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1.
The endangered Ohlone tiger beetle (Cicindela ohlone) depends on bare ground areas in California coastal grasslands to encounter mates, oviposit, and find prey. We tested habitat creation as a potential management strategy to increase the availability of oviposition sites for C. ohlone. We compared three different bare ground treatments by scraping off surface vegetation, ripping, and tamping the plots. We also tested whether bare ground creation expands C. ohlone range within a habitat patch by scraping plots at increasing distances from the core habitat and monitoring C. ohlone colonization. C. ohlone oviposited significantly more in artificial bare ground plots compared to controls both one and 2 years after the scrapes were created. Distance from the core habitat did not affect colonization nor did decompaction of scraped plots. Percent bare ground significantly predicted incidence of colonization. For the conservation of the endangered Ohlone tiger beetle, we recommend continued creation of scraped plots every 2 years in order to maintain bare ground and to ensure maximum usage by female C. ohlone as oviposition sites.  相似文献   

2.
Conservation of metapopulations requires managing extirpated sites, particularly with current threats of increased fragmentation and displacement from global warming. Determining the habitat requirements of threatened species and how they relate to defining characteristics of occupied and unoccupied sites is key to managing suitable habitat in extirpated patches. Due to habitat destruction and degradation, the endangered Ohlone tiger beetle (Cicindela ohlone) is found in only five sites of a once more extensive metapopulation in Santa Cruz County, California. To determine the role of habitat quality in classifying sites, I measured vegetation and ground cover as well as plant and soil composition in sites in which C. ohlone are present, extirpated, and absent. I used conditional inference trees to determine what habitat factors significantly predicted the different sites types. I also analyzed habitat characteristics within present sites to determine factors that predicted egg-laying habitat. As isolation has been shown to be an important driver of metapopulation patch extirpation, I tested the spatial autocorrelation of C. ohlone occupancy to determine if extirpated patches were significantly isolated. Habitat characteristics successfully differentiated nearly 90 % of extirpated plots, which were not isolated from occupied sites. Sites in which C. ohlone are currently present were classified as having at least 10 % cover of bare ground, high forb cover, low litter cover and depth, and high soil bulk density, characteristics that extirpated sites lacked. I illustrate how the defining characteristics could be used to manage habitat in extirpated and absents sites for potential recolonization or translocation, which is vital for metapopulation persistence.  相似文献   

3.
Carabid beetles were sampled by pitfall trapping on Brentmoor Heath, Surrey, UK during the summers of 2009 and 2010 to determine the effects of bare ground patch size on beetle abundance, richness and diversity. Four patch sizes were investigated: 1, 4, 25 and 100?m2 as well as the adjacent mown and unmown areas. A range of environmental parameters relating to soil characteristics, stones and nearby vegetation were measured at each patch and control habitat in order to distinguish the effect of patch size. Results show that bare ground is a valuable habitat for carabids, but that the response of their abundance, richness and diversity to bare ground patch size depends on a large number of environmental variables on and around the patches. When all variables are taken into account, smaller patches appear to benefit carabid abundance, richness and diversity. In the presence of Molinia caerulea at the patch edges, however, larger patches were more beneficial. Given this dependence on environmental variables, the perfect patch size for conservation of biodiversity is likely to be site specific and the best approach may be to use a variety of patch sizes at a range of successional stages.  相似文献   

4.
Biota dependant on early seral stages or frequently disturbed habitats belong to the most rapidly declining components of European biodiversity. This is also the case for Carabus nitens, which is threatened across Western and Central Europe. We studied one of the last remaining populations of this ground beetle in the Czech Republic, which inhabits post-extraction peat bogs. In line with findings from previous studies, we show that C. nitens prefers patches characterized by higher light intensity and lower vegetation cover. Abundance of females was positively correlated with the cover of plant species requiring higher temperature. In addition, we demonstrate its preference for periodically moist, but not wet or inundated plots, suggesting that the transition between dry heathland and wet peat bog might be the optimal habitat for this species. This hypothesis is further supported by results showing a positive correlation between the abundance of C. nitens and vegetation cover comprising of a mix of species typical for heathland, peat bog, and boreal habitats. Our results show that C. nitens mobility is comparable to other large wingless carabids. The maximum covered distance was ~?500 m in a month. To ensure the survival of this population, sites of recent peat extraction should be spared from reclamation and afforestation. In contrast, active measures should be taken to facilitate nutrient removal, disturbance of vegetation cover, and the creation of depressions with a humid microclimate. These actions will create a mosaic of heath, bog, and bare ground, which seems to be the preferred habitat of C. nitens at our study site.  相似文献   

