Effects of Climate Change on Habitat Availability and Configuration for an Endemic Coastal Alpine Bird

North America’s coastal mountains are particularly vulnerable to climate change, yet harbour a number of endemic species. With little room “at the top” to track shifting climate envelopes, alpine species may be especially negatively affected by climate-induced habitat fragmentation. We ask how climate change will affect the total amount, mean patch size, and number of patches of suitable habitat for Vancouver Island White-tailed Ptarmigan (Lagopus leucura saxatilis; VIWTP), a threatened, endemic alpine bird. Using a Random Forest model and a unique dataset consisting of citizen science observations combined with field surveys, we predict the distribution and configuration of potential suitable summer habitat for VIWTP under baseline and future (2020s, 2050s, and 2080s) climates using three general circulation models and two greenhouse gas scenarios. VIWTP summer habitat is predicted to decline by an average of 25%, 44%, and 56% by the 2020s, 2050s, and 2080s, respectively, under the low greenhouse gas scenario and 27%, 59%, and 74% under the high scenario. Habitat patches are predicted to become fragmented, with a 52–79% reduction in mean patch size. The average elevation of suitable habitat patches is expected to increase, reflecting a loss of patches at lower elevations. Thus ptarmigan are in danger of being “squeezed off the mountain”, as their remaining suitable habitat will be increasingly confined to mountaintops in the center of the island. The extent to which ptarmigan will be able to persist in increasingly fragmented habitat is unclear. Much will depend on their ability to move throughout a more heterogeneous landscape, utilize smaller breeding areas, and survive increasingly variable climate extremes. Our results emphasize the importance of continued monitoring and protection for high elevation specialist species, and suggest that White-tailed Ptarmigan should be considered an indicator species for alpine ecosystems in the face of climate change.     

Hopes and challenges for giant panda conservation under climate change in the Qinling Mountains of China

One way that climate change will impact animal distributions is by altering habitat suitability and habitat fragmentation. Understanding the impacts of climate change on currently threatened species is of immediate importance because complex conservation planning will be required. Here, we mapped changes to the distribution, suitability, and fragmentation of giant panda habitat under climate change and quantified the direction and elevation of habitat shift and fragmentation patterns. These data were used to develop a series of new conservation strategies for the giant panda. Qinling Mountains, Shaanxi, China. Data from the most recent giant panda census, habitat factors, anthropogenic disturbance, climate variables, and climate predictions for the year 2050 (averaged across four general circulation models) were used to project giant panda habitat in Maxent. Differences in habitat patches were compared between now and 2050. While climate change will cause a 9.1% increase in suitable habitat and 9% reduction in subsuitable habitat by 2050, no significant net variation in the proportion of suitable and subsuitable habitat was found. However, a distinct climate change‐induced habitat shift of 11 km eastward by 2050 is predicted firstly. Climate change will reduce the fragmentation of suitable habitat at high elevations and exacerbate the fragmentation of subsuitable habitat below 1,900 m above sea level. Reduced fragmentation at higher elevations and worsening fragmentation at lower elevations have the potential to cause overcrowding of giant pandas at higher altitudes, further exacerbating habitat shortage in the central Qinling Mountains. The habitat shift to the east due to climate change may provide new areas for giant pandas but poses severe challenges for future conservation.     

A simple landscape-scale test of a spatially explicit population model: patch occupancy in fragmented south-eastern Australian forests

