The influences of snow cover,vegetation and topography on the upper range limit of common wombats Vombatus ursinus in the subalpine zone,Australia

Aim In subalpine and alpine environments, range shifts of species to higher altitudes are predicted to occur in response to reductions in the snow cover from climate change. However, the distribution of key resources may constrain the range of animal populations and prevent any upward migration. This study examined the local resource constraints on the upper range limit of a large, native herbivore in Australia, the common wombat Vombatus ursinus. Location The subalpine zone of the Snowy Mountains, Australia. Methods Logistic regression analyses of snow and habitat predictors were conducted on the presence/absence of wombat signs recorded along an altitudinal gradient during winter and summer, using parametric and nonparametric methods. Results Wombats responded strongly to the altitudinal gradient, but snow cover alone did not fully explain their upper range limit. Wombat occurrence in the subalpine zone was influenced by local habitat features in combination with maximum snow depth. More rugged, high‐relief terrain was important to wombats in winter, allowing individuals access to a wider range of altitudes, snow depths and shelter sites. During summer, high soil bulk density was an important predictor of occurrence, and in both seasons, occurrence declined in response to a higher cover of burnt grass. Main conclusions These models demonstrate that local habitat factors play a role even where there are strong regulating environmental factors. For wombats, this may limit future range expansion into the alpine zone despite the potential for an increase in abundance at their present range limit. These findings show the need for local ecological studies to be conducted in parallel with broad scale climate modelling if we are to understand shifts in species distributions as the climate rapidly changes.     

Impacts of global change on species distributions: obstacles and solutions to integrate climate and land use

Aim The impact of multiple stressors on biodiversity is one of the most pressing questions in ecology and biodiversity conservation. Here we critically assess how often and efficiently two main drivers of global change have been simultaneously integrated into research, with the aim of providing practical solutions for better integration in the future. We focus on the integration of climate change (CC) and land‐use change (LUC) when studying changes in species distributions. Location Global. Methods We analysed the peer‐reviewed literature on the effects of CC and LUC on observed changes in species distributions, i.e. including species range and abundance, between 2000 and 2014. Results Studies integrating CC and LUC remain extremely scarce, which hampers our ability to develop appropriate conservation strategies. The lack of CC–LUC integration is likely to be a result of insufficient recognition of the co‐occurrence of CC and LUC at all scales, covariation and interactions between CC and LUC, as well as correlations between species thermal and habitat requirements. Practical guidelines for the study of these interactive effects include considering multiple drivers and processes when designing studies, using available long‐term datasets on multiple drivers, revisiting single‐driver studies with additional drivers or conducting comparative studies and meta‐analyses. Combining various methodological approaches, including time lags and adaptation processes, represent further avenues to improve global change science. Main conclusions Despite repeated claims for a better integration of multiple drivers, the effects of CC and LUC on species distributions and abundances have been mostly studied in isolation, which calls for a shift of standards towards more integrative global change science. The guidelines proposed here will encourage study designs that account for multiple drivers and improve our understanding of synergies or antagonisms among drivers.     

Congruent morphological and genetic differentiation as a signature of range expansion in a fragmented landscape

Phenotypic differentiation is often interpreted as a result of local adaptation of individuals to their environment. Here, we investigated the skull morphological differentiation in 11 populations of the white‐footed mouse (Peromyscus leucopus). These populations were sampled in an agricultural landscape in the Montérégie region (Québec, Canada), at the northern edge of the distribution of the white‐footed mouse. We found a strong pattern of phenotypic differentiation matching the genetic structure across these populations. Landscape fragmentation and the presence of geographic barriers, in particular north–south oriented rivers, contribute to this differentiation and modulate the pattern of rapid ongoing northward range expansion of the white‐footed mouse in response to climate warming. We conclude that while large rivers and postglacial recolonization routes have shaped the current pattern of distribution and differentiation of white‐footed mouse populations, further local differentiation is occurring, at the scale of the landscape. We posit that the northern expansion of the white‐footed mouse is achieved through successive independent founder events in a fragmented landscape at the northern range edge of the species. The phenotypic differentiation we observe is thus a result of a number of mechanisms operating at different spatial and temporal scales.     

