传粉网络的研究进展: 网络的结构和动态
Progress in pollination networks: network structure and dynamics
Qiang Fang1,2, Shuangquan Huang ,1,*
生物多样性不仅体现为生物种类和生态系统的多样性, 更体现在生物之间关系的多样性上。不同物种之间的复杂联系, 是地球生态系统中生物多样性的重要组成部分。因而在群落中, 研究物种之间的关系对于认识群落的结构、物种的演化以及生物多样性保护都有重要意义(Waser & Ollerton, 2006)。在群落中, 生物之间存在着直接或间接的相互作用, 如植物与传粉者(Waser et al., 1996)、植物与种子散播者(Burns, 2006)、捕食与被捕食者(Allesina & Pascual, 2008)等的关系。这些物种之间相互影响, 构成了复杂的网络, 这就是群落的生态网络。
由于植物有固着生长的习性, 其花粉传递依赖一定的媒介, 植物与传粉者的相互作用就构成了植物有性繁殖过程的重要环节。植物-传粉者互作的研究, 可为理解花部特征的多样性提供证据(Vázquez et al., 2009); Faegri和van der Piji(1979)曾指出, 只有与传粉生态学联系在一起, 即把花作为一个适应于传粉的功能单位, 才能获得对花性状的客观认识。在20世纪中期, 传粉综合征(pollination syndrome)的概念在植物-传粉者关系和花部进化的研究中渐渐受到重视, 即花部特征反映了其对某一类传粉者的适应(Fenster et al., 2004)。基于物种水平上的观察发现, 具有特殊结构(特化)的花往往被特定的传粉者访问, 推测特化的花部特征具有吸引特化传粉者的作用, 而泛化的花则会吸引多种传粉者(Faegri & van der Pijl, 1979)。在一些类群中(例如兰科、大戟科、鸢尾科等), 植物-传粉者存在着近似一一对应的关系(Armbruster, 1986)。
然而Waser等(1996)对特化的传粉系统占自然界主导地位这一传统观点提出了质疑, 认为泛化的传粉系统应为主流。主要证据是植物的传粉系统并不是一成不变的, 而是存在着较大的时空变异。例如, Herrera(1988)在4个地区对唇形科的宽叶薰衣草(Lavandula latifolia)开展了6年的研究, 发现该种植物的传粉者达85种, 包括长吻的膜翅目、双翅目以及鳞翅目等昆虫。调查还显示, 仅有35.7%的传粉者能够连续6年访问该种植物, 此外仅有约41%的昆虫在4个地区都被观察到访问该花。
所以只有在群落水平上开展大规模的调查, 使用社会网络分析方法比较不同地域和不同尺度的网络结构和动态, 才能够确切揭示植物与传粉者形成互惠关系的过程和模式。
1 传粉网络的研究方法
研究群落水平上物种之间的关系, 首先需要构建物种的网络。早期的研究试图描述植物与传粉者连接的网络, 但由于缺乏计算技术的支持, 仅限于描述性统计。这些研究绘制了成对连接的植物与传粉者的名录(如Robertson, 1928; 见Fenster et al., 2004), 或者是描述了物种多样性丰富程度在不同海拔、地理位置梯度之间的差异(如Moldenke & Lincoln, 1979; Arroyo et al., 1982)。近年来计算科学的发展和社会网络分析逐渐兴起, 基于拓扑学开发了可用于群落分析的软件, 如Ucinet、Pajek、R语言的bipartite程序包、Gephi、Cytoscape等软件, 都可以用来分析复杂网络的结构特征。复杂的社会网络分析, 包括从互联网拓扑结构到社会中人际关系网络, 从蚁群中蚂蚁之间的信息传递网络到细胞内代谢途径网络, 这些进步为不同学科提供了更多可供选择的研究方法和手段。在生态网络中, 每一个物种就是一个节点(node), 而物种之间的联系构成了连接(link)。在传粉网络中, 群落的传粉可以用植物种类(P)×传粉者种类(A)的矩阵表示。在构建定性(qualitative)的网络中, 如果物种之间有联系, 连接就被定义为1; 如果没有关系, 就定义为0。而在定量(quantitative)的网络中, 物种之间关系的强度就是连接的强度, 比如传粉者访问的次数、虫体携带的花粉数目等可以量化的特征。物种之间的连接可以是定向的(directed), 比如捕食与被捕食的关系; 也可以是非定向的(undirected), 比如植物与传粉者的关系。
