Potential impacts of climatic change on the breeding and non-breeding ranges and migration distance of European Sylvia warblers

Aim  To explore the potential impacts of climatic change on species with different migratory strategies using Sylvia warblers breeding in Europe as a ‘model’ species group. Location  Europe and Africa. Methods  Climate response surfaces and generalized additive models (GAMs) were used to model relationships between species recorded breeding and non‐breeding ranges and recent climate. Species potential future breeding and non‐breeding ranges were simulated for three scenarios of late 21st‐century climate. The simulated potential future and present ranges were compared in terms of their relative extent and overlap, as well as their location. The impact of any shifts in potential range location on migration distance were quantified. Results  Potential breeding ranges consistently showed a shift northwards, whereas potential non‐breeding ranges showed no consistent directional shift, even when trans‐Saharan migrants were considered separately from resident/short‐distance or partial migrants. Future potential range extent relative to simulated recent range extent varied considerably among species, although on average range extent increased. Overlap between future and recent simulated range was generally low, averaging < 36% for both breeding and non‐breeding ranges. Overlap was consistently less for range‐restricted than for widespread species. Migration distance increased generally, by about twice as much in the case of trans‐Saharan migrant species than for short‐distance migrants. In many cases potential future non‐breeding areas were simulated in regions far from the species present non‐breeding area, suggesting that new migration strategies and routes may need to be developed in response to climatic change. Main conclusions  Migratory species can be expected to suffer greater negative impacts from climatic change than species that are resident or undertake only short‐distance or partial migrations. Trans‐Saharan migrants face the greatest potential increases in migration distances, whereas range‐restricted species are expected to experience major population reductions because of the limited, or in some cases lack of, overlap between their present and potential future ranges.     

Disparity in elevational shifts of European trees in response to recent climate warming

Predicting climate‐driven changes in plant distribution is crucial for biodiversity conservation and management under recent climate change. Climate warming is expected to induce movement of species upslope and towards higher latitudes. However, the mechanisms and physiological processes behind the altitudinal and latitudinal distribution range of a tree species are complex and depend on each tree species features and vary over ontogenetic stages. We investigated the altitudinal distribution differences between juvenile and adult individuals of seven major European tree species along elevational transects covering a wide latitudinal range from southern Spain (37°N) to northern Sweden (67°N). By comparing juvenile and adult distributions (shifts on the optimum position and the range limits) we assessed the response of species to present climate conditions in relation to previous conditions that prevailed when adults were established. Mean temperature increased by 0.86 °C on average at our sites during the last decade compared with previous 30‐year period. Only one of the species studied, Abies alba, matched the expected predictions under the observed warming, with a maximum abundance of juveniles at higher altitudes than adults. Three species, Fagus sylvatica, Picea abies and Pinus sylvestris, showed an opposite pattern while for other three species, such as Quercus ilex, Acer pseudoplatanus and Q. petraea, we were no able to detect changes in distribution. These findings are in contrast with theoretical predictions and show that tree responses to climate change are complex and are obscured not only by other environmental factors but also by internal processes related to ontogeny and demography.     

Co‐occurrence patterns of trees along macro‐climatic gradients and their potential influence on the present and future distribution of Fagus sylvatica L.

Aim During recent and future climate change, shifts in large‐scale species ranges are expected due to the hypothesized major role of climatic factors in regulating species distributions. The stress‐gradient hypothesis suggests that biotic interactions may act as major constraints on species distributions under more favourable growing conditions, while climatic constraints may dominate under unfavourable conditions. We tested this hypothesis for one focal tree species having three major competitors using broad‐scale environmental data. We evaluated the variation of species co‐occurrence patterns in climate space and estimated the influence of these patterns on the distribution of the focal species for current and projected future climates. Location Europe. Methods We used ICP Forest Level 1 data as well as climatic, topographic and edaphic variables. First, correlations between the relative abundance of European beech (Fagus sylvatica) and three major competitor species (Picea abies, Pinus sylvestris and Quercus robur) were analysed in environmental space, and then projected to geographic space. Second, a sensitivity analysis was performed using generalized additive models (GAM) to evaluate where and how much the predicted F. sylvatica distribution varied under current and future climates if potential competitor species were included or excluded. We evaluated if these areas coincide with current species co‐occurrence patterns. Results Correlation analyses supported the stress‐gradient hypothesis: towards favourable growing conditions of F. sylvatica, its abundance was strongly linked to the abundance of its competitors, while this link weakened towards unfavourable growing conditions, with stronger correlations in the south and at low elevations than in the north and at high elevations. The sensitivity analysis showed a potential spatial segregation of species with changing climate and a pronounced shift of zones where co‐occurrence patterns may play a major role. Main conclusions Our results demonstrate the importance of species co‐occurrence patterns for calibrating improved species distribution models for use in projections of climate effects. The correlation approach is able to localize European areas where inclusion of biotic predictors is effective. The climate‐induced spatial segregation of the major tree species could have ecological and economic consequences.     

