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1.
Habitat loss and fragmentation are recognized as primary drivers of biodiversity loss worldwide. To understand the functional effects of habitat fragmentation on bird populations, data on movement across gaps in habitat cover are necessary, although rarely available. In this study, we used call playback to simulate a conspecific territorial intruder to entice birds to move through the landscape in a predictable and directional manner. We then quantified the probability of movement in continuous forest and across cleared gaps for two forest‐dependent species, the grey shrike‐thrush (Colluricincla harmonica) and the white‐throated treecreeper (Cormobates leucophaeus). Fifty‐four playback trials were conducted for each species across distances ranging from 25 to 480 m in continuous forest and 15–260 m across gaps in a forest‐agricultural landscape in southern Victoria, Australia. The probability of movement was significantly reduced by gaps in forest cover for both species. Shrike‐thrushes were six times more likely to move 170 m in continuous forest than to cross 170‐m gaps. The mean probability that treecreepers would cross any gap at all was less than 0.5, and they were three times less likely to move 50 m across a gap than through continuous forest. Both species displayed non‐linear responses to increasing gap distance: we identified a gap‐tolerance threshold of 85 m for the shrike‐thrush and 65 m for the treecreeper beyond which individuals were most unlikely to cross. The presence of scattered paddock trees increased functional connectivity for the shrike‐thrush, with individuals crossing up to 260 m when scattered trees were present. We conclude that gaps in habitat cover are barriers to movement, and that characteristics of the intervening matrix influence landscape permeability. 相似文献
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气候变化和人类活动导致的自然生境丧失和生境片断化使全球生物多样性面临威胁,而有效缓解这类问题的手段之一是维持自然生境的景观连接度。图论分析法作为景观连接度研究的新途径成为研究领域热点,但仍然存在提高距离阈值取值的科学性、充分解读图论连接度指数等有待探究的问题。以闽清县自然森林为对象使用图论分析方法进行了景观连接度的量化研究,提出并使用了距离阈值综合取值方法,联合使用了多种景观连接度指数。研究结果表明,距离阈值综合取值方法能够提高取值的准确性并具有广泛适用性,二进制连接度指数与概率连接度指数能够从不同角度指示景观结构和斑块重要性格局。研究区域90%以上的景观连接度由主要景观组分维持,数量很少的极高重要值斑块数能够对整体连接度水平产生显著影响。面积越大的斑块重要性指数越高,但是极高重要值斑块的重要性指数并不完全取决于斑块面积,而更多的与斑块位置等因素相关。本研究进一步完善图论分析法在景观连接度研究方面的应用,对生物多样性保护工作具有参考价值。 相似文献
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《Addiction biology》2017,22(2):523-534
Alcohol dependence (AD) is characterized by corticostriatal impairments in individual brain areas such as the striatum. As yet however, complex brain network topology in AD and its association with disease progression are unknown. We applied graph theory to resting‐state functional magnetic resonance imaging (RS‐fMRI) to examine weighted global efficiency and local (clustering coefficient, degree and eigenvector centrality) network topology and the functional role of the striatum in 24 AD patients compared with 20 matched healthy controls (HCs), and their association with dependence characteristics. Graph analyses were performed based on Pearson's correlations between RS‐fMRI time series, while correcting for age, gender and head motion. We found no significant group differences between AD patients and HCs in network topology. Notably, within the patient group, but not in HCs, the whole‐brain network showed reduced average cluster coefficient with more severe alcohol use, whereas longer AD duration within the patient group was associated with a global decrease in efficiency, degree and clustering coefficient. Additionally, within four a‐priori chosen bilateral striatal nodes, alcohol use severity was associated with lower clustering coefficient in the left caudate. Longer AD duration was associated with reduced clustering coefficient in caudate and putamen, and reduced degree in bilateral caudate, but with increased eigenvector centrality in left posterior putamen. Especially changes in global network topology and clustering coefficient in anterior striatum remained strikingly robust after exploratory variations in network weight. Our results show adverse effects of AD on overall network integration and possibly on striatal efficiency, putatively contributing to the increasing behavioral impairments seen in chronically addicted patients. 相似文献