5.
Tiger beetles (Insecta: Coleoptera: Cicindelidae) often occupy small patches of suitable habitat in otherwise unsuitable landscapes. Such patches are easily overlooked, which may lead to underestimates of both the number of occurrences and the overall population size. In this study, simple World Wide Web-based tools (Google Earth and Microsoft Terraserver) were used to search high-resolution satellite imagery for patches of suitable habitat for globally and regionally rare tiger beetles on a 3,278 ha wildlife refuge in Maryland, USA. This tract is largely forested but contains scattered small open areas of sand and clay soils that are potential habitat for tiger beetles of conservation concern. Visual inspection of remotely sensed imagery resulted in the identification of 19 potential habitat patches, 15 of which yielded tiger beetle populations when surveyed on the ground. The number of species of tiger beetles recorded from this tract was increased from 3 to 8 and two new sites were discovered for the state sensitive species Cicindela scutellaris rugifrons Dejean. In addition, a small population of C. splendida Hentz was discovered, a species last reported from Maryland in 1948. The technique described here shows great promise for locating small patches of potential tiger beetle habitat in otherwise unsuitable landscapes.  相似文献   

6.
Fragmentation, deterioration, and loss of habitat patches threaten the survival of many insect species. Depending on their trophic level, species may be differently affected by these factors. However, studies investigating more than one trophic level on a landscape scale are still rare. In the present study we analyzed the effects of habitat size, isolation, and quality for the occurrence and population density of the endangered leaf beetle Cassida canaliculata Laich. (Coleoptera: Chrysomelidae) and its egg parasitoid, the hymenopteran wasp Foersterella reptans Nees (Hymenoptera: Tetracampidae). C. canaliculata is strictly monophagous on meadow sage (Salvia pratensis), while F. reptans can also parasitize other hosts. Both size and isolation of habitat patches strongly determined the occurrence of the beetle. However, population density increased to a much greater extent with increasing host plant density ( = habitat quality) than with habitat size. The occurrence probability of the egg parasitoid increased with increasing population density of C. canaliculata. In conclusion, although maintaining large, well-connected patches with high host plant density is surely the major conservation goal for the specialized herbivore C. canaliculata, also small patches with high host plant densities can support viable populations and should thus be conserved. The less specialized parasitoid F. reptans is more likely to be found on patches with high beetle density, while patch size and isolation seem to be less important.  相似文献   

7.

Background

The effects of landscape modifications on the long-term persistence of wild animal populations is of crucial importance to wildlife managers and conservation biologists, but obtaining experimental evidence using real landscapes is usually impossible. To circumvent this problem we used individual-based models (IBMs) of interacting animals in experimental modifications of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of four species with contrasting life-history characteristics: skylark (Alauda arvensis), vole (Microtus agrestis), a ground beetle (Bembidion lampros) and a linyphiid spider (Erigone atra). This allows us to quantify the population implications of experimental modifications of landscape configuration and composition.

Methodology/Principal Findings

Starting with a real agricultural landscape, we progressively reduced landscape complexity by (i) homogenizing habitat patch shapes, (ii) randomizing the locations of the patches, and (iii) randomizing the size of the patches. The first two steps increased landscape fragmentation. We assessed the effects of these manipulations on the long-term persistence of animal populations by measuring equilibrium population sizes and time to recovery after disturbance. Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain. Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance. The species that were most strongly affected by large disturbances fluctuated little in population sizes in years when no perturbations took place.

