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Habitat Suitability (habitat + suitability)
Selected AbstractsEcological niche modelling as a technique for assessing threats and setting conservation priorities for Asian slow lorises (Primates: Nycticebus)DIVERSITY AND DISTRIBUTIONS, Issue 2 2009J. S. Thorn ABSTRACT Aim, Data on geographical ranges are essential when defining the conservation status of a species, and in evaluating levels of human disturbance. Where locality data are deficient, presence-only ecological niche modelling (ENM) can provide insights into a species' potential distribution, and can aid in conservation planning. Presence-only ENM is especially important for rare, cryptic and nocturnal species, where absence is difficult to define. Here we applied ENM to carry out an anthropogenic risk assessment and set conservation priorities for three threatened species of Asian slow loris (Primates: Nycticebus). Location, Borneo, Java and Sumatra, Southeast Asia. Methods, Distribution models were built using maximum entropy (MaxEnt) ENM. We input 20 environmental variables comprising temperature, precipitation and altitude, along with species locality data. We clipped predicted distributions to forest cover and altitudinal data to generate remnant distributions. These were then applied to protected area (PA) and human land-use data, using specific criteria to define low-, medium- or high-risk areas. These data were analysed to pinpoint priority study sites, suitable reintroduction zones and protected area extensions. Results, A jackknife validation method indicated highly significant models for all three species with small sample sizes (n = 10 to 23 occurrences). The distribution models represented high habitat suitability within each species' geographical range. High-risk areas were most prevalent for the Javan slow loris (Nycticebus javanicus) on Java, with the highest proportion of low-risk areas for the Bornean slow loris (N. menagensis) on Borneo. Eighteen PA extensions and 23 priority survey sites were identified across the study region. Main conclusions, Discriminating areas of high habitat suitability lays the foundations for planning field studies and conservation initiatives. This study highlights potential reintroduction zones that will minimize anthropogenic threats to animals that are released. These data reiterate the conclusion of previous research, showing MaxEnt is a viable technique for modelling species distributions with small sample sizes. [source] Prediction and validation of the potential global distribution of a problematic alien invasive species , the American bullfrogDIVERSITY AND DISTRIBUTIONS, Issue 4 2007Gentile Francesco Ficetola ABSTRACT Predicting the probability of successful establishment and invasion of alien species at global scale, by matching climatic and land use data, is a priority for the risk assessment. Both large- and local-scale factors contribute to the outcome of invasions, and should be integrated to improve the predictions. At global scale, we used climatic and land use layers to evaluate the habitat suitability for the American bullfrog Rana catesbeiana, a major invasive species that is among the causes of amphibian decline. Environmental models were built by using Maxent, a machine learning method. Then, we integrated global data with information on richness of native communities and hunting pressure collected at the local scale. Global-scale data allowed us to delineate the areas with the highest suitability for this species. Predicted suitability was significantly related to the invasiveness observed for bullfrog populations historically introduced in Europe, but did not explain a large portion of variability in invasion success. The integration of data at the global and local scales greatly improved the performance of models, and explained > 57% of the variance in introduction success: bullfrogs were more invasive in areas with high suitability and low hunting pressure over frogs. Our study identified the climatic factors entailing the risk of invasion by bullfrogs, and stresses the importance of the integration of biotic and abiotic data collected at different spatial scales, to evaluate the areas where monitoring and management efforts need to be focused. [source] Challenging Wallacean and Linnean shortfalls: knowledge gradients and conservation planning in a biodiversity hotspotDIVERSITY AND DISTRIBUTIONS, Issue 5 2006Luis Mauricio Bini ABSTRACT Knowledge about biodiversity remains inadequate because most species living on Earth were still not formally described (the Linnean shortfall) and because geographical distributions of most species are poorly understood and usually contain many gaps (the Wallacean shortfall). In this paper, we developed models to infer the size and placement of geographical ranges of hypothetical non-described species, based on the range size frequency distribution of anurans recently described in the Cerrado Biome, on the level of knowledge (number of inventories) and on surrogates for habitat suitability. The rationale for these models is as follow: (1) the range size frequency distribution of these species should be similar to the range-restricted species, which have been most recently described in the Cerrado Biome; (2) the probability of new discoveries will increase in areas with low biodiversity knowledge, mainly in suitable areas, and (3) assuming range continuity, new species should occupy adjacent cells only if the level of knowledge is low enough to allow the existence of undiscovered species. We ran a model based on the number of inventories only, and two models combining effects of number of inventories and two different estimates of habitat suitability, for a total of 100 replicates each. Finally, we performed a complementary analysis using simulated annealing to solve the set-covering problem for each simulation (i.e. finding the smallest number of cells so that all species are represented at least once), using extents of occurrence of 160 species (131 real anuran species plus 29 new simulated species). The revised reserve system that included information about unknown or poorly sampled taxa significantly shifted northwards, when compared to a system based on currently known species. This main result can be explained by the paucity of biodiversity data in this part of the biome, associated with its relatively high habitat suitability. As a precautionary measure, weighted by the inferred distribution data, the prioritization of a system of reserves in the north part of the biome appears to be defensible. [source] Bilby distribution and fire: a test of alternative models of habitat suitability in the Tanami Desert, AustraliaECOGRAPHY, Issue 6 2007Richard Southgate The distribution of the bilby Macrotis lagotis was assessed in the Tanami Desert using stratified random plots, repetitively sampled transects, aerial survey transects, and ground truth plots. Compared to a previous assessment of distribution, the extent of occurrence has changed little in the last 20 yr. However, the area of occupancy is small relative to the extent of occurrence and <25% of the current geographic range has bilby sign <20 km apart. Generalised linear modelling was used to determine the strength of association between bilby occurrence and habitat variables and identify refugia characteristics. Four competing candidate models were examined to determine whether bilby occurrence associated significantly with productive