A fuzzy classification technique for predicting species’ distributions: applications using invasive alien plants and indigenous insects

Phytochemical Analysis and Habitat Suitability Mapping of Cardiocrinum cordatum (Thunb.) Makino Collected at Chiburijima, Oki Islands, Japan

Cardiocrinum cordatum, known as ubayuri in Japan, has antihypertensive properties and has been shown to inhibit angiotensin-converting enzyme (ACE), which contributes to the production of angiotensin II, a hypotensive substance in the renin−angiotensin system. C. cordatum has been the subject of various studies as a useful plant and is applied as a functional food. Due to the limited distribution, loss of natural habitat by frequent natural disasters, and environmental conditions, the chemical content and biological activity of C. cordatum have been drastically affected. Obtaining a stable supply of Cardiocrinu cordatum material with high biological activity is still a challenge. Understanding the native habitat environment and suitable cultivation sites could help in solving this issue. Therefore, in the current study we investigated the effect of environmental parameters on the hypertensive and antioxidant activities of C. cordatum collected at Chiburijima, Oki Islands, Shimane Prefecture, Japan. We also predicted the habitat suitability of C. cordatum using a geographic information system (GIS) and MaxEnt model with various conditioning factors, including the topographic, soil, environmental, and climatic factors of the study area. A total of 37 individual plant samples along with soil data were collected for this study. In vitro assays of ACE inhibitory and antioxidant activity were conducted on the collected samples. The results show that plants at 14 out of 37 sites had very strong ACE inhibitory activity (IC50 < 1 mg mL−1). However, the collected plants showed no signs of strong antioxidant activity. Statistical analysis using analysis of variance (ANOVA) showed that BIO05 (F value = 2.93, p < 0.05), nitrate−nitrogen (F value = 2.46, p < 0.05), and silt (F value = 3.443, p < 0.05) significantly affected ACE inhibitory activity. On the other hand, organic carbon content (F value = 10.986, p < 0.01) was found to significantly affect antioxidant activity. The final habitat suitability map shows 3.3% very high and 6.8% high suitability regions, and samples with ACE inhibition activity were located within these regions. It is recommended further investigations and studies are conducted on C. cordatum in these locations. The prediction suitability model showed accuracy with AUC-ROC of 96.7% for the study area.

The danger and indeterminacy of forfeiting perching space of bryophytes from climate shift: a case study for 115 species in China

Identifying the danger and expressing the indeterminacy of forfeiting perching space of species induced by rapid climate warming is crucial for biodiversity risk management under future changes in climate conditions. The scenarios of climate shift named the representative concentration pathways, the categorizing technique with regard to fuzzy-set, and Monte Carlo scheme was employed to survey the indeterminacy and the danger of forfeiting perching space caused by climate warming for 115 bryophytes in China. For the deterministic scenarios of climate shift, the richness of 115 bryophytes improved in several areas in north-eastern China, while it dropped in some areas in southern, eastern, south-eastern, and central China. In addition, for the deterministic scheme of altering climatic state, the count for bryophytes with the proportion of contracting the present areal range as less than 20%, 20-40%, 40-60%, 60-80%, and over 80% was belike 34-38, 19-38, 24-35, 9-19, and 4-9, separately; the count of bryophytes with the ratio of the occupying entire areal range as over 80%, 60-80%, and less than 20% was roughly 97-109, 4-14, and 2-8, separately. For the scenarios of randomly change in climate state, the number of bryophytes with a various proportion of forfeiting the present perching space dropped with enhancing the possibility; with the likelihood beyond 0.6, the count of bryophytes with forfeiting present perching space as less than 20%, 20-40%, 40-60%, 60-80% and high than 80% of the present areal range was approximately 7-14, 2-10, 0-7, 2-9, and 13-20, separately; the number of bryophytes with the ratio of occupying the whole areal range as less than 20%, 20-40%, 40-60%, 60-80%, and over 80% was more or less 1-3, 0-3, 1-5, 1-3, and 38-44, separately. Roughly 48 bryophytes would face the risk of extinction from climate warming, including endemic and non-endemic species. Forfeiting perching space induced by climate warming would cause variations in species composition and the disappearance of some ecological functions associated with these bryophytes. The inconstancy of forfeiting areal range caused by climate warming should be incorporated into the policy-making of conservation bryophytes for adaptation of climate warming.

