共查询到20条相似文献，搜索用时 15 毫秒
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Erwan Quéméré Julie Champeau Aubin Besolo Emmanuel Rasolondraibe Clément Rabarivola Brigitte Crouau‐Roy Lounès Chikhi 《American journal of primatology》2010,72(1):72-80
The golden‐crowned sifaka (Propithecus tattersalli) is an endangered lemur species found only in the Daraina region, a very restricted area in north‐eastern Madagascar. Its forest habitat is highly fragmented and expected to suffer from significant changes in the near future. The species is poorly known and only one census study, carried out in 2000, has ever been published. It is thus crucial to update the conservation status of the golden‐crowned sifaka before major anthropogenic environmental changes take place. Using the line‐transect approach, we estimated the species density in the main forest fragments located in both the peripheral and central parts of the distribution range, including both protected and unprotected areas. In parallel, we tried to determine whether an edge effect could be detected by comparing densities at different distances from the forest edges. We found important variation of sifaka densities among forest fragments. The total species abundance is thus difficult to determine, but we estimated that it is likely to be over 18,000, two to three times higher than previously thought. However, our data also suggested that most P. tattersalli live in forests located in the central part of the distribution range and that the estimated densities in the central part were high (>80 individuals/km2). Two forest fragments, found to host a large part of the total population, are currently outside the managed area and their incorporation to the managed area is strongly recommended. Lastly, as expected for a folivorous and not heavily hunted species, our results are consistent with the hypothesis that this species does not experience a clear edge effect, at least during the first half of the dry season. This could be due to a high resiliency to habitat fragmentation or to the fact that fragmentation has been going on for some time. Am. J. Primatol. 72:72–80, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
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栖息地破碎化给野生动物带来的不良后果是全球生态学家和保护生物学家共同关心的问题.自从提出栖息地破碎化是导致生物多样性丧失的关键因素之一的论点后,近20年来,栖息地破碎化研究一直是生态学和保护生物学最活跃的前沿研究领域之一.栖息地破碎化是一动态过程,可在多尺度上发生并蕴涵着复杂的空间模式变化.栖息地破碎化对鸟类的生态学效应主要体现在面积效应、隔离效应和边缘效应等.这些效应影响着鸟类的分布、基因交流、种群动态、扩散行为、种间关系和生活史特征等,最终影响着鸟类的生存.介绍和总结了栖息地破碎化过程、研究的理论依据及栖息地破碎化对鸟类生存产生的诸多影响. 相似文献
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Brian A. Lerch Kimberly A. Dautel Sharee Brewer Alan Liang Nourridine Siewe Sarah Flanagan 《Population Ecology》2020,62(2):269-283
Many territorial species have a mating system characterized by males establishing home ranges in the breeding grounds prior to females, resulting in males competing for territories and females choosing a mate upon their arrival. It remains unknown, however, how the outcomes of decisions surrounding territory establishment and mate choice are influenced by the spatial configuration of the breeding grounds. We use a spatially explicit, individual-based model to investigate the sex-specific effects of these decisions on reproductive success. In our model, males that arrive earlier obtain higher quality territories and improve their chances for extra-pair copulations. Females can choose their mate to maximize the quality of the male or to attempt to minimize the density of other females near their nesting site to avoid competition. Females therefore face a tradeoff between high-density regions around high-quality males and low-quality males in areas of low competition. Our model predicts a negative correlation between male and female reproductive success under a wide range of conditions when the majority of the territories are on the margins of the breeding area. Most notably, this sexual conflict arises as an edge effect suggesting that fragmentation of breeding habitats could impact the consequences of mate choice in many species with territorial breeding habits. 相似文献
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Irwin MT 《American journal of primatology》2007,69(4):434-447
Forest fragmentation is thought to threaten primate populations, yet the mechanisms by which this occurs remain largely unknown. However, fragmentation is known to cause dietary shifts in several primate species, and links between food resource distribution and within-group spatial dynamics are well documented. Thus, fragmentation has the potential to indirectly affect spatial dynamics, and these changes may present additional stresses to fragmented populations. I present the results from a 12-month study of Propithecus diadema at Tsinjoarivo, eastern Madagascar, including two groups in fragments and two in continuous forest. Instantaneous data on activity and spatial position were collected during all-day focal animal follows. Fragment groups had much lower cohesion, being more likely to have no neighbor within 5 and 10 m. For continuous forest groups, cohesion was highest in the rainy season (when food patches are large) and lowest in winter (when the animals rely on small-crowned mistletoes), and the chance of having no neighbor within 5 m was positively correlated with mistletoe consumption. Thus their decreased cohesion in fragment groups is inferred to result from their increased reliance on mistletoes and other small resources, which causes them to spread out among multiple patches. This scenario is consistent with the reduced body mass of subordinate individuals (males and immatures) in fragments, and suggests the occurrence of steeper within-group fitness gradients. Further research is necessary to determine whether these patterns apply to other primates; however, since fragmentation tends to cause the loss of the largest trees, many primates in fragments may lose their largest food resources and undergo similar behavioral shifts. 相似文献
