Species Range Changes Research Articles

Accounting for tree line shift, glacier retreat and primary succession in mountain plant distribution models

AbstractAimTo incorporate changes in alpine land cover (tree line shift, glacier retreat and primary succession) into species distribution model (SDM) predictions for a selection of 31 high‐elevation plants.LocationChamonix Valley, French Alps.MethodsWe fit linear mixed effects (LME) models to historical changes in forest and glacier cover and projected these trends forward to align with 21st century IPCC climate scenarios. We used a logistic function to model the probability of plant establishment in glacial forelands zones expected to become ice free between 2008 and 2051–2080. Habitat filtering consisted of intersecting land cover maps with climate‐driven SDMs to refine habitat suitability predictions. SDM outputs for tree, heath and alpine species were compared based on whether habitat filtering during the prediction period was carried out using present‐day (static) land cover, future (dynamic) land cover filters or no land cover filter (unfiltered). Species range change (SRC) was used to measure differences in habitat suitability predictions across methods.ResultsLME predictions for 2021–2080 showed continued glacier retreat, tree line rise and primary succession in glacier forelands. SRC was highest in the unfiltered scenario (−10%), intermediate in the dynamic scenario (−15%) and lowest in the static scenario (−31%). Tree species were the only group predicted to gain overall range by 2051–2080. Although alpine plants lost range in all three land cover scenarios, new habitat made available by glacier retreat in the dynamic land cover scenario buffered alpine plant range loss due to climate change.Main conclusionsWe provide a framework for combining trajectories of land cover change with SDM predictions. Our pilot study shows that incorporating shifts in land cover improves habitat suitability predictions and leads to contrasting outcomes of future mountain plant distribution. Alpine plants in particular may lose less suitable habitat than standard SDMs predict due to 21st century glacier retreat.

Genetic structure of earthworm populations at a regional scale: inferences from mitochondrial and microsatellite molecular markers in Aporrectodea icterica (Savigny 1826).

Despite the fundamental role that soil invertebrates (e.g. earthworms) play in soil ecosystems, the magnitude of their spatial genetic variation is still largely unknown and only a few studies have investigated the population genetic structure of these organisms. Here, we investigated the genetic structure of seven populations of a common endogeic earthworm (Aporrectodea icterica) sampled in northern France to explore how historical species range changes, microevolutionary processes and human activities interact in shaping genetic variation at a regional scale. Because combining markers with distinct modes of inheritance can provide extra, complementary information on gene flow, we compared the patterns of genetic structure revealed using nuclear (7 microsatellite loci) and mitochondrial markers (COI). Both types of markers indicated low genetic polymorphism compared to other earthworm species, a result that can be attributed to ancient bottlenecks, for instance due to species isolation in southern refugia during the ice ages with subsequent expansion toward northern Europe. Historical events can also be responsible for the existence of two divergent, but randomly interbreeding mitochondrial lineages within all study populations. In addition, the comparison of observed heterozygosity among microsatellite loci and heterozygosity expected under mutation-drift equilibrium suggested a recent decrease in effective size in some populations that could be due to contemporary events such as habitat fragmentation. The absence of relationship between geographic and genetic distances estimated from microsatellite allele frequency data also suggested that dispersal is haphazard and that human activities favour passive dispersal among geographically distant populations.

Can trait‐based analyses of changes in species distribution be transferred to new geographic areas?

AbstractAimAnthropogenic environmental change is having a major impact on biodiversity. By identifying traits that correlate with changes in species range, comparative studies can shed light on the mechanisms driving this change; but such studies will be more useful for conservation if they have true predictive power, i.e. if their trait‐based models can be transferred to new regions. We aim to examine the ability of trait‐based models to predict changes in plant distribution across seven geographic regions that varied in terms of land cover and species composition.LocationBritain and Flanders (Belgium).MethodsWe estimated distribution change for more than 1000 species for over 70 years of data (1930s to 2004), using data from published plant atlases. We identified regional trait‐based models of plant distribution change. Traits included morphological characteristics, Ellenberg values and distribution‐based traits. The trait models were then used to predict change in all other regions, with the level of linear correlation between predicted and observed changes in range used as a measure of transferability. We then related transferability to land cover and species similarity between regions.ResultsWe found that trait correlates of range change varied regionally, highlighting the regional variation in the drivers of range change in plants. These trait models also varied in the amount of variation explained, with r2 values ranging from 0.05 to 0.17. A key cross‐regional difference was the variation in the relationship between soil nutrient association (Ellenberg N) and distribution change, which was strongly positive in Flanders and southern England but significantly negative in northern Scotland. We found that transferability between regions was significantly correlated with the level of similarity in land cover.Main conclusionsWe conclude that trait‐based models can predict broad‐scale changes in species distributions in regions that share similar land‐cover composition; however, predictions between regions with differing land‐cover cover tend to be poor.