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生态连接度对生物迁移扩散、基因流动、干扰扩散等生态过程具有重要作用,是目前景观生态学研究的热点内容.生态连接度是测度景观对于资源斑块间运动的促进或者阻碍作用程度的指标.它主要基于渗透和图论两大理论,通过实验、模型模拟以及指数等量化方法描述区域景观结构和功能的变化,广泛应用在自然景观和城市景观格局优化中,对生物多样性保护以及城市开放空间规划具有重要作用.介绍生态连接度的理论基础、评价方法,应用以及主要结论,并对景观生态学中生态连接度的未来研究方向进行展望,以促进生态连接度研究的进一步发展. 相似文献
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景观连接度反映了景观对物种或某种生态过程在生境斑块之间运动的促进或阻碍作用,对维持景观格局及生态过程的完整性和连续性具有重要指示意义。在当前全球环境变化,自然生境丧失和破碎化不可避免的情况下,景观连接度的评价、模拟与应用已成为景观生态学、保护生物学等相关学科的研究热点。基于CNKI和Web of Science数据库,检索1999—2015年间国内发表的景观连接度期刊论文,通过文献计量法,分别从年发文量、来源期刊、研究机构、研究区域、研究目的、景观类型、景观尺度以及研究方法等多个视角分析国内该领域应用研究进展以及发展趋势。经检索共得到文献240篇,其中英文43篇。分析发现,近20年国内该领域年发文量总体呈显著增长趋势;《生态学报》、《生态学杂志》和Urban and Landscape Planning为主要刊载期刊;研究力量集中分布在北京、南京等东部18所科研机构,文献量占到43.75%;研究目标区域也以东部为主(52.2%),而对中西部生态敏感脆弱区研究较少;研究目的以景观规划为主,但针对物种保护的研究较弱,仅占11.25%,且主要关注大熊猫等被公众熟知的珍稀濒危物种;城市、城乡等人工景观是常见的景观研究类型,相比之下,自然景观所占比例较低;研究的空间尺度集中在5000 km2的中小尺度域,占72.5%,景观粒度以30 m的中等分辨率居多。识别出14种具体度量方法,常用的包括最小费用模型、基于图论原理的功能连接度指数和网络结构指数,以及景观格局指数等;关注功能性连接和多方法的综合应用已成为当前研究的趋势;度量方法的一些参数,如最小费用模型阻力赋值或距离阈值选择主要依据专家经验或已有文献,而针对目标物种采用实证研究的则较少。最后,对国内当前该领域的研究现状和不足展开讨论并展望了未来发展,以促进我国景观连接度后续研究。 相似文献
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Many ecologists believe birds disappear from tropical forest fragments because they are poor dispersers. We test this idea using a spatially explicit capture data base from the Biological Dynamics of Forest Fragments Project near Manaus, Brazil. We measure bird movements directly, over relatively large scales of space and time, both before and after landscape fragmentation. We found that species which disappear from fragments move extensively between plots before isolation, but not after, and often disperse to longer distances in continuous forest than in fragmented forest. Such species also preferentially emigrate from smaller to larger fragments, showing no preference in continuous forest. In contrast, species that persist in fragments are generally less mobile, do not cross gaps as often, yet disperse further after fragmentation than before. 'Heavy tailed' probability models usually explain dispersal kernels better than exponential or Gaussian models, suggesting tropical forest birds may be better dispersers than assumed with some individuals moving very long distances. 相似文献
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Carlos A. Rivas;José Guerrero-Casado;Rafael M. Navarro-Cerrillo; 《应用植被学》2024,27(2):e12770
Connectivity is a parameter that plays a fundamental role in highly fragmented ecosystems, such as the seasonal tropical dry forest. 相似文献
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- At the landscape level, intensification of agriculture, fragmentation, and destruction of natural habitats are major causes of biodiversity loss that can be mitigated at small spatial scales. However, the complex relationships between human activities, landscapes, and biodiversity are poorly known. Yet, this knowledge could help private stakeholders managing seminatural areas to play a positive role in biodiversity conservation.
- We investigated how water‐abstraction sites could sustain species diversity in vascular‐plant communities and two taxonomic groups of insect communities in a fragmented agricultural landscape.
- Landscape‐scale variables (connectivity indices and surrounding levels of herbicide use), as well as site‐specific variables (soil type for vascular plants, floral availability for Rhopalocera, and low herbaceous cover for Orthoptera), were correlated to structural and functional metrics of species community diversity for these taxonomic groups, measured on 35 industrial sites in the Ile‐de‐France region in 2018–2019.
- Rhopalocera and Orthoptera consisted essentially of species with a high degree of dispersal and low specialization, able to reach the habitat patches of the fragmented landscape of the study area. Sandy soil harbored more diverse vascular‐plant communities. Plant diversity was correlated to a greater abundance of Rhopalocera and a lower richness of Orthoptera.