How climate,migration ability and habitat fragmentation affect the projected future distribution of European beech

Recent efforts to incorporate migration processes into species distribution models (SDMs) are allowing assessments of whether species are likely to be able to track their future climate optimum and the possible causes of failing to do so. Here, we projected the range shift of European beech over the 21st century using a process‐based SDM coupled to a phenomenological migration model accounting for population dynamics, according to two climate change scenarios and one land use change scenario. Our model predicts that the climatically suitable habitat for European beech will shift north‐eastward and upward mainly because (i) higher temperature and precipitation, at the northern range margins, will increase survival and fruit maturation success, while (ii) lower precipitations and higher winter temperature, at the southern range margins, will increase drought mortality and prevent bud dormancy breaking. Beech colonization rate of newly climatically suitable habitats in 2100 is projected to be very low (1–2% of the newly suitable habitats colonised). Unexpectedly, the projected realized contraction rate was higher than the projected potential contraction rate. As a result, the realized distribution of beech is projected to strongly contract by 2100 (by 36–61%) mainly due to a substantial increase in climate variability after 2050, which generates local extinctions, even at the core of the distribution, the frequency of which prevents beech recolonization during more favourable years. Although European beech will be able to persist in some parts of the trailing edge of its distribution, the combined effects of climate and land use changes, limited migration ability, and a slow life‐history are likely to increase its threat status in the near future.     

Multiscale modelling of the drivers of rainforest boundary dynamics in Kakadu National Park, northern Australia

Understanding the relative importance of factors driving savanna–forest dynamics is vital as changes in the extent of tropical forests can have major impacts on global climate and carbon balance, biodiversity, and human well-being. Comparison of aerial photographs for 50 rainforest patches in Kakadu National Park had previously revealed a landscape wide expansion of rainforest boundaries between 1964 and 2004. Here, we used generalized linear and mixed effects models to assess the role of fire, buffalo impact, and patch characteristics in determining the rate of boundary change. The analysis was conducted at both the patch scale, and within-patch (plot) scale, to capture the different processes operating. At the patch scale, the rate of change was best explained by rainforest type and historical buffalo impact. Fire activity, patch size, and fragmentation were not important predictors of the rate of change. At the plot scale, distance from rainforest edge was the most important predictor of the probability of change, while the fragmentation and aspect of the boundary were unimportant. Rainforest expansion has occurred through a process of margin extension rather than eruption of new patches. The rainforest expansion is consistent with having been driven primarily by shifts in global change phenomena, such as increased rainfall and atmospheric CO₂, rather than changes in disturbance regime. It appears that the current fire regimes are not sufficiently destructive to limit the overall expansion of the rainforest patches. Rainforest type and historical buffalo impact have mediated the rate of change at the patch scale.     

Climate change impacts on tree ranges: model intercomparison facilitates understanding and quantification of uncertainty

Model-based projections of shifts in tree species range due to climate change are becoming an important decision support tool for forest management. However, poorly evaluated sources of uncertainty require more scrutiny before relying heavily on models for decision-making. We evaluated uncertainty arising from differences in model formulations of tree response to climate change based on a rigorous intercomparison of projections of tree distributions in France. We compared eight models ranging from niche-based to process-based models. On average, models project large range contractions of temperate tree species in lowlands due to climate change. There was substantial disagreement between models for temperate broadleaf deciduous tree species, but differences in the capacity of models to account for rising CO(2) impacts explained much of the disagreement. There was good quantitative agreement among models concerning the range contractions for Scots pine. For the dominant Mediterranean tree species, Holm oak, all models foresee substantial range expansion.     

