Marginal Habitats Research Articles

Abundance and distribution of immature mosquitoes in urban rivers proximate to their larval habitats

Whether ecological restoration of polluted urban rivers would provide suitable breeding habitats for some mosquitoes was not clear yet. It was therefore important to determine how altered river conditions influence mosquito ecology. Monthly data on water quality and larval density were obtained to determine the effects of river systems on the distribution and abundance of immature mosquitoes in two coastal cities in Eastern China. In total, 5 species within two genera of mosquitoes were collected and identified in habitat with vegetation from three positive rivers. Culex pipiens pallens was the most abundant and widely distributed species. A new species (Culex fuscanus) was reported in certain districts. Physico-chemical parameters of river water were important, but not the only, set of influences on immature mosquito breeding. Aquatic vegetation could increase the likelihood of mosquito breeding while artificial aeration might prevent the approach of mosquitoes. Slow-moving water might be a new potential marginal habitat type for some Culex and Aedes albopictus. Variation of river system with ecological restoration might influence the abundance and distribution of immature mosquitoes.

Genetic connectivity across marginal habitats: the elephants of the Namib Desert.

Locally isolated populations in marginal habitats may be genetically distinctive and of heightened conservation concern. Elephants inhabiting the Namib Desert have been reported to show distinctive behavioral and phenotypic adaptations in that severely arid environment. The genetic distinctiveness of Namibian desert elephants relative to other African savanna elephant (Loxodonta africana) populations has not been established. To investigate the genetic structure of elephants in Namibia, we determined the mitochondrial (mt) DNA control region sequences and genotyped 17 microsatellite loci in desert elephants (n = 8) from the Hoanib River catchment and the Hoarusib River catchment. We compared these to the genotypes of elephants (n = 77) from other localities in Namibia. The mtDNA haplotype sequences and frequencies among desert elephants were similar to those of elephants in Etosha National Park, the Huab River catchment, the Ugab River catchment, and central Kunene, although the geographically distant Caprivi Strip had different mtDNA haplotypes. Likewise, analysis of the microsatellite genotypes of desert‐dwelling elephants revealed that they were not genetically distinctive from Etosha elephants, and there was no evidence for isolation by distance across the Etosha region. These results, and a review of the historical record, suggest that a high learning capacity and long‐distance migrations allowed Namibian elephants to regularly shift their ranges to survive in the face of high variability in climate and in hunting pressure.

Size-related habitat use in juvenile Atlantic salmon: the importance of intercohort competition

In stream-living salmonids, an underlying mechanism for the critical period after emergence has generally been assumed to be size-dependent swimming capacity constraining fry (age-0) to low-velocity habitats with reduced food availability and intense competition. A further plausible mechanism is that intercohort habitat exclusion confines fry to marginal habitats. This possibility was tested using a seminatural stream with 16 test arenas, each comprising one high-velocity, deep habitat and one low-velocity, shallow habitat. We observed groups of newly emerged Atlantic salmon (Salmo salar) fry, either alone or in sympatry with one or two age-1 salmon. Salmon fry used high-velocity areas (42.2 ± 0.4 cm·s−1) most extensively in the absence of intercohort competition, where they obtained more food than in low-velocity areas (3.3 ± 0.3 cm·s−1), even though foraging efficiency was lower (though not significantly so). In sympatry with older cohorts, fry increased their use of the low-velocity habitat, with a reduced foraging activity, suggesting that strong older cohorts in natural populations may have the potential to influence the strength of the recruiting cohort by negative density dependence due to interference competition for habitat.

