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1.
Understanding the relationship between spatial patterns of landscape attributes and population presence and abundance is essential for understanding population processes as well as supporting management and conservation strategies. This study evaluates the influence of three factors: environment, habitat management, and season on the presence and abundance of the wild rabbit (Oryctolagus cuniculus), an important prey species for Mediterranean endangered predator species. To address this issue, we estimated wild rabbit presence and abundance by latrine counting in transects located in 45 plots within a 250?×?250 m grid from June 2007 until June 2009 in a 1,200 ha hunting area in southern Portugal. We then analyzed how wild rabbit presence and abundance correlate with the aforementioned factors. Our results showed that the main variable influencing wild rabbit presence and abundance was the distance to the artificial warrens. North and northeast slope directions were negatively related to wild rabbit presence. Conversely, rabbit presence was positively correlated with short distances to ecotone, artificial warrens, and spring. Regarding rabbit abundance, in addition to artificial warrens, soft soils, bushes, and season also had a positive effect. We found that environmental variables, management practices, and season each affect wild rabbit presence and abundance differently at a home range scale in low-density population. Thus, our major recommendations are reducing the distance to artificial warrens and ecotone, ideally to less than 100 m, and promoting habitat quality improvement on slopes with plenty of sun exposure.  相似文献   

2.
We examined environmental and anthropogenic factors drive range loss in large mammals, using presence data of Amur tigers opportunistically collected between 2000 and 2012, and anthropogenic and environmental variables to model the distribution of the Amur tiger in northeastern China. Our results suggested that population distribution models of different subregions showed different habitat factors determining tiger population distribution patterns. Where farmland cover was over 50 km2 per pixel (196 km2), distance was within 15 km to the railway in Changbaishan and road density (length per pixel) increased in Wandashan, the relative probability of Amur tiger occurrence exhibited monotonic avoidance responses; however, where distance was within 150 km of the Sino-Russia border, the occurrence probability of Amur tiger was relatively high. We analyzed the avoidance or preference responses of Amur tiger distribution to elevation, snow depth and Viewshed. Furthermore, different subregional models detected a variety of spatial autocorrelation distances due to different population clustering patterns. We found that spatial models significantly improved model fits for non-spatial models and made more robust habitat suitability predications than that of non-spatial models. Consequently, these findings provide useful guidance for habitat conservation and management.  相似文献   

3.
Protected area managers need reliable information to detect spatial and temporal trends of the species they intend to protect. This information is crucial for population monitoring, understanding ecological processes, and evaluating the effectiveness of management and conservation policies. In under-funded protected areas, managers often prioritize ungulates and carnivores for monitoring given their socio-economic value and sensitivity to human disturbance. Aircraft-based surveys are typically utilized for monitoring ungulates because they can cover large areas regardless of the terrain, but such work is expensive and subject to bias. Recently, unmanned aerial vehicles have shown great promise for ungulate monitoring, but these technologies are not yet widely available and are subject to many of the same analytical challenges associated with traditional aircraft-based surveys. Here, we explore use of inexpensive and robust distance sampling methods in Kafue National Park (KNP) (22,400 km2), carried out by government-employed game scouts. Ground-based surveys spanning 101, 5-km transects resulted in 369 ungulate group detections from 20 species. Using generalized linear models and distance sampling, we determined the environmental and anthropogenic variables influencing ungulate species richness, density, and distribution. Species richness was positively associated with permanent water and percent cover of closed woodland vegetation. Distance to permanent water had the strongest overall effect on ungulate densities, but the magnitude and direction of this effect varied by species. This ground-based approach provided a more cost-effective, unbiased, and repeatable method than aerial surveys in KNP, and could be widely implemented by local personnel across under-funded protected areas in Africa.  相似文献   