2 传粉网络的结构和特点
2.1 观察到的连接数量有限
2.2 连接的不对称性
物种的连接具有不对称性(degree asymmetry),表现在:
(1)连接数量的不对称。少数物种的连接伙伴数目很多, 而大量物种的连接伙伴很少。物种连接数如果符合幂律分布(power-law distribution)或者截尾幂律分布(truncated power-law distribution), 表明泛化物种对于群落很重要, 因为大多数物种与它们建立了连接。在截尾幂律分布中, 超级泛化者(super- generalist), 也就是连接绝大部分物种的泛化者相当稀少(Jordano et al., 2003); 如果连接数符合指数分布, 可能说明泛化者在群落中很稀少, 或者植物和昆虫所建立的连接更倾向于随机。Jordano等(2003)认为植物与动物的相互作用网络应当是无限尺度的(scale free), 或者是大尺度的(broad scale), 无限尺度时物种连接度会呈现幂律分布。他们检验了多个传粉网络, 发现65.6%的物种连接符合截尾幂律分布, 22.2%符合幂律分布, 并认为这样的模式是由于植物与动物表型上的不对应或者是错位造成的: 即有些植物与动物的存续时间和表型能够对应, 从而构成优先连接(preferential attachment); 有些物种则没有共同的存续时间, 或者表型不匹配, 一些受限连接(forbidden link)不可能被观察到。
(2)连接强度的不对称。尽管少数物种拥有大量的传粉者, 但是不同传粉者的访问量不一样, 于是在传粉网络上就表现出连接强度的不一致。Alarcón等(2008)使用特征向量中心度(eigenvector centrality)代表物种的连接强度, 发现只有少数物种拥有很强的连接, 而且部分植物和传粉者之间连续多年构成了稳定的强连接。只有传粉者与植物构建了稳定而且紧密的关系, 传粉者才有可能对植物造成稳定的选择作用。相对于定性的网络, 定量的传粉网络更能代表植物与传粉者之间的真正关系(Bascompte et al., 2006; Blüthgen et al., 2006; Vázquez et al., 2007)。在定性的传粉网络中, 某种传粉者可能访问5种植物, 表现为泛化的传粉者, 但是在定量的网络中, 该种传粉者可能只对1种植物访问量很大, 而对其他4种植物访问稀少, 说明该传粉者可能是特化的。只有所观察的网络包含了更多的信息, 才能更加真实地反映自然的访问情况。
2.3 嵌套结构与模块化
传粉网络的研究已开始深入到对网络结构和特征的生态学意义的探讨, 比如嵌套(nested)、连接数目的分布、非对称性等(Bascompte et al., 2003, Jordano et al., 2003, Vázquez & Aizen, 2004)。传粉网络的结构始终遵循着嵌套的模式, 这可能是生态网络共有的模式。捕食、种子散播和不同鱼类的清洁互助网络, 也遵循着嵌套的结构(Bascompte et al., 2003)。所谓嵌套结构, 就是某一物种的连接伙伴都是相对其更为泛化的物种的连接伙伴的一个子集。例如在一个群落中, 蝶类只能够访问少数植物, 而蜜蜂能够为所有的植物传粉, 蝶类传粉的植物种类只是蜜蜂传粉植物种类的一个子集。如果所有植物和传粉者都遵循这一准则, 传粉网络就是完全嵌套的。传粉网络的嵌套结构对生态网络的稳定性有着重要意义, 说明传粉是一项有冗余的生态服务, 即使部分传粉者消失, 其他泛化的传粉者也能够接替传粉。通常最泛化的传粉者也是最为普遍、最不容易灭绝的。
3 传粉网络的动态研究
3.1 长期动态与实时动态
随着网络的特征描述逐渐完善, 对于网络动态的研究也随之深入, 从静态的网络结构发展为多季度或者连续数年的动态结构研究(Alarcón et al., 2008; Petanidou et al., 2008; Dupont et al., 2009)。过去的几年中, 一些研究描述了传粉网络2-4年的变化模式, 尽管这些研究的地点和方法不同, 传粉者鉴定的精度也不一致, 有的是定性网络, 有的是定量网络, 但是都得出了相似的结论, 这说明生态网络可能有着共同的特征。比如, Alarcón等(2008)比较了美国南加州山区传粉网络连续3年的动态变化, 发现虽然网络构成(即植物和传粉者的构成)在年际间变化非常大, 但是网络仍然保持着稳定的结构, 一些泛化的植物和传粉者维持了相对稳定的连接关系。