The risk of forfeiting the ranges of reptiles under nonrandom and stochastic scenarios of moving climate conditions: a case study for 115 species in China

Revealing the hazard features of forfeiting areal ranges for nonidentical scenarios of shifting climatic conditions is pivotal for the conformation of reptiles to climatic warming. Taking 115 reptiles in China as an example, the indefiniteness and danger of shrinking geographical range for the reptiles under stochastic and nonrandom scenarios of moving climatic situations were inspected via exploiting the scenarios of shifting climatic status associated with the representative concentration pathways, Monte Carlo simulation, and the classifications scheme based on the fuzzy set. For non-stochastic states of altering climatic elements, the richness of 115 reptiles improved in certain sites of northeastern, and western China and dropped in several areas of northern, eastern, central China, and southeastern China: roughly 59-74 reptiles forfeiting less than 20% of their present ranges, roughly 25-34 reptiles narrowing less than 20-40% of their present areal ranges, and roughly 105-111 reptiles inhabited more than 80% of their overall areal ranges. For the random status of shifting climatic elements, the count of reptiles that forfeited the various extent of the present or entire areal ranges descended with raising the eventuality; with a possibility of over 0.6, the count of reptiles that minified less than 20%, 20-40%, 40-60%, 60-80% and over 80% of the present ranges was roughly 28-49, 5-10, 1-3, 0-1 and 13-18, separately; the count of reptiles that inhabited below 20%, 20-40%, 40-60%, 60-80% and more than 80% of the entire real ranges was roughly 0-1, 5-6, 1-5, 0-2 and 35-36, separately. About 30% of 115 reptiles would face disappearance danger in response to moving climate conditions in the absence of adaption steps, and the conformation measures were indispensable for the reptiles that shrunk their areas.

A Stepwise Assessment of Parsimony and Fuzzy Entropy in Species Distribution Modelling

Entropy is intrinsic to the geographical distribution of a biological species. A species distribution with higher entropy involves more uncertainty, i.e., is more gradually constrained by the environment. Species distribution modelling tries to yield models with low uncertainty but normally has to reduce uncertainty by increasing their complexity, which is detrimental for another desirable property of the models, parsimony. By modelling the distribution of 18 vertebrate species in mainland Spain, we show that entropy may be computed along the forward-backwards stepwise selection of variables in Logistic Regression Models to check whether uncertainty is reduced at each step. In general, a reduction of entropy was produced asymptotically at each step of the model. This asymptote could be used to distinguish the entropy attributable to the species distribution from that attributable to model misspecification. We discussed the use of fuzzy entropy for this end because it produces results that are commensurable between species and study areas. Using a stepwise approach and fuzzy entropy may be helpful to counterbalance the uncertainty and the complexity of the models. The model yielded at the step with the lowest fuzzy entropy combines the reduction of uncertainty with parsimony, which results in high efficiency.

Fuzzy sets allow gaging the extent and rate of species range shift due to climate change

The recent modification of species distribution ranges in response to a warmer climate has constituted a major and generalized biogeographic change. The main driver of the shift in distribution is the disequilibrium of the species ranges with their climatic favourability. Most species distribution modelling approaches assume equilibrium of the distribution with the environment, which hinders their applicability to the analysis of this change. Using fuzzy set theory we assessed the response to climate change of a historically African species, the Atlas Long-legged Buzzard. With this approach we were able to quantify that the Buzzard's distribution is in a latitudinal disequilibrium of the species distribution with the current climate of 4 km, which is driving the species range northwards at a speed of around 1.3 km/year, i.e., it takes 3 years for the species to occupy new climatically favourable areas. This speed is expected to decelerate to 0.5 km/year in 2060-2080.