4.
Species distribution models (SDMs) are often limited by the use of coarse-resolution environmental variables and by the number of observations required for their calibration. This is particularly true in the case of elusive animals. Here, we developed a SDM by combining three elements: a database of explanatory variables, mapped at a fine resolution; a systematic sampling scheme; and an intensive survey of indirect observations. Using MaxEnt, we developed the SDM for the population of the Asiatic wild ass (Equus hemionus), a rare and elusive species, at three spatial scales: 10, 100, and 1000 m per pixel. We used indirect observations of feces mounds. We constructed 14 layers of explanatory variables, in five categories: water, topography, biotic conditions, climatic variables and anthropogenic variables. Woody vegetation cover and slopes were found to have the strongest effect on the distribution of wild ass and were included as the main predictors in the SDM. Model validation revealed that an intensive survey of feces mounds and high-resolution predictor layers resulted in a highly accurate and informative SDM. Fine-grain (10 and 100 m) SDMs can be utilized to: (1) characterize the variables influencing species distribution at high resolution and local scale, including anthropogenic effects and geomorphologic features; (2) detect potential population activity centers; (3) locate potential corridors of movement and possible isolated habitat patches. Such information may be useful for the conservation efforts of the Asiatic wild ass. This approach could be applied to other elusive species, particularly large mammals.  相似文献   

5.
Due to its relict nature, the unique Baroninae swallowtail, Baronia brevicornis, is considered a “living fossil”. It is also one of the most enigmatic butterfly species with contentious origins and peculiar ecological characteristics. The aim of this study is to evaluate the genetic diversity and population structure of this endemic species of butterfly in Mexico. We sampled populations in two areas within its restricted geographical range in central Mexico and the isolated subspecies population in the state of Chiapas. Three ISSR primers produced 66 loci, indicating a high genetic diversity (P = 100 %, H e  = 0.22) and variation range in these populations (62 % < P < 85 %, 0.18 < H e  < 0.25). The Chiapas population presented the lowest values. The observed high values can be explained by the population dynamic of this species characterized by a very high density of individuals over very limited areas. Variation between populations appears to reflect both the age of colonization and locality perturbation level. Two methods of genetic structure analysis (Self-Organizing Map and Structure analysis) match to define three clusters. Natural and anthropogenic barriers may explain the separation between two clusters (cluster 1 and 2) of central Mexico but an unexpected result revealed that the Chiapas population is not genetically distinguishable from the central Mexico populations (cluster 3) leading us to hypothesize a possible “recent” separation or anthropogenic introduction. Habitat and host plant specificity probably limits the exchange of individuals between populations thus increasing fragmentation and leading to a complex genetic structure. We should put in place population monitoring schemes at different spatial scales, combining field occurrences and genetic tools, in order to reduce extinction susceptibility and keep track of recolonization events for this enigmatic species.  相似文献   

6.
Population density data on depleted and endangered wildlife species are essential to assure their effective management and, ultimately, conservation. The European wildcat is an elusive and threatened species inhabiting the Iberian Peninsula, with fragmented populations and living in low densities. We fitted spatial capture–recapture models on camera-trap data, to provide the first estimate of wildcat density for Portugal and assess the most influential drivers determining it. The study was implemented in Montesinho Natural Park (NE Portugal), where we identified nine individuals, over a total effort of 3,477 trap-nights. The mean density estimate was 0.032 ± 0.012 wildcat/km2, and density tended to increase with distance to humanized areas, often linked to lower human disturbance and domestic cat presence, with forest and herbaceous vegetation cover and with European rabbit abundance. Although, this density estimate is within the range of values estimated for protected areas elsewhere in the Iberian Peninsula, our estimates are low at the European level. When put in context, our results highlight that European wildcats may be living in low population densities across the Iberian Mediterranean biogeographic region. No phenotypic domestic or hybrid cats were detected, suggesting potentially low admixture rates between the two species, although genetic sampling would be required to corroborate this assertion. We provide evidence that Montesinho Natural Park may be a suitable area to host a healthy wildcat population, and thus be an important protected area in this species' conservation context.  相似文献   

