Developing landscape habitat models for rare amphibians with small geographic ranges: a case study of Siskiyou Mountains salamanders in the western USA

To advance the development of conservation planning for rare species with small geographic ranges, we determined habitat associations of Siskiyou Mountains salamanders (Plethodon stormi) and developed habitat suitability models at fine (10 ha), medium (40 ha), and broad (202 ha) spatial scales using available Geographic Information Systems data and logistic regression analysis with an information theoretic approach. Across spatial scales, there was very little support for models with structural habitat features, such as tree canopy cover and conifer diameter. Model-averaged 95% confidence intervals for regression coefficients and associated odds ratios indicated that the occurrence of Siskiyou Mountains salamanders was positively associated with rocky soils and Pacific madrone (Abutus menziesii) and negatively associated with elevation and white fir (Abies concolor); these associations were consistent across 3 spatial scales. The occurrence of this species also was positively associated with hardwood density at the medium spatial scale. Odds ratios projected that a 10% decrease in white fir abundance would increase the odds of salamander occurrence 3.02–4.47 times, depending on spatial scale. We selected the model with rocky soils, white fir, and Oregon white oak (Quercus garryana) as the best model across 3 spatial scales and created habitat suitability maps for Siskiyou Mountains salamanders by projecting habitat suitability scores across the landscape. Our habitat suitability models and maps are applicable to selection of priority conservation areas for Siskiyou Mountains salamanders, and our approach can be easily adapted to conservation of other rare species in any geographical location.     

Habitat suitability models for the conservation of thermophilic grasshoppers and bush crickets—simple or complex?

One goal of conservation biology is the assessment of effects of land use change on species distribution. One approach for identifying the factors, which determine habitat suitability for a species are statistical habitat distribution models. These models are quantitative and can be used for predictions in management scenarios. However, they often have one major shortcoming, which is their complexity. This means that they need several, often costly-to-determine parameters for predictions of species occurrence. We first used habitat suitability models to investigate and determine habitat preferences of three different Orthoptera species. Second, we compared the predictive powers of simple habitat suitability models considering only the ‘habitat type’ as predictor with more complex models taking different habitat factors into account. We found that the habitat type is the most reliable and robust factor, which determines the occurrence of the species studied. Thus, analyses of habitat suitability can easily be carried out on the basis of existing vegetation maps for the conservation of the three species under study. Our results can serve as a basis for the estimation of spatio-temporal distribution and survival probabilities of the species studied and might also be valuable for other species living in dry grasslands.     

The generality of habitat suitability models: A practical test with two insect groups

For the design and declaration of conservation areas as well as for planning habitat management it is important to quantitatively know the habitat preferences of the focal species. To take into account the requirements of as many species as possible, it would be of great advantage if one would either (i) find one or several species whose habitat requirements cover those of a large number of other species or if one could (ii) identify a common set of habitat parameters that is important for the occurrence of many species. Ideally such common habitat parameters should be easy to measure. Only then they may be of practical value in applied conservation biology.In this study, we compared the habitat preferences of different insect species (grasshoppers, bush crickets, butterflies, moths) in the same region by applying identical methods. To identify common explanatory variables that predict the occurrence probability of these species, we first tested the transferability of the specific ‘species models’ to other species within the same insect group. We tested how well the incidence of one species can be predicted by the occurrence probability of another species. The ‘best’ models within each group were then tested for transferability between the different groups. Additionally, we tested the predictive power of the predictor variable ‘habitat type’ as an easy and often available measure for conservation practice.Although in the different ‘species models’ different key factors determine habitat suitability, some models were successfully transferred and were able to reasonably predict the distribution of other species. The habitat preferences of the burnet moth Zygaena carniolica were particularly well suited for the prediction of suitable habitats for all other species. In addition, the predictor variable ‘habitat type’ played a dominant role in all models. Models using this aggregated predictor variable may well predict suitable habitat for all species.     