Fitness declines towards range limits and local adaptation to climate affect dispersal evolution during climate‐induced range shifts

Dispersal ability will largely determine whether species track their climatic niches during climate change, a process especially important for populations at contracting (low‐latitude/low‐elevation) range limits that otherwise risk extinction. We investigate whether dispersal evolution at contracting range limits is facilitated by two processes that potentially enable edge populations to experience and adjust to the effects of climate deterioration before they cause extinction: (i) climate‐induced fitness declines towards range limits and (ii) local adaptation to a shifting climate gradient. We simulate a species distributed continuously along a temperature gradient using a spatially explicit, individual‐based model. We compare range‐wide dispersal evolution during climate stability vs. directional climate change, with uniform fitness vs. fitness that declines towards range limits (RLs), and for a single climate genotype vs. multiple genotypes locally adapted to temperature. During climate stability, dispersal decreased towards RLs when fitness was uniform, but increased when fitness declined towards RLs, due to highly dispersive genotypes maintaining sink populations at RLs, increased kin selection in smaller populations, and an emergent fitness asymmetry that favoured dispersal in low‐quality habitat. However, this initial dispersal advantage at low‐fitness RLs did not facilitate climate tracking, as it was outweighed by an increased probability of extinction. Locally adapted genotypes benefited from staying close to their climate optima; this selected against dispersal under stable climates but for increased dispersal throughout shifting ranges, compared to cases without local adaptation. Dispersal increased at expanding RLs in most scenarios, but only increased at the range centre and contracting RLs given local adaptation to climate.     

Are fish outside their usual ranges early indicators of climate‐driven range shifts?

Shifts in species ranges are a global phenomenon, well known to occur in response to a changing climate. New species arriving in an area may become pest species, modify ecosystem structure, or represent challenges or opportunities for fisheries and recreation. Early detection of range shifts and prompt implementation of any appropriate management strategies is therefore crucial. This study investigates whether ‘first sightings’ of marine species outside their normal ranges could provide an early warning of impending climate‐driven range shifts. We examine the relationships between first sightings and marine regions defined by patterns of local climate velocities (calculated on a 50‐year timescale), while also considering the distribution of observational effort (i.e. number of sampling days recorded with biological observations in global databases). The marine trajectory regions include climate ‘source’ regions (areas lacking connections to warmer areas), ‘corridor’ regions (areas where moving isotherms converge), and ‘sink’ regions (areas where isotherms locally disappear). Additionally, we investigate the latitudinal band in which first sightings were recorded, and species’ thermal affiliations. We found that first sightings are more likely to occur in climate sink and ‘divergent’ regions (areas where many rapid and diverging climate trajectories pass through) indicating a role of temperature in driving changes in marine species distributions. The majority of our fish first sightings appear to be tropical and subtropical species moving towards high latitudes, as would be expected in climate warming. Our results indicate that first sightings are likely related to longer‐term climatic processes, and therefore have potential use to indicate likely climate‐driven range shifts. The development of an approach to detect impending range shifts at an early stage will allow resource managers and researchers to better manage opportunities resulting from range‐shifting species before they potentially colonize.     

Community assembly rules affect the diversity of expanding communities

Despite centuries of interest in species range limits, few studies have taken a whole community into consideration. Actually, multiple species may simultaneously respond to environmental changes, for example, global warming, leading a series of dynamical communities toward the advancing front. We investigated multiple species range expansions through the analysis of a two‐species dispersion model and simulations of multiple species assemblages regulated by neutral and fecundity–survival trade‐offs (FSTs), respectively, and found that species assemblages regulated by different mechanisms would initiate different expanding patterns in geographic ranges in response to environmental changes. The neutral model generally predicts a higher biodiversity near the core of an expanding range, and a lower community similarity compared with a FST model. Without considering the evolution of life history traits, an assortment of the reproduction ability happens at the advancing front under FSTs at the expense of a higher death rate or lower competitive ability. These results emphasize the importance of community assembly rules to the biodiversity maintenance of range expanding communities.     