- Increasing landscape connectivity was related to higher abundance of plants and Rhopalocera, and a higher evenness index for Orthoptera communities. Higher levels of herbicide use were related to a decrease in the biodiversity of plants and Rhopalocera abundance. High levels of herbicide favored high‐dispersal generalist plants, while high levels of connectivity favored low‐dispersal plants. Specialist Orthoptera species were associated with low herbaceous cover and connectivity.
- Water‐abstraction sites are valuable seminatural habitats for biodiversity. Changing intensive agricultural practices in surrounding areas would better contribute to conserving and restoring biodiversity on these sites.
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对森林空间结构的研究一直是生态学重要研究内容之一,林分中大径级个体直接影响周围林分的空间格局,当大径级个体成为倒木或枯立木时会造成较大林隙,这也将导致周围空间格局发生变化。利用小兴安岭凉水自然保护区内10.4 hm2样地的调查数据,统计了样地内乔木树种组成,分析计算样地内树木个体间的分布规律,探究大径级个体对周围邻木空间分布的影响。研究结果表明:样地中共有乔木24种,共计7412株(去除分株),隶属于11科18属,林分中大径级个体周围存在由小径级树木聚集生长形成的环形结构,该环形结构随着邻木径级的变化而变化,2级邻木(5.0≤DBH10.0 cm)主要在距离大径级个体3—7m范围内形成环形结构,3级邻木(10.0≤DBH30.0 cm)主要在距离大径级个体3—6 m范围内形成环形结构,而1级邻木(1.0≤DBH5.0 cm)与4级邻木(30.0≤DBH50.0 cm)并未形成环形结构,经分析环形结构的产生与林分内个体间的竞争存在密切关系,并且该结构与林隙斑块动态理论间存在内在联系,该结构是森林动态变化的一种表现形式,会伴随林木的生长产生或消失。另外研究表明大径级个体胸径的变化对邻木的环形结构分布范围也有一定影响,当大径级个体胸径增加时邻木的聚集范围有收缩的趋势。本次实验采用单次获取的林木数据,对于环形结构随时间的变化情况还有待进一步探究。 相似文献
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Alesandro S. Santos Eliana Cazetta Pavel Dodonov Deborah Faria Fernanda A. Gaiotto 《Ecology and evolution》2016,6(18):6586-6598
Habitat loss represents one of the main threats to tropical forests, which have reached extremely high rates of species extinction. Forest loss negatively impacts biodiversity, affecting ecological (e.g., seed dispersal) and genetic (e.g., genetic diversity and structure) processes. Therefore, understanding how deforestation influences genetic resources is strategic for conservation. Our aim was to empirically evaluate the effects of landscape‐scale forest reduction on the spatial genetic structure and gene flow of Euterpe edulis Mart (Arecaceae), a palm tree considered a keystone resource for many vertebrate species. This study was carried out in nine forest remnants in the Atlantic Forest, northeastern Brazil, located in landscapes within a gradient of forest cover (19–83%). We collected leaves of 246 adults and 271 seedlings and performed genotyping using microsatellite markers. Our results showed that the palm populations had low spatial genetic structure, indicating that forest reduction did not influence this genetic parameter for neither seedlings nor adults. However, forest loss decreased the gene flow distance, which may negatively affect the genetic diversity of future generations by increasing the risk of local extinction of this keystone palm. For efficient strategies of genetic variability conservation and maintenance of gene flow in E. edulis, we recommend the maintenance of landscapes with intermediary to high levels of forest cover, that is, forest cover above 40%. 相似文献
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Foraging behaviour of a frugivorous bat helps bridge landscape connectivity and ecological processes in a fragmented rainforest 总被引：1，自引：0，他引：1
