A Stochastic Dynamic Methodology (StDM) to simulate the effects of fire on vegetation and bird communities in Pinus pinaster stands

Worldwide forests have been impacted by broad-scale anthropogenic pressures, such as fire and logging, leading to the disruption of the structure and functioning of these systems. The present paper examined the applicability of a holistic Stochastic Dynamic Methodology (StDM) in predicting the tendencies of passerine bird communities in maritime pine (Pinus pinaster) stands as a response to the changes induced by fire occurrence. The StDM is a sequential modelling process developed in order to predict the ecological status of changed ecosystems, from which management strategies can be designed. The case of the pine stands of central Portugal was used to test the StDM performance in the scope of the wildfire problems. The datasets used in the dynamic model construction included the main gradients of environmental and biological characteristics of the studied maritime pine stands over space and time. The ecological integrity of the pine stands can be partly assessed by the observation of the occurrence of passerine indicators. The dynamic model developed was preceded by a conventional multivariate statistical procedure performed to discriminate the significant relationships between conceptually isolated key-components of the studied ecosystems. The final model provided some basis to analyse the responses of selected passerine indicators to fire scenarios that characterize the region. In this context, the simulation results are encouraging since they seem to demonstrate the StDM reliability in capturing the passerine community dynamics by predicting the behavioural pattern of indicators roughly associated with their structural and functional composition and habitat main characteristics.     

Development of a stochastic dynamic model for ecological indicators’ prediction in changed Mediterranean agroecosystems of north-eastern Portugal

A holistic stochastic dynamic model was developed by focusing on the interactions between conceptually isolated key-components, such as local passerine guilds and changes in habitat conditions, in Mediterranean agroecosystems of the “Terra Quente Transmontana region” (north-eastern Portugal). The ecological integrity of the typical patchwork of this region, with respect to land use, can be partly assessed by the observation of the occurrence of passerine guilds. These important indicators and state variables are the underlying database of our model. This model aimed the prediction of the ecological changes which can be expected when olive orchards are being intensified. The model proposed was preceded by a conventional multivariate statistical procedure (stepwise multiple regression analysis) performed to discriminate the significant relationships between guild richness and environmental variables. Since this statistical analysis is static, the dataset recorded from the field included true gradients of habitat changes. The model parameters were estimated from the results of the stochastic treatment and from regional data regarding tendencies within the use of land. A period of 50 years was considered. The final model provided some basis to analyse the responses of passerine guilds to the environmental scenarios that will characterize the new agroecosystems of the region. The model simulations were incorporated into a Geographical Information System (GIS) approach. The results of the simulation revealed a structural drift within the different guild richness in response to the expected gradient of habitat changes. The possible local extinction of several species within the less well-represented guilds, such as the steppe passerine species, may be associated with a predictable reduction in ecological integrity of the typical agroecosystems. Therefore, a new structure of the passerine communities indicates that future agroecosystems will diverge from the initial or actual ecological state.     

Simulating the impact of socio-economic trends on threatened Iberian wolf populations Canis lupus signatus in north-eastern Portugal

The IP4 highway and the new projected road network have been changing the critical Iberian wolf (Canis lupus signatus) habitat in Trás-os-Montes e Alto Douro region (north-eastern Portugal). A holistic stochastic dynamic methodology (SDM) was developed for predicting changes in Iberian wolf population due to the new highways construction, increasing road traffic density and urbanization. The ecological indicators for wolf presence and abundance were estimated indirectly from the density of attacks on livestock. The low density of wild ungulates in the area makes livestock the main source of food for wolves. These indirect ecological indicators and state variables are the underlying database of our SDM model. This model focus on the interactions between conceptually isolated key-components, such as the density of attacks on livestock and changes in habitat conditions, providing some basis to analyse the responses of wolf populations to the environmental scenarios that will characterize the region in the future. The model proposed was preceded by a conventional multivariate statistical procedure (stepwise multiple regression analysis) performed to discriminate the significant relationships between livestock attacks and socio-environmental variables. The holistic parameters of the model were estimated from the results of the statistical treatment and from regional data regarding tendencies within the use of land. The simulation results demonstrate the SDM capability in capturing the trends of this changing region, namely by showing a dramatically decrease of wolf attacks in the region for the next decade.     