Effects of climate change on potential habitats of the cold temperate coniferous forest in Yunnan province, southwestern China

We built a classification tree (CT) model to estimate climatic factors controllingthe cold temperate coniferous forest (CTCF) distributions in Yunnan provinceand to predict its potential habitats under the current and future climates, using seven climate change scenarios, projected over the years of 2070-2099. The accurate CT model on CTCFs showed that minimum temperature of coldest month (TMW) was the overwhelmingly potent factor among the six climate variables.The areas of TMW<-4.05 were suitable habitats of CTCF, and the areas of -1.35 < TMW were non-habitats, where temperate conifer and broad-leaved mixed forests (TCBLFs) were distribute in lower elevation, bordering on the CTCF. Dominant species of Abies, Picea, and Larix in the CTCFs, are more tolerant to winter coldness than Tsuga and broad-leaved trees including deciduous broad-leaved Acer and Betula, evergreen broad-leavedCyclobalanopsisand Lithocarpus inTCBLFs. Winter coldness may actually limit the cool-side distributions of TCBLFs in the areas between -1.35°C and -4.05°C, and the warm-side distributions of CTCFs may be controlled by competition to the species of TCBLFs. Under future climate scenarios, the vulnerable area, where current potential (suitable + marginal) habitats (80,749km2) shift to non-habitats, was predicted to decrease to 55.91% (45,053 km2) of the current area.Inferring from the current vegetation distribution pattern, TCBLFs will replace declining CTCFs. Vulnerable areas predicted by models are important in determining priorityof ecosystem conservation.

Recovery from hybrid breakdown in a marine invertebrate is faster, stronger and more repeatable under environmental stress

Understanding how environmental stress alters the consequences of hybridization is important, because the rate of hybridization and the likelihood of hybrid speciation both appear elevated in harsh, disturbed or marginal habitats. We assessed fitness, morphometrics and molecular genetic composition over 14 generations of hybridization between two highly divergent populations of the marine copepod Tigriopus californicus. Replicated, experimental hybrid populations in both control and high-salinity conditions showed a decline in fitness, followed by a recovery. Recovery was faster in the salinity stress treatment, returning to parental levels up to two generations earlier than in the control. This recovery was stable in the high-salinity treatment, whereas in the control treatment, fitness dropped back below parental levels at the final time point. Recovery in the high-salinity treatment was also stronger in terms of competitive fitness and heat-shock tolerance. Finally, consequences of hybridization were more repeatable under salinity stress, where among-replicate variance for survivorship and molecular genetic composition was lower than in the control treatment. In a system with low effective population sizes (estimates ranged from 17 to 63), where genetic drift might be expected to be the predominate force, strong selection under harsh environmental conditions apparently promoted faster, stronger and more repeatable recovery from depressed hybrid fitness.

Male Reproductive Morphology Across Latitudinal Clines and Under Long-Term Female Sex-Ratio Bias.

SynopsisRecent work in evolutionary ecology has capitalized on the species-specific, rapidly evolving nature of male reproductive traits, but it is unclear how the strength of sexual selection mechanisms, such as female choice and intersexual conflict, changes with ecological factors-shifts in latitude, elevation, and sex-ratio. Marginal habitats, such as those found at high elevation or latitude, might be expected to exert energetic hardships on males such that they do not invest heavily in reproductive structures. Conversely, males in these habitats may adapt to limited breeding opportunities, evolving morphologies with efficacy in antagonistic mating. Sex-ratio biases elicited by facultative parthenogenesis may also signal increasing selective pressure for reproductive organs that improve coercion ability, as males must capitalize on mating opportunities when females have alternate reproductive options. We studied the reproductive organs of males of five species of a group of polygynandrous Japanese harvestmen, collected from populations that varied in their elevation, latitude, and observed male: female ratio. Morphological data were analyzed with modern comparative methods, using a phylogenomic framework built with molecular data from double-digest restriction associated DNA sequencing. Although no features with hypothesized utility in coercive mating significantly covaried with elevational change, penis length was found to decrease with increasing latitude, supporting the existence of physiological constraints in marginal habitats. We also found males of parthenogenetic species, with primarily female-biased populations, had potentially greater precopulatory clasping ability, as compared to males of non-parthenogenetic species with more even sex-ratios. Ultimately, our findings suggest long-term sex-ratio biases are one of many factors with the potential to influence evolution of primary and secondary reproductive morphology.