The results of a landscape‐scale test of ALEX, a widely used metapopulation model for Population Viability Analysis (PVA), are described. ALEX was used to predict patch occupancy by the laughing kookkaburra and the sacred kingfisher in patches of eucalypt forest in south‐eastern Australia. These predictions were compared to field surveys to determine the accuracy of the model. Predictions also were compared to a “naïve” null model assuming no fragmentation effects.
The naïve null model significantly over‐predicted the number of eucalypt patches occupied by the sacred kingfisher, but the observed patch occupancy was not significantly different from that predicted using ALEX. ALEX produced a better fit to the field data than the naïve null model for the number of patches occupied by the laughing kookaburra. Nevertheless, ALEX still significantly over‐predicted the number of occupied patches, particularly remnants dominated by certain forest types – ribbon gum and narrow‐leaved peppermint. The predictions remained significantly different from observations, even when the habitat quality of these patches was reduced to zero. Changing the rate of dispersal improved overall predicted patch occupancy, but occupancy rates for the different forest types remained significantly different from the field observations. The lack of congruence between field data and model predictions could have arisen because the laughing kookaburra may move between an array of patches to access spatially separated food and nesting resources in response to fragmentation. Alternatively, inter‐specific competition may be heightened in a fragmented habitat. These types of responses to fragmentation are not incorporated as part of traditionally applied metapopulation models. Assessments of predictions from PVA models are rare but important because they can reveal the types of species for which forecasts are accurate and those for which they are not. This can assist the collection of additional empirical data to identify important factors affecting population dynamics.     

Assessing the climate change effects on the distribution pattern of the Azerbaijan Mountain Newt (Neurergus crocatus)

Climate change is a grave danger for humans and a looming threat to Earth's biodiversity in the twenty-first century. Assessing the vulnerability of species to climate change is critical for practical conservation efforts. Due to their limited dispersal ability, amphibians are one of the most vulnerable groups of vertebrates to climate change. Among them, the species that inhabit mountains suffer a tremendous amount of climate change-induced pressures. We, therefore, adopted the Azerbaijan Mountain Newt (Neurergus crocatus), which currently inhabits Northwest Iran, North Iraq, and Southeast Turkey, as a case study for assessing the effects of climate change on the distribution patterns of mountain amphibians. By applying the species distribution models (SDMs) in this study, we tried to hindcast the species distribution area in the past and illustrate the impacts of climate change on its distribution in the present and future (the 2050s and 2070s) climate conditions. Also, the patch metrics have been deployed for identifying habitat fragmentation. Our results indicate a more than 50% rise in the species’ current suitable habitats compared to its glacial refugia. The suitable habitat is expected to gradually decrease in RCP 2.6 and RCP 8.5. Among the three countries in which the species occurs, its distribution overlaps with protected areas only in Iraq. The number of habitat patches will grow and reach approximately 20 to 60 patches by 2070 and the average area of the patches will decrease throughout this time. Aside from the numerous threats that endanger the species, climate change puts the long-term existence of Azerbaijan Newt in jeopardy. The results of this study stress the urgent need for taking extreme measures on the species management and conserving its remnant habitat patches.     

Regional changes in the elevational distribution of the Alpine Rock Ptarmigan Lagopus muta helvetica in Switzerland

The Alpine Rock Ptarmigan Lagopus muta helvetica is considered to be particularly vulnerable to climate change because it lives exclusively above the treeline in alpine habitats and is adapted to cold climates. Its Swiss population index has decreased over the last two decades. A considerable shrinkage in distributional area is predicted with further climate change. We assess whether the Alpine Rock Ptarmigan has moved to higher elevations in recent years in the Swiss Alps, and whether such elevational shifts have differed between regions and seasons, using observations recorded by volunteers over a 29‐year period. The elevational shifts differed greatly between regions. In the Eastern and Southern Alps, Ptarmigans were increasingly recorded at higher elevations, with a mean uphill shift of 6.4–9.4 m/year over the last three decades, a pattern that could not be explained by the yearly variation in weather conditions, whereas there was only a moderate upward shift (1.5–3.2 m/year) in the Northern Alps and almost no shift in the Western Alps. Elevational changes were generally greater than those observed in other bird species. The observed upward shift in the Eastern and Southern Alps is among the fastest observed in animals and plants, and may be caused by an upward shift of the treeline and reforestation of formerly cut or unforested areas. The observed elevational shift of the distribution of the Alpine Rock Ptarmigan has led to a reduction in the range of this subspecies, which is restricted to the Alps and isolated from other populations.     