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HIROSHI TOMIMATSU IPPEI TANAKA MASATOSHI SATO RENZO KONDO YASUO KONNO 《Plant Species Biology》2011,26(1):3-12
Understory bamboo species are important and influential components of temperate forests in at least several parts of the world. Here we report a study testing the effect of forest fragmentation on the dynamics of the dwarf bamboo Sasa chartacea and on forest herb communities in the Tokachi plain of Hokkaido, Japan. We studied 16 forest fragments of different sizes and small plots established in these fragments to examine the relationship between the abundance of S. chartacea, landscape and environmental conditions, and forest herb communities. Sasa chartacea was more abundant near forest edges and in smaller fragments, suggesting that the species has expanded its local range and increased its abundance in response to forest fragmentation. Edge‐related changes in light and soil moisture might have facilitated this range expansion. The species richness of forest herbs was strongly negatively related to the density of S. chartacea. Because much larger variation in species richness was explained by S. chartacea density than distance to the nearest forest edge, the expansion of S. chartacea has likely excluded other understory species by competition. In addition, the density of S. chartacea significantly explained variation in the species composition of forest herbs across plots. Taken together, our results emphasize the key roles of dwarf bamboos in changing plant communities following forest fragmentation. 相似文献
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ROBERT M. EWERS 《Insect Conservation and Diversity》2008,1(1):40-47
Abstract.
- 1 Edge effects are a highly cited issue in conservation biology with a wealth of empirically described impacts on invertebrates, but the mechanisms underlying the responses of individual species to habitat edges have been seldom tested. One often‐raised hypothesis is that individual species vary in their ability to survive along a gradient of changing microclimatic conditions across habitat edges.
- 2 I used a phylogenetically controlled, translocation experiment to investigate edge‐driven variation in adult mortality rate for two closely related species that have contrasting abundance patterns with respect to forest‐grassland edges; the habitat generalist Mecodema fulgidum Broun (Coleoptera: Carabidae) and the forest‐dwelling Mecodema rugiceps Sharp.
- 3 Adult individuals of both species were live‐caught and translocated into containers at varying distances along an edge gradient extending from 1024 m inside a large forest fragment and 64 m into the surrounding grassland matrix. Experimental containers were connected to the above‐ and below‐ground environments via mesh‐covered panels, and beetle mortality over a 4‐month period in the 2006/2007 austral summer was recorded.
- 4 Overall, mortality was higher for the habitat specialist M. rugiceps than for the generalist M. fulgidum. Neither species exhibited an edge‐related trend in mortality, nor were mortality rates correlated with microclimatic gradients across the edge.
- 5 Weather records for the summer indicated that M. rugiceps was more sensitive than M. fulgidum to a soil moisture deficit that became more pronounced as summer progressed. Analysis of a 10‐year climate record shows that soil moisture deficits occur annually, suggesting that seasonal variation in soil moisture may contribute to the variation in the distribution and abundance of the two species.
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Nest predation is widely regarded as a major driver underlying the population dynamics of small forest birds. Following forest fragmentation and the subsequent invasion by species from non-forested landscape matrices, shifts in predator communities may increase nest predation near forest edges. However, effects of human-driven habitat change on nest predation have mainly been inferred from studies with artificial nests, despite being regarded as poor surrogates for natural ones. We studied variation in predation rates, and relationships with timing of breeding and characteristics of microhabitats and fragments, on natural white-starred robin Pogonocichla stellata nests during three consecutive breeding seasons (2004–2007) in a Kenyan fragmented cloud forest. More than 70% of all initiated nests were predated during each breeding season. Predation rates nearly quadrupled between the earliest and the latest nests within a single breeding season, increased with distance to the forest edge, and decreased with the edge-to-area ratio of forest fragments. These spatial relationships oppose the traditional perception of edge and fragmentation effects on nest predation, but are in line with results from artificial nest experiments in other East African forests. In case of inverse edge and fragmentation effects on nest predation, such as shown in this study, species that tolerate edges for breeding may be affected positively, rather than negatively, by forest fragmentation, while the opposite can be expected for species restricted to the forest interior. The possibility of inverse edge effects, and its conservation implications, should therefore be taken into account when drafting habitat restoration plans. 相似文献
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Corina A. Barrera Liliana M. Buffa Graciela Valladares 《Insect Conservation and Diversity》2015,8(5):456-463
- The expansion of agriculture has led to forest loss and fragmentation, resulting in dramatic biodiversity impoverishment. Surprisingly, few studies have assessed forest fragmentation effects on leaf‐cutting ant assemblages, and none has dealt with effects on their community richness and composition, despite their known role as key herbivores and ecosystem engineers.