Stepping-stones and dispersal flow: establishment of a meta-population of Milu (Elaphurus davidianus) through natural re-wilding.

The Milu (Père David’s deer, Elaphurus davidianus) became extinct in China in the early 20th century but was reintroduced to the country. The reintroduced Milu escaped from a nature reserve and dispersed to the south of the Yangtze River. We monitored these accidentally escaped Milu from 1995 to 2012. The escaped Milu searched for vacant habitat patches as “stepping stones” and established refuge populations. We recorded 122 dispersal events of the escaped Milu. Most dispersal events occurred in 1998, 2003, 2006 and 2010. Milu normally disperse in March, July and November. Average dispersal distance was 14.08 ± 9.03 km, with 91.41% shorter than 25 km. After 5 generations, by the end of 2012, 300 wild Milu were scattered in refuge populations in the eastern and southern edges of the Dongting Lake. We suggest that population density is the ultimate cause for Milu dispersal, whereas floods and human disturbance are proximate causes. The case of the Milu shows that accidentally escaped animals can establish viable populations; however, the dispersed animals were subject to chance in finding “stepping stones”. The re-wilded Milu persist as a meta-population with sub-populations linked by dispersals through marginal habitats in an anthropogenic landscape.

Pine marten density in lowland riparian woods: A test of the Random Encounter Model based on genetic data

In marginal habitats, populations should reach lower densities, as a consequence of both lower overall abundance and increasing home range size. To test if recently colonized riparian woods crossing intensively cultivated lowlands of NW Italy represent marginal habitats for the forest-specialist pine marten Martes martes, we assessed its population density by a recently developed, camera-trap-based non-invasive method, the Random Encounter Model (REM). As the central assumption of the REM is that animals move randomly with respect to cameras, we suspected that this method may be unsuitable for species with a strong tendency to use linear elements of the territory as usual paths and select habitats, such as woodland, which are likely to be under-represented in fragmented landscapes. To test for the efficacy of the REM, we also applied a faecal DNA-based genetic census to obtain an independent estimate of the minimum number of individuals occurring in the study area. Camera-trapping used 10 camera-traps, deployed for 10days within a 2km2 large unit, for a total of 6 units and 12km2. Pine marten density was estimated at 0.48 (0.36–0.60) ind/km2. All the faecal samples identified by a mDNA-based PCR-RFLP method as pine marten were genotyped at 15 microsatellite loci using a multiplex protocol. We identified 15 different individuals, corresponding to a density ranging between 0.8 and 2.0ind/km2. Using the most conservative genetic estimate, the REM underestimated population density of about 60% proving to be unreliable for estimating pine marten population size. We suggest that this may be the case for elusive species for which the assessment of average daily movements cannot be achieved without the use of invasive methods.

Habitat suitability models indicate the White-breasted ThrasherRamphocinclus brachyurusoccupies all suitable habitat in Saint Lucia

SummaryHabitat suitability models can guide species conservation by identifying correlates of occurrence and predicting where species are likely to occur. We created habitat suitability models for the White-breasted ThrasherRamphocinclus brachyurus, a narrowly distributed endangered songbird that occupies dry forest in Saint Lucia and Martinique. Eighty-five percent of the global population inhabits two ranges in Saint Lucia, both of which are largely unprotected and threatened by development. We developed three habitat suitability models using Maxent techniques and published occupancy datasets collected from the species’ two Saint Lucian ranges, and used abiotic, land cover, and predator distribution predictors. We built one model with occupancy data from both ranges, and two others with occupancy data specific to each range. The best full-range model included 11 predictors; high suitability was associated with close proximity to Saint Lucia fer-de-lanceBothrops caribbeausrange, moderately low precipitation, and areas near streams. Our assessment of suitable sites island-wide was more restricted than results from a recent model that considered older land cover data and omitted predator distributions. All sites identified in our full-range model as highly suitable were in or adjacent to the species’ current designated range. The model trained on southern range occurrences predicted zero suitable habitat in the northern range, where the population is much smaller. In contrast, the model trained on northern range occurrences identified areas of moderate suitability within the southern range and patches of moderately suitable habitat in the western part of the island, where no White-breasted Thrashers currently occur. We interpret these results as suggesting that White-breasted Thrashers currently occupy virtually all suitable habitat on the island, that birds in the northern range occupy marginal habitat, or that an important correlate of suitability is missing from the model. Our results suggest that habitat management should focus on currently occupied areas.

