食果动物与被取食植物的相互关系:协同进化?

在种子传播过程中动植物是否存在协同进化关系一直是争论的焦点。有观点认为,植物通过食果动物对其种子的传播可能获得逃避种子捕食者、占据新的生境斑块和基因流动等好处,而动物通过消化果肉获得营养和能量作为回报,动植物彼此相互作用,进而可能建立协同进化关系。动植物之间还可能发生在种、属或科水平以上的多物种的多配协同进化,或者通过关键种的协同进化来带动其他食果动物和植物相关性状的进化。“果肉防御假说”则认为果肉原本是保护种子的防御组织,后来才进化成为吸引食果动物以促进种子传播的物质。然而,食果动物和植物一对一的协同进化的例证并不多见;适合种子萌发和生长的环境在时空上难以确定;食果动物和植物的进化速度不一致;植物与种子传播者的选择压力存在着高度的不对称和不平衡,加上环境因素的重要影响,这种选择压力受到极大的限制而有可能变得不显著。种子传播中动植物在进化意义上的关系尚需进一步研究。未来研究应对食果动物和植物关系的复杂性和多样性有足够的认识。通过对系统发育中相联系的不同种的动植物关系的比较研究来揭示动植物关系对物种分化的影响,有可能为检验食果动物和植物之间的协同进化关系提供新的证据。食果动物传播种子对植物群落动态变化的影响、动植物关系和生物多样性保护等仍将是该领域研究的热点。     

食果动物传播植物种子的有效性

传播有效性是评估食果动物对植物种群更新贡献的关键指标,它决定了植物种群的续存,影响着群落生物多样性的维系。本文从种子传播数量、质量角度分析了影响动物传播有效性的因素,并从有效传播动物组合角度分析了其对植物种群更新的影响。传播数量的多少与动物的取食行为有关。以整吞取食的食果动物常被认为是植物的有效传播动物,而植物的果实为动物偏好选择的食物时,势必导致该种植物拥有高的种子传播数量。传播质量与食果动物肠道种子滞留时间以及其后的种子传播距离和排放地相关。体型较大、生境适应能力和迁徙性较强的动物常为植物提供较远的传播距离,而被认为传播质量较高。取食后动物的生境选择决定了种子的排放地,进而影响它们的种子传播质量。如果取食后动物偏好利用植物适宜更新的生境时,动物则拥有较高的传播质量。有效传播动物通常在传播数量和传播质量以互补形成一些组合对植物种群更新起贡献。今后工作应将动物行为野外监测和种子萌发实验相结合、取食后多种行为相结合来分析动物的传播有效性;而以一些国内特有濒危植物为研究对象开展传播有效性研究应是今后恢复生态学研究的重点。     

动物传播者对植物更新的促进与限制

在动物 植物的关系网络中,传播者对植物更新具有促进与限制两方面作用.本文从种群尺度总结了传播者取食、空间利用等行为对植物更新的影响;从群落尺度分析了多种传播者传播有效性对植物更新的促进与限制.传播者对食物的处理方式决定了种子的命运,且具有明显的种间差异;植物在传播者食谱中的地位亦决定其更新的成败,成为动物偏好的食物可助其摆脱森林破碎化等不利事件的影响.动物的空间行为可导致种子命运发生改变.传播者移动距离能否逃逸同种成树对种子的距离限制,影响种子的更新命运;动物偏好的适宜生境与适于植物萌发生境的空间一致性程度影响传播者传播的成效.有效传播者的非冗余性促使种子传播网络更稳定,利于植物更新;无效传播直接限制植物更新,但为其他植物定殖提供了可用空间.今后应将传播者行为融入植物种群更新研究,而从生态系统服务角度揭示传播者在植被恢复的作用应是未来恢复生态学研究的重点.     