Diversity, ecological structure, and conservation of the landbird community of Dadia reserve, Greece

Birds are integral to many environmental monitoring schemes. However, there has been little research on the ecological basis of utilizing bird species as indicators of their respective communities and habitats. We used point counts to survey 72 landbird species, 16 of conservation concern, in the Dadia Nature Reserve, Greece, in order to understand the ecology of bird diversity patterns, analyse community composition, identify species characteristic of major vegetation types, and improve long-term management and monitoring protocols. We sampled 36 sites representing 21 vegetation types. Highly heterogeneous sites were the most species rich and rural mosaics (small fields and pastures of low intensity land use, separated by thick hedgerows and tree lines) were twice as rich as intensified crop monocultures. Using multivariate analysis, we found that vegetation cover and height affected the composition of the avifauna. Twenty-one predefined vegetation categories clustered into eight distinct bird habitat types: field crops, rural mosaics, mosaic sites, poplar trees, broadleaved woods, pinewoods, shrubs, and heaths. Ten bird species were highly characteristic of the main bird habitat types in the study area. Our results emphasize the importance of conserving rural mosaics, hedgerows, and openings within forests for landbird conservation in the Mediterranean countryside. We also provide evidence in support of maintaining horizontal heterogeneity at a local scale. Finally, we suggest that monitoring populations of certain indicator bird species can be a cost-effective and efficient way to monitor the state and habitat quality of the entire landbird community, thereby integrating the knowledge of community structure into conservation decision-making.     

Prediction of changes in the occurrence of forest herbs in hedgerow networks along a climate gradient in north-western Europe

Many herbaceous forest plant species are endangered and suffer from habitat loss and fragmentation, especially in agricultural landscapes. Hedgerow networks represent a forested habitat that may serve as a refuge for forest herbs, even though also hedges have recently been strongly reduced in number and size. It is yet disputed to which extent hedgerows offer a suitable environment for forest herbs and which environmental factors may affect the frequency of these species in hedgerows. To develop an effective conservation strategy for forest herbs in hedgerows on a larger spatial scale, we aimed to combine a set of ecological and life history traits for predicting the frequency of these species in a local data set. A literature data set was used to examine the regional differences in the species composition of forest herbs and environmental conditions in hedgerows along a climate gradient across north-western Europe. Contrary to our expectations, the chosen set of variables in combination had a lower ability of predicting the local frequency of forest herbs in hedgerows than the single variable light availability. An ordination of species lists in the literature data set showed pronounced regional differences in the species pools of forest herbs in hedgerows, the floristic gradient being closely related to climatic continentality. Hedgerows in more continental regions had lower proportions of chamaephytes and, according to an indicator species analysis, drier and less acid soils.     

Modelling the performance of bird surveys in non-standard weather conditions: General applications with special reference to mountain ecosystems