Predicting the distributions of Pouteria adolfi-friederici and Prunus africana tree species under current and future climate change scenarios in Ethiopia

Distributions of potential ranges of plant species are not yet fully known in Ethiopia where high climatic variability and vegetation types are found. This study was undertaken to predict distributions of suitable habitats of Pouteria adolfi-friederici and Prunus africana under current and two future climate scenarios (RCP 4.5 and RCP 8.5 in 2050 and 2070) in Ethiopia. Eleven environmental variables with less correlation coefficients (r < 0.7) were used to make the prediction. Shifting in extents of habitat suitability and effects of elevation, solar radiation and topographic position in relation to the current and future climatic scenarios were statistically analysed using independent t-test and linear model. We found decreasing area of highly suitable habitat from 0.51% to 0.46%, 0.36% and 0.33%, 0.24% for Prunus africana and 1.13% to 1.02%, 0.77% and 0.76%, 0.60% for Pouteria adolfi-friederici, under RCP 4.5 and RCP 8.5 by 2050 and 2070 respectively. Moist and dry afromontane forests are identified as the most suitable habitat for both species. Overall, our results suggest that climate change can promote dynamic suitable habitat niches under different future climate scenarios. Therefore, biodiversity conservation strategies should take into account habitat suitability dynamics issues and identify where to conserve species before implementing conservation practices.     

ARE RANGE‐SIZE DISTRIBUTIONS CONSISTENT WITH SPECIES‐LEVEL HERITABILITY?

The concept of species-level heritability is widely contested. Because it is most likely to apply to emergent, species-level traits, one of the central discussions has focused on the potential heritability of geographic range size. However, a central argument against range-size heritability has been that it is not compatible with the observed shape of present-day species range-size distributions (SRDs), a claim that has never been tested. To assess this claim, we used forward simulation of range-size evolution in clades with varying degrees of range-size heritability, and compared the output of three different models to the range-size distribution of the South American avifauna. Although there were differences among the models, a moderate-to-high degree of range-size heritability consistently leads to SRDs that were similar to empirical data. These results suggest that range-size heritability can generate realistic SRDs, and may play an important role in shaping observed patterns of range sizes.     

Interrogating recent range changes in South African birds: confounding signals from land use and climate change present a challenge for attribution

Aim Apparent anthropogenic warming has been underway in South Africa for several decades, a period over which significant range shifts have been observed in some indigenous bird species. We asked whether these range shifts by birds are clearly consistent with either climate change or land use change being the primary driver. Location South Africa. Methods We categorized recent range changes among 408 South African terrestrial bird species and, using generalized linear mixed models, analysed ecological attributes of those species that have and have not changed their ranges. Results Fifty‐six of the 408 taxa studied have undergone significant range shifts. Most extended their ranges towards the south (towards cooler latitudes, consistent with climate‐change drivers) or west (towards drier and warmer habitats, inconsistent with climate drivers but consistent with land use drivers); very few moved east or north. Both southward and westward movers were habitat generalists. Furthermore, southward movers were mobile taxa (migrants and nomads), whereas westward movers were associated with human‐modified elements in the landscape, such as croplands, plantations or buildings. Main conclusions The results suggest that both land use changes and climate change may simultaneously be influencing dynamic range shifts by South African birds, but separating the relative strengths of these two drivers is challenging, not least because both are operating concurrently and may influence some species simultaneously. Those species that respond to land use change by contracting their ranges are likely to be among the species that will be most impacted by climate change if land use practices with negative impacts are occurring in areas anticipated to become climatic refugia for these species. This highlights a pressing need to develop dynamic models of species’ potential range shifts and changing abundances that incorporate population and dispersal processes, as well as ecological processes that influence habitat suitability.     