Habitat suitability models to make conservation decisions based on areas of high species richness and endemism

Biodiversity positively relates with the provisioning of ecosystem services and preserving areas with elevated diversity of highly-functional species could help to ensure human well-being. Most studies addressed to make these decisions use maps relying on species occurrences, where sites containing several species are proposed as priority conservation areas. These maps, however, may underestimate species richness because of the incompleteness of occurrence data. To improve this methodology, we propose using habitat suitability models to estimate the potential distribution of species from occurrence data, and later shaping richness maps by overlapping these predicted distribution ranges. We tested this proposal with Mexican oaks because they provide several ecosystem services and habitat suitability models of species were calibrated with MaxEnt. We used linear regressions to compare the outputs of these predictive maps with those of maps based on species occurrences only and, for both mapping methods, we assessed how much surface of sites with elevated richness and endemism of oaks is currently included within nature reserves. Both mapping methods indicated that oak species are concentrated in mountain regions of Mexico, but predictive maps based on habitat suitability models indicated higher oak richness and endemism that maps based on species occurrences only. Our results also indicated that nature reserves cover a small fraction of areas harboring elevated richness and endemism of oaks. These results suggest that estimating richness across extensive geographic regions using habitat suitability models quickly provides accurate information to make conservation decisions for highly-functional species groups.     

Habitat suitability models for the sand lizard Liolaemus wiegmannii based on landscape characteristics in temperate coastal dunes in Argentina

The knowledge of environmental variables associated with the species occurrence allows the recognition of sites which fulfil ecological requirements eventually used for conservation of species. The coastal dunes of Argentina are inhabited by sand lizards. Anthropic activities have severely degraded this ecosystem, affecting the habitat structure at a large scale. In this context, the effects of landscape characteristics on the sand lizard's (Liolaemus wiegmannii, Liolaemidae) presence were analysed to build habitat suitability maps along the coastal dunes of Argentina. A thematic map of study area was obtained from supervised classification of satellite images to identify landscape characteristics. Surveys were conducted during the lizard activity season, and landscape variables were measured in two spatial units. All information collected was compiled into a Geographic Information System. The relationship between the presence of lizards and landscape variables was evaluated by Generalized Linear Models. The predictions of these models were transferred by using Geographic Information System to habitat suitability maps. Almost all individuals (80%) were observed in semi‐fixed dunes. The analysis of landscape metrics in the two spatial extents showed complementary results. The habitat suitability models suggest that: (i) heterogeneous landscapes composed by disaggregated patches of semi‐fixed dunes and low or null percentages of active dunes distant from the coastline are the preferred environments, and (ii) human modifications such as urbanizations and forestation of dunes, have a negative impact on species occurrence. Suitable habitats were almost absent in those sectors of coastal dunes with highest level of urbanization, whereas they were distributed almost continuously in those areas without human disturbances.     

Community Associations of Chalk Grassland Leafhoppers (Hemiptera: Auchenorrhyncha): Conclusions for Habitat Conservation

Due to their confinement to specific hostplants or restricted habitat types, Auchenorrhyncha have the potential to make suitable biological indicators to measure the quality of chalk grassland under different management practices for nature conservation. The Auchenorrhyncha data from a study designed to identify the factors influencing the invertebrate diversity of chalk grasslands in southern England was used to evaluate the potential use of this group of insects as biological indicators. Between 1998 and 2002 altogether 81 chalk grassland sites were sampled. Vegetation structure and composition were recorded, and Auchenorrhyncha were sampled at each site on three occasions in each of two seasons using a ‘Vortis’ suction sampler. Auchenorrhyncha assemblages were then linked to the different grassland plant communities occurring on chalk soils according to the British National Vegetation Classification (NVC). Altogether 96 Auchenorrhyncha species were recorded during the study. Using data on the frequency and dominance of species, as is commonly done for plant communities, it was possible to identify the preferential and differential species of distinct Auchenorrhyncha assemblages. Significant differences between the Auchenorrhyncha assemblages associated with the various chalk grassland plant communities of the NVC were observed down to a level of sub-communities. We conclude that data on Auchenorrhyncha assemblages can provide valuable information for the setting of conservation management priorities, where data on floristic composition alone may not be sufficient, providing additional information on aspects of vegetation structure and condition.     

Are Species Coexistence Areas a Good Option for Conservation Management? Applications from Fine Scale Modelling in Two Steppe Birds

Biotic interactions and land uses have been proposed as factors that determine the distribution of the species at local scale. The presence of heterospecifics may modify the habitat selection pattern of the individuals and this may have important implications for the design of effective conservation strategies. However, conservation proposals are often focused on a single flagship or umbrella species taken as representative of an entire assemblage requirements. Our aim is to identify and evaluate the role of coexistence areas at local scale as conservation tools, by using distribution data of two endangered birds, the Little Bustard and the Great Bustard. Presence-only based suitability models for each species were built with MaxEnt using variables of substrate type and topography. Probability maps of habitat suitability for each species were combined to generate a map in which coexistence and exclusive use areas were delimitated. Probabilities of suitable habitat for each species inside coexistence and exclusive areas were compared. As expected, habitat requirements of Little and Great Bustards differed. Coexistence areas presented lower probabilities of habitat suitability than exclusive use ones. We conclude that differences in species'' habitat preferences can hinder the efficiency of protected areas with multi-species conservation purposes. Our results highlight the importance of taking into account the role of biotic interactions when designing conservation measurements.     