Grassland connectivity explains entomophilous plant species assemblages in an agricultural landscape of the Pampa Region,Argentina

The Pampa grassland of Argentina is one of the most highly threatened biomes in the world. A high proportion of the original grassland cover has been transformed into land for agriculture or degraded. In the southern part of the region, fragmented semi‐natural grasslands over exposed rock still persist and connectivity between them is assumed to be crucial for maintaining viable populations. We quantified overall connectivity of grassland patches in a sector of the Southern Pampa region, and investigated the degree to which landscape connectivity explains entomophilous plant species assemblages in a subset of patches. We characterized each of the 301 patches in the landscape by their degree of intra‐patch and inter‐patch connectivity based on graph theory, and considering threshold dispersal distances from 100 to 1000 m. We surveyed entomophilous plant species in 39 grassland patches and classified the species in three categories (annual herbs, perennial herbs and shrubs) considering their different growth form and longevity. The influence of connectivity variables on entomophilous plant species assemblages variation was explored using Canonical Correspondence Analysis. Although grassland patches were poorly connected at all threshold distances, some of them were found to be critical for global connectivity. Connectivity significantly explained total, annual‐biennial and shrub assemblages for all threshold dispersal distances (6–13% of total variation). Variation in annual species assemblages was associated with intra‐patch and inter‐patch connectivity at short distance (100 m), while variation in shrub species assemblages was explained by intra‐patch and inter‐patch connectivity for distances between 100 m and 1000 m. This study evidenced the low connectivity of the study system, allowed the identification of critical areas for conservation, and provided valuable information to develop management strategies in increasingly human‐dominated landscapes.     

Rarity,geography, and plant exposure to global change in the California Floristic Province

Aim

Rarity and geographic aspects of species distributions mediate their vulnerability to global change. We explore the relationships between species rarity and geography and their exposure to climate and land use change in a biodiversity hotspot.

Location

California, USA.

Taxa

One hundred and six terrestrial plants.

Methods

We estimated four rarity traits: range size, niche breadth, number of habitat patches, and patch isolation; and three geographic traits: mean elevation, topographic heterogeneity, and distance to coast. We used species distribution models to measure species exposure—predicted change in continuous habitat suitability within currently occupied habitat—under climate and land use change scenarios. Using regression models, decision-tree models and variance partitioning, we assessed the relationships between species rarity, geography, and exposure to climate and land use change.

Results

Rarity, geography and greenhouse gas emissions scenario explained >35% of variance in climate change exposure and >61% for land use change exposure. While rarity traits (range size and number of habitat patches) were most important for explaining species exposure to climate change, geographic traits (elevation and topographic heterogeneity) were more strongly associated with species' exposure to land use change.

Main conclusions

Species with restricted range sizes and low topographic heterogeneity across their distributions were predicted to be the most exposed to climate change, while species at low elevations were the most exposed to habitat loss via land use change. However, even some broadly distributed species were projected to lose >70% of their currently suitable habitat due to climate and land use change if they are in geographically vulnerable areas, emphasizing the need to consider both species rarity traits and geography in vulnerability assessments.     