7.
8.
Solid understanding of species’ range and local population densities is important for successful wildlife management and research. Specific behavioral and ecological characteristics make brown bear Ursus arctos a difficult species to study. We present a map of range and local population densities of brown bears in Slovenia, made with the use of a new approach similar to voting classifications based on a combination of four datasets: Global Positioning System telemetry data, records of bear removals, systematic and opportunistic direct observations and signs of bear presence, and noninvasive genetic samples. Results indicate that the majority of bears in Slovenia live in Dinaric Mountains in the southern part of the country where local bear population densities exceed 40 bears/100 km2. This is one of the highest population densities reported so far for this species worldwide. Population densities decrease towards the north (Alpine region) and are very low along the border with Italy and Austria where almost no females are present. This explains slow past and present expansion of this transboundary bear population into the Alps and should be considered in future bear re-colonization management strategies. Results also showed that data from observations and removals overestimate bear population densities at low values, while mortality and genetic data overestimate population densities in areas with more people. Nevertheless, all data types appeared useful for describing the general bear distribution patterns. Similar approach could be applied to studies of other charismatic or game species, for which several types of data are often available.  相似文献   

9.
Calcium is an important nutrient that can be limiting in many forest ecosystems, where acid deposition and other natural and anthropogenic activities have resulted in significant soil calcium depletion. Calcium’s critical role in physiological and structural processes and its limited mobility and storage in many organisms, make it a potential driver of ecosystem structure and function, but little is known about how changes in soil calcium affect community composition, especially in terrestrial vertebrates. The aim of this study was to establish relationships between the abundances of forest songbird species and soil calcium and to elucidate linking mechanisms by establishing simultaneous relationships with trophic and habitat variables. We measured soil calcium and pH, calcium-rich invertebrate abundances, vegetation, and songbird abundances at 14 interior forest sites across central Pennsylvania representing a range of soil calcium levels. Bird community composition varied with soil calcium and pH, with 10 bird species having the highest abundances in forests with high calcium soils, and five species having the highest abundances with low calcium soils. Bird species associated with low-calcium soils were associated with high densities of mountain laurel (Kalmia latifolia), an acid-loving shrub, whereas bird species associated with high-calcium soils were associated with high densities of saplings and high basal area of acid-sensitive tree species. Homogenization of soil conditions through land-use patterns and soil calcium depletion pose the risk of reducing the beta diversity of bird species across forest areas because community composition varied with soil calcium.  相似文献   

10.
1. Native crayfishes are often extirpated from portions of their range because of interactions with invasive species, anthropogenic alterations to environmental conditions or a combination of these factors. Our goal was to identify coarse‐scale natural and anthropogenic factors related to the current distributions of the invasive crayfish, Orconectes hylas, and two endemic crayfishes, Orconectes peruncus and Orconectes quadruncus in the St. Francis River drainage, Missouri, U.S.A. and to provide wider insights into the potential role of anthropogenic factors in facilitating species displacement. 2. We used classification trees to model coarse‐scale natural and anthropogenic environmental factors and their relation to the presence or absence of each species. Model results were then used to predict probability of presence for each species within each stream segment throughout the entire St. Francis River drainage. 3. Factors related to geology and soils were the best predictors of species distributions. A dichotomy of these factors explained much of the discrete distributions of the two native species. Agricultural‐related factors were identified as the most influential anthropogenic activity related to species distributions. All associations between the invasive species and anthropogenic factors were negative which suggested the invader was not likely to establish in heavily impacted areas. Overall, our models had high correct classification rates, and we were able to reliably predict the presence of the invader in the invaded drainage. 4. Given the negative associations of the invader with anthropogenic alterations at a coarse spatial scale, we believe other mechanisms are likely to be responsible for the widespread displacement of the two native species. These findings can be used to assist in conservation activities such as creation of refugia for native species and may direct future research to identify the mechanism(s) of species displacement.  相似文献   