斑块生境中食果鸟类对南方红豆杉种子的取食和传播

生境斑块化对食果鸟类的移动行为产生影响,进而影响其对植物种子的传播格局和效率。南方红豆杉(Taxus chinensis var.mairei)是我国一级保护植物,在南方山区多因人为干扰而呈斑块状分布。2011年,2012年10月底到12月中,以分布于福建梅花山国家级自然保护区红豆杉生态园中南方红豆杉种群为对象,研究斑块生境中鸟类对南方红豆杉种子的取食和传播行为,并评估专性鸟类和泛性鸟类的传播效率。结果发现:南方红豆杉源斑块共吸引22种食果鸟类取食红豆杉种子,并与13种鸟类形成了种子传播关系。不同年间,黑短脚鹎(Hypsipetes leucocephalus)都是植物的主要传播鸟类,而其他鸟类传播者种类具有一定的年间变化。生境斑块化导致专性鸟类黑短脚鹎和泛性鸟类红嘴蓝鹊(Urocissa erythrorhyncha)种子传播效率差异。与红嘴蓝鹊相比,黑短脚鹎飞行的平均距离较短((16.3±11.0)m,Mean±SD,n=125),传播距离相对较近;且它们取食后偏好在源斑块中活动,喜栖息在同种成树、甜楮(Castanopsis eyrei)及其他阔叶树等栖树上。红嘴蓝鹊取食后常在斑块间移动,常停歇在同种成树和毛竹(Phyllostachys heterocycla)上,传播距离相对较远((24.9±20.0)m,Mean±SD,n=95)。空间一致性结果表明,黑短脚鹎移动距离对幼苗更新距离的空间一致性程度高;而红嘴蓝鹊偏好生境与幼苗更新生境一致性程度高。结果表明,斑块生境中植物能与专性鸟类、泛性鸟类之间形成种子传播互惠关系,且种子传播效率受到专性鸟类和泛性鸟类传播距离和传播生境的影响。     

脊椎动物传播植物肉质果中的次生物质及其生态作用

在种子植物-动物的互惠关系中,植物果实成熟后需要吸引种子传播者取食果实,传播其种子至适宜萌发的生境,同时又要防御种子捕食者过度消耗种子。果实内的次生物质(如:配糖生物碱、大黄素、辣椒素)在此过程中起到重要的调控作用。依赖脊椎动物传播的肉质果中往往含有与植物茎、叶内相同的次生物质,其种类繁多,主要分为含氮化合物、酚类化合物和萜类化合物。未成熟果实内富含次生物质(如:单宁、大黄素),主要保护未成熟种子不被潜在的捕食者和食果动物取食,这些次生物质的含量通常随果实成熟而降低;其它次生物质(如:脱辅基类胡萝卜素)的含量随果实成熟而增多,可能起到吸引食果动物的作用。在对脊椎动物捕食的抵御中,果实内不同类型的次生物质促使成熟果实对所有脊椎动物都有毒性(专毒性)或者仅对种子捕食者有毒性(泛毒性)。肉质果内的次生物质对植物-食果动物相互关系的调控作用,还可以通过调节动物取食频次和数量、抑制和促进种子萌发、改变种子在肠道的滞留时间、吸引传播者等生态作用而实现。某种次生物质往往集多种生态作用于一身。目前对肉质果内次生物质与脊椎动物相互关系的探讨还不够深入。未来研究需要综合考虑植物次生物质与果实生理生化、形态学等特征对食果者的综合调控机理;次生物质在种子传播后的调控作用对植物种群或群落结构和分布格局的影响;从动植物协同进化角度探讨植物次生物质的产生、防御和吸引策略与脊椎动物对果实的选择和消费之间的关系等。开展脊椎动物传播肉质果实中次生物质的研究,对完善种子传播机制、植物繁殖和更新格局,丰富动植物相互作用、协同进化理论具有重要的意义。     

植物种群更新限制——从种子生产到幼树建成

更新限制是指种子由于各种原因,不能够萌发并生长成幼树。它作为解释生物多样性的理论,一直受到国内外群落生态学家关注。从种源限制、传播限制和建成限制3个角度,对更新限制机制研究进展进行了综述。从种源限制而言,时空因素是影响植物种群更新限制的重要因素,因为植物结实量存在明显时空变化,造成植物更新个体出现明显的时空规律。从传播限制而言,传播数量、距离和食果动物行为均限制植物种群更新。数量上,缺乏有限传播者势必减少传播数量,但如果种子拥有较高质量,则能逃脱数量限制;距离上,植物更新个体显示出明显的Janzen-Connell格局,但传播距离趋向稳定,形成植物种群的进化稳定对策;食果动物行为上,不同传播者对更新贡献存在差异,捕食者直接降低更新,融入两类动物行为的模型更能反映食果动物对更新的限制。从建成限制而言,环境因子制约植物生长。小尺度下,微生境的好坏对于植物幼苗建成至关重要;大尺度下,植物提供较好的广告效应则能摆脱生境限制。将传播者行为、捕食者行为与幼苗的空间分布格局、种子传播机理模型等结合,建立植物更新限制机理模型应是更新限制未来的研究热点。选择稀有种和古老种为主题的长期更新限制研究,为种群恢复提供指导,也是未来重要研究方向。     