生态保护区外斑块对景观连接度的影响评价

快速的城市化过程带来的生境斑块破碎化及损失会影响物种迁移、捕食等生态活动,对生物多样性构成威胁。然而,现有生态保护区可能无法覆盖其内生物的必要活动范围。生态保护区外的生境斑块对于维持生态过程也具有重要作用,因此识别生态保护区外的关键斑块并加以保护非常重要。以北京市延庆区为研究区,划分两种生境斑块,即核心生境斑块和潜在生境斑块,并基于图论构建生境网络。考虑地表覆盖类型、坡度、人类活动等因素构建生境阻力面。结合未来土地利用类型变化的模拟,研究城市化过程对区域生境网络和景观连接度的影响,选用CLUE-S模型模拟土地利用类型变化的格局。结合生境斑块特征和未来城市土地利用变化情况设计了3种未来生境变化情景。利用连接概率指数(PC)和网络连接度变化率(dI)评价不同生境变化情景下生态保护区外潜在生境斑块的景观连接度重要性,判断保护优先顺序,并分析景观格局变化对不同迁移能力物种的影响。结果表明：生态保护区外的全部潜在生境斑块对维持生境整体景观连接度有最大2.15%的影响,单个潜在生境斑块对维持景观连接度有最大0.28%的影响。此外,景观格局及其变化对不同迁移能力物种的影响差异显著,因此需针对保护物种和城市生境特征设计保护方案,研究区需要优先保护大中型斑块和位于关键位置的小型斑块。为了满足对生物多样性保护的需求,建议在区分生境斑块保护优先顺序时考虑生境斑块对景观连接度的贡献和城市化扩展过程的压力。研究为城市生物多样性保护和生境管理提供了方法参考。     

Climate and land use changes will degrade the configuration of the landscape for titi monkeys in eastern Brazil

Land use changes have profound effects on populations of Neotropical primates, and ongoing climate change is expected to aggravate this scenario. The titi monkeys from eastern Brazil (Callicebus personatus group) have been particularly affected by this process, with four of the five species now allocated to threatened conservation status categories. Here, we estimate the changes in the distribution of these titi monkeys caused by changes in both climate and land use. We also use demographic‐based, functional landscape metrics to assess the magnitude of the change in landscape conditions for the distribution predicted for each species. We built species distribution models (SDMs) based on maximum entropy for current and future conditions (2070), allowing for different global circulation models and contrasting scenarios of glasshouse gas concentrations. We refined the SDMs using a high‐resolution map of habitat remnants. We then calculated habitat availability and connectivity based on home‐range size and the dispersal limitations of the individual, in the context of a predicted loss of 10% of forest cover in the future. The landscape configuration is predicted to be degraded for all species, regardless of the climatic settings. This include reductions in the total cover of forest remnants, patch size and functional connectivity. As the landscape configuration should deteriorate severely in the future for all species, the prevention of further loss of populations will only be achieved through habitat restoration and reconnection to counteract the negative effects for these and several other co‐occurring species.     

Metacommunity,mainland‐island system or island communities? Assessing the regional dynamics of plant communities in a fragmented landscape

Understanding the regional dynamics of plant communities is crucial for predicting the response of plant diversity to habitat fragmentation. However, for fragmented landscapes the importance of regional processes, such as seed dispersal among isolated habitat patches, has been controversially debated. Due to the stochasticity and rarity of among‐patch dispersal and colonization events, we still lack a quantitative understanding of the consequences of these processes at the landscape‐scale. In this study, we used extensive field data from a fragmented, semi‐arid landscape in Israel to parameterize a multi‐species incidence‐function model. This model simulates species occupancy pattern based on patch areas and habitat configuration and explicitly considers the locations and the shapes of habitat patches for the derivation of patch connectivity. We implemented an approximate Bayesian computation approach for parameter inference and uncertainty assessment. We tested which of the three types of regional dynamics – the metacommunity, the mainland‐island, or the island communities type – best represents the community dynamics in the study area and applied the simulation model to estimate the extinction debt in the investigated landscape. We found that the regional dynamics in the patch‐matrix study landscape is best represented as a system of highly isolated ‘island’ communities with low rates of propagule exchange among habitat patches and consequently low colonization rates in local communities. Accordingly, the extinction rates in the local communities are the main drivers of community dynamics. Our findings indicate that the landscape carries a significant extinction debt and in model projections 33–60% of all species went extinct within 1000 yr. Our study demonstrates that the combination of dynamic simulation models with field data provides a promising approach for understanding regional community dynamics and for projecting community responses to habitat fragmentation. The approach bears the potential for efficient tests of conservation activities aimed at mitigating future losses of biodiversity.     