Risk and Uncertainty of Losing Suitable Habitat Areas Under Climate Change Scenarios: A Case Study for 109 Gymnosperm Species in China

Taking 109 gymnosperm species in China as a case, the uncertainty and risk of losing habitat areas of gymnosperm species under future climate conditions were investigated via representative concentration pathways climate change scenarios, fuzzy set classifications and Monte Carlo techniques. Under nonrandom climate change scenarios, the richness of 109 species increased in the partial locations of northwestern and northeastern China and declined in the partial locations of eastern and central and southeastern China; the numbers of species that losing <20%, 20-40%, 40-60%, 60-80%, and over 80% of their current habitat areas were ~33-49, 36-40, 11-24, 7-9, and 2-8, respectively; ~99-105 species occupied over 80% of their total suitable areas and ~4-9 species occupied 60-80% their total suitable areas. Under random climate change scenarios, the number of species that losing various level of the habitat areas declined with enhancing probability; with a probabilities of over 0.6, the numbers of species that losing <20%, 20-40%, 40-60%, 60-80% and over 80% of their current habitat areas were ~19-28, 3-19, 0-3, 1-2, and 9-14, respectively, and the numbers of species that occupying ~20%, 20-40%, 40-60%, 60-80%, and over 80% of their total suitable areas were ~9-14, 4-11, 2-6, 1-3, and 34-45, respectively. Approximately 41% of 109 species will face extinction risks from climate change; the losing habitat areas in future climate condition will cause the varying of coniferous forest composition and the losing of ecosystem service related to the species; the uncertainty of losing distribution areas for species should not be ignored.

Prioritising potential incursions for contingency planning: pathways, species, and sites in Durban (eThekwini), South Africa as an example

Increased trade and travel have resulted in an increasing rate of introduction of biological organisms to new regions. Urban environments, such as cities, are hubs for human activities facilitating the introduction of alien species. Additionally, cities are susceptible to invading organisms as a result of the highly altered and transformed nature of these environments. Despite best efforts at prevention, new incursions of alien species will occur; therefore, prioritising incursion response efforts is essential. This study explores these ideas to identify priorities for strategic prevention planning in a South African city, Durban (eThekwini), by combining data from alien species watch lists, environmental criteria, and the pathways which facilitate the introduction of alien species in the city. Three species (with known adverse impacts elsewhere in the world) were identified as highly likely to be introduced and established in Durban (Alternantheraphiloxeroides,LithobatescatesbeianusandSolenopsisinvicta). These species are most likely to enter at either the Durban Harbour; pet and aquarium stores; or plant nurseries and garden centres – therefore active surveillance should target these sites as well as adjacent major river systems and infrastructure. We suggest that the integrated approach (species, pathways, and sites) demonstrated in this study will help prioritise resources to detect the most likely and damaging future incursions of alien species.

A web-based GIS system for wildlife species: a case study from Khouzestan Province, Iran

Recent efforts to aggregate, process, and use biodiversity information have appended novel opportunities and challenges for the field, and a rapid increase in studies that integrate and analyze data in the biological-ecological realm. We developed a web-based GIS system for the wildlife of Khouzestan Province that provides potential distribution maps and other spatial and nonspatial data on the wildlife of Khouzestan Province and its protected areas. We used MaxEnt and a fuzzy inference system to model distributions of species. Our application was structured using a client/server architecture, and the database design and construction was carried out using PostgreSQL/PostGIS, and GeoServer to serve maps. The mapping interface was developed using OpenLayers; ASP.NET was selected for designing the user interface. We used qualitative-quantitative methods to develop, design, refine, and finalize our system particularly as regards usability. The design approach resulted in a user-friendly interface that allows both specialists and non-specialists to quickly and efficiently run models to estimate potential distributions of species. Our application highlights what can be accomplished with a biodiversity-oriented web application.

Spatial multi-criteria decision analysis for modelling suitable habitats of Ornithodoros soft ticks in the Western Palearctic region