干扰对动物传播森林植物种子有效性影响的研究进展

干扰在森林生态系统中普遍存在,并影响森林的更新和演替.动物传播种子是种子更新的必经阶段,其对森林干扰的响应在一定程度上能够预测未来的森林群落组成和结构变化,对于明确森林演替方向具有重要意义.本文论述了森林干扰对动物传播种子有效性(包括动物传播种子的数量和质量)影响研究的生态学意义,全面揭示了自然干扰(火干扰、林窗干扰等)和人为干扰(生境破碎化、狩猎、采伐等)对动物传播种子数量、传播距离以及传播后幼苗更新影响的研究进展,指出干扰通过影响动物种群动态,进而造成动物传播种子数量发生了改变,动物传播种子的距离对干扰的响应基本表现出轻微负相关;干扰对传播后幼苗更新的影响结果因干扰类型的不同而复杂多变,干扰迹地环境因子的变化也影响着传播后的种子萌发和幼苗更新.干扰对动物传播种子有效性影响研究中存在的问题,主要表现为火干扰迹地恢复过程、增益性的干扰(如抚育、间伐、林窗)等对种子传播有效性影响研究的匮乏,以及忽略了温带森林内的干扰对动物传播种子的影响等.今后,应开展干扰对种子传播有效性的长期研究;对于干扰多发地带的森林,应高度重视增益性干扰影响动物传播植物种子的研究.     

黄檗的更新特点及食果实鸟类对其种子的传播

在帽儿山实验林场和哈尔滨实验林场 ,黄檗母树下没有幼苗分布 ,不能进行天然更新 ,需要靠食果实鸟类等将果实和种子传播至远离母树的其他林下。捕食黄檗果实的食果实鸟类有 9种。其中 6种是食果肉鸟类 ,吞入果实后 ,消化果肉 ,而种子完整地随粪便排出而得以传播。其余 3种是食种子鸟类 ,没有传播作用。果实在鸟类消化道内的滞留时间达 2 0～ 30min ,具有很长的潜在传播距离。将鸟类消化后的种子与完整果实和人为去果肉种子进行萌发对比实验 ,消化后种子的累计萌发率与其余二者之间均没有显著性差异 ,说明食果实鸟类的消化 (道 )过程对种子萌发没有明显影响 ,同时证明果肉对种子萌发率没有显著影响 ,果肉中不含萌发抑制物质。黄檗提供多种鸟类以食物 ,而鸟类也同时以多种肉质果植物为食物。因此食果实鸟类和肉质果植物 (包括黄檗 )之间形成了松散的互利共生关系     

破碎化生境中粗柄独尾草种群大小对繁殖特性的影响

景观破碎化是目前存在的一种普遍现象,导致物种生存的原有生境总面积减小,产生许多大小不一的斑块种群。不同斑块生境中植物种群的大小直接反映植物对环境的响应特征和适应对策,与植物繁殖有关的开花结实特性、种子形态及萌发特性的研究将有助于深入了解植物在不同生境中的生存策略。以粗柄独尾草(Eremurus inderiensis)为研究对象,以野外调查为基础,对比研究不同斑块粗柄独尾草种群的种群大小和生殖成功,揭示不同生境中粗柄独尾草的生态适应性。结果表明:(1)不同斑块生境中,种群大小差异较大,且较小的种群幼苗比例也较小,种群大小与种群幼苗比例呈显著相关;(2)较小的种群自然座果率、结籽率较低,种群间差异显著;(3)随着生境破碎化程度增加,种子千粒重,种子长、宽等形态特征呈减小趋势,但种翅占比增大;(4)在粗柄独尾草最适萌发温度下,随着生境破碎化程度增加,种子萌发率有下降趋势。针对人类干扰程度强的衰退型粗柄独尾草种群,亟需减少人为干扰,依据不同生境中的干扰因素及种群生存现状,制定科学与切实可行的保护和恢复策略。     