Petanidou等(2008)通过对希腊地中海气候山区的植物区系和传粉者的调查, 构建并且比较了连续4年的传粉网络动态。他们发现植物和传粉者的物种构成变化非常大, 虽然年际之间植物和传粉者的泛化水平不尽相同, 但是结果支持泛化的传粉系统占主导地位, 即植物是由多种传粉者访问的。不同海拔、不同气候环境下的传粉网络结构也是相似的, Dupont等(2009)调查了6个地点的传粉网络的动态, 结果表明在不同海拔和气候环境下, 传粉网络的动态和结构参数(如嵌套度、填充度、中心度和模块化程度)在年际间都是稳定的。这说明了传粉网络具有稳定的特征, 能抵抗干旱、外来物种入侵、物种灭绝等环境变化。
3.2 传粉网络结构的生态学意义
3.3 传粉网络结构的成因
4 传粉网络对生物多样性的意义
物种多样性保护日益受到广泛的重视, 而种间存在互惠关系的网络及其结构与群落物种多样性之间的关系, 为理解物种多样性的维持机制以及预测物种灭绝对群落的影响提供了新的视角。Albrecht等(2010)比较了冰川消融后, 在不同消融时间的裸地上先后建立起来的群落和相应的传粉网络。由于群落的构建历史不同, 其物种多样性和传粉网络都有差异, 研究这些随时间而变化的网络, 可以更好地理解群落动态。物种多样性随着群落建立时间而增加, 蜂类传粉者主导了早期建立的群落, 而蝇类则主导了建立时间较长的群落。群落水平的特化程度(H′2)随着物种多样性的增加而降低, 说明在年轻的群落中, 传粉者相对特化, 访问倾向性更明显, 对物种缺失的不利影响抵抗力更弱; 随着群落的发育, 物种多样性升高, 传粉网络变得更加复杂, 也更加稳定。另外, 成熟群落也可能同时保持着相对稳定的较高特化水平, 传粉者的访问偏好并不会受到群落的物种多样性变化的影响, 这说明了传粉者的偏好对维持稳定传粉网络结构有重要作用(Fründ et al., 2010)。
5 结语和展望
5.1 用实验性手段验证影响网络结构的因素
大量传粉网络的研究都是基于一年或者多年的野外观察, 缺乏实验性的工作来验证影响网络结构的因素(de Ruiter et al., 2005)。Burkle和Irwin (2009)的研究表明, 在小群落内施加氮肥, 可以显著影响植物群落以及吸引传粉者的花部特征, 但是并不会对传粉网络的结构和年际变化造成显著影响。Llandres等(2011)研究表明, 当捕食者存在时, 蜜蜂的访问比食蚜蝇更容易受到影响, 因为蜜蜂更倾向于访问安全的资源。蜜蜂访问偏好的变化, 可能潜在地改变了传粉网络的结构, 影响了植物的繁殖成功。
5.2 传粉网络时空变异与植物繁殖成功的关系
花粉只有最终落置在同种植物的柱头上, 才会对植物的繁殖产生影响, 同种的花粉才能结实, 而异种的花粉则会影响结实。而目前传粉网络的研究, 无论是定性或是定量的, 都只是建立在传粉者对植物的访问次数的基础上, 无法衡量不同传粉者在花粉流动和植物有性生殖中的真正作用, 如传粉者的访问是否会带来花粉, 会带来多少同种的花粉, 多少异种的花粉, 以及如何影响植物的繁殖。上述植物与传粉者的网络结构表明, 大多数传粉者是泛化的。不同于植物-传粉者访问的非定向网络, 传粉者将一种植物的花粉传递到另一种植物的柱头上, 这种传递是定向的(directed)。定向网络包含了更多的信息。所以从传粉者的角度建立花粉传递网络, 更能体现植物与传粉者之间的内在关系和植物之间的花粉传播途径。通过调查传粉者携带的花粉种类和数量构建的花粉传递网络(Alarcón, 2010; Bosch et al., 2009), 与调查植物-传粉者访问构建的访问网络相比, 一些基本结构明显不同, 如网络更为特化、填充度(connectance)更高、植物和传粉者的中心度(connectivity)也更高等, 这些特征都增强了生态网络的稳定性。在定向网络中, 可以计算物种的权威值(authority)和收纳值(hub)。就花粉输出而言, 物种对群落的权威值越大, 说明物种更容易输出花粉, 更容易干扰其他物种的繁殖; 而收纳越大, 则说明物种更容易接受外来的花粉。另外, 研究虫体携带的花粉, 还能构建一些不易观察的网络结构, 比如夜间开放的花与蛾类传粉者的关系。Devoto等(2010)通过灯光诱捕蛾类, 鉴定虫体携带的花粉种类和数目, 构建了夜间传粉网络, 发现夜间的传粉网络也具有嵌套、非对称等特征。