Significance

Traditional approaches to the management and conservation of populations use either classical methods of population analysis, which fail to adequately account for the spatial configurations of landscapes, or landscape ecology, which accounts for landscape structure but has difficulty predicting the dynamics of populations living in them. Here we show how realistic and replicable individual-based models can bridge the gap between non-spatial population theory and non-dynamic landscape ecology. A major strength of the approach is its ability to identify population vulnerabilities not detected by standard population viability analyses.  相似文献   

8.
AimAs habitat loss continues to accelerate with global human population growth, identifying landscape characteristics that influence species occurrence is a key conservation priority in order to prevent global biodiversity loss. In South Africa, the arboreal samango monkey (Cercopithecus albogularis sp.) is threatened due to loss and fragmentation of the indigenous forests it inhabits. The aim of this study was to determine the habitat preferences of the samango monkey at different spatial scales, and to identify key conservation areas to inform management plans for this species.LocationThis study was carried out in the western Soutpansberg Mountains, which represents the northernmost population of samango monkeys within South Africa, and the only endangered subspecies (C. aschwarzi).MethodsWe used sequentially collected GPS points from two samango monkey groups followed between 2012 and 2017 to quantify the used and available habitat for this species within the western Soutpansberg Mountains. We developed 2nd‐order (selection of ranging area), 3rd‐order (selection within range), and 4th‐order (feeding site selection) resource selection functions (RSFs) to identify important habitat features at each scale. Through scale integration, we identified three key conservation areas for samango monkeys across Limpopo Province, South Africa.ResultsHabitat productivity was the most important landscape variable predicting probability of use at each order of selection, indicating the dependence of these arboreal primates on tall‐canopy indigenous forests. Critical habitat across Limpopo was highly fragmented, meaning complete isolation between subpopulations is likely.Main conclusionsUnderstanding the habitat characteristics that influence samango monkey distribution across South Africa is crucial for prioritizing critical habitat for this species. Our results indicated that large, contiguous patches of tall‐canopy indigenous forest are fundamental to samango monkey persistence. As such, protected area expansion of large forest patches and creation of forest corridors are identified as key conservation interventions for this species.  相似文献   

9.
Species responses are influenced by processes operating at multiple scales, yet many conservation studies and management actions are focused on a single scale. Although landscape-level habitat conditions (i.e., habitat amount, fragmentation and landscape quality) are likely to drive the regional persistence of spatially structured populations, patch-level factors (i.e., patch size, isolation, and quality) may also be important. To determine the spatial scales at which habitat factors influence the regional persistence of endangered Ord's kangaroo rats (Dipodomys ordii) in Alberta, Canada, we simulated population dynamics under a range of habitat conditions. Using a spatially-explicit population model, we removed groups of habitat patches based on their characteristics and measured the resulting time to extinction. We used proportional hazards models to rank the influence of landscape and interacting patch-level variables. Landscape quality was the most influential variable followed by patch quality, with both outweighing landscape- and patch-level measures of habitat quantity and fragmentation/proximity. Although habitat conservation and restoration priorities for this population should be in maximizing the overall quality of the landscape, population persistence depends on how this goal is achieved. Patch quality exerted a significant influence on regional persistence, with the removal of low quality road margin patches (sinks) reducing the risk of regional extinction. Strategies for maximizing overall landscape quality that omit patch-level considerations may produce suboptimal or detrimental results for regional population persistence, particularly where complex local population dynamics (e.g., source-sink dynamics) exist. This study contributes to a growing body literature that suggests that the prediction of species responses and future conservation actions may best be assessed with a multi-scale approach that considers habitat quality and that the success of conservation actions may depend on assessing the influences of habitat factors at multiple scales.  相似文献   

10.
Two centuries ago large areas of north-west Europe were covered by coherent heathlands which hosted numerous specialized species. Changes in land use made heathlands fragmented and rare, consequently, they are in the focus of nature conservation efforts today. But how large should remaining heathland patches be in order to secure the survival of populations of specialized species? We investigated the genetic diversity at five allozyme loci of Poecilus lepidus, a flightless and stenotopic heathland ground beetle. 29 populations from differently sized heathland patches in north-west Germany were analyzed. Results show a weak but significant genetic differentiation and no evidence for isolation by distance or other patterns of spatial autocorrelation. Linear regression analysis revealed significant relationships between patch size, allelic richness, number of alleles and expected heterozygosity. These findings are explained by severe habitat fragmentation together with strong fluctuations in population size which have been reported for this species in the past. To conserve the vast majority of the species’ genetic diversity for a period of 100 years we suggest to maintain heathland patches of at least 50 ha in size.  相似文献   