Indiana bat summer maternity distribution: effects of current and future climates

Temperate zone bats may be more sensitive to climate change than other groups of mammals because many aspects of their ecology are closely linked to temperature. However, few studies have tried to predict the responses of bats to climate change. The Indiana bat (Myotis sodalis) is a federally listed endangered species that is found in the eastern United States. The northerly distribution of Indiana bat summer maternity colonies relative to their winter distributions suggests that warmer climates may result in a shift in their summer distribution. Our objectives were to determine the climatic factors associated with Indiana bat maternity range and forecast changes in the amount and distribution of the range under future climates. We used Maxent to model the suitable climatic habitat of Indiana bats under current conditions and four future climate forecasts for 2021–30, 2031–40, 2041–50, and 2051–60. Average maximum temperature across the maternity season (May–August) was the most important variable in the model of current distribution of Indiana bat maternity colonies with suitability decreasing considerably above 28ºC. The areal extent of the summer maternity distribution of Indiana bats was forecasted to decline and be concentrated in the northeastern United States and Appalachian Mountains; the western part of the current maternity range (Missouri, Iowa, Illinois, Kentucky, Indiana, and Ohio) was forecasted to become climatically unsuitable under most future climates. Our models suggest that high temperatures may be a factor in roost‐site selection at the regional scale and in the future, may also be an important variable at the microhabitat scale. When behavioral changes fail to mitigate the effects of high temperature, range shifts are likely to occur. Thus, habitat management for Indiana bat maternity colonies in the northeastern United States and Appalachian Mountains of the Southeast is critical as these areas will most likely serve as climatic refugia.     

Climate change and the future distributions of aquatic macrophytes across boreal catchments

Aim Aquatic–terrestrial ecotones are vulnerable to climate change, and degradation of the emergent aquatic macrophyte zone would have severe ecological consequences for freshwater, wetland and terrestrial ecosystems. Our aim was to uncover future changes in boreal emergent aquatic macrophyte zones by modelling the occurrence and percentage cover of emergent aquatic vegetation under different climate scenarios in Finland by the 2050s. Location Finland, northern Europe. Methods Data derived from different GIS sources were used to estimate future emergent aquatic macrophyte distributions in all catchments in Finland (848 in total). We used generalized additive models (GAM) with a full stepwise selection algorithm and Akaike information criterion to explore the main environmental determinates (climate and geomorphology) of emergent aquatic macrophyte distributions, which were derived from the national subclass of CORINE land‐cover classification. The accuracy of the distribution models (GAMs) was cross‐validated, using percentage of explained deviance and the area under the curve derived from the receiver‐operating characteristic plots. Results Our results indicated that emergent aquatic macrophytes will expand their distributions northwards from the current catchments and percentage cover will increase in all of the catchments in all climate scenarios. Growing degree‐days was the primary determinant affecting distributions of emergent aquatic macrophytes. Inclusion of geomorphological variables clearly improved model performance in both model exercises compared with pure climate variables. Main conclusions Emergent aquatic macrophyte distributions will expand due to climate change. Many emergent aquatic plant species have already expanded their distributions during the past decades, and this process will continue in the years 2051–80. Emergent aquatic macrophytes pose an increasing overgrowth risk for sensitive macrophyte species in boreal freshwater ecosystems, which should be acknowledged in management and conservation actions. We conclude that predictions based on GIS data can provide useful ‘first‐filter’ estimates of changes in aquatic–terrestrial ecotones.     

森林植被中优势种的形成和分布规律及其应用

一森林多是天然植被(人工林除外),它经历了千百年的演化,在改造环境和适应环境过程中,形成了物种与外界环境的高度吻合,最后形成了多种稳定的森林植被类型,因而研究森林植被中优势种的形成和分布规律,较之农田生态系统等人工植被具有更多的便利条件。森林树种的分布遵循着一定的规律,搞清     

Climate change and rates of vagrancy of Siberian bird species to Europe

To assess whether increasing numbers of Siberian vagrants observed in Europe in recent autumns can be linked to climate change, we predicted changes in the climatic suitability of the breeding ranges of 46 Siberian bird species known to show vagrancy to Europe and compared these predictions with observed changes in recorded rates of autumn vagrancy across eight European countries during the last three decades. There was a positive correlation between predicted increase in breeding range and vagrancy rates. A positive impact of climate change on range and population size could promote vagrancy, while the increasing use of such alternative migration flyways could provide adaptive advantages in a changing environment.     