Niche models tell half the story: spatial context and life‐history traits influence species responses to global change

Aim While niche models are typically used to assess the vulnerability of species to climate change, they have been criticized for their limited assessment of threats other than climate change. We attempt to evaluate this limitation by combining niche models with life‐history models to investigate the relative influence of climate change and a range of fire regimes on the viability of a long‐lived plant population. Specifically, we investigate whether range shift due to climate change is a greater threat to an obligate seeding fire‐prone shrub than altered fire frequency and how these two threatening processes might interact. Location Australian sclerophyll woodland and heathland. Methods The study species is Leucopogon setiger, an obligate seeding fire‐prone shrub. A spatially explicit stochastic matrix model was constructed for this species and linked with a dynamic niche model and fire risk functions representing a suite of average fire return intervals. We compared scenarios with a variety of hypothetical patches, a patch framework based upon current habitat suitability and one with dynamic habitat suitability based on climate change scenarios A1FI and A2. Results Leucopogon setiger was found to be sensitive to fire frequency, with shorter intervals reducing expected minimum abundances (EMAs). Spatial decoupling of fires across the landscape reduced the vulnerability of the species to shortened fire frequencies. Shifting habitat, while reducing EMAs, was less of a threat to the species than frequent fire. Main conclusions Altered fire regime, in particular more frequent fires relative to the historical regime, was predicted to be a strong threat to this species, which may reflect a vulnerability of obligate seeders in general. Range shifts induced by climate change were a secondary threat when habitat reductions were predicted. Incorporating life‐history traits into habitat suitability models by linking species distribution models with population models allowed for the population‐level evaluation of multiple stressors that affect population dynamics and habitat, ultimately providing a greater understanding of the impacts of global change than would be gained by niche models alone. Further investigations of this type could elucidate how particular bioecological factors can affect certain types of species under global change.     

MigClim: Predicting plant distribution and dispersal in a changing climate

Aim Many studies have forecasted the possible impact of climate change on plant distributions using models based on ecological niche theory, but most of them have ignored dispersal‐limitations, assuming dispersal to be either unlimited or null. Depending on the rate of climatic change, the landscape fragmentation and the dispersal capabilities of individual species, these assumptions are likely to prove inaccurate, leading to under‐ or overestimation of future species distributions and yielding large uncertainty between these two extremes. As a result, the concepts of ‘potentially suitable’ and ‘potentially colonizable’ habitat are expected to differ significantly. To quantify to what extent these two concepts can differ, we developed Mig Clim, a model simulating plant dispersal under climate change and landscape fragmentation scenarios. Mig Clim implements various parameters, such as dispersal distance, increase in reproductive potential over time, landscape fragmentation or long‐distance dispersal. Location Western Swiss Alps. Methods Using our Mig Clim model, several simulations were run for two virtual species by varying dispersal distance and other parameters. Each simulation covered the 100‐year period 2001–2100 and three different IPCC‐based temperature warming scenarios were considered. Results of dispersal‐limited projections were compared with unlimited and no‐dispersal projections. Results Our simulations indicate that: (1) using realistic parameter values, the future potential distributions generated using Mig Clim can differ significantly (up to more than 95% difference in colonized surface) from those that ignore dispersal; (2) this divergence increases under more extreme climate warming scenarios and over longer time periods; and (3) the uncertainty associated with the warming scenario can be as large as the one related to dispersal parameters. Main conclusions Accounting for dispersal, even roughly, can importantly reduce uncertainty in projections of species distribution under climate change scenarios.     