substrates and introduced herbivores, the distribution of key predator species, the pattern of fire, and climatic gradients including rainfall and temperature. For the entire study area, bilby presence associated most strongly with variables of mean annual rainfall, substrate type and the probability of dingo occurrence. Proximity to recently burnt habitat formed a significant predictor of bilby occurrence in a model derived for a reduced part of the study area where most sign was found. The work suggested that the current frameworks underpinning understanding of biotic distributions in arid Australia are deficient, and that climatic gradients, lateritic and rocky systems, and predators need to be incorporated into our thinking in the future. The extent of occurrence based on outlier records from opportunistic reports provided a misleading indication of the true status of the bilby. [source] Contrasting spatial and temporal global change impacts on butterfly species richness during the 20th centuryECOGRAPHY, Issue 6 2006Peter White Regional patterns of species richness are often explained by models using temperature or measures habitat suitability. Generally, species richness is positively associated with temperature, and negatively associated with habitat degradation. While these models have been well tested across spatial scales, they have rarely been tested on a temporal scale , in part due to the difficulty in ascertaining accurate historical data at an appropriate resolution. In this study, we compared the results of temporal and spatial models, each incorporating two predictors of species richness: temperature, and human population density (as a surrogate of human-related habitat impacts). We found that the change in species richness from the early to late part of the 20th century was positively correlated with temperature change, and negatively correlated with human population density change. When we compared these results to two spatial models using contemporary and historic data, the spatial effects of temperature on butterfly richness were similar to its temporal effects, while the effect of human population density through time is the opposite of its spatial effect. More generally, the assumption that spatial patterns are equivalent to temporal ones when applying macroecological data to global change is clearly unreliable. [source] Patterns of commonness and rarity in central European birds: reliability of the core-satellite hypothesis within a large scaleECOGRAPHY, Issue 4 2002David Storch The frequency distribution of species' area of occupancy is often bimodal, most species being either very rare or very common in terms of number of occupied sites. This pattern has been attributed to the nonlinearity associated with metapopulation dynamics of the species, but there are also other explanations comprising sampling artifact and frequency distribution of suitable habitats. We tested whether the bimodal frequency distribution of occupied squares in central European birds could be derived solely from the frequency distribution of species population sizes (i.e. the sampling artifact hypothesis) or from the spatial distribution of their preferred habitats. Both models predict high proportion of very common species, i.e. the right side of frequency distribution. Bimodality itself is well predicted by models based on random placement of individuals according to their abundances but neither model predicts the observed prevalence of rare species. Even the combined models that assume random placement of individuals within the squares with suitable habitat do not predict such a high proportion of rare species. The observed distribution is more aggregated, rare species occupying a smaller portion of suitable habitat than predicted on the basis of their abundance. The pattern is consistent with metapopulation processes involving local population extinctions. The involvement of these processes is supported by two further observations. First, species rarity is associated with significant population trend and/or location on the edge of their ranges within central Europe, both situations presumably associated with metapopulation processes. Second, suitable habitats seem to be either saturated or almost unoccupied, which is consistent with the predictions of the metapopulation model based on nonlinear dynamics of extinction and colonization. Although the habitat suitability is an important determinant of species distribution, the rarity of many species of birds within this scale of observation seems to be affected by other factors, including local population extinctions associated with fragmentation of species' habitats. [source] Relating streamflow characteristics to specialized insectivores in the Tennessee River Valley: a regional approach,ECOHYDROLOGY, Issue 4 2008Rodney R. Knight Abstract Analysis of hydrologic time series and fish community data across the Tennessee River Valley identified three hydrologic metrics essential to habitat suitability and food availability for insectivorous fish communities in streams of the Tennessee River Valley: constancy (flow stability or temporal invariance), frequency of moderate flooding (frequency of habitat disturbance), and rate of streamflow recession. Initial datasets included 1100 fish community sites and 300 streamgages. Reduction of these datasets to sites with coexisting data yielded 33 sites with streamflow and fish community data for analysis. Identification of critical hydrologic metrics was completed using a multivariate correlation procedure that maximizes the rank correlation between the hydrologic metrics and fish community resemblance matrices. Quantile regression was used to define thresholds of potential ranges of insectivore scores for given values of the hydrologic metrics. Increased values of constancy and insectivore scores were positively correlated. Constancy of streamflow maintains wetted perimeter, which is important for providing habitat for fish spawning and increased surface area for invertebrate colonization and reproduction. Site scores for insectivorous fish increased as the frequency of moderate flooding (3 times the median annual streamflow) decreased, suggesting that insectivorous fish communities respond positively to less frequent disturbance and a more stable habitat. Increased streamflow recession rates were associated with decreased insectivore scores. Increased streamflow recession can strand fish in pools and other areas that are disconnected from flowing water and remove invertebrates as food sources that were suspended during high-streamflow events. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the relationship between niche and distributionECOLOGY LETTERS, Issue 4 2000H.R. Pulliam Applications of Hutchinson's n -dimensional niche concept are often focused on the role of interspecific competition in shaping species distribution patterns. In this paper, I discuss a variety of factors, in addition to competition, that influence the observed relationship between species distribution and the availability of suitable habitat. In particular, I show that Hutchinson's niche concept can be modified to incorporate the influences of niche width, habitat availability and dispersal, as well as interspecific competition per se. I introduce a simulation model called NICHE that embodies many of Hutchinson's original niche concepts and use this model to predict patterns of species distribution. The model may help to clarify how dispersal, niche size and competition interact, and under what conditions species might be common in unsuitable habitat or absent from suitable habitat. A brief review of the pertinent literature suggests that species are often absent from suitable habitat and present in unsuitable habitat, in ways predicted by theory. However, most tests of niche theory are hampered by inadequate consideration of what does and does not constitute suitable habitat. More conclusive evidence for these predictions will require rigorous determination of habitat suitability under field conditions. I suggest that to do this, ecologists must measure habitat specific demography and quantify how demographic parameters vary in response to temporal and spatial variation in measurable niche dimensions. [source] Comparison of three expert elicitation methods for logistic regression on predicting the presence of the threatened brush-tailed rock-wallaby Petrogale penicillataENVIRONMETRICS, Issue 4 2009Rebecca A. O'Leary Abstract Numerous expert elicitation methods have been suggested for generalised linear models (GLMs). This paper compares three relatively new approaches to eliciting expert knowledge in a form suitable for Bayesian logistic regression. These methods were trialled on two experts in order to model the habitat suitability of the threatened Australian brush-tailed rock-wallaby (Petrogale penicillata). The first elicitation approach is a geographically assisted indirect predictive method with a geographic information system (GIS) interface. The second approach is a predictive indirect method which uses an interactive graphical tool. The third method uses a questionnaire to elicit expert knowledge directly about the impact of a habitat variable on the response. Two variables (slope and aspect) are used to examine prior and posterior distributions of the three methods. The results indicate that there are some similarities and dissimilarities between the expert informed priors of the two experts formulated from the different approaches. The choice of elicitation method depends on the statistical knowledge of the expert, their mapping skills, time constraints, accessibility to experts and funding available. This trial reveals that expert knowledge can be important when modelling rare event data, such as threatened species, because experts can provide additional information that may not be represented in the dataset. However care must be taken with the way in which this information is elicited and formulated. Copyright © 2008 John Wiley & Sons, Ltd. [source] Crayfish as geomorphic agents and ecosystem engineers: effect of a biomass gradient on baseflow and flood-induced transport of gravel and sand in experimental streamsFRESHWATER BIOLOGY, Issue 1 2003B. Statzner SUMMARY 1.,Using experimental streams, we studied the impact of the crayfish Orconectes limosus on (i) the transport of gravel and sand at baseflow; (ii) the sediment surface (bedform, particle consolidation, proportion of sand, algal and gravel cover); and (iii) the critical shear stress (,C) causing incipient gravel and sand motion during simulated floods. We examined (i) and (ii) in experimental outdoor flumes that replicated riffle-pool sequences and (iii) in a larger laboratory flume, in which we exposed sediments retrieved from the outdoor flumes to a progressively increasing discharge. 2.,Habitat changes induced by crayfish, such as bedform alterations in riffles (downstream displacement of riffle heads) and the increase of gravel on sand dunes in pools, had major impacts on the spatial and temporal patterns of the baseflow transport of gravel and sand. 3.,In addition to their impact on bedform in riffles and on gravel cover in pools, crayfish prevented the physical consolidation of particles in riffles and reduced the algal cover and the proportion of sand in the surface layer in both riffles and pools. These crayfish impacts on sediment surface variables had complex, interacting effects on the mobilisation of gravel and sand during subsequent flood simulations. For sand, crayfish progressively decreased the ,C (i.e. the sum of bedform drag and skin friction) by about 50% along the entire biomass gradient in pools, whereas the presence of crayfish abruptly decreased the ,C by about 75% in riffles. For gravel, the discharge causing motion in riffles produced a shear stress (in terms of skin friction) on an even bedform that was about 75% lower in all flumes with crayfish compared with the flumes without crayfish. Crayfish had no impact on ,C for gravel in pools. 4.,Scaling-up these experimental results to real streams suggests that crayfish could affect the patch dynamics of major sediment transport events and habitat suitability for other organisms that, at larger spatial scales, could increase the overall spatio-temporal habitat diversity and thus the overall structural and functional biodiversity of lotic communities. [source] Effects of ultraviolet radiation on the eggs of landlocked Galaxias maculatus (Galaxiidae, Pisces) in northwestern PatagoniaFRESHWATER BIOLOGY, Issue 3 2000M. Battini Summary 1Ultraviolet radiation (UVR) damages early life stages of several fish species. Galaxias maculatus is a small catadromous fish, with landlocked forms occurring in many lakes within the Nahuel Huapi National Park (Patagonia, Argentina). In this work, the vulnerability of G. maculatus eggs exposed to both natural and artificial UVR was investigated in relation to water transparency. 2Field experiments were performed in two lakes differing in UVR attenuation. Galaxias maculatus eggs were exposed to in situ levels of UVR in quartz tubes incubated at various depths. For laboratory experiments, the eggs were exposed to five levels of artificial UVB radiation. 3Exposure to natural UVR causes various degrees of egg mortality depending on water transparency and incubation depth. In the less transparent lake (Kd320 = 3.08 m -1), almost complete mortality was observed near the surface. At a depth of 43 cm the observed mortality was only 22%, but was still significantly different from the dark control. In the most transparent lake (Kd320 = 0.438 m -1), almost total mortality was observed in tubes incubated at 2.56 m or shallower. A gradual decline in mortality was recorded from that depth to 3.78 m where the values approached those in the dark control treatments. 4A monotonic relationship between mortality and UV exposure could be observed both in field and laboratory experiments. Using the results from field incubations, a LD50 of 2.5 J cm -2 nm -1 was estimated. In a few mountain lakes, this value would be exceeded even if the eggs were laid at the maximum depth of the lake. Thus UVR seems a sufficient cause to explain the absence of G. maculatus populations in some mountain lakes. For most lakes, however, UVR is probably one of several important environmental factors, which together determine the habitat suitability. [source] Predator perches: a visual search perspectiveFUNCTIONAL ECOLOGY, Issue 2 2009Malte Andersson Summary 1Predators hunting by sight often search for prey from elevated perches or hovering positions above the prey habitat. Theory suggests that prey visibility depends strongly on predator perch height and distance, but their quantitative effects have not been experimentally tested in natural habitats. 2We estimate for the first time how prey visibility depends on predator perch height, distance and vegetation height in an open natural habitat, based on visibility measurements of two targets: a mounted bird and a graduated plate, from five perch heights (0·2,8 m) and six distances (5,120 m). 