1. Landscape connectivity may greatly influence the distribution of animals when it alters their movements and their ability to reach food patches. Depending on their foraging behaviour, organisms may or may not adapt to anthropogenic changes in landscape connectivity and may eventually undergo local extinctions. 2. Recent studies underlined the need to use indicators of functional landscape connectivity based on the behaviour and movement abilities of studied animals to better link landscape structure to ecological processes in disturbed and fragmented areas. 3. The objectives of this study were: to elaborate an index of functional connectivity for Rhinophylla pumilio, a Neotropical understorey frugivorous bat; to use this index to investigate the possible mechanisms controlling its distribution and sustainability in a fragmented landscape; and to test whether this index could be applied to other species of the same guild. 4. We pursued a 10-year bat mist-net survey, coupled to local estimates of food availability, in a mature forest of French Guiana that was recently fragmented by the completion of a reservoir lake. The 18 sampling sites range from undisturbed continuous forest sites to small remote forest fragments. A connectivity value, based on radio-tracking surveys, was attributed to each site. Connectivity measures mean forest cover within neighbouring landscape units, weighted by the probability that bats would use them, as estimated by frequency distribution of flight distance data. 5. The abundance of R. pumilio was positively correlated with landscape connectivity and not correlated with local food availability. Its foraging strategy has evolved in response to the highly scattered distribution of its fruit resource. In spite of its high mobility, R. pumilio apparently failed to exploit a food resource that is distributed patchily over a low-connective habitat because its foraging movements are not well adapted to habitat disruptions. 6. The connectivity index contributed to explain general tendencies of abundance variations in other understorey frugivorous bats, although the spatial scale we examined was probably too small for these species. We make recommendations to adapt a functional connectivity index to species whose large-scale movements are difficult to survey. 相似文献
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城市生态网络是景观生态学应用领域研究的热点和重点之一,识别、评估生境之间的连接是构建生态网络的关键环节。在总结已有连接辨识方法的基础上,提出采用最小费用模型和图论分析相结合的方法,探讨功能性连接的辨识和优先恢复途径。以新西兰基督城为案例,分别利用景观发展强度指数建立阻力面,新西兰鸡毛松(Dacrycarpus dacrydioides)种子最大传播距离作为连接阈值来模拟、评价网络连接。结果表明:在1200 m距离阈值下,共有408条连接,其重要性分为10类。其中Richmond—Petrie公园,Hansons—Auburn保护地,Centaurus公园—King George保护地是整个生态网络的关键连接;若去除,景观整体连接度将下降31.73%。此外,研究发现连接重要值与两端的源面积之和没有显著相关性,即面积大的源斑块之间的连接不一定对网络构建起关键作用,这一结论还有待进一步证明。针对缺少动物迁移资料的城市环境,改进最小费用模型和网络连接分析的部分参数;可操作性与实用性强,对中国城市区域生态恢复建设、栖息地选择具有借鉴意义。 相似文献
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Migratory animals present a unique challenge for understanding the consequences of habitat loss on population dynamics because individuals are typically distributed over a series of interconnected breeding and non‐breeding sites (termed migratory network). Using replicated breeding and non‐breeding populations of Drosophila melanogaster and a mathematical model, we investigated three hypotheses to explain how habitat loss influenced the dynamics of populations in networks with different degrees of connectivity between breeding and non‐breeding seasons. We found that habitat loss increased the degree of connectivity in the network and influenced population size at sites that were not directly connected to the site where habitat loss occurred. However, connected networks only buffered global population declines at high levels of habitat loss. Our results demonstrate why knowledge of the patterns of connectivity across a species range is critical for predicting the effects of environmental change and provide empirical evidence for why connected migratory networks are commonly found in nature. 相似文献
17.