Climate,competition and connectivity affect future migration and ranges of European trees

Aim Species ranges have adapted during the Holocene to altering climate conditions, but it remains unclear if species will be able to keep pace with recent and future climate change. The goal of our study is to assess the influence of changing macroclimate, competition and habitat connectivity on the migration rates of 14 tree species. We also compare the projections of range shifts from species distribution models (SDMs) that incorporate realistic migration rates with classical models that assume no or unlimited migration. Location Europe. Methods We calibrated SDMs with species abundance data from 5768 forest plots from ICP Forest Level 1 in relation to climate, topography, soil and land‐use data to predict current and future tree distributions. To predict future species ranges from these models, we applied three migration scenarios: no migration, unlimited migration and realistic migration. The migration rates for the SDMs incorporating realistic migration were estimated according to macroclimate, inter‐specific competition and habitat connectivity from simulation experiments with a spatially explicit process model (TreeMig). From these relationships, we then developed a migration cost surface to constrain the predicted distributions of the SDMs. Results The distributions of early‐successional species during the 21st century predicted by SDMs that incorporate realistic migration matched quite well with the unlimited migration assumption (mean migration rate over Europe for A1fi/GRAS climate and land‐use change scenario 156.7 ± 79.1 m year^?1 and for B1/SEDG 164.3 ± 84.2 m year^?1). The predicted distributions of mid‐ to late‐successional species matched better with the no migration assumption (A1fi/GRAS, 15.2 ± 24.5 m year^?1 and B1/SEDG, 16.0 ± 25.6 m year^?1). Inter‐specific competition, which is higher under favourable growing conditions, reduced range shift velocity more than did adverse macroclimatic conditions (i.e. very cold or dry climate). Habitat fragmentation also led to considerable time lags in range shifts. Main conclusions Migration rates depend on species traits, competition, spatial habitat configuration and climatic conditions. As a result, re‐adjustments of species ranges to climate and land‐use change are complex and very individualistic, yet still quite predictable. Early‐successional species track climate change almost instantaneously while mid‐ to late‐ successional species were predicted to migrate very slowly.     

Isolation determines patterns of species presence in highly fragmented landscapes

In fragmented landscapes, changes in habitat availability, patch size, shape and isolation may affect survival of local populations. Proposing efficient conservation strategies for such species relies initially on distinguishing the particular effects of those factors. To address these issues, we investigated the occurrence of 3 bird species in fragmented Brazilian Atlantic Forest landscapes. Playback techniques were used to collect presence/absence data of these species inside 80 forest patches, and incidence models were used to infer their occupancy pattern from landscape spatial structure. The relative importance of patch size, shape and surrounding forest cover and isolation was assessed using a model selection approach based on maximum likelihood estimation. The presence of all species was in general positively affected by the amount of surrounding habitat and negatively affected by inter‐patch distances. The joint effects of patch size and the surrounding landscape characteristics were important determinants of occupancy for two species. The third species was affected only by forest cover and mean patch isolation. Our results suggest that local species presence is in general more influenced by the isolation from surrounding forests than by patch size alone. We found evidence that, in highly fragmented landscapes, birds that can not find patches large enough to settle may be able to overcome short distances through the matrix and include several nearby patches within their home‐ranges to complement their resource needs. In these cases, patches must be defined as functionally connected habitat networks rather than mere continuous forest segments. Bird conservation strategies in the Atlantic forest should focus on increasing patch density and connectivity, in order to implement forest networks that reduce the functional isolation between large remnants with remaining core habitat.     

Process‐based long‐term evaluation of an ecological network of calcareous grasslands connected by sheep herding