Ocean warming hotspots provide early warning laboratories for climate change impacts

A growing literature describes a wide range of negative impacts of climate change on marine resources and the people and communities they support, including species range changes, changes in productivity of fisheries and declines in economic performance (Doney et al. 2012; Poloczanska et al. 2013). These impacts, many of which are projected to increase in future, are compounded by growing pressures on marine resources (Halpern et al. 2008; Maxwell et al. 2013). An estimated 260 million people are involved directly or indirectly in global marine fisheries (Teh and Sumaila 2013) with many of the resources for capture fisheries already fully (?57 % in 2009) or over exploited (30 %) (FAO 2012). Nevertheless, production of marine resources will need to increase to accommodate the demands of a growing population, and the impacts of climate change on food security will need to be minimised (FAO 2009). Identifying opportunities and threats, and developing adaptation options in response to climate change on food security will need to be minimised (FAO 2009 ).

The European functional tree of bird life in the face of global change.

Despite the recognized joint impact of climate and land cover change on facets of biodiversity and their associated functions, risk assessments have primarily evaluated impacts on species ranges and richness. Here we quantify the sensitivity of the functional structure of European avian assemblages to changes in both regional climate and land cover. We combine species range forecasts with functional-trait information. We show that species sensitivity to environmental change is randomly distributed across the functional tree of the European avifauna and that functionally unique species are not disproportionately threatened by 2080. However, projected species range changes will modify the mean species richness and functional diversity of bird diets and feeding behaviours. This will unequally affect the spatial structure of functional diversity, leading to homogenization across Europe. Therefore, global changes may alter the functional structure of species assemblages in the future in ways that need to be accounted for in conservation planning.

Methods to detect species range size change from biological atlas data: A comparison using the South African Frog Atlas Project

Comparing historical species distribution data with recent biological surveys has the potential to quantify changes to species geographic ranges, and to detect declining species. The primary concern in making species range size comparisons between dissimilar datasets is the problem of incomparable sampling intensities. For South African amphibian data, an increase in sampling intensity over time was associated with a move from ad hoc to more coordinated sampling. The consequent increased geographic coverage and higher detection probabilities resulted in false range expansions. We assessed several approaches for managing variable sampling intensity: categorical comparisons, sub-sampling and correction factors. These methods were first applied to hypothetical ranges for evaluation, and then to the observed data of the South African Frog Atlas Project. Categorical comparisons oversimplified quantitative data and correctly measured the sign of change for fewer than 56% of the hypothetical ranges. Sub-sampling methods correctly estimated the sign of change for up to 78% of the hypothetical ranges, but it is essential to balance data removal with a reduction of false range expansions. The best measure of hypothetical range change was a mathematical correction factor, which achieved 83% accuracy in detecting the correct sign of change and 50% for the magnitude of change. According to this method, 68 (60.2%) South African frog species are likely to have undergone range contractions. The careful use of methods such as those assessed here allows for ad hoc data collections and biological surveys to be valuable in quantifying species range change, and hence for identifying potentially declining species.