生境破碎对古尔班通古特沙漠南缘骆驼刺种群生物学特性的影响

在破碎化生境中,植物种群的生物学特性直接反映植物对环境的响应特征和适应对策,探讨不同破碎化程度生境中植株的大小、密度、结实率、种子大小、种子质量以及萌发特性等,对深入了解植物在不同生境中的生存和繁殖状况有重要的指导意义。对古尔班通古特沙漠南缘9个斑块化骆驼刺种群的形态特征和繁殖生物学参数进行了连续2年的调查研究,研究结果表明：随着生境破碎化程度的加剧,骆驼刺的株高、冠幅、密度、结实率、种子大小、种子质量以及萌发率等均显著下降（P < 0.05）。生境破碎不仅强烈抑制了骆驼刺植株的营养生长,使其生长矮小,个体分布稀疏,而且严重阻碍了骆驼刺的繁殖成功和种群更新,增加了种群衰退甚至灭绝的风险。     

How does landscape context contribute to effects of habitat fragmentation on diversity and population density of butterflies?

Aim Studies on habitat fragmentation of insect communities mostly ignore the impact of the surrounding landscape matrix and treat all species equally. In our study, on habitat fragmentation and the importance of landscape context, we expected that habitat specialists are more affected by area and isolation, and habitat generalists more by landscape context. Location and methods The study was conducted in the vicinity of the city of Göttingen in Germany in the year 2000. We analysed butterfly communities by transect counts on thirty‐two calcareous grasslands differing in size (0.03–5.14 ha), isolation index (2100–86,000/edge‐to‐edge distance 55–1894 m), and landscape diversity (Shannon–Wiener: 0.09–1.56), which is correlated to percentage grassland in the landscape. Results A total of 15,185 butterfly specimens belonging to fifty‐four species are recorded. In multiple regression analysis, the number of habitat specialist (n = 20) and habitat generalist (n = 34) butterfly species increased with habitat area, but z‐values (slopes) of the species–area relationships for specialists (z = 0.399) were significantly steeper compared with generalists (z = 0.096). Generalists, but not specialists, showed a marginally significant increase with landscape diversity. Effects of landscape diversity were scale‐dependent and significant only at the smallest scale (landscape context within a 250 m radius around the habitat). Habitat isolation was not related to specialist and generalist species numbers. In multiple regression analysis the density of specialists increased significantly with habitat area, whereas generalist density increased only marginally. Habitat isolation and landscape diversity did not show any effects. Main conclusions Habitat area was the most important predictor of butterfly community structure and influenced habitat specialists more than habitat generalists. In contrast to our expectations, habitat isolation had no effect as most butterflies could cope with the degree of isolation in our study region. Landscape diversity appeared to be important for generalist butterflies only.     

Biogeography of the Primates of Guyana: Effects of Habitat Use and Diet on Geographic Distribution

Species that exploit a wide range of resources or habitats (generalists) tend to be widely distributed, whereas species that exploit a narrow range of resources or habitats (specialists) often have a limited distribution. The distribution patterns are thought to result from specialists using relatively smaller habitats than those exploited by generalists. I used data from 1,725 km of primate surveys that I conducted in Guyana to test these hypotheses. Habitat breadth is the total number of different habitat types occupied by each species. I used the total number of different food categories exploited by each species to measure dietary breadth. Geographic range size is correlated with habitat breadth but not with dietary breadth or body size for the 8 primate species in Guyana. Habitat generalists—red howlers and wedge-capped capuchins—range into all habitats. Habitat specialists—spider monkeys, brown bearded sakis, and golden-handed tamarins—range only into large habitats. Habitat generalists tend to be dietary type specialists in Guyana. I suggest that only habitat generalists can subsist on the low-quality foods in small habitats in Guyana. Conversely, habitat specialists tend to be dietary type generalists in Guyana. They must feed on a variety of food types in large habitats. However, using the number of food categories exploited as a measure of dietary breadth may be only a weak aspect of multidimensional niche. Researchers testing biogeographic hypotheses associated with dietary breadth should consider including multivariate indicators of both the types of food categories eaten and the number of plant species exploited.     