Although considerable effort has been made to identify the appropriate climatic conditions for bird surveys, considered as standard conditions, in many occasions these conditions are not fulfilled. These are for instance the case of environmental impact assessments (EIA), where the field work is, recurrently, carried out in variable and non-standard weather conditions or in the scope of general ecological monitoring (GEM) programs, where different taxa (birds and other animal groups) are sampled simultaneously with distinct methodological requirements. The present work examined the applicability of a stochastic dynamic methodology (StDM) for predicting the richness and diversity of passerine surveys in mountain habitats characterized by variable and, predominantly, non-standard weather conditions. The relative variations of these metrics are the underlying database of our StDM model, providing some basis to analyse the accuracy of bird surveys. This model focuses on the interactions between conceptually isolated key-components, such as the passerine richness and diversity, and the influence of the prevailing climatic conditions.The proposed model was preceded by a conventional multivariate statistical procedure performed to discriminate the significant relationships between the selected metrics versus climatic variables. Since this statistical analysis is static, the dataset recorded from the field included true gradients of weather conditions (ranging from standard to extreme conditions). The results of the StDM simulations revealed significant variations in the performance of passerine surveys in response to several combinations of non-standard weather conditions, which enable us to calculate the appropriated correction factors for discrete climatic scenarios. This could be used, in the future, to improve the quality of passerine diversity and richness estimates, namely in the scope of EIA studies when the climatic conditions are inevitably adverse for rigorous passerine surveys.     

A multi-scale looping approach to predict spatially dynamic patterns of functional species richness in changing landscapes

Land-use/land-cover (LU/LC) change is one of the main drivers of global biodiversity change. However, the lack of detailed data on species’ local distributions is frequently a major constraint to identify effective indicators of impact and to prescribe effective conservation and management measures. Here we aim to describe and demonstrate the applicability of a novel looping approach to predict spatially dynamic ecological responses to LU/LC changes. The methodology integrates statistical downscaling, multi-model inference, stochastic-dynamic modelling and simulations, and spatial projections under a common and interactive framework. We illustrate the approach with a study of passerine foraging groups and their potential indicator role under LU/LC change scenarios. Based on the coarse occurrence data from published atlases, this approach allowed transposing species richness to fine resolutions in order to assess regional ecological integrity by up scaling the local responses of those indicators again at the landscape level. Overall, our proposed framework was able to provide realistic patterns of passerine foraging responses to LU/LC changes, highlighting the usefulness of existing databases for model-based research in addressing complex emergent problems across scales. Comparative analysis between simulations and independent field data showed a promising model performance, with consistent projections of the local passerine functional composition for a significant number of point-counts tested. Our approach represents a contribution for more universal applications in the scope of conservation and landscape planning, especially when fine resolution data is difficult to obtain due to resources constraints.     

Modeling bird species distribution change in fire prone Mediterranean landscapes: incorporating species dispersal and landscape dynamics

Species distribution models (SDMs) have traditionally been founded on the assumption that species distributions are in equilibrium with environmental conditions and that these species–environment relationships can be used to estimate species responses to environmental changes. Insight into the validity of this assumption can be obtained from comparing the performance of correlative species distribution models with more complex hybrid approaches, i.e. correlative and process‐based models that explicitly include ecological processes, thereby accounting for mismatches between habitat suitability and species occupancy patterns. Here we compared the ability of correlative SDMs and hybrid models, which can accommodate non‐equilibrium situations arising from dispersal constraints, to reproduce the distribution dynamics of the ortolan bunting Emberiza hortulana in highly dynamic, early successional, fire driven Mediterranean landscapes. Whereas, habitat availability was derived from a correlative statistical SDM, occupancy was modeled using a hybrid approach combining a grid‐based, spatially‐explicit population model that explicitly included bird dispersal with the correlative model. We compared species occupancy patterns under the equilibrium assumption and different scenarios of species dispersal capabilities. To evaluate the predictive capability of the different models, we used independent species data collected in areas affected to different degree by fires. In accordance with the view that disturbance leads to a disparity between the suitable habitat and the occupancy patterns of the ortolan bunting, our results indicated that hybrid modeling approaches were superior to correlative models in predicting species spatial dynamics. Furthermore, hybrid models that incorporated short dispersal distances were more likely to reproduce the observed changes in ortolan bunting distribution patterns, suggesting that dispersal plays a key role in limiting the colonization of recently burnt areas. We conclude that SDMs used in a dynamic context can be significantly improved by using combined hybrid modeling approaches that explicitly account for interactions between key ecological constraints such as dispersal and habitat suitability that drive species response to environmental changes.     