- We analysed forest area and edge effects on leaf‐cutting ant abundance, richness and assemblage composition, by recording and identifying colonies along edge and interior transects in 12 Chaco Serrano forest remnants of different sizes, in Central Argentina. We also explored leaf‐cutting ant presence in the adjacent soybean matrix.
- We recorded five leaf‐cutting ant species, in the genus Acromyrmex. In the soybean matrix, colonies of three species were observed, which were also found at the forest edge. Within the forest, edges sustained more species and colonies than interior habitats, whereas forest area was linked positively to colony abundance. Taxonomic composition of leaf‐cutting ant assemblages reflected both area and edge effects.
- Our results revealed overall positive edge and area effects on leaf‐cutting ant communities, highlighting differential species‐specific responses and a possible role for Acromyrmex crassispinus as a forest status indicator. According to our findings, an increase in edge habitats may favour most leaf‐cutting ant species, providing a suitable interface for access to the cultivated matrix, but hindering species associated with undisturbed forest conditions. As leaf‐cutting ants are acknowledged as cornerstones of ecosystem functioning, the consequences of these trends may be far reaching.
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JOSS M. BENTLEY 《Austral ecology》2008,33(2):184-196
Abstract Habitat fragmentation and disturbance affect patterns of habitat use, animal movement and spatial behaviour and might have significant effects upon population dynamics and trends, and ultimately population persistence. Previous studies have suggested that the ability to disperse between remnants and a positive or neutral response to edges should be associated with species capable of persisting in remnant habitat. Using both radiotracking and trapping data, movement patterns, dispersal and response to habitat edges of Rattus fuscipes were examined within forests, corridors, remnants and pastures in south‐east Queensland, Australia. Rattus fuscipes has previously been shown to be robust to the effects of habitat fragmentation; however, contrary to expectations, R. fuscipes was found to be sensitive to edges, and no evidence of interremnant dispersal was detected, despite interremnant distances that were substantially smaller than the distances R. fuscipes was found to move in continuous habitat. Using only trapping data, the same factors were examined in relation to Melomys cervinipes, a species sensitive to fragmentation. Melomys cervinipes was found to utilize edge habitat, but no evidence of interremnant dispersal was detected, although the capacity to detect such movement was limited by low abundance in remnants where M. cervinipes was extant, and the species absence from many remnants. Movement patterns, interremnant dispersal capacity, and sensitivity to edges did not prove to be good predictors of these species responses to habitat fragmentation. Alternative explanations, such as population fluctuation and the capacity for rapid population growth in remnants for these two species, and the influence habitat quality has on these parameters should be investigated. 相似文献
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Regina Berjano Perrine Gauthier Chiara Parisi Valentine Vaudey Virginie Pons Alain Renaux David Doblas John D. Thompson 《Journal of Plant Ecology》2016,9(3):333
Aims Habitat fragmentation impacts the spatial extent and isolation of local populations and communities. Although the biological consequences of these impacts have been well studied at the site level, effects directly related to changes in the spatial configuration of populations in the landscape remain less clear. The objective of this study is to examine how changes in the spatial-scale configuration of populations are associated with variability in morph rations in the floral polymorphic Mediterranean geophyte Narcissus assoanus .Methods We performed a nested analysis of morph ratio variation at three spatial scales: a 50×50 km regional scale in SE France, in fourteen 1×1 km landscapes located in the same region, and within 12 spatially extensive population patches. We also quantified variation in the behaviour of pollinators in population patches of contrasting spatial configuration.Important findings At a regional scale, morph ratios show a geographic pattern of increasing isoplethy (1:1 morph ratio) away from centres of human population development and in upland pastures. At the landscape scale, isoplethy of local population patches is more correlated with decreased isolation among patches than with patch size. Finally, within local isoplethic populations, small patches can show significantly biased morph ratios. In small isolated patches, pollinators perform shorter flight distances among consecutive flower visits than in spatially extensive patches. This study of variation in a genetic polymorphism at multiple spatial scales provides new insights into the scale-dependent effects of habitat fragmentation and the potential occurrence of metapopulation dynamics in natural plant populations. 相似文献
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- Roads are a potential threat to bat conservation. In addition to the direct risk of collision of bats with vehicles, roads could pose a threat to bat populations as a result of habitat loss, degradation and fragmentation, and could act as barriers to movements of bats between habitats.