3For both targets, their proportion visible increases strongly with observer perch height and proximity. From the lowest perch, visibility of the target bird declines to < 5% beyond 20 m distance, but 40% of it remains visible from the highest perch even at 120 m. 4Models of predator search suggest that hunting success and predation rate depend strongly on the prey detection rate, which is expected to decline with distance r approximately as r,d. However, d, the distance decay parameter, has not previously been empirically estimated in natural predator habitats. For distance , prey visibility relationships similar to those observed here, we find a realistic estimate of d to be 2·1,2·4. 5The results demonstrate the crucial role of relative perch and vegetation height for prey visibility, which is of relevance for habitat management. The strong increase of prey visibility with predator search height suggests that removal of predator perches can improve the survival of endangered prey populations in open habitats. Conversely, perch preservation or addition can improve habitat suitability for some predator species where perches are rare or lacking. [source] Is biofuel policy harming biodiversity in Europe?GCB BIOENERGY, Issue 1 2009JEANNETTE EGGERS Abstract We assessed the potential impacts of land-use changes resulting from a change in the current biofuel policy on biodiversity in Europe. We evaluated the possible impact of both arable and woody biofuel crops on changes in distribution of 313 species pertaining to different taxonomic groups. Using species-specific information on habitat suitability as well as land use simulations for three different biofuel policy options, we downscaled available species distribution data from the original resolution of 50 to 1 km. The downscaled maps were then applied to analyse potential changes in habitat size and species composition at different spatial levels. Our results indicate that more species might suffer from habitat losses rather than benefit from a doubled biofuel target, while abolishing the biofuel target would mainly have positive effects. However, the possible impacts vary spatially and depend on the biofuel crop choice, with woody crops being less detrimental than arable crops. Our results give an indication for policy and decision makers of what might happen to biodiversity under a changed biofuel policy in the European Union. The presented approach is considered to be innovative as to date no comparable policy impact assessment has been applied to such a large set of key species at the European scale. [source] Macroecology meets macroevolution: evolutionary niche dynamics in the seaweed HalimedaGLOBAL ECOLOGY, Issue 4 2009Heroen Verbruggen ABSTRACT Aim Because of their broad distribution in geographical and ecological dimensions, seaweeds (marine macroalgae) offer great potential as models for marine biogeographical inquiry and exploration of the interface between macroecology and macroevolution. This study aims to characterize evolutionary niche dynamics in the common green seaweed genus Halimeda, use the observed insights to gain understanding of the biogeographical history of the genus and predict habitats that can be targeted for the discovery of species of special biogeographical interest. Location Tropical and subtropical coastal waters. Methods The evolutionary history of the genus is characterized using molecular phylogenetics and relaxed molecular clock analysis. Niche modelling is carried out with maximum entropy techniques and uses macroecological data derived from global satellite imagery. Evolutionary niche dynamics are inferred through application of ancestral character state estimation. Results A nearly comprehensive molecular phylogeny of the genus was inferred from a six-locus dataset. Macroecological niche models showed that species distribution ranges are considerably smaller than their potential ranges. We show strong phylogenetic signal in various macroecological niche features. Main conclusions The evolution of Halimeda is characterized by conservatism for tropical, nutrient-depleted habitats, yet one section of the genus managed to invade colder habitats multiple times independently. Niche models indicate that the restricted geographical ranges of Halimeda species are not due to habitat unsuitability, strengthening the case for dispersal limitation. Niche models identified hotspots of habitat suitability of Caribbean species in the eastern Pacific Ocean. We propose that these hotspots be targeted for discovery of new species separated from their Caribbean siblings since the Pliocene rise of the Central American Isthmus. [source] Experimental evidence that deer browsing reduces habitat suitability for breeding Common Nightingales Luscinia megarhynchosIBIS, Issue 2 2010CHAS A. HOLT The ecological impacts of increasing populations of deer (Cervidae) in Europe and North America are becoming more widespread and pronounced. Within Britain, it has been suggested that declines in several woodland bird species, particularly those dependent on dense understorey vegetation, may be at least partly due to these effects. Here we present experimental evidence of the effects of deer browsing on the fine-scale habitat selection and habitat use by a bird species in Europe. The study was conducted in a wood in eastern England where a decrease in Common Nightingale Luscinia megarhynchos numbers has coincided with a large increase in deer numbers. Eight woodland plots were cut to produce young coppice regrowth (a favoured habitat for Nightingales). Deer were excluded from half of each plot using steel fences, thus creating eight experimental pairs of exclosures (unbrowsed) and controls (browsed). Radiotelemetry and territory mapping of male Nightingales showed strong selection of exclosures. The density of territories was 15 times greater in the exclosures than in grazed controls. Selection for exclosures was significant for the minimum convex polygon, 95% kernel and 50% core home-ranges used by seven radiotracked males. Tracked birds spent 69% of their time in the 6% of the study area protected from deer. Intensified browsing by deer influenced local settlement patterns of Nightingales, supporting the conclusion that increased deer populations are likely to have contributed to declines of Nightingales in Britain, and potentially those of other bird species dependent on dense understorey. [source] Modelling habitat selection of Common Cranes Grus grus wintering in Portugal using multiple logistic regressionIBIS, Issue 3 2000ALDINA M.A. FRANCO Predictive models of habitat suitability for the Common Crane Grus grus in a wintering area of southern Portugal were derived using logistic multiple regression and Geographic Information Systems. The study area was characterized by landscape variables and surveyed uniformly for the presence of cranes. The most important variables were distance to roosts, to open Holm Oak woods and to villages, and the occurrence of unpaved roads, shrubby vegetation, slope and orchards. Two models were built, the second having one variable fewer than the first. The selection of the best model was based on statistical and biological criteria. Crane distribution was negatively related to: distance to open Holm Oak Quercus rotundifolia woods and roosts. Additionally, unsuitable vegetation