The impact of soybean expansion on mammal and bird,in the Balsas region,north Brasilian Cerrado

In order to analyse the impact of land use change, it is particularly important to know how organisms use resources distributed across a heterogeneous landscape. The main objective of this study is to analyse the potential impact of land use change on bird and mammal fauna, by using a coupled model approach. The CLUE (Conversion of Land Use and its Effects) model has been applied to obtain the spatial pattern of land use change for a scenario with soybean expansion in the Cerrado of Maranhão State in Brazil. These land use change maps were used as the input for the LEDESS (Landscape Ecological Decision and Evaluation Support System) model to evaluate the impact of habitat fragmentation on mammal and bird species. The scenarios demonstrated that high quality habitat for all studied species will be lost in the future when current trends in agricultural expansion continue, but these changes will have species-specific impacts. The most relevant ecological impact under the explored scenarios was habitat fragmentation expressed by the increase the number of habitat clusters. The coupled model approach of LEDESS and CLUE made it possible to project the spatial impact of soybean expansion on habitat dynamics in the studied region. This model approach can help to design effective ecological infrastructure to facilitate species survival and to implement an effective habitat network in the Balsas region.     

The value of woody hedgerows for moth diversity on organic and conventional farms

Habitat destruction and degradation are important drivers of biodiversity loss within agro-ecosystems. However, little is known about the effect of farming practices and the value of woody hedgerows on Lepidoptera in North America. The purpose of this work was to study moth diversity in woody hedgerows and croplands of organic and conventional farms. In addition, the influence of vegetation composition and abiotic variables on species richness, abundance, and composition was examined. Moths were sampled with light traps during six weeks in the summer of 2001. Vegetation data and abiotic variables were obtained for all sites. In total, 26,020 individuals from 12 families and 408 species were captured. Most species were uncommon. Only 35 species included >100 individuals while for 71% of species <10 individuals were found. The Noctuidae represented 221 species and 85% of all individuals captured. Woody hedgerows harbored more species and in greater number than croplands. There was no significant difference in moth diversity between organic and conventional farms, except that the Notodontidae were significantly more species rich in organic than in conventional sites. Results show that species richness, abundance, and composition were greatly influenced by habitat types (hedgerow versus crop field) and abiotic variables (minimum temperature which was correlated to moon illumination, rainfall, and cloud cover). Moth species composition was significantly correlated to vegetation composition. This study broadens our understanding of the factors driving moth diversity and expands our knowledge of their geographic range. The maintenance of noncrop habitats such as woody hedgerows within agro-ecosystems seems paramount to preserving the biodiversity and abundance of many organisms, including moths.     

The winter distribution of seed-eating birds: habitat structure, seed density and seasonal depletion

To understand the reasons for population change we need to understand the mechanisms through which it occurs. Throughout western Europe there have been declines in farmland birds. These declines have been paralleled by major changes in agricultural management. Which have resulted in major changes in habitat structure. This paper describes the habitat selection at two scales (within and between fields) of a number of seed-eating farmland birds. Habitat preferences for most species were related to the density of seeds present. Which differed markedly between habitats. Seed density declined with distance from hedgerow in cultivated fields but not stubble fields. Yellow hammers were restricted to foraging close to hedgerows, whilst skylarks foraged in the centre of fields, but moved closer towards the edges as the winter progressed and seed densities declined. This work has clear consequences for agricultural management and the conservation of declining bird populations.     

The importance of key marginal habitat features for birds in farmland: an assessment of habitat preferences of Red-backed Shrikes Lanius collurio in the Italian Alps

Capsule Key marginal habitat features maintain their importance even when they occur at very low density.

Aims To assess the importance for breeding birds of key habitat elements, such as isolated shrubs, hedgerows and untilled vegetation patches.