Phenological synchrony between eastern spruce budworm and its host trees increases with warmer temperatures in the boreal forest

Climate change is predicted to alter relationships between trophic levels by changing the phenology of interacting species. We tested whether synchrony between two critical phenological events, budburst of host species and larval emergence from diapause of eastern spruce budworm, increased at warmer temperatures in the boreal forest in northeastern Canada. Budburst was up to 4.6 ± 0.7 days earlier in balsam fir and up to 2.8 ± 0.8 days earlier in black spruce per degree increase in temperature, in naturally occurring microclimates. Larval emergence from diapause did not exhibit a similar response. Instead, larvae emerged once average ambient temperatures reached 10°C, regardless of differences in microclimate. Phenological synchrony increased with warmer microclimates, tightening the relationship between spruce budworm and its host species. Synchrony increased by up to 4.5 ± 0.7 days for balsam fir and up to 2.8 ± 0.8 days for black spruce per degree increase in temperature. Under a warmer climate, defoliation could potentially begin earlier in the season, in which case, damage on the primary host, balsam fir may increase. Black spruce, which escapes severe herbivory because of a 2‐week delay in budburst, would become more suitable as a resource for the spruce budworm. The northern boreal forest could become more vulnerable to outbreaks in the future.     

Racing against change: understanding dispersal and persistence to improve species' conservation prospects

Climate change is contributing to the widespread redistribution, and increasingly the loss, of species. Geographical range shifts among many species were detected rapidly after predictions of the potential importance of climate change were specified 35 years ago: species are shifting their ranges towards the poles and often to higher elevations in mountainous areas. Early tests of these predictions were largely qualitative, though extraordinarily rapid and broadly based, and statistical tests distinguishing between climate change and other global change drivers provided quantitative evidence that climate change had already begun to cause species’ geographical ranges to shift. I review two mechanisms enabling this process, namely development of approaches for accounting for dispersal that contributes to range expansion, and identification of factors that alter persistence and lead to range loss. Dispersal in the context of range expansion depends on an array of processes, like population growth rates in novel environments, rates of individual species movements to new locations, and how quickly areas of climatically tolerable habitat shift. These factors can be tied together in well-understood mathematical frameworks or modelled statistically, leading to better prediction of extinction risk as climate changes. Yet, species'' increasing exposures to novel climate conditions can exceed their tolerances and raise the likelihood of local extinction and consequent range losses. Such losses are the consequence of processes acting on individuals, driven by factors, such as the growing frequency and severity of extreme weather, that contribute local extinction risks for populations and species. Many mechanisms can govern how species respond to climate change, and rapid progress in global change research creates many opportunities to inform policy and improve conservation outcomes in the early stages of the sixth mass extinction.     

Increased activity and growth rate in the non‐dispersive aquatic larval stage of a damselfly at an expanding range edge

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Range position and climate sensitivity: The structure of among‐population demographic responses to climatic variation

Species’ distributions will respond to climate change based on the relationship between local demographic processes and climate and how this relationship varies based on range position. A rarely tested demographic prediction is that populations at the extremes of a species’ climate envelope (e.g., populations in areas with the highest mean annual temperature) will be most sensitive to local shifts in climate (i.e., warming). We tested this prediction using a dynamic species distribution model linking demographic rates to variation in temperature and precipitation for wood frogs (Lithobates sylvaticus) in North America. Using long‐term monitoring data from 746 populations in 27 study areas, we determined how climatic variation affected population growth rates and how these relationships varied with respect to long‐term climate. Some models supported the predicted pattern, with negative effects of extreme summer temperatures in hotter areas and positive effects on recruitment for summer water availability in drier areas. We also found evidence of interacting temperature and precipitation influencing population size, such as extreme heat having less of a negative effect in wetter areas. Other results were contrary to predictions, such as positive effects of summer water availability in wetter parts of the range and positive responses to winter warming especially in milder areas. In general, we found wood frogs were more sensitive to changes in temperature or temperature interacting with precipitation than to changes in precipitation alone. Our results suggest that sensitivity to changes in climate cannot be predicted simply by knowing locations within the species’ climate envelope. Many climate processes did not affect population growth rates in the predicted direction based on range position. Processes such as species‐interactions, local adaptation, and interactions with the physical landscape likely affect the responses we observed. Our work highlights the need to measure demographic responses to changing climate.     