- We performed a systematic review of the literature and conducted meta‐analyses to assess the threat posed by roads to bats as a result of 1) collisions between bats and vehicles and 2) roads acting as barriers to movements of bats.
- Based on collated records of 1207 bat road casualties in Europe, we found that low‐flying species are more prone to collisions than high‐flying species, and that juveniles are more vulnerable to collisions than adults. In addition, meta‐analysis identified a significant bias towards male casualties. Casualties included rare species such as Barbastella barbastellus and geographically restricted species such as Rhinolophus species.
- The bias towards male casualties could be indicative of greater natal philopatry or lower dispersal among females, or of sexual segregation in habitats of varying quality, i.e. females may occupy better quality habitats than males, and road density may be lower in better quality habitats.
- Whether or not roads act as barriers to the movement of bats depends on a complex interplay of habitat and species‐specific behaviour. For example, the presence of favourable habitat for bats – notably woodland – was found in this review to be linked with significantly reduced barrier effects but a heightened risk of collision.
- Our data suggest that roads do pose a threat to bats. Future research should assess the contribution of traffic noise and street lighting to the barrier effect of roads. Where new road schemes are monitored by ecological practitioners, it is vital that consistent protocols are employed to ensure that bat activity can be compared before and after the road is built. Evidence from such research should be used to minimize the risks for bats of any roads built in the future, and to design safe crossing points for bats.
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Abstract Wind disturbance is an important ecological force in the tropics, especially in the cyclonic and hurricane zones from about 7–20° latitude. Damage from intense winds may be especially severe in fragmented forests because of their abrupt artificial margins and denuded surrounding landscapes. We review available information on the effects of windstorms on fragmented forests, synthesizing studies from Australasia, Amazonia and elsewhere in the tropics. Wind damage in fragmented landscapes can be influenced by a range of factors, such as forest‐edge orientation, edge structure, the size of nearby clearings and local topography. We argue that wind disturbances are likely to interact with, and exacerbate, a range of deleterious environmental changes in fragmented forests. Among the most important of these are altered forest structure, shifts in plant species composition, exotic‐plant invasions, reduced carbon storage and elevated vulnerability to fire. The damaging impacts of winds on fragmented forests could potentially increase in the future, particularly if global warming leads to increasingly severe or frequent windstorms. 相似文献
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The abundance of wolf spiders (Lycosidae) was measured across woodland–pasture boundaries in the wheat‐belt of New South Wales, Australia, to determine the nature and magnitude of any edge effect. Spiders were collected by spotlighting along sample plots in woodlands located at distances of 5, 20, 35 and 200 m from the edge, and along sample plots in paddocks located at distances of 5 and 20 m from the edge. The wolf spider assemblage changed significantly across the edge, but the difference could be accounted for only by a change between the woodland and the paddock and not by any changes within the woodland at different distances from the edge. Ground cover (wolf spider microhabitat) changed significantly between the paddock and the woodland, but there were no consistent differences in microhabitat with distance from edge within either paddocks or woodlands. There was a significant correlation between an ordination of sites based on spider species abundance and an ordination based on microhabitat variables, suggesting that the wolf spider assemblage was responding to differences in microhabitat. Fine‐scale selection of microhabitat by most wolf spider species was non‐random, with most species preferring locations with grass cover, rather than more open locations. The present study indicates that wolf spiders are mostly unaffected by edge conditions at the woodland–paddock boundary. Accordingly, small and/or linear remnants with high edge‐to‐area ratios may constitute suitable faunal habitat for wolf spiders and perhaps other terrestrial arthropod species, despite the fact that this configuration is unsuitable for many vertebrate species. 相似文献
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Shilu Zheng Bruce L. Webber Raphael K. Didham Chun Chen Mingjian Yu 《Ecology and evolution》2021,11(14):9728
In fragmented forests, edge effects can drive intraspecific variation in seedling performance that influences forest regeneration and plant composition. However, few studies have attempted to disentangle the relative biotic and abiotic drivers of intraspecific variation in seedling performance. In this study, we carried out a seedling transplant experiment with a factorial experimental design on three land‐bridge islands in the Thousand Island Lake, China, using four common native woody plant species. At different distances from the forest edge (2, 8, 32, 128 m), we transplanted four seedlings of each species into each of three cages: full‐cage, for herbivore exclusion; half‐cage, that allowed herbivore access but controlled for caging artifacts; and no‐cage control. In the 576 cages, we recorded branch architecture, leaf traits, and seedling survival for each seedling before and after the experimental