and orchard areas are avoided. In these areas movement is difficult, food availability is reduced and the risk of predation increased. We also found that villages and roads were avoided; disturbance is a significant factor for this species. Some management guidelines are proposed for the area: (1) maintenance of open Holm Oak woodlands, (2) incentives to avoid the abandonment of traditional agriculture and pastoral use of the area, which would lead to an increase of shrubby vegetation areas, (3) preservation of suitable roosting places and (4) management of new patches of forest and orchards. [source] Sequential analysis of lines of evidence,an advanced weight-of-evidence approach for ecological risk assessmentINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 4 2006Ruth N Hull Abstract Weight-of-evidence (WOE) approaches have been used in ecological risk assessment (ERA) for many years. The approaches integrate various types of data (e.g., from chemistry, bioassay, and field studies) to make an overall conclusion of risk. However, the current practice of WOE has several important difficulties, including a lack of transparency related to how each line of evidence is weighted or integrated into the overall weight-of-evidence conclusion. Therefore, a sequential analysis of lines of evidence (SALE) approach has been developed that advances the practice of WOE. It was developed for an ERA of chemical stressors but also can be used for nonchemical stressors and is equally applicable to the aquatic and terrestrial environments. The sequential aspect of the SALE process is a significant advancement and is based on 2 primary ideas. First, risks can be ruled out with the use of certain lines of evidence, including modeled hazard quotients (HQs) and comparisons of soil, water, or sediment quality with conservative soil, water or sediment quality guidelines. Thus, the SALE process recognizes that HQs are most useful in ruling out risk rather than predicting risk to ecological populations or communities. Second, the SALE process provides several opportunities to exit the risk assessment process, not only when risks are ruled out, but also when magnitude of effect is acceptable or when little or no evidence exists that associations between stressors and effects may be causal. Thus, the SALE approach explicitly includes interaction between assessors and managers. It illustrates to risk managers how risk management can go beyond the simple derivation of risk-based concentrations of chemicals of concern to risk management goals based on ecological metrics (e.g., species diversity). It also can be used to stimulate discussion of the limitations of the ERA science, and how scientists deal with uncertainty. It should assist risk managers by allowing their decisions to be based on a sequential, flexible, and transparent process that includes direct toxicity risks, indirect risks (via changes in habitat suitability), and the spatial and temporal factors that can influence the risk assessment. [source] Predicting avian patch occupancy in a fragmented landscape: do we know more than we think?JOURNAL OF APPLIED ECOLOGY, Issue 5 2009Danielle F. Shanahan Summary 1.,A recent and controversial topic in landscape ecology is whether populations of species respond to habitat fragmentation in a general fashion. Empirical research has provided mixed support, resulting in controversy about the use of general rules in landscape management. Rather than simply assessing post hoc whether individual species follow such rules, a priori testing could shed light on their accuracy and utility for predicting species response to landscape change. 2.,We aim to create an a priori model that predicts the presence or absence of multiple species in habitat patches. Our goal is to balance general theory with relevant species life-history traits to obtain high prediction accuracy. To increase the utility of this work, we aim to use accessible methods that can be applied using readily available inexpensive resources. 3.,The classification tree patch-occupancy model we create for birds is based on habitat suitability, minimum area requirements, dispersal potential of each species and overall landscape connectivity. 4.,To test our model we apply it to the South East Queensland region, Australia, for 17 bird species with varying dispersal potential and habitat specialization. We test the accuracy of our predictions using presence,absence information for 55 vegetation patches. 5.,Overall we achieve Cohen's kappa of 0·33, or ,fair' agreement between the model predictions and test data sets, and generally a very high level of absence prediction accuracy. Habitat specialization appeared to influence the accuracy of the model for different species. 6.,We also compare the a priori model to the statistically derived model for each species. Although this ,optimal model' generally differed from our original predictive model, the process revealed ways in which it could be improved for future attempts. 7.,Synthesis and applications. Our study demonstrates that ecological generalizations alongside basic resources (a vegetation map and some species-specific information) can provide conservative accuracy for predicting species occupancy in remnant vegetation patches. We show that the process of testing and developing models based on general rules could provide basic tools for conservation managers to understand the impact of current or planned landscape change on wildlife populations. [source] Modelling the distribution of a threatened habitat: the California sage scrubJOURNAL OF BIOGEOGRAPHY, Issue 11 2009Erin C. Riordan Abstract Aim, Using predictive species distribution and ecological niche modelling our objectives are: (1) to identify important climatic drivers of distribution at regional scales of a locally complex and dynamic system , California sage scrub; (2) to map suitable sage scrub habitat in California; and (3) to distinguish between bioclimatic niches of floristic groups within sage scrub to assess the conservation significance of analysing such species groups. Location, Coastal mediterranean-type shrublands of southern and central California. Methods, Using point localities from georeferenced herbarium records, we modelled the potential distribution and bioclimatic envelopes of 14 characteristic sage scrub species and three floristic groups (south-coastal, coastal,interior disjunct and broadly distributed species) based upon current climate conditions. Maxent was used to map climatically suitable habitat, while principal components analysis followed by canonical discriminant analysis were used to distinguish between floristic groups and visualize species and group distributions in multivariate ecological space. Results, Geographical distribution patterns of individual species were mirrored in the habitat suitability maps of floristic groups, notably the disjunct distribution of the coastal,interior species. Overlap in the distributions of floristic groups was evident in both geographical and multivariate niche space; however, discriminant analysis confirmed the separability of floristic groups based on bioclimatic variables. Higher performance of floristic group models compared with sage scrub as a whole suggests that groups have differing climate requirements for habitat suitability at regional scales and that breaking sage scrub into floristic groups improves the discrimination between climatically suitable and unsuitable habitat. Main conclusions, The finding that presence-only data and climatic variables can produce useful information on habitat suitability of California sage scrub species and floristic groups at a regional scale has important implications for ongoing efforts of habitat restoration for sage scrub. In addition, modelling at a group level provides important information about the differences in climatic niches within California sage scrub. Finally, the high performance of our floristic group models highlights the potential a community-level modelling approach holds for investigating plant distribution patterns. [source] Could we live with reintroduced large carnivores in the UK?MAMMAL REVIEW, Issue 3 2004CHARLES J. WILSON ABSTRACT 1.,Literature on the wolf Canis lupus, brown bear Ursus arctos and lynx Lynx lynx is reviewed to determine if sufficient semi-natural habitat exists in the UK for a viable population of any of these species and to assess the potential risks to human safety, livestock and economically valuable wildlife. Public attitudes to the recovery and reintroduction of some other mammals are also briefly reviewed. 