Habitat evaluation for Asian elephants (Elephas maximus) in Lincang: Conservation planning for an extremely small population of elephants in China

Fewer than 250 Asian elephants remain in China, occupying fragmented habitats of Yunnan Province. One such fragmented population of 18–23 individuals occupies the Nangunhe Nature Reserve Area in Lincang City, Yunnan Province, China. The greatest threat to the survival of this population is the loss and fragmentation of habitat. In this study, we applied an ecological niche factor analysis (ENFA) model to evaluate the habitat suitability of Lincang City for Asian elephants based on geographical factors, vegetation type, and human disturbance. Optimal, relatively suitable, and marginal habitat accounted for 0.16% (38.45km2), 0.61% (150.00km2), and 3.34% (817.26km2) of the total study area, whereas non-suitable habitat accounted for 95.89% (23,463.29km2) of this area. The marginality of Asian elephant habitat in Lincang was 1.954, indicating nonrandom selection of various eco-geographical variables in the environment. The primary factor affecting Asian elephant habitat quality was vegetation type, followed by geographical factors and human disturbance. A habitat quality map for the total distribution of Asian elephants remaining in China (i.e., Yunnan Province: Xishuangbanna, Lincang, and Pu'er) based on our current and previous study showed that just 1400.57km2 and 2689.62km2 relatively suitable and optimal habitat is available, owing to significant deforestation. In addition to reintroduction programs, conservation strategies should focus on improving the quality of marginal habitats for elephants, in parallel to placing ecological corridors through non-suitable habitat to connect all suitable habitats for this and other extremely small elephant populations in China to reduce genetic isolation and secure long-term survival for the species.

Forest specialist and generalist small mammals in forest edges and hedges

Agricultural intensification often leads to fragmentation of natural habitats, such as forests, and thereby negatively affects forest specialist species. However, human introduced habitats, such as hedges, may counteract negative effects of forest fragmentation and increase dispersal, particularly of forest specialists. We studied effects of habitat type (forest edge versus hedge) and hedge isolation from forests (connected versus isolated hedge) in agricultural landscapes on abundance, species richness and community composition of mice, voles and shrews in forest edges and hedges. Simultaneously to these effects of forest edge/hedge type we analysed impacts of habitat structure, namely percentage of bare ground and forest edge/hedge width, on abundance, species richness and community composition of small mammals. Total abundance and forest specialist abundance (both driven by the most abundant species Myodes glareolus, bank vole) were higher in forest edges than in hedges, while hedge isolation had no effect. In contrast, abundance of habitat generalists was higher in isolated compared to connected hedges, with no effect of habitat type (forest edge versus hedge). Species richness as well as abundance of the most abundant habitat generalist Sorex araneus (common shrew), were not affected by habitat type or hedge isolation. Decreasing percentage of bare ground and increasing forest edge/hedge width was associated with increased abundance of forest specialists, while habitat structure was unrelated to species richness or abundance of any other group. Community composition was driven by forest specialists, which exceeded habitat generalist abundance in forest edges and connected hedges, while abundances were similar to each other in isolated hedges. Our results show that small mammal forest specialists prefer forest edges as habitats over hedges, while habitat generalists are able to use unoccupied ecological niches in isolated hedges. Consequently even isolated hedges can be marginal habitats for forest specialists and habitat generalists and thereby may increase regional farmland biodiversity.

