predictive effects, questions remain, particularly why so many birds in North America do not occupy climatically suitable areas close to their existing ranges.
Across large parts of the world, wildlife has to coexist with human activity in highly modified and fragmented landscapes. Combining concepts from population viability analysis and spatial reserve ...design, this study develops efficient quantitative methods for identifying conservation core areas at large, even national or continental scales. The proposed methods emphasize long-term population persistence, are applicable to both fragmented and natural landscape structures, and produce a hierarchical zonation of regional conservation priority. The methods are applied to both observational data for threatened butterflies at the scale of Britain and modelled probability of occurrence surfaces for indicator species in part of Australia. In both cases, priority landscapes important for conservation management are identified.
Extreme climatic events (ECEs) - such as unusual heat waves, hurricanes, floods, and droughts - can dramatically affect ecological and evolutionary processes, and these events are projected to become ...more frequent and more intense with ongoing climate change. However, the implications of ECEs for biological invasions remain poorly understood. Using concepts and empirical evidence from invasion ecology, we identify mechanisms by which ECEs may influence the invasion process, from initial introduction through establishment and spread. We summarize how ECEs can enhance invasions by promoting the transport of propagules into new regions, by decreasing the resistance of native communities to establishment, and also sometimes by putting existing non-native species at a competitive disadvantage. Finally, we outline priority research areas and management approaches for anticipating future risks of unwanted invasions following ECEs. Given predicted increases in both ECE occurrence and rates of species introductions around the globe during the coming decades, there is an urgent need to understand how these two processes interact to affect ecosystem composition and functioning.
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