2.,The large home range sizes and low population densities of large carnivores mean that the Scottish Highlands is the only UK region with the potential to support a viable population. Human population density is also lower in the Highlands and the density of wild ungulate prey higher than in many parts of Europe where large carnivores survive. 3.,Attacks on people have been recorded in Europe for healthy bears and for rabid bears and wolves but there are no reports of attacks by lynx. Bears are more carnivorous in the north of their range than in the south and although wild mammals seldom appear to be important prey serious predation of livestock can occur. Livestock predation is also reported for the wolf and the lynx but they appear to prefer wild prey if available. However, mass kills of up to 100 or more sheep are occasionally recorded for wolves. 4.,Attitudes to reintroductions and carnivores generally tend to be favourable amongst the general public, but negative amongst those most likely to be adversely affected. Fears for human safety and significant livestock predation with bears and wolves, respectively, suggest that reintroduction of these species is unlikely to be acceptable in the foreseeable future. Reintroduction of the lynx may be feasible but habitat suitability and potential impact on vulnerable native wildlife need to be assessed. Socio-economic and legal issues also need to be addressed before such a reintroduction is considered. [source] The tick Ixodes ricinus: distribution and climate preferences in the western PalaearcticMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2006A. ESTRADA-PEÑA Abstract In this study, multivariate spatial clustering on monthly normalized difference vegetation index (NDVI) maps is used to classify ecological regions over the western Palaearctic. This classification is then used to delineate the distribution and climate preferences of populations (clades) of the tick Ixodes ricinus L. (Acari: Ixodidae) from a geographically extensive dataset of tick records and a gridded 2.5-km resolution climate dataset. Using monthly layers of the NDVI, regions of similar ecological attributes were defined and nine populations with significant differences in critical climate parameters (P < 0.005) were detected. Grouping of tick records according to other categories, such as political divisions, a 4°× 4° grid overlying the study area, or the CORINE) and USGS) vegetation classification schemes did not provided significantly separated populations (P= 0.094,0.304). Factor analysis and hierarchical tree clustering provided an ecological overview of these tick clades: two Mediterranean and one Scandinavian (western) clades are clearly separated from a node that includes clades of different parts of central Europe and the British Isles, with contrasting affinities between the different clades. The capture records of these ecologically separated clades produce a clear bias when bioclimate envelope modelling is applied to the mapping of habitat suitability for the tick in the western Palaearctic. The best-performing methods (Cohen's kappa = 0.834,0.912) use partial models developed with data from each ecoregion, which are then overlapped over the region of study. It is concluded that the use of ecologically derived ecoregions is an objective step in assessing the presence of ecologically different clades, and provides a guide in the development of data partitioning for habitat suitability modelling. [source] Use of resistance surfaces for landscape genetic studies: considerations for parameterization and analysisMOLECULAR ECOLOGY, Issue 17 2010STEPHEN F. SPEAR Abstract Measures of genetic structure among individuals or populations collected at different spatial locations across a landscape are commonly used as surrogate measures of functional (i.e. demographic or genetic) connectivity. In order to understand how landscape characteristics influence functional connectivity, resistance surfaces are typically created in a raster GIS environment. These resistance surfaces represent hypothesized relationships between landscape features and gene flow, and are based on underlying biological functions such as relative abundance or movement probabilities in different land cover types. The biggest challenge for calculating resistance surfaces is assignment of resistance values to different landscape features. Here, we first identify study objectives that are consistent with the use of resistance surfaces and critically review the various approaches that have been used to parameterize resistance surfaces and select optimal models in landscape genetics. We then discuss the biological assumptions and considerations that influence analyses using resistance surfaces, such as the relationship between gene flow and dispersal, how habitat suitability may influence animal movement, and how resistance surfaces can be translated into estimates of functional landscape connectivity. Finally, we outline novel approaches for creating optimal resistance surfaces using either simulation or computational methods, as well as alternatives to resistance surfaces (e.g. network and buffered paths). These approaches have the potential to improve landscape genetic analyses, but they also create new challenges. We conclude that no single way of using resistance surfaces is appropriate for every situation. We suggest that researchers carefully consider objectives, important biological assumptions and available parameterization and validation techniques when planning landscape genetic studies. [source] Ecological dynamics of extinct species in empty habitat networks.OIKOS, Issue 3 2003This paper explores the relative effects of host plant dynamics and butterfly-related parameters on butterfly persistence. It considers an empty habitat network where a rare butterfly (Cupido minimus) became extinct in 1939 in part of its historical range in north Wales, UK. Surviving populations of the butterfly in southern Britain were visited to assess use of its host plant (Anthyllis vulneraria) in order to calibrate habitat suitability and carrying capacity in the empty network in north Wales. These data were used to deduce that only a portion (,19%) of the host plant network from north Wales was likely to be highly suitable for oviposition. Nonetheless, roughly 65,460 eggs (3273 adult equivalents) could be expected to be