11.
Understanding the environmental factors that affect the distribution and abundance of rare and threatened species can help identify priority sites for conservation action such as habitat management. The moth Cucullia lychnitis is identified in UK legislation as a priority species for conservation. Its conspicuous larvae feed on a patchily distributed host plant Verbascum nigrum, but are entirely absent from some host plant patches within the species’ range. Environmental variability among patches was investigated to understand factors affecting (i) patch occupancy by C. lychnitis and (ii) abundance of C. lychnitis, where present. Occupancy of individual V. nigrum plants within occupied patches was also investigated. The likelihood of patch occupancy increased with patch size, and decreased with patch isolation. Abundance of C. lychnitis was negatively correlated with patch isolation and with abundance of the weevil Cionus nigritarsis, which exploits the same host plant and may be a competitor. Within occupied patches, larvae of C. lychnitis were significantly more likely to be found on taller plants with more flower spikes; such plants are typical of established rather than newly-created patches. These results may help to guide efforts to conserve C. lychnitis, highlighting the importance of habitat connectivity and indicating potential management actions to promote features positively associated with larval incidence and abundance.  相似文献   

12.
The Ortolan Bunting Emberiza hortulana is a long-distance migrant that has suffered major population declines across much of its European breeding range. While northern populations are bound largely to farmland, Mediterranean populations are largely confined to habitats subject to recurrent wildfires. Habitat selection of the Ortolan Bunting was assessed in a recently burnt area in Catalonia at landscape and habitat scales. A Zero-inflated Poisson procedure was used to model the abundance of birds in relation to landscape and habitat variables. The most parsimonious landscape model predicted the highest abundance on south-facing slopes, with a gradient above 10°. The most parsimonious habitat model showed a positive quadratic effect of bare ground and regenerating oak Quercus spp., with predicted optima for abundance around 20–30% and 20% cover, respectively. There was a clear relationship between predicted abundance of the Ortolan Bunting and post-fire regenerating oak shrubs. South-facing, moderately sloping areas were favoured and bare ground was a key feature of the species' habitat. A matrix combining patches of sparse oak shrubs and patches of bare ground appears to be the optimal breeding habitat in the Mediterranean. The maintenance or provision of similar habitat features, especially patches of bare ground, may prove crucial for the conservation of rapidly declining Ortolan Bunting populations on farmland across temperate Europe.  相似文献   

13.
A paucity of genetic information and the drastic decline in population size of the beetle Cerambyx cerdo has made this species a high priority for research and conservation management. The state-listed beetle, a saproxylic insect associated with oaks, has a discontinuous range, with larger and more connected populations in southern Europe and small and isolated populations in the continent’s central and northern parts. Here, we used seven microsatellite loci and one DNA fragment of the mitochondrial gene COI to examine the population structure, genetic diversity, and contemporary gene flow between two Polish populations of the beetle. A population viability analysis summarizing collected genetic data as well as field records and species-specific information was performed to investigate the probability of the populations’ persistence over 20 years under different simulation scenarios. Genetic drift due to spatial isolation and bottleneck(s) is probably a major evolutionary force responsible for a low number of haplotypes and lower gene diversity in these populations as compared to the neighboring Czech populations. Despite a large geographic distance between the Polish populations, genetic differentiation between them was low, which could reflect shared ancestral polymorphism and stochasticity of retained alleles rather than the homogenizing effect of gene flow. Differences among probabilities of extinction over 20 years were detected between populations, and, in the worst-case scenarios, one population will disappear within four generations. Conservation efforts must focus on supplementation, habitat restoration, and post-release monitoring. The results of our study provided information that can be incorporated into future management actions to aid in the conservation of the beetle.  相似文献   