Corridors and barriers in biodiversity conservation: a novel resource-based habitat perspective for butterflies

Habitat loss and fragmentation, exacerbated by projected climate change, present the greatest threats to preservation of global biodiversity. As increasing habitat fragmentation and isolation of residual fragments exceeds the dispersal capacity of species, there is the growing need to address connectivity to maintain diversity. Traditionally, habitat corridors have been proposed as a solution. But, the concept of corridors (barriers) is poorly understood; typically they are defined as linear habitats linking up habitat patchwork, and are advocated without a detailed understanding of the elements making up species’ habitats and the cost-effectiveness of alternative solutions. Yet, landscapes comprise an enormous range of ‘linear’ structures that can function in different ways to promote species’ persistence and diversity. In this review, a functional definition of corridor (barrier) is developed to give prominence to connectivity as opposed to ad hoc structures purported to advance connectivity. In developing the concept, urgency to accommodate environmental changes compels a growing emphasis on organism diversity rather than a preoccupation with single species conservation. The review, in focusing on butterflies to address the issue of corridors for patchwork connectivity, draws attention to fundamental divisions among organisms in any taxon: generalists and specialists. Both groups benefit from large patches as these necessarily house species with specialist resources as well as generalists with very different resource types. But, generalists and specialists require very different solutions for connectivity, from short-range habitat corridors and gateways for specialists to habitat and resource stepping stones (nodes, surfaces) for generalists. Connectivity over extensive areas is most critical for moderate generalists and their conservation requires emphasis being placed on space–time resource heterogeneity; landscape features, of whatever dimensionality and structure, provide a vital framework for developing the variety of suitable conditions and resources for enhancing their diversity.     

Both spatiotemporal connectivity and habitat quality limit the immigration of forest plants into wooded corridors

Extensive afforestation of agricultural areas has increased the importance of green corridors as a dispersal network. We tested the effect of spatiotemporal connectivity, edge effect and habitat structural quality of wooded corridors on the long-term immigration success of forest specialist plants relative to the performance of forest generalists. In agricultural landscapes of central and southern Estonia, we sampled 28 historically connected and 52 isolated tree lines and alleys with a minimum age of 50 years, and 93 edges of ancient forests. The regional pool of common forest plants was compiled using species’ frequency data in 91 ancient forests. Both landscape connectivity and habitat quality affected the richness of response groups, but specialists and generalists responded to different drivers. Forest specialists required long-term neighbourhoods of ancient forest and benefited from a direct connection between forest and corridor. Habitat generalists reacted positively to the recently modified structure of the landscape. When a corridor was connected to forest, the dual edge in the corridor did not result in an increased negative edge effect on forest specialist arrival. Even if both specialists and generalists required wide corridors with optimum shade, forest specialists also benefited from mature overstorey and outward overhanging branches, whereas forest generalists used disturbance-created microhabitats. We conclude that only wooded corridors with long-term connectivity to seed source forests and widely branched tree canopies will function as a green infrastructure supporting forest-specific biodiversity.     

Temporal bird community dynamics are strongly affected by landscape fragmentation in a Central American tropical forest region

Habitat loss and fragmentation are considered the main causes of species extinctions, particularly in tropical ecosystems. The objective of this work was to evaluate the temporal dynamics of tropical bird communities in landscapes with different levels of fragmentation in eastern Guatemala. We evaluated five bird community dynamic parameters for forest specialists and generalists: (1) species extinction, (2) species turnover, (3) number of colonizing species, (4) relative species richness, and (5) a homogeneity index. For each of 24 landscapes, community dynamic parameters were estimated from bird point count data, for the 1998–1999 and 2008–2009 periods, accounting for species’ detection probability. Forest specialists had higher extinction rates and a smaller number of colonizing species in landscapes with higher fragmentation, thus having lower species richness in both time periods. Alternatively, forest generalists elicited a completely different pattern, showing a curvilinear association to forest fragmentation for most parameters. Thus, greater community dynamism for forest generalists was shown in landscapes with intermediate levels of fragmentation. Our study supports general theory regarding the expected negative effects of habitat loss and fragmentation on the temporal dynamics of biotic communities, particularly for forest specialists, providing strong evidence from understudied tropical bird communities.     

Fragmentation in calcareous grasslands: species specialization matters

Habitat fragmentation resulting from anthropogenic land-use change may negatively affect both biodiversity and ecosystem structure and function. However, susceptibility to fragmentation varies between species and may be influenced by for instance specialization, functional traits and trophic level. We examined how total and specialist species richness, species composition and functional trait composition at two trophic levels (vascular plants and sap-feeding hoppers) vary with habitat fragmentation (patch size and connectivity) in dry calcareous grasslands in southeast Norway. We found that fragmentation affected plant and hopper species composition both totally and of habitat specialists, but with a net species loss only for the specialists, indicating greater susceptibility of specialized species. Reductions in patch size and increasing isolation negatively affected plant specialists with different sets of traits, effectively reducing the number of species with trait combinations suitable to persist in small and isolated patches. Fragmentation influenced trait composition of the total hopper community, but not of habitat specialists. A lesser degree of habitat association could explain why hoppers, despite belonging to a higher tropic level, seemed to be less susceptible to fragmentation than plants. Nonetheless, our study shows that habitat fragmentation affects both species richness, species composition and trait composition of plants and hoppers, indicating that fragmentation leads not only to a loss of species, but also alters dominance hierarchies and the functionality of grassland communities.     