treatment. Overall, after one full growing season, edge‐induced abiotic drivers and varied herbivory pressure led to intraspecific variation in seedling performance, including trade‐offs in seedling architecture and resource‐use strategies. However, responses varied across species with different life‐history strategies and depended on the driver in question, such that the abiotic and biotic effects were additive across species, rather than interactive. Edge‐induced abiotic variation modified seedling architecture of a shade‐tolerant species, leading to more vertical rather than lateral growth at edges. Meanwhile, increased herbivory pressure resulted in a shift toward lower dry matter investment in leaves of a light‐demanding species. Our results suggest that edge effects can drive rapid directional shifts in the performance and intraspecific traits of some woody plants from early ontogenetic stages, but most species in this study showed negligible phenotypic responses to edge effects. Moreover, species‐specific responses suggest the importance of interspecific differences modulating the degree of trait plasticity, implying the need to incorporate individual‐level responses when understanding the impact of forest fragmentation on plant communities. 相似文献
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Loss and fragmentation of natural ecosystems are widely recognized as the most important threats to biodiversity conservation, with Neotropical dry forests among the most endangered ecosystems. Area and edge effects are major factors in fragmented landscapes. Here, we examine area and edge effects and their interaction, on ensembles of arthropods associated to native vegetation in a fragmented Chaco Serrano forest. We analyzed family richness and community composition of herbivores, predators, and parasitoids on three native plant species in 12 fragments of varying size and at edge/interior positions. We also looked for indicator families by using Indicator Species Analysis. Loss of family richness with the reduction of forest fragment area was observed for the three functional groups, with similar magnitude. Herbivores were richer at the edges without interaction between edge and area effects, whereas predators were not affected by edge/interior position and parasitoid richness showed an interaction between area and position, with a steeper area slope at the edges. Family composition of herbivore, predator, and parasitoid assemblages was also affected by forest area and/or edge/interior situation. We found three indicator families for large remnants and five for edges. Our results support the key role of forest area for conservation of arthropods taxonomic and functional diversity in a highly threatened region, and emphasize the need to understand the interactions between area and edge effects on such diversity. 相似文献
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We investigated the effects of agriculture and the availability of edge habitat on populations of Helmeted Guineafowl Numida meleagris and associated avian diversity and species composition in woodland and grassland biomes in the Midlands of KwaZulu-Natal province, South Africa. Study sites within woodland biome had greater species diversity than those in grassland, whereas adjacent, high-quality, protected habitat in grassland sites, enhanced diversity within this biome. Both guineafowl populations and overall avian diversity declined with increasingly intensive agriculture and disappearance of edge habitat and associated, optimally fragmented habitat mosaic. Furthermore, traditional agriculture in the form of contouring in a pesticide-free environment, resulted in extensive edge habitat that appeared to provide additional food and cover for birds. This, in turn, caused an increase in overall bird diversity, and in guineafowl populations in particular. The widespread decline in Helmeted Guineafowl populations in the Midlands that started in the 1980s, and possibly the decline in species associated with this variegated landscape, was therefore caused by the loss of the habitat mosaic to intensive, modern, monoculture, crop agriculture. Maintaining species diversity and healthy guineafowl populations within these habitats requires the persistence or re-creation of a habitat mosaic and the resulting edge habitat on a landscape scale. 相似文献
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Habitat fragmentation is a complex process that affects ecological systems in diverse ways, altering everything from population persistence to ecosystem function. Despite widespread recognition that habitat fragmentation can influence food web interactions, consensus on the factors underlying variation in the impacts of fragmentation across systems remains elusive. In this study, we conduct a systematic review and meta‐analysis to quantify the effects of habitat fragmentation and spatial habitat structure on resource consumption in terrestrial arthropod food webs. Across 419 studies, we found a negative overall effect of fragmentation on resource consumption. Variation in effect size was extensive but predictable. Specifically, resource consumption was reduced on small, isolated habitat fragments, higher at patch edges, and neutral with respect to landscape‐scale spatial variables. In general, resource consumption increased in fragmented settings for habitat generalist consumers but decreased for specialist consumers. Our study demonstrates widespread disruption of trophic interactions in fragmented habitats and describes variation among studies that is largely predictable based on the ecological traits of the interacting species. We highlight future prospects for understanding how changes in spatial habitat structure may influence trophic modules and food webs. 相似文献