Ticks are economically and medically important ectoparasites due to the injuries inflicted through their bite, and their ability to transmit pathogens to humans, livestock, and wildlife. Whereas hard ticks have been intensively studied, little is known about soft ticks, even though they can also transmit pathogens, including African Swine Fever Virus (ASFV) affecting domestic and wild suids or Borrelia bacteria causing tick-borne relapsing fever (TBRF) in humans. We thus developed a regional model to identify suitable spatial areas for a community of nine Ornithodoros tick species (O. erraticus, O. sonrai, O. alactagalis, O. nereensis, O. tholozani, O. papillipes, O. tartakovskyi, O. asperus, O. verrucosus), which may be of medical and veterinary importance in the Western Palearctic region. Multi-Criteria Decision Analysis was used due to the relative scarcity of high-quality occurrence data. After an in-depth literature review on the ecological requirements of the selected tick community, five climate-related factors appeared critical for feeding activity and tick development: (i) a spring temperature exceeding 10°C to induce the end of winter soft tick quiescent period, (ii) a three-months summer temperature above 20°C to allow tick physiological activities, (iii) annual precipitation ranging from 60mm to 750mm and, in very arid areas, (iv) dry seasons interrupted by small rain showers to maintain minimum moisture inside their habitat along the year or (v) residual water provided by perennial rivers near habitats. We deliberately chose not to include biological factors such as host availability or vegetation patterns. A sensitivity analysis was done by performing multiple runs of the model altering the environmental variables, their suitability function, and their attributed weights. To validate the models, we used 355 occurrence data points, complemented by random points within sampled ecoregions. All models indicated suitable areas in the Mediterranean Basin and semi-desert areas in South-West and Central Asia. Most variability between models was observed along northern and southern edges of highly suitable areas. The predictions featured a relatively good accuracy with an average Area Under Curve (AUC) of 0.779. These first models provide a useful tool for estimating the global distribution of Ornithodoros ticks and targeting their surveillance in the Western Palearctic region.

Detecting and Attributing the Effects of Climate Change on the Distributions of Snake Species Over the Past 50 Years

It is unclear whether the distributions of snakes have changed in association with climate change over the past years. We detected the distribution changes of snakes over the past 50 years and determined whether the changes could be attributed to recent climate change in China. Long-term records of the distribution of nine snake species in China, grey relationship analysis, fuzzy sets classification techniques, the consistency index, and attributed methods were used. Over the past 50 years, the distributions of snake species have changed in multiple directions, primarily shifting northwards, and most of the changes were related to the thermal index. Driven by climatic factors over the past 50 years, the distribution boundary and distribution centers of some species changed with the fluctuations. The observed and predicted changes in distribution were highly consistent for some snake species. The changes in the northern limits of distributions of nearly half of the species, as well as the southern and eastern limits, and the distribution centers of some snake species can be attributed to climate change.

Paradigm of plant invasion: multifaceted review on sustainable management

A cascade of reviews and growing body of literature exists on forest invasion ecology, its mechanism or causes; however, no review addressed the sustainable management of invasive plants of forest in totality. Henceforth, the present paper aims to provide a critical review on the management of invasive species particularly in the context of forest plants. Plant invasion in forest is now increasingly being recognized as a global problem, and various continents are adversely affected, although to a differential scale. Quest for the ecological mechanism lying behind the success of invasive species over native species of forest has drawn the attention of researches worldwide particularly in the context of diversity-stability relationship. Transport, colonization, establishment, and landscape spread may be different steps in success of invasive plants in forest, and each and every step is checked through several ecological attributes. Further, several ecological attribute and hypothesis (enemy release, novel weapon, empty niche, evolution of increased competitive ability, etc.) were proposed pertaining to success of invasive plant species in forest ecosystems. However, a single theory will not be able to account for invasion success among all environments as it may vary spatially and temporally. Therefore, in order to formulate a sustainable management plan for invasive plants of forest, it is necessary to develop a synoptic view of the dynamic processes involved in the invasion process. Moreover, invasive species of forest can act synergistically with other elements of global change, including land-use change, climate change, increased concentrations of atmospheric carbon dioxide, and nitrogen deposition. Henceforth, a unified framework for biological invasions that reconciles and integrates the key features of the most commonly used invasion frameworks into a single conceptual model that can be applied to all human-mediated invasions.

The distributions of Chinese yak breeds in response to climate change over the past 50 years

The effects of prior climate change on yak breed distributions are uncertain. Here, we measured changes in the distributions of 12 yak breeds over the past 50 years in China and examined whether the changes could be attributed to climate change. Long-term records of yak breed distribution, grey relational analysis, fuzzy sets classification techniques and attribution methods were used. Over the past 50 years, the distributions of several yak breeds have changed in multiple directions, mainly shifting northward or westward, and most of these changes are related to the thermal index. Driven by climate change over the past years, the suitable range and the distribution centers of certain yak breeds have changed with fluctuation and have mainly shifted northward, eastward or southward. The consistency of observed versus predicted changes in distribution boundaries or distribution centers is higher for certain yak breeds. Changes in the eastern distribution boundary of two yak breeds over the past 50 years can be attributed to climate change.

Can changes in the distributions of resident birds in China over the past 50 years be attributed to climate change?