11.
Understanding the ecological and anthropogenic drivers of population dynamics requires detailed studies on habitat selection and spatial distribution. Although small pelagic fish aggregate in large shoals and usually exhibit important spatial structure, their dynamics in time and space remain unpredictable and challenging. In the Gulf of Lions (north-western Mediterranean), sardine and anchovy biomasses have declined over the past 5 years causing an important fishery crisis while sprat abundance rose. Applying geostatistical tools on scientific acoustic surveys conducted in the Gulf of Lions, we investigated anchovy, sardine and sprat spatial distributions and structures over 10 years. Our results show that sardines and sprats were more coastal than anchovies. The spatial structure of the three species was fairly stable over time according to variogram outputs, while year-to-year variations in kriged maps highlighted substantial changes in their location. Support for the McCall''s basin hypothesis (covariation of both population density and presence area with biomass) was found only in sprats, the most variable of the three species. An innovative method to investigate species collocation at different scales revealed that globally the three species strongly overlap. Although species often co-occurred in terms of presence/absence, their biomass density differed at local scale, suggesting potential interspecific avoidance or different sensitivity to local environmental characteristics. Persistent favourable areas were finally detected, but their environmental characteristics remain to be determined.  相似文献   

12.
Ecosystem vulnerability to climate change remains elusive in the species-rich Taiwan-Japan archipelago. We predicted potential habitats (PHs) of ten dominant evergreen broad-leaved tree species by using the current and twenty potential climate change scenarios using generalised additive models. The presence/absence records of each species, extracted from vegetation database, were used as response variables. Four climatic and one spatial variables were used as explanatory variables. The results showed that the interaction terms of spatial variable, indicating historical range shifts or species interactions, restricted the distribution of all the target species as much as that by the each climatic variable. The PHs of all the target species were predicted to consistently increase, and in particular, to expand northward and upward to the cool temperate zone. However, the PHs were predicted to decrease within the range of 23.6–38.1 % in the Ryukyu Islands for Castanopsis sieboldii and Elaeocarpus japonica, respectively, and within the range of 32.4–42.3 % in Taiwan for Camellia japonica and Distylium racemosum, respectively. These findings suggest that the four species will be vulnerable at the southern range limits; however, the remaining six species will potentially increase within the PH areas in the future at all regions.  相似文献   

13.
The inter-Andean tropical rainforests and dry forests of the Magdalena river basin (Tumbes-Choco-Magdalena biodiversity hotspot) in northern Colombia have undergone significant forest loss and degradation in recent decades. Six primate species inhabit this region, five of which are currently threatened with extinction and one of which—the brown spider monkey, Ateles hybridus—is considered critically endangered. Accurate and recent information on the distribution and conservation status of these threatened primate populations is scarce or nonexistent, even though such data are needed to implement successful conservation actions and management plans. Between 2006 and 2016, we evaluated the status and distribution of primates across inter-Andean lowland forests in northern Colombia. We visited 30 sites to evaluate the presence/absence of brown spider monkeys and other primate taxa in the region. We also carried out surveys at 10 of these sites to obtain estimates of primate population densities and demographic information from forests with different levels of anthropogenic disturbance. Novel data on primate presence/absence were obtained for 27 sites, and 136 records were collected in total. Only 33% of the sites visited were large forest fragments (>?500 Ha). This study confirms that at least six primate species are still present in the Rio Magdalena region, which represents the highest platyrrhine diversity west of the Andes. This study also confirms the persistence of a wild population of Colombian woolly monkeys (Lagothrix lagotricha lugens) in the Serranía de San Lucas. Assigning formal protected status to this region is an urgent priority for the conservation of primates in the Rio Magdalena region.  相似文献   

14.
Predictive models of the spatial distribution and abundance of species based on habitat characteristics are finding increasing use in management and conservation. The European badger attracts interest as a model species both for conservation reasons and because of the important role the species is playing in understanding carnivore sociality. We developed a statistical habitat model based on presence/absence data on badger setts. To maximise the utility of the model in management, we limited the choice of model variables to those that had a clear basis in badger ecology and that could be obtained on a nation-wide digital format. We extrapolated the habitat model to a region in Denmark and developed a threshold-independent sett distribution algorithm to estimate sett densities. The habitat model was simpler than previously published models of badger sett habitat selection, but nevertheless had a predictive ability in excess of 80% judged against independent data. The sett distribution algorithm was able to simultaneously reproduce several observed patterns of sett density and distribution over the probability gradient. It thus represents a significant improvement over threshold-dependent methods used to discriminate between suitable and unsuitable habitat predicted by presence/absence regression models. Our approach demonstrates that a model of badger sett habitat suitability with high predictive power can be obtained using easily accessible map-variables and presence/absence data. This is a prerequisite for using habitat models as predictive tools over large areas. The use of a simple sett distribution algorithm circumvents the common problem of subjectively fixing a threshold to discriminate between suitable and unsuitable habitat. In conjunction the models presented here constitute an important contribution to the management of the badger in Denmark and, upon further validation, possibly to similar regions in Northern Europe.  相似文献   