14.
Many species living in man-shaped landscapes are restricted to small natural habitat patches and form metapopulations; predicting their future is a central issue in applied ecology. We examined the viability of the bog fritillary butterfly Proclossiana eunomia Esper, a specialist glacial relict species, in a highly fragmented landscape (<1% of suitable habitat in 10 km2), by way of population viability analysis. We used comprehensive data from a long-term study in which a patchy population was monitored during ten consecutive years to parameterise a spatially structured metapopulation model using commercially available platform RAMAS/GIS 3.0. Population growth rate was density-dependent and modulated by various climatic variables acting on different developmental stages of the butterfly. Density dependence was probably related to larval parasitism by a specific parasitoid. Population size was negatively affected by an increase in the mean temperature. Dispersal was modelled as the observed proportion of movements between patches, taking into account the probability of emigration out of a given patch. Our model provided results close to the picture of the system drawn from the field data and was considered as useful in making predictions about the metapopulation. Demographic parameters proved to have a far higher impact on metapopulation persistence than dispersal or correlation of local dynamics. Scenarios simulating both global warming and management of habitat patches by rustic herbivore grazing indicated a decrease in the viability of the metapopulation. Our results prompted the regional nature conservation agency to modify the planned management regime. We urge conservation biologists to use structured population models including local population dynamics for viability analysis targeted to such threatened metapopulations in highly fragmented landscapes.  相似文献   

15.
We investigated species richness of ground dwelling beetle assemblages in two non-reclaimed lignite mines and a dump in Central Germany by means of pitfall trapping. During a period of five months, a total of 203 beetle species within 27 families represented by 4099 individuals were trapped. This included 75 species of ground beetles represented in a sample of 957 individuals from which 10 species are regionally endangered. The number of individuals, species richness, as well as the proportions of endangered species did not differ between successional stages whereas species composition of sites could be related well to a set of environmental variables. High values of beta-diversity between sites indicated that the total number of species recorded is caused by habitat diversity. From the viewpoint of nature conservation, we conclude that postmining areas can play a key role in conservation of beetle diversity in agricultural areas since they harbour threatened species whose original habitats are now rare due to human impact. An important task for future management of postmining areas is to maintain successional processes and to prevent loss of habitat diversity through afforestation. Areas with extreme soil conditions should also be preserved for long-term availability of bare soil and pioneer vegetation and associated fauna.  相似文献   

16.
In shrubland ecosystems, shrubs as ecosystem engineers play an important role in structuring ground beetle communities. However, the influence of shrub vegetation on the distribution and diversity of ground beetles remains unknown in Gobi desert, northwest China, where shrubland is a major biome type. Using Gobi shrubland dominated by shrub species Nitraria sphaerocarpa and Reaumuria soongorica as a model system, we sampled ground beetle communities using a pitfall trapping method under canopies of both shrubs and in intershrub bare areas during spring, summer and autumn corresponding to the main period of beetle activity. Simultaneously, physical environment of the three microhabitats and plant characteristics of both shrubs were measured. We determined whether shrubs and species identity influence ground beetle distribution and diversity patterns and whether the response of beetles to the presence and species of shrubs is consistent across species. At the community level, total beetle abundance and species richness were significantly greater under shrubs than in intershrub bare areas, whereas more beetles were captured under N. sphaerocarpa than under R. soongorica. At the population level, eight dominant beetle species responded differently to the presence and species of shrubs. The abundance of Anatolica sp., Carabus sp., Cyphogenia chinensis, Microdera sp. and Sternoplax setosa was consistently much greater under shrubs than in intershrub bare areas, whereas the abundance of Blaps gobiensis, Lethrus apterus and Pterocoma reitteri under shrubs was similar to that in intershrub bare areas. The shrub N. sphaerocarpa was commonly preferred by Anatolica sp., C. chinensis and S. setosa, whereas the shrub R. soongorica was commonly preferred by L. apterus, but the abundance of B. gobiensis, Carabus sp., Microdera sp. and P. reitteri was unaffected by shrub species. Differences in the abundance, species richness and composition of ground beetles among microhabitat types were largely related to among-microhabitat differences in the physical environment and resource availability. Our results suggest that shrubs and species identity play key roles in structuring ground beetle communities, but their influence differed between species. This study emphasizes the importance of protecting shrub habitats for the maintenances of beetle biodiversity in this Gobi desert ecosystem.  相似文献   