The distributions of bird species have changed over the past 50 years in China. To evaluate whether the changes can be attributed to the changing climate, we analyzed the distributions of 20 subspecies of resident birds in relation to climate change. Long-term records of bird distributions, gray relational analysis, fuzzy-set classification techniques, and attribution methods were used. Among the 20 subspecies of resident birds, the northern limits of over half of the subspecies have shifted northward since the 1960s, and most changes have been related to the thermal index. Driven by climate change over the past 50 years, the suitable range and latitude or longitude of the distribution centers of certain birds have exhibited increased fluctuations. The northern boundaries of over half of the subspecies have shifted northward compared with those in the 1960s. The consistency between the observed and predicted changes in the range limits was quite high for some subspecies. The changes in the northern boundaries or the latitudes of the centers of distribution of nearly half of the subspecies can be attributed to climate change. The results suggest that climate change has affected the distributions of particular birds. The method used to attribute changes in bird distributions to climate change may also be effective for other animals.

How climate change might influence the potential distribution of weed, bushmint (Hyptis suaveolens)?

Invasive species and climate change are considered as the most serious global environmental threats. In this study, we investigated the influence of projected global climate change on the potential distribution of one of the world's most successful invader weed, bushmint (Hyptis suaveolens (L.) Poit.). We used spatial data on 20 environmental variables at a grid resolution of 5 km, and 564 presence records of bushmint from its native and introduced range. The climatic profiles of the native and invaded sites were analyzed in a multi-variate space in order to examine the differences in the position of climatic niches. Maximum Entropy (MaxEnt) model was used to predict the potential distribution of bushmint using presence records from entire range (invaded and native) along with 14 eco-physiologically relevant predictor variables. Subsequently, the trained MaxEnt model was fed with Hadley Centre Coupled Model (HadCM3) climate projections to predict potential distribution of bushmint by the year 2050 under A2a and B2a emission scenarios. MaxEnt predictions were very accurate with an Area Under Curve (AUC) value of 0.95. The results of Principal Component Analysis (PCA) indicated that climatic niche of bushmint on the invaded sites is not entirely similar to its climatic niche in the native range. A vast area spread between 34 ° 02' north and 28 ° 18' south latitudes in tropics was predicted climatically suitable for bushmint. West and middle Africa, tropical southeast Asia, and northern Australia were predicted at high invasion risk. Study indicates enlargement, retreat, or shift across bushmint's invasion range under the influence of climate change. Globally, bushmint's potential distribution might shrink in future with more shrinkage for A2a scenario than B2a. The study outcome has immense potential for undertaking effective preventive/control measures and long-term management strategies for regions/countries, which are at higher risk of bushmint's invasion.

Sensitivity analysis of CLIMEX parameters in modeling potential distribution of Phoenix dactylifera L

Using CLIMEX and the Taguchi Method, a process-based niche model was developed to estimate potential distributions of Phoenix dactylifera L. (date palm), an economically important crop in many counties. Development of the model was based on both its native and invasive distribution and validation was carried out in terms of its extensive distribution in Iran. To identify model parameters having greatest influence on distribution of date palm, a sensitivity analysis was carried out. Changes in suitability were established by mapping of regions where the estimated distribution changed with parameter alterations. This facilitated the assessment of certain areas in Iran where parameter modifications impacted the most, particularly in relation to suitable and highly suitable locations. Parameter sensitivities were also evaluated by the calculation of area changes within the suitable and highly suitable categories. The low temperature limit (DV2), high temperature limit (DV3), upper optimal temperature (SM2) and high soil moisture limit (SM3) had the greatest impact on sensitivity, while other parameters showed relatively less sensitivity or were insensitive to change. For an accurate fit in species distribution models, highly sensitive parameters require more extensive research and data collection methods. Results of this study demonstrate a more cost effective method for developing date palm distribution models, an integral element in species management, and may prove useful for streamlining requirements for data collection in potential distribution modeling for other species as well.