laid in north Wales, were the empty network to be populated at the same levels as observed on comparable plants in surviving populations elsewhere. Simulated metapopulations of C. minimus in the empty network revealed that time to extinction and patch occupancy were significantly influenced by carrying capacity, butterfly mean dispersal distance and environmental stochasticity, although for most reasonable parameter values, the model system persisted. Simulation outputs differed greatly when host plant dynamics was incorporated into the modelled butterfly dynamics. Cupido minimus usually went extinct when host plant were at low densities. In these simulations host plant dynamics appeared to be the most important determinant of the butterfly's regional extirpation. Modelling the outcome of a reintroduction programme to C. minimus variation at high quality locations, revealed that 65% of systems survived at least 100 years. Given the current amount of resources of the north Wales landscape, the persistence of C. minimus under a realistic reintroduction programme has a good chance of being successful, if carried out in conjunction with a host plant management programme. [source] Ranging behavior and habitat selection of terrestrial insectivorous birds in north-east Tanzania: implications for corridor design in the Eastern Arc MountainsANIMAL CONSERVATION, Issue 5 2010W. D. Newmark Abstract Understanding the ranging behavior and habitat selection of understory tropical birds is important for corridor design and enhancing functional connectivity in fragmented tropical landscapes. Here we report on the ranging behavior and habitat selection of three terrestrial insectivorous bird species, the spot-throat Modulatrix stictigula, Usambara thrush Turdus roehli and orange ground thrush Zoothera gurneyi, in the East (EUM) and West (WUM) Usambara Mountains in north-east Tanzania. Based on 5945 locations and 3676 bird radio-tracking hours conducted between 2001 and 2008 at four study sites in the EUM and WUM, we determined that the 95% kernel home range and 50% kernel core range for the spot-throat, Usambara thrush, and orange ground thrush are similar yet large (aggregate mean home range=10.3±1.1 ha; aggregate mean core range 1.5±0.4 ha); that these species are adverse to crossing non-forested openings , no bird was recorded over the course of the study to cross a non-forested opening >15 m; and that the most extinction-prone species in our study system, the spot-throat and Usambara thrush, preferentially used slightly disturbed and primary forest, respectively. These results indicate that maintaining continuous forest cover and minimizing forest disturbance in corridors in the Eastern Arc Mountains is important for enhancing their habitat suitability for these species. [source] Conservation diagnosis of reintroducing Mediterranean pond turtles: what is wrong?ANIMAL CONSERVATION, Issue 6 2009A. Bertolero Abstract The presence of the Mediterranean pond turtle Mauremys leprosa in the Ebre Delta (Catalonia, north-east Spain) is well documented after the late 1970s, when the first reptile distribution lists were published. Owing to the fact that the species was considered scarce, a reintroduction programme based on the release of individuals at sites with potential habitat suitability was launched. From 1999 to 2001, 234 turtles of different ages were released and subsequently monitored until 2007, in order to make a conservation diagnosis using five assessment criteria. These criteria were body condition, individual growth, reproduction, survival and population growth rate. Despite the relatively large number of turtles released, no viable population resulted from the programme. Assessment criteria suggested that: (1) released individuals showed good physical condition and satisfactory growth (the only positive results); (2) reproduction was almost absent; (3) local survival was reduced compared with that of Spanish wild populations of the species; (4) temporary emigration was high; (5) the growth rate of the population was negative. In conclusion, the results suggested that the habitat at the Ebre Delta marshes may not be favourable to the species, and that the scarce historical data record may indicate a relatively low-quality habitat; the few records may correspond to individuals dispersing from the river, a more suitable habitat. Thus, we conclude that historically scarce records may be the result of natural patchiness and heterogeneous distributions, and they are not necessarily a good indicator of relict, decimated populations. Good assessment criteria, as those proposed and used here, are necessary tools to assess results in reintroduction projects to recover endangered chelonian populations. [source] An ecosystem-scale predictive model of coastal seagrass distributionAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2010A. Grech Abstract 1.Maintaining ecological processes that underpin the functioning of marine ecosystems requires planning and management of marine resources at an appropriate spatial scale. 2.The Great Barrier Reef World Heritage Area (GBR) is the world's largest World Heritage Area (approximately 348,000,km2) and second largest marine protected area. It is difficult to inform the planning and management of marine ecosystems at that scale because of the high cost associated with collecting data. To address this and to inform the management of coastal (approximately 15,m below mean sea level) habitats at the scale of the GBR, this study determined the presence and distribution of seagrass by generating a Geographic Information System (GIS)-based habitat suitability model. 3.A Bayesian belief network was used to quantify the relationship (dependencies) between seagrass and eight environmental drivers: relative wave exposure, bathymetry, spatial extent of flood plumes, season, substrate, region, tidal range and sea surface temperature. The analysis showed at the scale of the entire coastal GBR that the main drivers of seagrass presence were tidal range and relative wave exposure. Outputs of the model include probabilistic GIS-surfaces of seagrass habitat suitability in two seasons and at a planning unit of cell size 2,km×2,km. 4.The habitat suitability maps developed in this study extend along the entire GBR coast, and can inform the management of coastal seagrasses at an ecosystem scale. The predictive modelling approach addresses the problems associated with delineating habitats at the scale appropriate for the management of ecosystems and the cost of collecting field data. Copyright © 2010 John Wiley & Sons, Ltd. [source] Habitat suitability analysis for lacustrine brown trout (Salmo trutta) in Lake Walchensee, Germany: implications for the conservation of an endangered flagship speciesAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2010Marco Denic Abstract 1.The lacustrine brown trout (Salmo trutta) is endangered and of high conservation importance. In the only spawning habitat of the population in the Bavarian Lake Walchensee, the River Obernach, a substantial decrease in spawning runs has been reported. In this study, the present ecological state of the spawning stream was analysed with the objective of identifying life-stage specific limitations to successful recruitment attributable to deficiencies in (i) spawning migration, (ii) spawning habitat quality, and (iii) habitat quality for juveniles. 