Fragmentation and the context-dependence of dispersal syndromes: matrix harshness modifies resident-disperser phenotypic differences in microcosms

Habitat fragmentation, the conversion of landscapes into patchy habitats separated by unsuitable environments, is expected to reduce dispersal among patches. However, its effects on dispersal should depend on dispersal syndromes, i.e. how dispersal covaries with phenotypic traits, because these syndromes can drastically alter dispersal and subsequent ecological and evolutionary dynamics. Our comprehension of whether environmental factors such as habitat fragmentation generate and/or modify dispersal syndromes (i.e. conditional dispersal syndromes) is therefore key for biodiversity forecasting. Here we tested whether habitat fragmentation modulates dispersal syndromes by experimentally manipulating matrix harshness, a critical feature of habitat fragmentation, in ciliate microcosms. We found evidence for dispersal syndromes involving multiple traits linked to morphology (elongation and size), movement (velocity and linearity) and demography (growth rate and maximal population density). More importantly, these syndromes were modified by matrix harshness, with increased differences between residents and dispersers in morphology and movement traits, and decreased differences in growth rate as the matrix became increasingly harsh. Our findings thus reveal that habitat fragmentation can mediate the intensity and form of dispersal syndromes, a context-dependence that could have important consequences for ecological and evolutionary dynamics under environmental changes.     

Phyllostomid Bats of Lowland Amazonia: Effects of Habitat Alteration on Abundance

Habitat fragmentation and conversion are among the human activities that pose the greatest threat to species persistence and conservation of biodiversity. This is particularly true in the Neotropics, where bats represent important components of biodiversity from taxonomic and functional perspectives, and provide critical ecosystem services ( e.g ., seed dispersal and pollination). We assessed the degree to which conversion of lowland Amazonian rain forest to agriculture, and its subsequent abandonment and secondary succession, affect the abundances of populations of phyllostomid bats in the vicinity of Iquitos, Perú. During 90,720 net-m-h of sampling, we captured 3789 bats of five families; of these 3764 were phyllostomids representing 44 species, 23 genera, and three feeding guilds. We focus on the 24 most abundant species of phyllostomids. In terms of abundance, frugivores dominated assemblages in all habitat types and seasons. Eight species consistently responded to habitat conversion, two species consistently responded to season, two species responded consistently to both habitat and season, and five species responded to habitat conversion in a season-specific manner. Frugivores and nectarivores were abundant in areas that had been converted to agriculture, which suggests that these bats are resilient to extant levels of disturbance and may be important in promoting secondary succession. However, this result may be scale- or context-dependent. If habitat conversion continues and dramatically reduces the areal extent and increases fragmentation of mature forest, then a complex metacommunity dynamic may characterize the region and source populations of bats may become threatened or extirpated locally.     

Cryptic differences in dispersal lead to differential sensitivity to habitat fragmentation in two bumblebee species

Habitat loss has led to fragmentation of populations of many invertebrates, but social hymenopterans may be particularly sensitive to habitat fragmentation due to their low effective population sizes. The impacts of fragmentation depend strongly on dispersal abilities, but these are difficult to quantify. Here, we quantify and compare dispersal abilities of two bumblebee species, Bombus muscorum and Bombus jonellus , in a model island system. We use microsatellites to investigate population genetic structuring, dispersal and spatial patterns in genetic diversity. Populations of both species showed significant structuring, and isolation by distance, but this was markedly greater in B. muscorum (θ = 0.13) than in B. jonellus (θ = 0.034). This difference could reflect a higher effective population size in B. jonellus compared to B. muscorum , but this is not consistent with the observed abundance of the two species. We argue that it is more likely that B. jonellus has a higher propensity to disperse than B. muscorum . This will influence their relative susceptibility to habitat fragmentation and may in part explain differential declines of mainland populations of these and other bumblebee species.     

栖息地破碎化与鸟类生存

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.