Speciation in tropical seas: Allopatry followed by range change

We investigated whether present distribution ranges in marine organisms are reliable indicators of the geographic pattern of past speciation events by assessing the level of geographic overlap (sympatric index) as a function of node age in four phylogenies of tropical marine species groups. The analyses led to remarkably similar results among the four groups examined with (1) most nodes associated with a sympatry index of either 0 (allopatry) or 1 (entire overlap) and (2) statistical support that sister species have an allopatric distribution significantly more frequently than sister clades (i.e. groups of species). Species divergences were expressed on a time scale and very similar times were needed for species range overlap to occur since sharp transitions from allopatry to sympatry occurred around 4Ma in all groups. Present results supports that species range changes were not random as previous simulations results supports that species range probably evolve through occasional shifts of large amplitude. In front of the time needed for species range overlapping, our study suggests that species interaction and competitive exclusion can no longer be excluded as a driver of marine species distribution.

The use of historical collections to estimate population trends: A case study using Swedish longhorn beetles (Coleoptera: Cerambycidae)

Long term data to estimate population trends among species are generally lacking. However, Natural History Collections (NHCs) can provide such information, but may suffer from biases due to varying sampling effort. To analyze population trends and range–abundance dynamics of Swedish longhorn beetles (Coleoptera: Cerambycidae), we used collections of 108 species stretching over 100 years. We controlled for varying sampling effort by using the total number of database records as a reference for non-red-listed species. Because the general frequency of red-listed species increased over time, a separate estimate of sampling effort was used for that group. We observed large interspecific variation in population changes, from declines of 60% to several hundred percent increases. Most species showed stable or increasing ranges, whereas few seemed to decline in range. Among increasing species, rare species seemed to expand their range more than common species did, but this pattern was not observed in declining species. Historically, rare species did not seem to be at larger risk of local extinction, and population declines were mostly due to lower population density and not loss of sub-populations. We also evaluated the species’ declines under IUCN red-list criterion A, and four currently not red-listed species meet the suggested threshold for Near Threatened (NT). The results also suggested that species’ declines may be overlooked if estimated only from changes in species range.

Uncertainty in ensemble forecasting of species distribution

AbstractSpecies distribution modelling has been widely applied in order to assess the potential impacts of climate change on biodiversity. Many methodological decisions, taken during the modelling process and forecasts, may, however, lead to a large variability in the assessment of future impacts. Using measures of species range change and turnover, the potential impacts of climate change on French stream fish species and assemblages were evaluated. Our main focus was to quantify the uncertainty in the projections of these impacts arising from four sources of uncertainty: initial datasets (Data), statistical methods [species distribution models (SDM)], general circulation models (GCM), and gas emission scenarios (GES). Several modalities of the aforementioned uncertainty sources were combined in an ensemble forecasting framework resulting in 8400 different projections. The variance explained by each source was then extracted from this whole ensemble of projections. Overall, SDM contributed to the largest variation in projections, followed by GCM, whose contribution increased over time equalling almost the proportion of variance explained by SDM in 2080. Data and GES had little influence on the variability in projections. Future projections of range change were more consistent for species with a large geographical extent (i.e., distribution along latitudinal or stream gradients) or with restricted environmental requirements (i.e., small thermal or elevation ranges). Variability in projections of turnover was spatially structured at the scale of France, indicating that certain particular geographical areas should be considered with care when projecting the potential impacts of climate change. The results of this study, therefore, emphasized that particular attention should be paid to the use of predictions ensembles resulting from the application of several statistical methods and climate models. Moreover, forecasted impacts of climate change should always be provided with an assessment of their uncertainty, so that management and conservation decisions can be taken in the full knowledge of their reliability.

Eight years of entomological surveillance in Italy show no evidence ofCulicoides imicolageographical range expansion