Sensitivity analysis of CLIMEX parameters in modelling potential distribution of Lantana camara L

A process-based niche model of L. camara L. (lantana), a highly invasive shrub species, was developed to estimate its potential distribution using CLIMEX. Model development was carried out using its native and invasive distribution and validation was carried out with the extensive Australian distribution. A good fit was observed, with 86.7% of herbarium specimens collected in Australia occurring within the suitable and highly suitable categories. A sensitivity analysis was conducted to identify the model parameters that had the most influence on lantana distribution. The changes in suitability were assessed by mapping the regions where the distribution changed with each parameter alteration. This allowed an assessment of where, within Australia, the modification of each parameter was having the most impact, particularly in terms of the suitable and highly suitable locations. The sensitivity of various parameters was also evaluated by calculating the changes in area within the suitable and highly suitable categories. The limiting low temperature (DV0), limiting high temperature (DV3) and limiting low soil moisture (SM0) showed highest sensitivity to change. The other model parameters were relatively insensitive to change. Highly sensitive parameters require extensive research and data collection to be fitted accurately in species distribution models. The results from this study can inform more cost effective development of species distribution models for lantana. Such models form an integral part of the management of invasive species and the results can be used to streamline data collection requirements for potential distribution modelling.

Favourability: concept, distinctive characteristics and potential usefulness

The idea of analysing the general favourability for the occurrence of an event was presented in 2006 through a mathematical function. However, even when favourability has been used in species distribution modelling, the conceptual framework of this function is not yet well perceived among many researchers. The present paper is conceived for providing a wider and more in-depth presentation of the idea of favourability; concretely, we aimed to clarify both the concept and the main distinctive characteristics of the favourability function, especially in relation to probability and suitability, the most common outputs in species distribution modelling. As the capabilities of the favourability function go beyond species distribution modelling, we also illustrate its usefulness for different research disciplines for which this function remains unknown. In particular, we stressed that the favourability function has potential to be applied in all the cases where the probability of occurrence of an event is analysed, such as, for example, habitat selection or epidemiological studies.

Applying fuzzy logic to comparative distribution modelling: a case study with two sympatric amphibians

We modelled the distributions of two toads (Bufo bufo and Epidalea calamita) in the Iberian Peninsula using the favourability function, which makes predictions directly comparable for different species and allows fuzzy logic operations to relate different models. The fuzzy intersection between individual models, representing favourability for the presence of both species simultaneously, was compared with another favourability model built on the presences shared by both species. The fuzzy union between individual models, representing favourability for the presence of any of the two species, was compared with another favourability model based on the presences of either or both of them. The fuzzy intersections between favourability for each species and the complementary of favourability for the other (corresponding to the logical operation “A and not B”) were compared with models of exclusive presence of one species versus the exclusive presence of the other. The results of modelling combined species data were highly similar to those of fuzzy logic operations between individual models, proving fuzzy logic and the favourability function valuable for comparative distribution modelling. We highlight several advantages of fuzzy logic over other forms of combining distribution models, including the possibility to combine multiple species models for management and conservation planning.

Quantifying species' range shifts in relation to climate change: a case study of Abies spp. in China

Predicting species range shifts in response to climatic change is a central aspect of global change studies. An ever growing number of species have been modeled using a variety of species distribution models (SDMs). However, quantitative studies of the characteristics of range shifts are rare, predictions of range changes are hard to interpret, analyze and summarize, and comparisons between the various models are difficult to make when the number of species modeled is large. Maxent was used to model the distribution of 12 Abies spp. in China under current and possible future climate conditions. Two fuzzy set defined indices, range increment index (I) and range overlapping index (O), were used to quantify range shifts of the chosen species. Correlation analyses were used to test the relationships between these indices and species distribution characteristics. Our results show that Abies spp. range increments (I) were highly correlated with longitude, latitude, and mean roughness of their current distributions. Species overlapping (O) was moderately, or not, correlated with these parameters. Neither range increments nor overlapping showed any correlation with species prevalence. These fuzzy sets defined indices provide ideal measures of species range shifts because they are stable and threshold-free. They are reliable indices that allow large numbers of species to be described, modeled, and compared on a variety of taxonomic levels.