Moving beyond presence and absence when examining changes in species distributions

Species distributions are often simplified to binary representations of the ranges where they are present and absent. It is then common to look for changes in these ranges as indicators of the effects of climate change, the expansion or control of invasive species or the impact of human land‐use changes. We argue that there are inherent problems with this approach, and more emphasis should be placed on species relative abundance rather than just presence. The sampling effort required to be confident of absence is often impractical to achieve, and estimates of species range changes based on survey data are therefore inherently sensitive to sampling intensity. Species niches estimated using presence‐absence or presence‐only models are broader than those for abundance and may exaggerate the viability of small marginal sink populations. We demonstrate that it is possible to transform models of predicted probability of presence to expected abundance if the sampling intensity is known. Using case studies of Antarctic mosses and temperate rain forest trees, we demonstrate additional insights into biotic change that can be gained using this method. While species becoming locally extinct or colonising new areas are extreme and obviously important impacts of global environmental change, changes in abundance could still signal important changes in biological systems and be an early warning indicator of larger future changes.     

Rapid range expansion and community reorganization in response to warming

Species ranges are expected to expand along their cooler boundaries in response to rising temperatures associated with current global climate change. However, this ‘fingerprint’ of climate change is yet to be assessed for an entire flora. Here, we examine patterns of altitudinal range change in the complete native vascular flora of sub‐Antarctic Marion Island. We demonstrate a rapid mean upslope expansion in the flora since 1966, in response to 1.2 °C warming on the island. The 3.4±0.8 m yr^?1 (mean±SE) upslope expansion rate documented is amongst the highest estimates from partial floras. However, less than half of the species in the flora were responsible for the expansion trend, demonstrating that the global fingerprint of warming may be driven by a highly responsive subset of the species pool. Individual range expansion rates varied greatly, with species‐specific niche requirements explaining some of this variation. As a result of the idiosyncratic expansion rates, altitudinal patterns of species richness and community composition changed considerably, with the formation of no‐analog communities at high and intermediate altitudes. Therefore, both species‐ and community‐level changes have occurred in the flora of Marion Island over a relatively short period of rapid warming, demonstrating the sensitivity of high latitude communities to climate change. Patterns of change within this flora illustrate the range of variation in species responses to climate change and the consequences thereof for species distributions and community reorganization.     

Climate change causes rapid changes in the distribution and site abundance of birds in winter

Detecting coherent signals of climate change is best achieved by conducting expansive, long‐term studies. Here, using counts of waders (Charadrii) collected from ca. 3500 sites over 30 years and covering a major portion of western Europe, we present the largest‐scale study to show that faunal abundance is influenced by climate in winter. We demonstrate that the ‘weighted centroids’ of populations of seven species of wader occurring in internationally important numbers have undergone substantial shifts of up to 115 km, generally in a northeasterly direction. To our knowledge, this shift is greater than that recorded in any other study, but closer to what would be expected as a result of the spatial distribution of ecological zones. We establish that year‐to‐year changes in site abundance have been positively correlated with concurrent changes in temperature, but that this relationship is most marked towards the colder extremities of the birds' range, suggesting that shifts have occurred as a result of range expansion and that responses to climate change are temperature dependent. Many attempts to model the future impacts of climate change on the distribution of organisms, assume uniform responses or shifts throughout a species' range or with temperature, but our results suggest that this may not be a valid approach. We propose that, with warming temperatures, hitherto unsuitable sites in northeastern Europe will host increasingly important wader numbers, but that this may not be matched by declines elsewhere within the study area. The need to establish that such changes are occurring is accentuated by the statutory importance of this taxon in the designation of protected areas.