Methods We investigated the habitat preferences of Red-backed Shrikes Lanius collurio in an agricultural environment where key habitat elements have been dramatically reduced. Based upon data from territorial maps, a fine-scale model of habitat preference was developed and the results of three different analytical approaches (binary logistic regression, multimodel inference and hierarchical partitioning) were compared.

Results The occurrence of Red-backed Shrikes was positively influenced by the extent of non-grazed/mown grassland, isolated bushes and hedgerows, and negatively influenced by woodland cover. The model highlighted the importance of bushes/hedgerows despite their very scarce occurrence in the study areas (overall, average cover only 7.94%). Breeding densities were rather low, but mean densities were slightly higher in pasture zones in which bushes/hedgerows availability was higher than elsewhere.

Conclusion These results confirm the crucial importance of these key marginal elements even in depauperated farmland landscapes. Maintaining and increasing their availability is a key management option for the encouragement of breeding Red-backed Shrikes, and potentially for other species which are also declining in these farmland habitats.     

Predicting the trends of vertebrate species richness as a response to wind farms installation in mountain ecosystems of northwest Portugal

The main objectives of this work were to examine the performance of a holistic stochastic dynamic methodology (StDM) in predicting the trends of the vertebrate species richness (amphibians, reptiles, birds and mammals) in response to changes induced by the ongoing wind farm installation in mountain areas of northwest Portugal. The StDM is a sequential modelling process developed in order to estimate the ecological status of changed ecosystems that have been damaged by anthropogenic disturbances. The performance of two complementary temporal approaches was tested, taking into account either annual or seasonal influences. The data used in the dynamic model construction included true gradients of environmental changes and was sampled from 2004 to 2006. The dynamic model developed was preceded by a conventional multivariate statistical procedure performed to discriminate the significant relationships between the selected ecological components, such as the species richness of each vertebrate group and the structural changes in habitat conditions. The results show the capacity of the model in capturing the dynamics of the studied system by predicting consistent trends for the global vertebrate species richness under complex and variable environmental scenarios. The average annual approach is considered sufficient for the aims of the most Environmental Impact Assessments while the seasonal approach is recommended for more detailed studies, namely regarding specific population, guilds or community dynamics.     

基于鸟类栖息地季节性变化的自然保护区动态分区管理——以安徽升金湖国家级自然保护区为例

鸟类栖息地会随着季节迁徙而改变,基于此对以珍稀濒危鸟类保护为主要目标的自然保护区进行动态分区管理,能够有效提高土地利用效率,协调生物多样性保护与其他生态系统服务功能利用。通过MaxEnt模型分析预测安徽升金湖国家级自然保护区鸟类繁殖季和越冬季的栖息地范围,并采用空间叠加分析方法得到动态分区方案。结果发现：繁殖季鸟类栖息地适宜性受到人口密度、丰水期土地利用类型、距居民点距离、距道路距离等环境因素的影响;越冬季鸟类受到距道路距离、人口密度、距枯水期水体距离、枯水期土地利用类型等环境因素的影响。运用ArcGIS水文工具分析出升金湖国家级自然保护区汇水单元作为其动态区划单元,根据鸟类栖息地季节性变化的特点结合分析结果叠加分析,将安徽升金湖国家级自然保护区划分为核心栖息地保护区、繁殖季栖息地保护区、越冬季栖息地保护区和一般控制区。核心栖息地保护区要进行全年严格保护,繁殖季栖息地保护区和越冬季栖息地保护区在相应鸟类栖息时段严格管控、非栖息时段可合理利用,一般控制区则全年可允许合理的行为活动。季节性动态分区方案注重解决安徽省升金湖国家级自然保护区生态环境保护和社区发展之间的矛盾问题,便于未来保护区生态保护规划决策的制定和实施,进一步丰富了以季节性栖息物种为主要保护对象的自然保护区的动态功能分区研究理论与方法体系,为制定提高自然保护区空间利用效率的生态管理策略提供了参考依据。综上,建议在升金湖国家级自然保护区生态环境保护和社区发展中,依据保护区季节性动态分区特征,实行分区管制,制定对应的生态环境保护和发展的措施。     

Strategic Grassland Bird Conservation throughout the Annual Cycle: Linking Policy Alternatives,Landowner Decisions,and Biological Population Outcomes

Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds.     