Fuzzy chorotypes as a conceptual tool to improve insight into biogeographic patterns

Chorotypes--statistically significant groups of coincident distribution areas--constitute biogeographic units that are fuzzy by nature. This quality has been referred to in the literature but has not been analyzed in depth or methodologically developed. The present work redefines chorotypes as fuzzy sets from a pragmatic perspective and basically focuses on the methodological and interpretative implications of this approach. The amphibian fauna in the Iberian Peninsula was used as an example to explore the fuzzy nature of chorotypes. The method on which this article is based is a widely used technique to define chorotypes. This method involves the fuzziness that is inherent to the identification between degree of similarity and degree of membership and includes a probabilistic analysis of the classification for the objective delimitation of chorotypes. The main innovation of this paper is a procedure to analyze chorotypes as fuzzy biogeographic units. A set of fuzzy parameters to deal with the biogeographic interpretation of fuzzy chorotypes is also described. A computer program has been developed and is freely available. History may be related to the degree of fuzziness of chorotypes. In our example, with amphibian distributions in Iberia, less fuzzy chorotypes could have a historical explanation, and the internal fuzziness of chorotypes increases with their distance to hypothetical Pleistocene refugia.

Combining local- and large-scale models to predict the distributions of invasive plant species

Habitat distribution models are increasingly used to predict the potential distributions of invasive species and to inform monitoring. However, these models assume that species are in equilibrium with the environment, which is clearly not true for most invasive species. Although this assumption is frequently acknowledged, solutions have not been adequately addressed. There are several potential methods for improving habitat distribution models. Models that require only presence data may be more effective for invasive species, but this assumption has rarely been tested. In addition, combining modeling types to form "ensemble" models may improve the accuracy of predictions. However, even with these improvements, models developed for recently invaded areas are greatly influenced by the current distributions of species and thus reflect near- rather than long-term potential for invasion. Larger scale models from species' native and invaded ranges may better reflect long-term invasion potential, but they lack finer scale resolution. We compared logistic regression (which uses presence/absence data) and two presence-only methods for modeling the potential distributions of three invasive plant species on the Olympic Peninsula in Washington, USA. We then combined the three methods to create ensemble models. We also developed climate envelope models for the same species based on larger scale distributions and combined models from multiple scales to create an index of near- and long-term invasion risk to inform monitoring in Olympic National Park (ONP). Neither presence-only nor ensemble models were more accurate than logistic regression for any of the species. Larger scale models predicted much greater areas at risk of invasion. Our index of near- and long-term invasion risk indicates that < 4% of ONP is at high near-term risk of invasion while 67-99% of the Park is at moderate or high long-term risk of invasion. We demonstrate how modeling results can be used to guide the design of monitoring protocols and monitoring results can in turn be used to refine models. We propose that, by using models from multiple scales to predict invasion risk and by explicitly linking model development to monitoring, it may be possible to overcome some of the limitations of habitat distribution models.

Habitat classification modeling with incomplete data: pushing the habitat envelope

Habitat classification models (HCMs) are invaluable tools for species conservation, land-use planning, reserve design, and metapopulation assessments, particularly at broad spatial scales. However, species occurrence data are often lacking and typically limited to presence points at broad scales. This lack of absence data precludes the use of many statistical techniques for HCMs. One option is to generate pseudo-absence points so that the many available statistical modeling tools can bb used. Traditional techniques generate pseudo-absence points at random across broadly defined species ranges, often failing to include biological knowledge concerning the species-habitat relationship. We incorporated biological knowledge of the species-habitat relationship into pseudo-absence points by creating habitat envelopes that constrain the region from which points were randomly selected. We define a habitat envelope as an ecological representation of a species, or species feature's (e.g., nest) observed distribution (i.e., realized niche) based on a single attribute, or the spatial intersection of multiple attributes. We created HCMs for Northern Goshawk (Accipiter gentilis atricapillus) nest habitat during the breeding season across Utah forests with extant nest presence points and ecologically based pseudo-absence points using logistic regression. Predictor variables were derived from 30-m USDA Landfire and 250-m Forest Inventory and Analysis (FIA) map products. These habitat-envelope-based models were then compared to null envelope models which use traditional practices for generating pseudo-absences. Models were assessed for fit and predictive capability using metrics such as kappa, threshold-independent receiver operating characteristic (ROC) plots, adjusted deviance (D(adj)2), and cross-validation, and were also assessed for ecological relevance. For all cases, habitat envelope-based models outperformed null envelope models and were more ecologically relevant, suggesting that incorporating biological knowledge into pseudo-absence point generation is a powerful tool for species habitat assessments. Furthermore, given some a priori knowledge of the species-habitat relationship, ecologically based pseudo-absence points can be applied to any species, ecosystem, data resolution, and spatial extent.