Andrea Avena-Koenigsberger Joaquín Go?i Richard F. Betzel Martijn P. van den Heuvel Alessandra Griffa Patric Hagmann Jean-Philippe Thiran Olaf Sporns 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2014,369(1653)
Graph theory has provided a key mathematical framework to analyse the architecture of human brain networks. This architecture embodies an inherently complex relationship between connection topology, the spatial arrangement of network elements, and the resulting network cost and functional performance. An exploration of these interacting factors and driving forces may reveal salient network features that are critically important for shaping and constraining the brain''s topological organization and its evolvability. Several studies have pointed to an economic balance between network cost and network efficiency with networks organized in an ‘economical’ small-world favouring high communication efficiency at a low wiring cost. In this study, we define and explore a network morphospace in order to characterize different aspects of communication efficiency in human brain networks. Using a multi-objective evolutionary approach that approximates a Pareto-optimal set within the morphospace, we investigate the capacity of anatomical brain networks to evolve towards topologies that exhibit optimal information processing features while preserving network cost. This approach allows us to investigate network topologies that emerge under specific selection pressures, thus providing some insight into the selectional forces that may have shaped the network architecture of existing human brains. 相似文献
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Justin Böhmer Pablo Reinhardt Maria Garbusow Michael Marxen Michael N. Smolka Ulrich S. Zimmermann Andreas Heinz Danilo Bzdok Eva Friedel Johann D. Kruschwitz Henrik Walter 《Addiction biology》2023,28(11):e13339
Alcohol dependence (AD) is a debilitating disease associated with high relapse rates even after long periods of abstinence. Thus, elucidating neurobiological substrates of relapse risk is fundamental for the development of novel targeted interventions that could promote long-lasting abstinence. In the present study, we analysed resting-state functional magnetic resonance imaging (rsfMRI) data from a sample of recently detoxified patients with AD (n = 93) who were followed up for 12 months after rsfMRI assessment. Specifically, we employed graph theoretic analyses to compare functional brain network topology and functional connectivity between future relapsers (REL, n = 59), future abstainers (ABS, n = 28) and age- and gender-matched controls (CON, n = 83). Our results suggest increased whole-brain network segregation, decreased global network integration and overall blunted connectivity strength in REL compared with CON. Conversely, we found evidence for a comparable network architecture in ABS relative to CON. At the nodal level, REL exhibited decreased integration and decoupling between multiple brain systems compared with CON, encompassing regions associated with higher-order executive functions, sensory and reward processing. Among patients with AD, increased coupling between nodes implicated in reward valuation and salience attribution constitutes a particular risk factor for future relapse. Importantly, aberrant network organization in REL was consistently associated with shorter abstinence duration during follow-up, portending to a putative neural signature of relapse risk in AD. Future research should further evaluate the potential diagnostic value of the identified changes in network topology and functional connectivity for relapse prediction at the individual subject level. 相似文献
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Many functions in behavioural processes of small passerines are regulated via vocal messages. Song plays an important role in the development of reproductive barriers and thus playback experiments can often be used for investigating the potential for reproductive isolation through behavioural mechanisms. Moltoni's warbler Sylvia (cantillans) moltonii is characterized by diagnostic vocalizations and a peculiar pattern of distribution, being parapatric and partly sympatric with the nominate Sylvia c. cantillans. With this work, we test whether these two closely related taxa react equally to their own song and to the song of the other taxon, shedding light on whether they perceive each other's songs as coming from the same species. We carried out 184 playback experiments within the mainland range of the two forms. We judged the response of the bird on a scale of scores. Each taxon responded more strongly to playback when faced with the song of its own taxon. This held true when applied only to males or females. Additionally, birds tested for both songs showed a stronger response to the song of their own taxon. The distributional context (sympatry vs. allopatry) did not affect bird response. Results indicate that a certain degree of reproductive isolation between the two taxa (because of diverged mate recognition systems) already exists; consistently with genetic data and with the peculiar pattern of distribution; this suggests that the two taxa have reached species status. 相似文献
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Luiz dos Anjos Gabriela Menezes Bochio Hugo Reis Medeiros Bia de Arruda Almeida Barbara Rocha Arakaki Lindsey Larissa Corsini Calsavara Milton Cezar Ribeiro Jos Marcelo Domingues Torezan 《Ecology and evolution》2019,9(11):6318-6328
A decline in species number often occurs after forest fragmentation and habitat loss, which usually results in the loss of ecological functions and a reduction in functional diversity in the forest fragments. However, it is uncertain whether these lost ecological functions are consistently maintained throughout continuous forests, and so the importance of these functions in continuous forests remains unknown. Point counts were used to assess both the taxonomic and functional diversity of specialist and generalist birds from sampling in a continuous primary forest compared with forest fragments in order to investigate the responses of these groups to forest fragmentation. We also measured alpha and beta diversity. The responses of specialists and generalists were similar when we assessed all bird species but were different when only passerines were considered. When examining passerines we found lower total taxonomic beta diversity for specialists than for generalists in the continuous forest, while taxonomic beta diversity was higher in the fragmented forest and similar between bird groups. However, total functional beta‐diversity values indicated clearly higher trait regularity in continuous forest for specialists and higher trait regularity in fragments for generalists. Specialists showed significantly higher functional alpha diversity in comparison with generalists in the continuous forest, while both groups showed similar values in fragments. In passerines, species richness and alpha functional diversity of both specialist and generalist were explained by forest connectivity; but, only fragment size explained those parameters for specialist passerines. We suggest that considering subsets of the community with high similarity among species, as passerines, provides a better tool for understanding responses to forest fragmentation. Due to the regularity of specialists in continuous forest, their lost could highly affect functionality in forest fragments. 相似文献