15.
Natural areas near human-modified landscapes experience factors that may affect local biodiversity at levels commensurate with natural environmental factors. The land snails of the Canary Islands provide excellent opportunities to evaluate the importance of anthropogenic agents in mediating the diversity and distribution of species. Land snails are particularly sensitive to disturbance and are an integral part of terrestrial ecosystems. This study analyzed the distributions and abundances of terrestrial macrosnail shell assemblages at 60 localities throughout the coastal scrub biome of the Canary Islands. This was accomplished using data on natural and anthropogenic variables to assess their relative importance in governing land snail diversity. A total of 34,801 dead shells represented a diverse malacofauna with highly localized endemism. Due to uncertain species identifications, samples from the 18 sites from the two easternmost islands are described, but excluded from statistical analyses. Regression tree analysis indicated that proximity to agricultural sites was the most important predictor of species diversity. Sites with no or very little agricultural area (≤ 0.167 km2) within a 1 km radius had significantly higher richness and diversity. These results have implications for Canary Islands conservation. Protected areas that are patchworks of natural and agricultural landscapes are still subject to native biodiversity loss because of anthropogenic impacts even when the footprint of agriculture is small.  相似文献   

16.
Biases in data availability have serious consequences on scientific inferences that can be derived. The potential consequences of these biases could be more detrimental in the less‐studied megadiverse regions, often characterized by high biodiversity and serious risks of human threats, as conservation and management actions could be misdirected. Here, focusing on 134 bat species in Mexico, we analyze spatial and taxonomic biases and their drivers in occurrence data; and identify priority areas for further data collection which are currently under‐sampled or at future environmental risk. We collated a comprehensive database of 26,192 presence‐only bat records in Mexico to characterize taxonomic and spatial biases and relate them to species' characteristics (range size and foraging behavior). Next, we examined variables related to accessibility, species richness and security to explain the spatial patterns in occurrence records. Finally, we compared the spatial distributions of existing data and future threats to these species to highlight those regions that are likely to experience an increased level of threats but are currently under‐surveyed. We found taxonomic biases, where species with wider geographical ranges and narrow‐space foragers (species easily captured with traditional methods), had more occurrence data. There was a significant oversampling toward tropical regions, and the presence and number of records was positively associated with areas of high topographic heterogeneity, road density, urban, and protected areas, and negatively associated with areas which were predicted to have future increases in temperature and precipitation. Sampling efforts for Mexican bats appear to have focused disproportionately on easily captured species, tropical regions, areas of high species richness and security; leading to under‐sampling in areas of high future threats. These biases could substantially influence the assessment of current status of, and future anthropogenic impacts on, this diverse species group in a tropical megadiverse country.  相似文献   

17.
Mosquito community composition and population dynamics were compared to weather variables and land use/cover data during 2008 to determine which variables affected population dynamics at the J.W. Jones Ecological Research Center in southwestern Georgia. Models relating adult mosquito distributions to weather variables and time of year were compared using Akaike's Information Criterion (AIC) model selection. Precipitation, temperature, humidity, and Keetch-Byram Drought Index were important factors correlated with mosquito abundance or presence/absence for the species considered. A cluster analysis, which grouped eight sites based on the percentages of land use/cover and hydric soils located in a 1-km radius surrounding collection sites, and an indicator species analysis were used to investigate the associations among 11 mosquito species and sites with similar land use/cover. Aedes albopictus (Skuse), Culex coronator Dyar & Knab, Culex quinquefasciatus Say, and Culex salinarius Coquillett were associated with sites that had the most anthropogenic influence, while Coquillettidia perturbans (Walker) and Psorophora ferox (von Humboldt) were associated with natural land cover such as wetlands and forested land. This study demonstrates that regional climate and land use/cover data can be predictive of the population dynamics of certain mosquito populations and is the first to examine how the distribution of Cx. coronator adults relate to land use/cover in the southeastern United States.  相似文献   