2.Structural stream analysis showed that discharge and several migration barriers , particularly near the river outlet into the lake , prevent successful spawning migrations at normal water levels. Migration barriers are probably the main limiting factor for reproduction of lacustrine brown trout, whereas structural variability of the Obernach meets the habitat requirements of both spawners and juveniles. 3.Spawning site quality was suitable for trout, as indicated by stream substratum texture and high exchange rates between free-flowing water and the interstitial zone in physico-chemical parameters (redox potential, dissolved oxygen, pH, temperature and conductivity). 4.Analyses of fish community structure revealed dominance of lithophilic species, in particular of riverine brown trout (Salmo trutta). Its density and intact demographic population structure suggest that spawning and juvenile habitat quality for salmonids is not limiting. Recapture of stocked lacustrine trout juveniles also indicates habitat suitability for the juvenile stage. 5.In conclusion, the results show that the methodology used in this study is suitable for the identification of life-stage specific habitat deficiencies in lacustrine brown trout and other fish species. Availability of habitat data throughout the species' distribution range is a first crucial step for the development of an effective recovery plan. Copyright © 2009 John Wiley & Sons, Ltd. [source] Lake habitat suitability for the rare European macrophyte Najas flexilis (Willd.) Rostk.AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2005& Schmidt Abstract 1.Najas flexilis (Willd.) Rostk. & Schmidt is a submerged annual macrophyte, rare in Europe, which is protected under the EC Habitats Directive. 2.N. flexilis grows in deep, often coloured or turbid water in mesotrophic lakes. Because of this habitat preference it is difficult to locate and assess the ecological state of populations of the species for conservation monitoring purposes. 3.A method is described based on plant community information that can be used to determine the baseline probability that conditions in a lake are suitable for supporting N. flexilis growth. This can be applied to conservation management decisions, such as whether a detailed underwater survey is justified for monitoring the integrity of existing populations of N. flexilis, or whether the lake may be a suitable site for introduction, or reintroduction, of populations of the plant. 4.Two methods of plant community description are compared: a quantitative micro-habitat scale approach and a whole-lake-scale qualitative approach. Plant community data collected using each method were grouped using TWINSPAN, and environmental descriptors of the sites comprising each plant community group were compared statistically. 5.Micro-habitat-scale community groups differed significantly only in the light extinction coefficient, indicating the zone within the lake in which N. flexilis occurred. 6.The whole-lake-scale community groups differed in a number of environmental variables indicative of eutrophication and acidification, two major environmental threats to N. flexilis survival. 7.This study suggests that a lake-scale qualitative plant community description would be a better indicator of site suitability for N. flexilis growth than a quantitative micro-habitat plant community description. This is because the whole-lake-scale approach could detect a difference in the environmental factors that affect N. flexilis growth, which the micro-habitat scale approach could not. Copyright © 2005 John Wiley & Sons, Ltd. [source] Characterization of freshwater pearl mussel (Margaritifera margaritifera) riverine habitat using River Habitat Survey dataAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2003L.C. Hastie Abstract 1.The feasibility of using River Habitat Survey (RHS) data to describe freshwater pearl mussel (Margaritifera margaritifera) macrohabitat in the River Spey, north-east Scotland, was investigated. 2.Mussels were found to be positively associated with a number of RHS variables. These included: boulder/cobble river bed substrates, broken/unbroken standing waves (channel flow types), aquatic liverworts/mosses/lichens and broadleaf/mixed woodland/bankside tree cover. Negative associations with gravel-pebble/silt substrates and emergent reeds/sedges/herbs were also found. 3.Two binary logistic regression models, based on seven and four variables, respectively, were constructed in order to predict the presence/absence of mussels at any given site. Predictive success rates of 83% and 78% were achieved. 4.Another binary logistic regression model, based on four variables, was constructed in order to predict the occurrence of ,optimal' M. margaritifera habitat (overall mussel densities , 1 m,2). A predictive success rate of 83% was achieved. 5.The results indicate two potentially important applications of RHS for the conservation management of M. margaritifera: (1) for monitoring the effects of physical changes on extant mussel beds (and predicting their effects on mussel populations), and (2) for determining the habitat suitability of historically occupied sites for re-introductions. Copyright © 2003 John Wiley & Sons, Ltd. [source] Microhabitat relationships among five lizard species associated with granite outcrops in fragmented agricultural landscapes of south-eastern AustraliaAUSTRAL ECOLOGY, Issue 2 2010DAMIAN R. MICHAEL Abstract A fundamental part of developing effective biodiversity conservation is to understand what factors affect the distribution and abundance of particular species. However, there is a paucity of data on ecological requirements and habitat relationships for many species, especially for groups such as reptiles. Furthermore, it is not clear whether habitat relationships for particular species in a given environment are transferable to other environments within their geographical range. This has implications for the type of ,landscape model' used to guide management decisions in different environments worldwide. To test the hypothesis that species-specific habitat relationships are transferable to other environments, we present microhabitat models for five common lizard species from a poorly studied habitat , insular granite outcrops, and then compared these relationships with studies from other environments in south-eastern Australia. We recorded twelve species from five families, representing 699 individuals, from 44 outcrops in the south-west slopes of New South Wales. Five lizard species were abundant and accounted for 95% of all observations: Egernia striolata, Ctenotus robustus, Cryptoblepharus carnabyi, Morethia boulengeri and Carlia tetradactyla (Scincidae). Linear regression modelling revealed suites of different variables related to the abundance patterns of individual species, some of which were broadly congruent with those measured for each species in other environments. However, additional variables, particular to rocky environments, were found to relate to reptile abundance in this environment. This finding means that species' habitat relationships in one habitat may not be readily transferable to other environments, even those relatively close by. Based on these data, management decisions targeting reptile conservation in agricultural landscapes, which contain rocky outcrops, will be best guided by landscape models that not only recognize gradients in habitat suitability, but are also flexible enough to incorporate intraspecies habitat variability. [source] | ||||||||||||||||||||||||||||