Summary1.Assessing changes in species range is based on identifying new occurrences in areas where absence has been inferred due to lack of previous records. This technique depends on creating a consistent observational dataset, based on comparable detection methods.2.In Mediterranean countries, the midgeCulicoides imicolais the principal vector of bluetongue virus (BTV) that causes an infectious disease of domestic and wild ruminants. Over the last 10 years, BTV has invaded Mediterranean countries (1998) and much of Northern Europe (2006); this unprecedented spread is reported to be a possible consequence of climate change. In southern Europe, based on recent observations found in northern latitudes, BTV spread has been attributed in part to changes inC. imicoladistribution. However, current sampling ofCulicoidesspp. is far more intensive and targeted than that undertaken before the first BTV epidemics; this obviously results in new information from areas in which collections would have had little chance of positive identification in the past.3.Since 2001, a national surveillance programme based on permanent traps was established in Italy to followC. imicolapopulation dynamics in space and time. Based on data from 2000 to 2001 cross‐sectional studies, Italy was divided into three zones (I: endemicity; II: transition; III: absence) in which longitudinal data onC. imicolapresence and abundance were analysed as a function of time between 2002 and 2007 through linear and quantile regressions.4.The results from the surveillance programme demonstrate no detectable range expansion of theC. imicolapopulation in Italy between 2002 and 2007.5.Synthesis and applications. This study provides strong evidence that there has been no measurable range expansion between 2002 and 2007 in a species previously described as moving northwards as a result of climate change. For any reliable conclusions to be drawn on the range distribution ofC. imicolaor other similar vector species in Southern Europe,theCulicoidessurveillance system across all European countries should be designed to provide comparable data based on a constant detection probability over time.

Animal temperature limits and ecological relevance: Effects of size, activity and rates of change

1. Climate change is affecting species distributions and will increasingly do so. However, current understanding of which individuals and species are most likely to survive and why is poor. Knowledge of assemblage or community level effects is limited and the balance of mechanisms that are important over different time-scales is poorly described. Laboratory experiments on marine animals predominantly employ rates of change 10-100 000 times faster than climate induced oceanic warming. To address this failure we investigated differences in individual and species abilities to tolerate warming, and also how rate of warming affected survival. 2. This study identifies community level effects of thermal biology by applying a multi-species, multi-trophic level approach to the analysis of temperature limits. 3. Within species analyses of 14 species from 6 phyla showed smaller individuals survived to higher temperatures than large animals when temperatures were raised acutely. If this trend continues at slower warming rates, the early loss of larger individuals has marked consequences at the population level as larger individuals form the major reproductive component. 4. Between species comparisons showed active species survived to higher temperatures than sessile or low activity groups. Thus active groups (e.g. predators) and juvenile or immature individuals should fare better in rapid warming scenarios. This would be expected to produce short-term ecological imbalances in warming events. 5. The rate of warming markedly affected temperature limits in a wide range of Antarctic marine species. Different species survived to temperatures of 8.3-17.6 degrees C when temperatures were raised by around 1 degrees C day(-1). However they only survived to temperatures between 4.0 degrees C and 12.3 degrees C when temperatures were raised by around 1-2 degrees C week(-1), and temperatures of only 1.0-6.0 degrees C were tolerated for acclimations over periods of months. 6. Current models predicting range changes of species in response to climate change are either correlative or mechanistic. Mechanistic models offer the potential to incorporate the ecophysiological adaptation and evolutionary processes which determine future responses and go beyond simple correlative approaches. These models depend on the incorporation of data on species capacities to resist and adapt to change. This study is an important step in the provision of such data from experimental manipulations.

Flowering range changes across an elevation gradient in response to warming summer temperatures

AbstractMany studies have demonstrated plant response to warming temperatures, both as advancement in the timing of phenological events and in range shifts. Mountain gradients are ideal laboratories for studying species range changes. In this study of 363 plant species in bloom collected in five segments across a 1200 m (4158 ft) elevation gradient, we look for changes in species flowering ranges over a 20‐year period. Ninety‐three species (25.6%) exhibited a significant change in the elevation at which they flowered from the first half to the second half of the record, with many of these changes occurring at higher elevations. Most of the species exhibiting the changes were perennial plants. Interestingly, though many changes in flowering range were specific to higher elevations, range changes occurred all across the gradient. The changes reported in this study are concurrent with significant increases in summer temperatures across the region and are consistent with observed changes around the globe.