Functional homogenization of bird communities along habitat gradients: accounting for niche multidimensionality

Aim To test whether functional homogenization of bird communities is promoted by anthropogenic landscape transformation, using specialization and habitat preference indices that account for the multidimensionality of niches. Location Catalonia, north‐east Iberian Peninsula. Methods We used data on bird species occurrences and landscape features in 2834 1‐km² squares. Three orthogonal landscape gradients, which were taken as niche dimensions, were defined by means of principal components analysis (PCA). Specialization and habitat preference indices were created for 103 terrestrial bird species on the basis of their frequency of occurrence variation along the landscape gradients. These indices, together with species rarity, were then averaged for bird communities. We then analysed the patterns of variation of communities’ mean specialization, mean rarity and mean habitat preference values along a gradient of agricultural–forest habitat mosaics. Results Wherever we found a significant variation in the degree of specialization along the agricultural–forest gradient, agricultural habitats held more specialized bird communities than did forest ones and bore, on average, rarer species. Thus, results contradicted our initial hypothesis that humanized areas would bear more functionally homogenized bird communities. Higher α‐diversity values tended to be associated with generalist communities and with those having rarer species. Main conclusions Estimations of bird community specialization for different niche dimensions can behave differently along certain landscape gradients, and some of these differences can be explained by the variation of mean habitat preferences. Thus, we argue that a multidimensional approach to assess average niche breadth of communities can be more informative than a unidimensional measure. Our results suggest that widespread land abandonment and current secondary forest expansion throughout the Mediterranean area are promoting functional homogenization of bird communities. It would be desirable to construct larger‐scale indicators of functional homogenization in order to monitor communities’ responses to widespread landscape changes.     

Behavioural context of multi-scale species distribution models assessed by radio-tracking

Incorporating ecological processes and animal behaviour into Species Distribution Models (SDMs) is difficult. In species with a central resting or breeding place, there can be conflict between the environmental requirements of the ‘central place’ and foraging habitat. We apply a multi-scale SDM to examine habitat trade-offs between the central place, roost sites, and foraging habitat in Myotis nattereri. We validate these derived associations using habitat selection from behavioural observations of radio-tracked bats. A Generalised Linear Model (GLM) of roost occurrence using land cover variables with mixed spatial scales indicated roost occurrence was positively associated with woodland on a fine scale and pasture on a broad scale. Habitat selection of radio-tracked bats mirrored the SDM with bats selecting for woodland in the immediate vicinity of individual roosts but avoiding this habitat in foraging areas, whilst pasture was significantly positively selected for in foraging areas. Using habitat selection derived from radio-tracking enables a multi-scale SDM to be interpreted in a behavioural context. We suggest that the multi-scale SDM of M. nattereri describes a trade-off between the central place and foraging habitat. Multi-scale methods provide a greater understanding of the ecological processes which determine where species occur and allow integration of behavioural processes into SDMs. The findings have implications when assessing the resource use of a species at a single point in time. Doing so could lead to misinterpretation of habitat requirements as these can change within a short time period depending on specific behaviour, particularly if detectability changes depending on behaviour.     