Novel distribution pattern between coexisting sexual and obligate asexual variants of the true estuarine macroalga Ulva prolifera.

Where sexual and asexual forms coexist within a species, the asexuals are often found to be prevalent in marginal habitats. This asexual distribution pattern has received evolutionary attention linked to the paradox of sex. In many marine species, there is a distributional trend of asexual modes being more common in lower salinity waters regarded as the ecogeographic marginal, being explained by negative effects of low salinities on sexual reproductive success. However, the distribution pattern of estuarine species recently adapted to low salinity waters has remained unknown. The brackish macroalga Ulva prolifera being a major benthic component of estuarine ecosystems includes a sexual variant and obligate asexual variants by means of motile spores. We examined the sexual–asexual distribution pattern of this alga along a salinity gradient in river estuaries. Surprisingly, opposite to the distributional trend of marine organisms, the results clearly showed the persistent predominance of sexuals in the lower salinity reaches than the asexuals. In addition, a frequent alternating of dioecious gametophytes and sporophytes in the sexual population was observed, suggesting the sexual reproductive process would be robustly performed in the low salinity waters. Considering U. prolifera had evolved from the ancestral marine species to become a true estuarine species of which the core habitat is the low salinity reaches, in a broad sense its sexual–asexual distribution pattern would be involved in asexual marginal occupations of the species range previously reported in other organisms. Based on the frozen niche variation model, we can give a concise explanation for the evolutionary process of this pattern; multiple asexuals with frozen genotypic variation had arisen from sexual ancestors undergoing low salinity adaptation and share the estuarine habitat with the sexuals at present.

Prospects for rewilding with camelids

The wild camelids wild Bactrian camel (Camelus ferus), guanaco (Lama guanicoe), and vicuña (Vicugna vicugna) as well as their domestic relatives llama (Lama glama), alpaca (Vicugna pacos), dromedary (Camelus dromedarius) and domestic Bactrian camel (Camelus bactrianus) may be good candidates for rewilding, either as proxy species for extinct camelids or other herbivores, or as reintroductions to their former ranges. Camels were among the first species recommended for Pleistocene rewilding. Camelids have been abundant and widely distributed since the mid-Cenozoic and were among the first species recommended for Pleistocene rewilding. They show a range of adaptations to dry and marginal habitats, and have been found in deserts, grasslands and savannas throughout paleohistory. Camelids have also developed close relationships with pastoralist and farming cultures wherever they occur. We review the evolutionary and paleoecological history of extinct and extant camelids, and then discuss their potential ecological roles within rewilding projects for deserts, grasslands and savannas. The functional ecosystem ecology of camelids has not been well researched, and we highlight functions that camelids are likely to have, but which require further study. We also discuss alternative rewilding-inspired land-use models given the close relationships between humans and some camelid species.

Diversity in the monotony? Habitat traits and management practices shape avian communities in intensive vineyards

Spreading of viticulture may pose serious threats to biodiversity and adequate policies targeted at decreasing its impact are urgently required. Current knowledge of viticulture effects on biodiversity is scarce and studies on bird communities in vineyards are even scarcer.We surveyed avian assemblages in Trentino vineyards (North-East Italy) in both breeding and wintering seasons to evaluate the effect of: i) landscape, ii) management and iii) topographic-climatic characteristics on birds and to derive implications for conservation. We calculated four community indexes (species richness, abundance, evenness and conservation index) and modelled their relative variation according to 18 environmental variables belonging to the three above-mentioned groups.Landscape models performed better than the others, except for winter evenness, for which management models were the most supported ones. Generally, models considering the three groups together explained more variation than models from an individual group.Landscape (and agricultural) heterogeneity, extent of marginal habitats, density of traditional elements (hedgerows, tree rows, isolated trees and rural buildings) all had positive effects, whereas vineyard cover had negative impact on the value of the four community indexes.Organic management had no apparent effect on avian communities. We detected a seasonal difference in the effects of environmental characteristics on bird communities, which suggested that local conservation efforts could be tuned according to the seasonal importance of vineyards in different regions.Key measures to promote biodiversity in vineyards include maintaining patches of residual habitats in the vineyard matrix and enhancing heterogeneity. Marginal features appeared particularly important in the homogeneous landscape of intensive vineyards to favour bird communities.