This paper evaluates the long‐term effect of an ecological network of calcareous grasslands, a habitat type that experienced dramatic habitat loss and fragmentation during the 20th century, on species richness of habitat specialist plants. Calcareous grasslands are of special conservation concern as the habitat type with the highest diversity in plant and invertebrate species in central Europe. A baseline survey in 1989 established complete vascular plant species lists for all 62 previously abandoned calcareous grassland patches in the study area and assessed the presence of 48 habitat specialist plant species. An ecological network was initiated in 1989 to reconnect these patches with existing grazed pastures (core areas) through large flock sheep herding where feasible, as sheep are thought to be the primary dispersal vectors for calcareous grassland plants. An evaluation survey in 2009 showed significant increase in species richness of habitat specialist plants in patches reconnected by sheep herding, indicating successful colonizations by habitat specialist plants, while ungrazed patches showed no significant change. Observed increase in species richness between 1989 and 2009 was related to connectivity by sheep herding and the presence of a diversity of structural elements providing microsites for establishment. Baseline species richness of the patches, which had been abandoned since at least 1960, was associated with patch area, supporting the effect of ecological drift, and with vegetation type, which suggests that delays in extinction may be related to site factors governing the strength of competition with later seral species. The implementation of this ecological network represents a long‐term ‘natural experiment’ with baseline data, manipulation, and evaluation of hypothesized effects on a clearly defined target variable. It thus provides much needed empirical evidence that species loss in fragmented calcareous grassland communities can be counteracted by restoring functional connectivity among remnant patches.     

Spring density and summer habitat use of alpine rock ptarmigan Lagopus muta helvetica in the southeastern Alps

In the Alps tourism, land-use practices and climate change may cause a loss of suitable habitat of rock ptarmigan (Lagopus muta helvetica). Hence, there is a need for basic research on population densities and habitat requirements of this species as a basis for long-term monitoring studies. So far, in the Austrian Alps, no accurate data on densities and trends of rock ptarmigan populations are available. We carried out counts of calling cocks in the southeastern part of the Austrian Alps (Nockberge National Park, Carinthia, Austria) between 31 May and 1 July 2003 and evaluated the distribution of male rock ptarmigan territories. The spring density of 5.4 territorial cocks per square kilometre was similar to densities in the Swiss Alps but higher than spring population densities in the Italian Alps and the Pyrenees. To investigate summer habitat use, we established a grid mapping of habitat parameters and rock ptarmigan signs. In total, 38 squares with signs of rock ptarmigan presence were recorded (i.e. 32% of all recorded squares). The presence of rock ptarmigan was significantly correlated with cover of rock and rock ptarmigan preferred habitat patchiness. Our study provides a useful reference for future monitoring of this species in the alpine distribution range considering the potential decrease and fragmentation of alpine habitats resulting from climate change and human impacts.     

Quantitative predictions for patch occupancy of capercaillie in fragmented habitats

A major conclusion of studying metapopulation biology is that species conservation should favor regional rather than local population persistence. Regional persistence is tightly linked to size, spatial configuration and quality of habitat patches. Hence it is important for the management of endangered species that priority patches can be identified. We developed a predictive model of patch occupancy by capercaillie, a threatened grouse species, based on a single snapshot of data. We used logistic regression to predict patch occupancy as a function of patch size, isolation, connectivity, relative altitude, and biogeographical area. The probability of a patch being occupied increased with patch size and increasing altitude, and decreased with increasing distance to the next occupied patch. Patch size was the most important predictor although occupied patches varied considerably in size. Our model only uses data on the number, size and spatial configuration of habitat patches. It is a useful tool to designate priority areas for conservation, i.e. large core patches with high resilience in habitat quality, smaller island‐patches that still have high probability of being inhabited or becoming recolonised, and patches functioning as “stepping stones”. If capercaillie is to be preserved, habitat suitability needs to be maintained in a functional network of patches that account for size and inter‐patch distance thresholds as found in this study. We suggest that similar area‐isolation relationships are valid for almost any region within the distribution range of capercaillie. The thresholds for occupancy are however likely to depend on characteristics of the respective landscape. The outcome of our study emphasises the need for future investigations that explore the relationship between patch occupancy, matrix quality and its resistance to dispersing individuals.     