Intraspecific variation buffers projected climate change impacts on Pinus contorta

Species distribution modeling (SDM) is an important tool to assess the impact of global environmental change. Many species exhibit ecologically relevant intraspecific variation, and few studies have analyzed its relevance for SDM. Here, we compared three SDM techniques for the highly variable species Pinus contorta. First, applying a conventional SDM approach, we used MaxEnt to model the subject as a single species (species model), based on presence–absence observations. Second, we used MaxEnt to model each of the three most prevalent subspecies independently and combined their projected distributions (subspecies model). Finally, we used a universal growth transfer function (UTF), an approach to incorporate intraspecific variation utilizing provenance trial tree growth data. Different model approaches performed similarly when predicting current distributions. MaxEnt model discrimination was greater (AUC – species model: 0.94, subspecies model: 0.95, UTF: 0.89), but the UTF was better calibrated (slope and bias – species model: 1.31 and −0.58, subspecies model: 1.44 and −0.43, UTF: 1.01 and 0.04, respectively). Contrastingly, for future climatic conditions, projections of lodgepole pine habitat suitability diverged. In particular, when the species'' intraspecific variability was acknowledged, the species was projected to better tolerate climatic change as related to suitable habitat without migration (subspecies model: 26% habitat loss or UTF: 24% habitat loss vs. species model: 60% habitat loss), and given unlimited migration may increase amount of suitable habitat (subspecies model: 8% habitat gain or UTF: 12% habitat gain vs. species model: 51% habitat loss) in the climatic period 2070–2100 (SRES A2 scenario, HADCM3). We conclude that models derived from within-species data produce different and better projections, and coincide with ecological theory. Furthermore, we conclude that intraspecific variation may buffer against adverse effects of climate change. A key future research challenge lies in assessing the extent to which species can utilize intraspecific variation under rapid environmental change.     

Incorporating intraspecific variation into species distribution models improves distribution predictions,but cannot predict species traits for a wide-spread plant species

The most common approach to predicting how species ranges and ecological functions will shift with climate change is to construct correlative species distribution models (SDMs). These models use a species’ climatic distribution to determine currently suitable areas for the species and project its potential distribution under future climate scenarios. A core, rarely tested, assumption of SDMs is that all populations will respond equivalently to climate. Few studies have examined this assumption, and those that have rarely dissect the reasons for intraspecific differences. Focusing on the arctic-alpine cushion plant Silene acaulis, we compared predictive accuracy from SDMs constructed using the species’ full global distribution with composite predictions from separate SDMs constructed using subpopulations defined either by genetic or habitat differences. This is one of the first studies to compare multiple ways of constructing intraspecific-level SDMs with a species-level SDM. We also examine the contested relationship between relative probability of occurrence and species performance or ecological function, testing if SDM output can predict individual performance (plant size) and biotic interactions (facilitation). We found that both genetic- and habitat-informed SDMs are considerably more accurate than a species-level SDM, and that the genetic model substantially differs from and outperforms the habitat model. While SDMs have been used to infer population performance and possibly even biotic interactions, in our system these relationships were extremely weak. Our results indicate that individual subpopulations may respond differently to climate, although we discuss and explore several alternative explanations for the superior performance of intraspecific-level SDMs. We emphasize the need to carefully examine how to best define intraspecific-level SDMs as well as how potential genetic, environmental, or sampling variation within species ranges can critically affect SDM predictions. We urge caution in inferring population performance or biotic interactions from SDM predictions, as these often-assumed relationships are not supported in our study.     

Comparisons of habitat structure and plant,arthropod and bird diversity between mainland and island sites near Perth,Western Australia

Detailed estimations of habitat structure, plant species diversity and diversity of arthropods were made at six 4.0 ha sites, two on mainland Western Australia near Perth and four on adjacent islands. The number of resident passerine bird species was also recorded at each site. Plant species diversity, and horizontal foliage diversity (=patchiness) varied only slightly between sites. There were significant positive correlations between arthropod Order diversity and bird diversity, and between vertical foliage diversity and bird diversity. In both Acacia and dune scrub, the Rottnest Island sites had more individuals of arthropods than the mainland sites but these belonged to fewer Orders. Numerical imbalance between arthropod Orders on Rottnest Island probably results from diminution of predators (passerine birds) there. As the actual number of arthropods is higher on the islands, the absence of so many species of passerine birds may result from other factors (ecological and historical).