Natural islands and habitat islands as refuges of vegetation cover and wild bees. The case of the Lednica Landscape Park in western Poland

Abstract The study has contributed to the identification of the apifauna of central Wielkopolska. The study identified 161 bee species, accounting for 34.2% of the Polish bee fauna. The highest contribution (28.7% of the fauna) comes from four species, namely Andrena haemorrhoa, A. helvola, Evylaeus calceatus and Osmia rufa, while Bombus terrestris and Evylaeus pauxillus are two subdominants. The assemblages of Apiformes in the study area are characterised by a significant contribution of spring-associated species, which is probably an effect of the presence of numerous willow thickets offering abundant host plants (mainly Salix sp. div.). Both the islands and the surroundings of the lake have a unique species composition, and there are differences in the proportions of the individual dominant species. The overall abundance of bees varies greatly, with mean seasonal density figures on Ostrów Lednicki Island being more than twice as high as that on the mainland grassland, with a distinct predominance of bumblebees. The exceptional richness of Apiformes, including bumblebees, on Ostrów Lednicki should be regarded as the basis for treating this island as a life refuge for bumblebees and including it and its environs in the list of sites of Community importance (SCI). A simultaneous study of the vegetation cover contributed significant data on the vascular plant flora and plant communities of the Lednica Landscape Park. For example, it was the first such investigation of Mewia Island. The study revealed the importance of marginal habitats (natural islands and habitat islands) for the preservation of protected and endangered plant species and plant communities receding from an agricultural landscape.

Effects of farming practice on populations of threatened amphibious plant species in temporarily flooded arable fields: implications for conservation management

Intensification of land use has led to a severe decline of arable plants in the past decades, particularly among species of marginal habitats, such as temporarily flooded fields. Few studies have focused on the factors controlling the population dynamics of these species, and on suitable strategies for more effective conservation. To investigate the effects of farming practice on plant populations of temporarily flooded fields, we determined above-ground and below-ground densities of four annuals (Elatine alsinastrum, Limosella aquatica, Myosurus minimus and Peplis portula) in a 3-year on-farm experiment. A fully-factorial experiment combined the treatments soil tillage, presence of crops, fertilisation and herbicide application. Soil tillage had a positive effect on plant establishment, whereas herbicide application had a negative effect on the establishment of all study species. Plant densities were controlled by application of fertilisers and herbicides, with the most significant effects on L. aquatica and M. minimus. Soil seed densities were mainly affected by environmental factors, but tillage also significantly reduced the seed densities of E. alsinastrum and P. portula. Other farming practices had a minor impact. Thus, reduced management can help in maintaining populations of rare amphibious plant species. The effect of different crops, crop rotation and the timing of management will help in developing the most appropriate management strategies for conservation of these plant species.

The "χ" of the Matter: Testing the Relationship between Paleoenvironments and Three Theropod Clades.

The view of spinosaurs as dinosaurs of semi-aquatic habits and strongly associated with marginal and coastal habitats are deeply rooted in both scientific and popular knowledge, but it was never statistically tested. Inspired by a previous analysis of other dinosaur clades and major paleoenvironmental categories, here we present our own statistical evaluation of the association between coastal and terrestrial paleoenvironments and spinosaurids, along with other two theropod taxa: abelisaurids and carcharodontosaurids. We also included a taphonomic perspective and classified the occurrences in categories related to potential biases in order to better address our interpretations. Our main results can be summarized as follows: 1) the taxon with the largest amount of statistical evidence showing it positively associated to coastal paleoenvironments is Spinosauridae; 2) abelisaurids and carcharodontosaurids had more statistical evidence showing them positively associated with terrestrial paleoenvironments; 3) it is likely that spinosaurids also occupied spatially inland areas in a way somehow comparable at least to carcharodontosaurids; 4) abelisaurids may have been more common than the other two taxa in inland habitats.