Using gap‐crossing capacity to evaluate functional connectivity of two Atlantic rainforest birds and their response to fragmentation

Abstract One of the main consequences of habitat loss and fragmentation is the increase in patch isolation and the consequent decrease in landscape connectivity. In this context, species persistence depends on their responses to this new landscape configuration, particularly on their capacity to move through the interhabitat matrix. Here, we aimed first to determine gap‐crossing probabilities related to different gap widths for two forest birds (Thamnophilus caerulescens, Thamnophilidae; and Basileuterus culicivorus, Parulidae) from the Brazilian Atlantic rainforest. These values were defined with a playback technique and then used in analyses based on graph theory to determine functional connections among forest patches. Both species were capable of crossing forest gaps between patches, and these movements were related to gap width. The probability of crossing 40 m gaps was 50% for both species. This probability falls to 10% when the gaps are 60 m (for B. culicivorus) or 80 m (for T. caerulescens). Actually, birds responded to stimulation about two times more distant inside forest trials (control) than in gap‐crossing trials. Models that included gap‐crossing capacity improved the explanatory power of species abundance variation in comparison to strictly structural models based merely on patch area and distance measurements. These results highlighted that even very simple functional connectivity measurements related to gap‐crossing capacity can improve the understanding of the effect of habitat fragmentation on bird occurrence and abundance.     

Forest species in an agricultural landscape in the Netherlands: Effects of habitat fragmentation

Abstract. For 312 forest patches on sandy soils in the Netherlands, effects of fragmentation are studied of forest habitat in the past on the present occurrence of forest plant species. Using regression techniques, the numbers of forest edge, interior, zoochorous and anemochorous species, as well as occurrence of 24 individual species were related to patch area and connectivity measures. Connectivity was defined as the amount of forest habitat around patches within three zones up to 1000 m. Plant categories were distinguished by habitat type and dispersal mechanism. The results showed that number of total species and number of species of all habitat and dispersal categories increased with area. The occurrence of ten individually studied species were also positively related to area. Most of them were interior species. The number of zoochorous species increased with increasing connectivity. Also occurrence of ten individually studied species were affected by connectivity. Interior zoochorous species showed the highest percentage of affected species. The relationship of interior, animal-dispersed plants to connectivity can be explained by the limited distances covered by their dispersal agents (forest birds and ants) in a non-forest habitat. Also, some anemochorous plants appeared to be affected by connectivity, especially those with heavy seeds and potentially short distance dispersal. As not all species within a certain dispersal or habitat category react similar to area or isolation, it is suggested that differences in underlying processes of fragmentation such as local extinction and colonization need more focus.     

The influence of patch demographics on metapopulations, with particular reference to successional landscapes

The classical view of metapopulations relates the regional abundance of a species to the balance between the extinction and colonization dynamics of identical local populations. Species in successional landscapes may represent the most appropriate examples of classical metapopulations. However, Levins‐type metapopulation models do not explicitly separate population loss due to successional habitat change from other causes of extinction. A further complication is that the chance of population loss due to successional habitat change may be related to the age of a patch. I developed simple patch occupancy models to include succession and included consideration of patch age structure to address two related questions: what are the implications of changes in patch demographic rates and when is a move to a structured patch occupancy model justified? Age‐related variation in patch demography could increase or decrease the equilibrium fraction of the available habitat occupied by a species when compared to the predictions of an unstructured model. Metapopulation persistence was enhanced when the age class of patches with the highest species occupancy suffered relatively low losses to habitat succession. Conversely, when the age class of patches with the highest species occupancy also had relatively high successional loss rates, extinction thresholds were higher that would be predicted by a simple unstructured model. Hence age‐related variation in patch successional rate introduces biases into the predictions of simple unstructured models. Such biases can be detected from field surveys of the fraction of occupied and unoccupied patches in each age class. Where a bias is demonstrated, unstructured models will not be adequate for making predictions about the effects of changing parameters on metapopulation size. Thinking in successional terms emphasizes how landscapes might be managed to enhance or reduce the patch occupancy by any particular metapopulation