Animal temperature limits and ecological relevance: effects of size, activity and rates of change

Summary 1Climate change is affecting species distributions and will increasingly do so. However, current understanding of which individuals and species are most likely to survive and why is poor. Knowledge of assemblage or community level effects is limited and the balance of mechanisms that are important over different time-scales is poorly described. Laboratory experiments on marine animals predominantly employ rates of change 10–100 000 times faster than climate induced oceanic warming. To address this failure we investigated differences in individual and species abilities to tolerate warming, and also how rate of warming affected survival. 2This study identifies community level effects of thermal biology by applying a multi-species, multi-trophic level approach to the analysis of temperature limits. 3Within species analyses of 14 species from 6 phyla showed smaller individuals survived to higher temperatures than large animals when temperatures were raised acutely. If this trend continues at slower warming rates, the early loss of larger individuals has marked consequences at the population level as larger individuals form the major reproductive component. 4Between species comparisons showed active species survived to higher temperatures than sessile or low activity groups. Thus active groups (e.g. predators) and juvenile or immature individuals should fare better in rapid warming scenarios. This would be expected to produce short-term ecological imbalances in warming events. 5The rate of warming markedly affected temperature limits in a wide range of Antarctic marine species. Different species survived to temperatures of 8·3–17·6 °C when temperatures were raised by around 1 °C day−1. However they only survived to temperatures between 4·0 °C and 12·3 °C when temperatures were raised by around 1–2 °C week−1, and temperatures of only 1·0–6·0 °C were tolerated for acclimations over periods of months. 6Current models predicting range changes of species in response to climate change are either correlative or mechanistic. Mechanistic models offer the potential to incorporate the ecophysiological adaptation and evolutionary processes which determine future responses and go beyond simple correlative approaches. These models depend on the incorporation of data on species capacities to resist and adapt to change. This study is an important step in the provision of such data from experimental manipulations.

The Distribution and Conservation Status of Amphibians in Dobrudja (Romania)

The distribution of amphibian species in Dobrudja has been studied for more than a century; however, the available information was scattered among tens of publications and museum collections. In the present paper we synthesized the available distribution records from published papers, museum collections, and our own field data. These distribution data were treated separately as historical data (before 1990), continuous data (records from both before and after 1990), and recent ones (after 1990). Based on distribution records we performed a cartographic analysis consisting of 3 indexes that attempt to indicate shifts in geographic range over time. Using these indexes as a measure of the conservation status, we propose a Red List for the amphibians of Dobrudja based on the distribution data and the changes in species range before and after 1990.

Climate and the range dynamics of species with imperfect detection.

Reliable predictions for species range changes require a mechanistic understanding of range dynamics in relation to environmental variation. One obstacle is that most current models are static and confound occurrence with the probability of detecting a species if it occurs at a site. Here we draw attention to recently developed occupancy models, which can be used to examine colonization and local extinction or changes in occupancy over time. These models further account for detection probabilities, which are likely to vary spatially and temporally in many datasets. Occupancy models require repeated presence/absence surveys, for example checklists used in bird atlas projects. As an example, we examine the recent range expansion of hadeda ibises (Bostrychia hagedash) in South African protected areas. Colonization exceeded local extinction in most biomes, and the probability of occurrence was related to local climate. Extensions of the basic occupancy models can estimate abundance or species richness. Occupancy models are an appealing additional tool for studying species' responses to global change.

Niche properties and geographical extent as predictors of species sensitivity to climate change

ABSTRACTAim Bioclimatic envelope models are often used to make projections of species’ potential responses to climate change. It can be hypothesized that species with different kinds of distributions in environmental niche and geographical space may respond differently to changes in climate. Here, we compare projections of shifts in species ranges with simple descriptors of species niche (position and breadth) and geographical (range size) distributions.Location Europe.Methods The future distribution for 1200 European plant species were predicted by niche‐based models using seven climate variables known to have an important role in limiting plant species distributions. Ecological niche properties were estimated using a multivariate analysis. Species range changes were then related to species niche properties using generalized linear models.Results Generally, percentage of remaining suitable habitat in the future increased linearly with niche position and breadth. Increases in potential suitable habitat were associated with greater range size, and had a hump‐shaped relationship with niche position on temperature gradient. By relating species chorotypes to percentage of remaining or gained habitat, we highlighted biogeographical patterns of species sensitivity to climate change. These were clearly related to the degree of exposure according to regional patterns of projected climate change.Main conclusion This study highlights general patterns about the relationships between sensitivity of species to climate change and their ecological properties. There is a strong convergence between simple inferences based on ecological characteristics of species and projections by bioclimatic ‘envelope’ models, confirming macroecological assumptions about species sensitivity based on niche properties. These patterns appear to be most strongly driven by the exposure of species to climate change, with additional effects of species niche characteristics. We conclude that simple species niche properties are powerful indicators of species’ sensitivity to climate change.