An assessment of endangered species habitat at large scale: chiru distribution across the Tibetan region of Chang Tang

Habitat degradation is a major threat to the survival of chiru (Pantholops hodgsonii). Detailed knowledge for habitat conservation in this steppe-dwelling ungulate is needed if effective conservation and management strategies are to be developed. The distribution of potential habitat and the relative value of habitat to chiru on a regional scale remains unknown, hindering landscape conservation planning. Our aim was to identify and rank chiru habitat across the Chang Tang region of the Tibetan Plateau. We assessed overall habitat suitability using geographical data, field surveys, and information contained within previous studies. We identified 10194 km2 of optimal habitat (1.71 % of the region), 256816 km2 of suitable habitat (43.17 % of the region), and 213799 km2 of marginal habitat (35.94 % of the region). Our habitat model shows that suitable habitat is located primarily in the central (Nyingma county and Shuanghu county) and western (Geze county) regions of the study area. When we looked specifically at a chiru reserve (Chang Tang Nature Reserve) located within the study area, we found that over half of the reserve could be classified as suitable habitat. This highlights the regional importance of this reserve to chiru conservation. Our findings further indicate that the protection of suitable habitat and improvement of habitat linkages will be important features of any regional chiru conservation plan.

普洱市亚洲象栖息地适宜度评价

PDF HTML阅读 XML下载 导出引用 引用提醒 普洱市亚洲象栖息地适宜度评价 DOI: 10.5846/stxb201411142260 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金会资助项目（31172108）；美国内政部鱼和野生动物管理局亚洲象保护基金资助项目（98210-8-G565） Habitat suitability assessment for Asian elephant in Pu'er prefecture in the Yunnan province of China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:亚洲象（Elephas maximus）属于我国Ⅰ级保护动物，在中国仅分布于云南省西双版纳国家级自然保护区、普洱市的思茅区、澜沧县和江城县，以及临沧南滚河国家级自然保护区。将普洱全境作为研究区域，利用野外调查数据，结合遥感与地理信息系统技术，运用生态位因子分析（ENFA）模型对普洱市亚洲象的栖息地适宜度进行了评价，并预测了适宜栖息地的分布。发现：普洱市亚洲象栖息地的边际值为0.991，表明亚洲象在普洱市境内对环境变量的选择不是随机的；耐受值为0.315，表明亚洲象在普洱市境内生态位较窄，受环境条件的制约。根据模型计算得到的栖息地适宜度指数，将普洱市的亚洲象栖息地分为最适栖息地，较适栖息地，边际栖息地和非栖息地4个等级，面积分别为409.32、574.32、2909.48、38722.32 km2。最适栖息地仅占全市面积的0.96%，而非栖息地占90.86%。利用GIS和Biomapper 4.0生成亚洲象栖息地分布图，发现普洱境内最适栖息地和较适栖息地面积狭小。对最适栖息地、较适栖息地和边际栖息地进行景观格局分析的结果表明，3种类型的栖息地破碎化均十分严重，连通度较低，栖息地内受到较大程度的人类活动的干扰。因此建议在普洱和西双版纳间尽快建立野生动物生态廊道，以加强亚洲象各种群间的交流。 Abstract:The Asian elephant (Elephas maximus) is listed as a first-class protected species in China, and is only distributed in Xishuangbanna, Pu'er, and Lincang prefectures of Yunnan Province. The main threats to the survival of elephants in China were habitat loss and fragmentation. Only 5 elephants were reported in Pu'er in 1996, and currently, there are over 80 elephants belonging to 8 groups living in the region. In this study, we collated 152 elephant occurrence points within the entire Pu'er range in 2010, and assessed habitat suitability for Asian elephant in Pu'er, based on Ecological Niche Factor Analysis (ENFA) of the field survey data. We also predicted the distribution of suitable habitats for elephants in Pu'er. The marginality value obtained from ENFA was 0.992. This result indicated that the deviation of the preferable niche of elephants was different from the average value of the environment, and that elephants chose their habitat non-randomly. The tolerance value was 0.315, which indicated that the niche of Asian elephant was narrow, and that environment indicators restricted the survival of elephants. Results showed that the elephants in Pu'er preferred natural forest with low elevation (<1419 m) and moderate slopes (<14°), as well as areas far from streams and human disturbance (villages and roads). We