18.
Interactions between invasive species can be difficult to predict and can result in unanticipated impacts of significance for native fauna. Here we show that introduced European rabbits (Oryctolagus cuniculus) create habitat that enables invasive redback spiders (Latrodectus hasselti Thorell, 1870) to establish and prey upon the nationally endangered, endemic Cromwell chafer beetle (Prodontria lewisii Broun, 1904). We examined the spatial relationship between rabbit holes and redback spider occurrence, recorded all prey caught in redback spider webs over a 4-month period, and tested the role rabbit holes play in providing habitat for redback spiders experimentally, by filling in rabbit holes in areas used by spiders and monitoring subsequent occupation of the areas over four months. Redback spiders predominately resided in old rabbit holes, with the highest densities of spiders coinciding with high densities of rabbit holes. Cromwell chafer beetles were commonly caught in webs. Filling in rabbit holes eliminated the presence of redback spiders at all treated sites and reduced prey capture in those areas. Conservation management to protect Cromwell chafer beetles should focus on eliminating rabbits and their holes from beetle habitat.  相似文献   

19.
Over the last four decades, the majority of European farmland birds have shown marked population declines attributed to the intensification of agriculture. The Common Quail is a widespread farmland breeder across most of Europe. Its populations have shown marked decline, particularly pronounced at the end of the previous century. Ongoing agriculture intensification may be the factor responsible for the observed declines; however, links between species occurrence and farming intensification have not been addressed so far. We analyzed factors affecting the occurrence of the Quail in Poland using data from 722 1 × 1-km study plots and a set of 22 environmental variables, including proxies for agriculture intensification. Predictors were aggregated using PCAs and related to species presence/absence data using GAMs. The best-supported model of the species’ occurrence included eight variables and was clearly better (AIC weight = 0.54) than other models. Quails preferred open fields, showing high photosynthetic activity in March or June, with rather low precipitation and often at relatively high altitudes (up to 900 m a.s.l.). Importantly, quails were more frequent on plots located in regions with rather high inorganic fertilizer input, and showed no avoidance of areas with a high level of agriculture mechanization. We postulate that singing male quails are attracted to areas with medium or high intensity of agriculture but it may represent a maladaptive habitat choice enhanced by changing agriculture practices and peculiarities of the quail’s breeding strategy. Given the results, the quail cannot be classified as a good indicator of extensive traditional agriculture.  相似文献   

20.
Presently, it is debated if regional conservation efforts can alone resolve the ecological problems that global climatic changes could bring. Biological invasion is one of such concerns. In the present study, we modeled how change in global climate and regional anthropogenic pressure can impact the distribution of invasive Lantana camara in the Upper Ganga valley of the Western Himalaya (India). The forest in the study area was stratified into 1 km2 grid and two 15 m radius plot were located in each of the forest types in the grid, for recording Lantana presence. In total, 2221 plots were sampled covering 22% of forest. We used predictors representing the climate, forest patch size, fire and natural disaster variables for modeling the species distribution using maximum entropy algorithm. We further simulated 12 future landscape scenarios based on the global trends of these parameters. The present species—environment relationship was projected to these future landscape scenarios. Lantana was presently estimated to spread in 231 km2 of the study area. It invaded larger forest patches in the sub-tropical region, and smaller disturbed forest patches in the warm and cold temperate region. Increased distribution of Lantana was projected across all the future scenarios. The study revealed how global climate changes and regional anthropogenic pressure can have a synergistic effect on the expansion of invasive species in the future. It thus questions the efficiency of conducting only regional efforts in absence of global initiative to reduce the greenhouse gases emission.  相似文献   

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