Post‐glacial migration lag restricts range filling of plants in the European Alps

Aim To evaluate the effect of post‐glacial migration lags on the current distribution of Alpine plants and the factors responsible for possible range‐filling differences among species. Location Austrian Alps. Methods We used species distribution models to predict environmentally suitable sites for 183 Alpine plants at a fine spatial resolution (100 × 100 m²). We overlaid these predictions with independent mapping data (3′× 5′) and calculated the extent to which species fill their potential ranges at this coarser grain based on several different approaches. Moreover, we correlated range‐filling estimates with the magnitude of improvement of distribution models when using the distance to putative glacial refugia as an additional independent variable. Finally, we compared species‐specific range‐filling estimates with traits related to dispersal capacity and competitive ability of these species as well as with characteristics of their habitats. Results Even under a conservative approach, incomplete range filling appears common, with 46% and 31% of the species studied occurring in less than 75% and 50% of their predicted suitable ranges, respectively. Proximity to glacial refugia generally accounts for a lower percentage of the deviance in species distribution data (0–20%, mean 4%) than environmental variables (9–57%, mean 27%). However, its importance correlates closely and negatively with the calculated range‐filling estimates. Range filling significantly increases with the dispersal capacity of a species' propagules and the breadth of its altitudinal niche. Calcicolous species have lower range filling than silicicolous plants and substrate generalists. Conclusions Our results suggest that the current ranges of many Alpine plants are still shaped by delayed Holocene recolonization of suitable sites. Hence, long‐term migration lags also affect plant distribution in mountainous areas, at least on regional scales. These findings question whether high mountain floras will be able to track the expected rapid, climate change driven shifts in habitat.     

Analysis of character divergence along environmental gradients and other covariates

Character displacement is typically identified by comparing phenotypic differences in sympatry and allopatry. Recently, however, Goldberg and Lande (2006) pointed out that when phenotypic characters vary along an environmental gradient, the standard approach may fail to identify sympatric character divergence. Here we present a general analytical procedure for identifying sympatric character divergence while accounting for phenotypic changes that covary with environmental variables. Our approach uses residual randomization from a generalized linear model, and allows the statistical comparison of sympatric phenotypic divergence to allopatric phenotypic divergence while accounting for phenotypic variation along a gradient. Through simulation we demonstrate that our approach correctly identifies patterns of sympatric character divergence when they are present, and does not identify such patterns when they are not. Our analytical approach complements and extends the suggestions of Goldberg and Lande (2006), by allowing a full statistical assessment of the varied patterns of character displacement along environmental gradients, or while accounting for other covariates and sources of variation.     

Ecological niche modelling of montane mammals in the Great Basin, North America: examining past and present connectivity of species across basins and ranges

Aim The goal of this study was to determine the extent of suitable habitats across the basins and ranges of the Great Basin for 13 montane mammals in the present and during the Last Glacial Maximum (LGM). For all these mammal species, we test whether: (1) more suitable habitat was available in basin areas during the LGM; (2) suitable habitat shifted upwards in elevation between the LGM and the present; (3) more ranges have suitable habitat than are currently occupied; and (4) these species are currently restricted to suitable habitats at higher‐elevation range areas. We also examine whether and how much distributional response varies among these montane mammal species. Location The Great Basin of western North America. Methods We re‐examine the past and present distributions of 13 Great Basin montane mammals using ecological niche modelling techniques that utilize now widely available species occurrence data and new, fine‐scale past climatological GIS layers in the present and at the LGM. These methods provide an objective, repeatable means for visual comparison of past and present modelled distributions for species examined in previous biogeographical studies. Results Our results indicate greater areal and lower elevational suitable habitat in the LGM than at present for nearly all montane mammals, and that there is more suitable habitat at present than is currently occupied. Our results also show that lowland areas provide suitable dispersal routes between ranges for most of the montane mammals both at the LGM and at present. However, three of the 13 species have little to no predicted suitable habitat in the LGM near currently occupied ranges, in contrast to the pattern for the other 10. For these species, the model results support more recent long‐distance colonization. Main conclusions Our finding of suitable lowland dispersal routes in the present for most species supports and greatly extends similar findings from single‐species studies. Our results also provide a visually striking confirmation that changes in species distribution and colonization histories of Great Basin montane mammals vary in a fashion related to the tolerances and requirements of each of these species; this has previously been hypothesized but not rigorously tested for multiple montane mammals in the region.     

Climate change,genetic markers and species distribution modelling

Ecologists and biogeographers are currently expending great effort forecasting shifts in species geographical ranges that may result from climate change. However, these efforts are problematic because they have mostly relied on presence‐only data that ignore within‐species genetic diversity. Technological advances in high‐throughput sequencing have now made it cost‐effective to survey the genetic structure of populations sampled throughout the range of a species. These data can be used to delineate two or more genetic clusters within the species range, and to identify admixtures of individuals within genetic clusters that reflect different patterns of ancestry. Species distribution models (SDMs) applied to the presence and absence of genetic clusters should provide more realistic forecasts of geographical range shifts that take account of genetic variability. High‐throughput sequencing and spatially explicit models may be used to further refine these projections.