Vulnerability of South African animal taxa to climate change

AbstractThe responsiveness of South African fauna to climate change events is poorly documented and not routinely incorporated into regional conservation planning. We model the likely range alterations of a representative suite of 179 animal species to climate change brought about by the doubling of CO2concentrations. This scenario is expected to cause a mean temperature increase of 2 °C. We applied a multivariate climate envelope approach and evaluated model performance using the most comprehensive bird data set. The results were encouraging, although model performance was inconsistent in the eastern coastal area of the country. The levels of climate change induced impacts on species ranges varied from little impact to local extinction. Some 17% of species expanded their ranges, 78% displayed range contraction (4–98%), 3% showed no response and 2% became locally extinct. The majority of range shifts (41%) were in an easterly direction, reflecting the east–west aridity gradient across the country. Species losses were highest in the west. Substantially smaller westward shifts were present in some eastern species. This may reflect a response to the strong altitudinal gradient in this region, or may be a model artifact. Species range change (composite measure reflecting range contraction and displacement) identified selected species that could act as climate change indicator taxa. Red‐data and vulnerable species showed similar responses but were more likely to display range change (58% vs. 43% for all species). Predictions suggest that the flagship, Kruger National Park conservation area may loose up to 66% of the species included in this analysis. This highlights the extent of the predicted range shifts, and indicates why conflicts between conservation and other land uses are likely to escalate under conditions of climate change.

Effects of dispersal, population delays, and forest fragmentation on tree migration rates

Examining the relation between the dispersal of seeds across landscapes and the migration of species can inform studies of processes such as invasions and response to climatic change. In this research a spatially explicit model is used to analyze the effects of dispersal probability, limits on establishment, generation time, seed crop probability, and varying proportions and patterns of landscape fragmentation on migration rate. Comparisons are made with rates inferred for migrations based on isopols of species range changes in the Holocene (20–200 km/century). The effects of the parameters on migration rate in the model are additive. Dispersal probability, related to diaspore type, is the most influential factor. Limits on establishment show effects only if severe. Lower seed crop probabilities can slow migration slightly. Generation times of 10 to 40 yr reduce migration rate moderately, while generations set long enough to reflect population doubling times would slow migration greatly. Extensive fine-scale fragmentation slows migration more than a single large barrier, but not greatly; multiple large barriers have greater effects. The factors have their greatest absolute and relative effects at higher dispersal probabilities; this result indicates that combinations of low dispersal probability and slow population development could increase the differences in migration rate among species while fragmentation could reduce these differences.

Coastal insect herbivore communities are affected more by local environmental conditions than by plant genotype

Abstract. 1 We compared the effects of plant genotype and local environment on population densities of a community of coastal insect herbivores in west-central Florida. Reciprocal transplants of four genotypes of three species of coastal plants, Borrichia frutescens, Iva frutescens and Limbricata, were made in July 1992 between a series of off-shore islands. 2 For each plant species, phytophagous insects with a wide range of feeding modes including gall-makers, stem borers, leaf miners and sap suckers were affected more by local environment than by plant genotype. Whereas host genotype had a significant effect on the population densities of gall-makers on B.frutescens in the spring of 1993, no significant effect on the denrities of any other insect species was found and the effect on the gall-makers on Borrichia disappeared in the summer, 1 year after the transplants had been made. In our study, local environment had by far the greatest effect on insect population densities among islands. This is an unusual result because in other studies over 80% of the insect species examined have been affected by plant genotype (Karban, 1992). This result is consistent with that reported by Stiling (1994), who censused populations of two phytophagous insects on reciprocal transplantr ot Borrichia in north Florida. 3 Local environment also had an effect on insect population densities within islands. This result contrasts with similar studies performed in north Florida (Stiling, 1994), where population densities did not differ within areas, and underlies how some biotic processes may change with in the same community even over relatively small changes in species range.