17.
张永宽  陶冶  刘会良  张道远  吴小波 《生态学报》2012,32(21):6715-6725
准噶尔无叶豆(Eremosparton songoricum) 是中亚荒漠特有小半灌木,稀有种,在我国仅片段化分布于新疆古尔班通古特沙漠;它是流动沙丘的先锋物种,也能成功定居于人工固沙区(草方格)。对比研究了人工固沙区及自然流沙区的准噶尔无叶豆群落物种组成、种群密度、高度、盖度、生物量等特征及种群空间分布格局。结果表明:人工固沙区内的准噶尔无叶豆群落物种的科、属、种数均明显多于流沙区,而且2种生境物种相似性指数仅为0.522,表明人工固沙生境显著改变了群落物种组成与结构。除植株密度外,人工固沙区种群的高度,盖度,地上、地下及总生物量密度,单株地上、地下及总生物量等数量特征均显著高于流沙区。2种生境中准噶尔无叶豆种群空间分布的关联维数均接近2.0,体现了较强的个体空间相关性和空间占据能力。2种尺度(1 m和2 m)下的聚集度分析表明,2种生境中种群基本为随机分布。因而,人工固沙生境并未明显改变种群空间分布格局,这可能是种群的固有特性。人工固沙区的土壤有机质、全氮和有效氮含量显著高于流沙区,且与种群数量特征(植株密度除外)呈显著正相关。总之,与流沙区相比,人工固沙使地表得到固定,提高了土壤有机质和氮素含量,明显改变了定居于其中的准噶尔无叶豆种群主要数量特征,增强了种群的生存和适应能力。该结论对荒漠濒危植物的保育具有重要指示意义。  相似文献   

18.
The specialized fauna of peat bogs declines strongly both in species numbers and population density and becomes fragmented because of anthropogenic land use changes. We investigated 15 populations of the stenotopic ground beetle species Agonum ericeti in south Sweden to address the question of reduced genetic variability in populations inhabiting smaller habitat patches. Our results reveal a generally low differentiation and a significant positive relationship between habitat size and allelic richness.  相似文献   

19.
The American burying beetle, Nicrophorus americanus, is a federally endangered insect that once occurred in 35 US states and 3 Canadian provinces. Today, it remains at the periphery of its former range with the largest populations concentrated in Nebraska and Oklahoma. We assessed beetle occurrence records throughout the western ranges in Nebraska and Oklahoma, but excluded a small eastern population on Block Island, Rhode Island. We compiled more than 2500 presence–absence records and used GIS-based random forest models to create distribution maps throughout the current western range of the American burying beetle based on habitat characteristics within 800 m of each trap. We also used generalized linear models to identify habitat characteristics associated with N. americanus occurrences and to document differences between northern and southern habitat associations. In its northern range, N. americanus was associated with wetter areas while avoiding agricultural and urban areas. In the southern range, N. americanus was associated with sandy soils, hayfields, and native forests and grasslands, while avoiding human population centers and agricultural areas. Our N. americanus distribution maps for the northern and southern regions highlight areas where N. americanus is likely to occur, providing a tool that may improve current management. This first attempt at a range-wide model of American burying beetle occurrences revealed important differences among regions and can improve region-specific management and conservation.  相似文献   

20.
The Rosalia longicorn or Alpine longhorn (Coleoptera: Cerambycidae) is an endangered and strictly protected icon of European saproxylic biodiversity. Despite its popularity, lack of information on its demography and mobility may compromise adoption of suitable conservation strategies. The beetle experienced marked retreat from NW part of its range; its single population survives N of the Alps and W of the Carpathians. The population inhabits several small patches of old beech forest on hill-tops of the Ralska Upland, Czech Republic. We performed mark-recapture study of the population and assessed its distribution pattern. Our results demonstrate the high mobility of the beetle, including dispersal between hills (up to 1.6 km). The system is thus interconnected; it contained ~2000 adult beetles in 2008. Estimated population densities were high, ranging between 42 and 84 adult beetles/hectare a year. The population survives at a former military-training ground despite long-term isolation and low cover of mature beech forest (~1%). Its survival could be attributed to lack of forestry activities between the 1950s and 1990s, slow succession preventing canopy closure and undergrowth expansion, and probably also to the distribution of habitat patches on conspicuous hill-tops. In order to increase chances of the population for long term survival, we propose to stop clear-cuts of old beech forests, increase semi-open beech woodlands in areas currently covered by conifer plantations and active habitat management at inhabited sites and their wider environs.  相似文献   

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