divided elephant habitat in Pu'er into 4 categories: optimal habitat (409.32 km2), suitable habitat (574.32 km2), marginal habitat (2909.48 km2), and unsuitable habitat (38722.32 km2). The unsuitable habitat accounted for 90.86% of the total area, whereas the optimal habitat occupied only 0.96%. Natural forest is the major vegetation type in optimal (55.6%), suitable (54.55%), and marginal (48.21%) habitats, but it constituted only 33.05% of the unsuitable habitat, indicating that natural forest is the preferred habitat for Asian elephants. According to landscape structure analysis using FRAGSTATS, the mean patch fractal dimension indices (FRAC_MN) for marginal, suitable, and optimal habitats were found to be close to 1, and the meancontiguity indices (CONTIG_MN) were found to be 0.12-0.15. Landscape analysis showed that the optimal, suitable, and marginal habitats all suffered severe fragmentation, low connectivity, and high levels of human disturbance. In comparison with real distribution, the predicted map incorporated some farmlands where Asian elephants forage. The proportion of optimal and suitable habitat in Pu'er is very low, owing to the loss of natural forest and the cultivation of economic plants. It is critical to establish protected areas in the habitat of Asian elephants, in combination with effective conservation measures. In addition, the three main areas of elephant distribution in Pu'er are isolated. It is understood that low connectivity among populations impedes important communication among different population groups. Therefore, it is also necessary to establish and restore ecological corridors to link the current elephant habitats in Pu'er, and to increase their connection with other elephant populations in Xishuangbanna. 参考文献 相似文献 引证文献

Spatial and Temporal Habitat Use by GPS Collared Male Cheetahs in Modified Bushland Habitat

Cheetahs and other apex predators are threatened by human-wildlife conflict and habitat degradation. Bush encroachment creates one of the biggest forms of habitat change, thus it is important to understand the impact this has on habitat use. We investigated habitat preferences of five male cheetahs in Namibian farmlands degraded by bush encroachment. Cheetahs were tracked using satellite based Global System for Mobile (GSM) collars providing a higher resolution on ranging behavior. We aimed to investigate: 1) habitat characteristics; 2) evidence for habitat selection; 3) temporal activity partitioning; and 4) whether revisits to locations were related to habitat type. There were differences in habitat characteristics, showing that cheetahs were able to utilise different habitats. Fecal pellet counts revealed that warthog, oryx, scrub hare and kudu were most abundant. The cheetahs spent more time in high visibility shrubland, suggesting they selected rewarding patches within predominantly bush-encroached landscapes. The usage in marginal habitat was strikingly influenced by habitat type, with both previously cleared and open vegetated areas showing high proportions in edge use. Individuals exhibited significant temporal activity partitioning, showing peaks between late afternoon and early morning hours. This finding could be key to managing human-wildlife conflict by showing that increased protection such as the use of herders and livestock guarding dogs should be used as mitigation methods to minimize the impact of cheetah specific temporal patterns at all times as defined in this research. Visits to the same locations were not correlated to habitat type; revisits may be dictated by other reasons such as social interaction, prey density or avoidance of other predators. Findings from this study will help build existing knowledge on the effects bush encroachment has on cheetah habitat preference.