Model‐based conservation planning of the genetic diversity of Phellodendron amurense Rupr due to climate change

Climate change affects both habitat suitability and the genetic diversity of wild plants. Therefore, predicting and establishing the most effective and coherent conservation areas is essential for the conservation of genetic diversity in response to climate change. This is because genetic variance is a product not only of habitat suitability in conservation areas but also of efficient protection and management. Phellodendron amurense Rupr. is a tree species (family Rutaceae) that is endangered due to excessive and illegal harvesting for use in Chinese medicine. Here, we test a general computational method for the prediction of priority conservation areas (PCAs) by measuring the genetic diversity of P. amurense across the entirety of northeast China using a single strand repeat analysis of twenty microsatellite markers. Using computational modeling, we evaluated the geographical distribution of the species, both now and in different future climate change scenarios. Different populations were analyzed according to genetic diversity, and PCAs were identified using a spatial conservation prioritization framework. These conservation areas were optimized to account for the geographical distribution of P. amurense both now and in the future, to effectively promote gene flow, and to have a long period of validity. In situ and ex situ conservation, strategies for vulnerable populations were proposed. Three populations with low genetic diversity are predicted to be negatively affected by climate change, making conservation of genetic diversity challenging due to decreasing habitat suitability. Habitat suitability was important for the assessment of genetic variability in existing nature reserves, which were found to be much smaller than the proposed PCAs. Finally, a simple set of conservation measures was established through modeling. This combined molecular and computational ecology approach provides a framework for planning the protection of species endangered by climate change.     

Urban brownfields as temporary habitats: driving forces for the diversity of phytophagous insects

In urban brownfields (derelict sites), we studied the influence of local factors (successional age, vegetation structure, soil) and landscape context (spatial arrangement of brownfields of different successional stages) on the diversity of phytophagous insects, grasshoppers and leafhoppers (Orthoptera and Hemiptera: Auchenorrhyncha). The study was conducted on a total of 246 plots in the cities of Bremen and Berlin, Germany. We used a habitat modelling approach, enabling us to predict the community from single species models (30 species in Bremen, 28 in Berlin).
The results revealed that communities were predominantly determined by vegetation structure, followed by landscape context, soil parameters and site age. For most species, local factors were the most important. Only few species were strongly influenced by landscape context, even though some showed clear negative reactions to low proportions of brownfields in the surroundings.
Along a successional gradient of vegetation structure, from scarce and low to dense and high vegetation, the insect community was not static. Even though species numbers remained comparatively constant, species composition changed considerably. Many species showed clear preferences for certain successional stages. Thus, maintaining the regional species pool of a city requires a mosaic of all successional stages.     

Current and future distribution of a parasite with complex life cycle under global change scenarios: Echinococcus multilocularis in Europe

Global change is expected to have complex effects on the distribution and transmission patterns of zoonotic parasites. Modelling habitat suitability for parasites with complex life cycles is essential to further our understanding of how disease systems respond to environmental changes, and to make spatial predictions of their future distributions. However, the limited availability of high quality occurrence data with high spatial resolution often constrains these investigations. Using 449 reliable occurrence records for Echinococcus multilocularis from across Europe published over the last 35 years, we modelled habitat suitability for this parasite, the aetiological agent of alveolar echinococcosis, in order to describe its environmental niche, predict its current and future distribution under three global change scenarios, and quantify the probability of occurrence for each European country. Using a machine learning approach, we developed large-scale (25 × 25 km) species distribution models based on seven sets of predictors, each set representing a distinct biological hypothesis supported by current knowledge of the autecology of the parasite. The best-supported hypothesis included climatic, orographic and land-use/land-cover variables such as the temperature of the coldest quarter, forest cover, urban cover and the precipitation seasonality. Future projections suggested the appearance of highly suitable areas for E. multilocularis towards northern latitudes and in the whole Alpine region under all scenarios, while decreases in habitat suitability were predicted for central Europe. Our spatially explicit predictions of habitat suitability shed light on the complex responses of parasites to ongoing global changes.