5.3 用多种方法真实地反映群落结构
传粉生态学的研究已经能够描述传粉网络的结构, 但是与理解年际结构动态的过程和模式还有很大距离。需要借用更多的数学工具来探索物种之间的关系以及可能影响传粉网络结构的因素, 如形态学和系统发育的限制。此外, 还需要通过多种观察手段, 使得构建的网络能够更加真实地反映自然界的传粉网络, 如通过鉴定传粉者使用筑巢材料的来源, 构建沙漠稀有物种的传粉网络(Dorado et al., 2011)。另外, 还需要长时间以及多生境类型的对比调查, 例如在希腊灌丛群落进行的连续4年的传粉网络结构调查(Petandiou et al., 2008)。只有通过较长时间的调查和数据采集, 才能更好地理解生态网络对气候变化的响应、物种入侵或者演替, 以及群落内物种之间关系的维持。
尽管在群落水平上研究传粉网络是近年来传粉生态学的一个趋势(黄双全和郭友好, 2000; 黄双全, 2007), 但是国内相关研究极少。杜巍等(2007)调查了神农架地区草本群落中访花昆虫在不同海拔的变异和昆虫访花行为。Gong和Huang(2011)在我国西南高山草甸设立固定样方, 连续3年考察了不同传粉昆虫对29种同时开花植物的访花偏好, 结果表明虽然传粉者的种类在年际变化明显, 但是不同植物的传粉者功能群的变化较小。特化的传粉者偏向于访问两侧对称的花, 而泛化的传粉者偏向于访问泛化的花。其结果表明, 虽然植物与传粉者的网络结构是嵌套的、不对称的, 传粉者的访问偏好仍支持了传粉者在花部特征中的选择作用。连续4年对云南香格里拉高山植物园内所有开花植物与传粉者之间相互作用的网络研究表明, 开花植物与传粉者的种类在年际间变动较大, 但连接与传粉网络中的核心类群在年际间替换率低, 揭示了该群落保持相对稳定的原因(Fang & Huang, 2012)。
有关传粉网络的结构与动态的研究在我国才刚刚开始, 随着计算机技术的应用和网络分析的发展, 相信在不远的将来, 有关传粉网络的研究会取得更大的成果。
参考文献
[1]
Alarcón R (2010)
Congruence between visitation and pollen-transport networks in a California plant-pollinator community
Oikos, 119, 35-44.[本文引用: 1]
[2]
Alarcón R, Waser NM, Ollerton J (2008)
Year-to-year variation in the topology of a plant-pollinator interaction network
Oikos, 117, 1796-1807.[本文引用: 3]
[3]
Albrecht M, Riesen M, Schmid B (2010)
Plant-pollinator network assembly along the chronosequence of a glacier foreland
Oikos, 119, 1610-1624.[本文引用: 1]
[4]
Allesina S, Pascual M (2008)
Network structure, predator-prey modules, and stability in large food webs
Theoretical Ecology, 1, 55-64.[本文引用: 1]
[5]
Armbruster WS (1986)
Reproductive interactions between sympatric Dalechampia species: Are natural assemblages "random" or organized?
Ecology, 67, 522-533.[本文引用: 1]
[6]
Arroyo MTK, Primack R, Armesto J (1982)
Community studies in pollination ecology in the high temperate Andes of central Chile. I. Pollination mechanisms and altitudinal variation
American Journal of Botany, 69, 82-97.[本文引用: 1]
[7]
Baldock KCR, Memmott J, Ruiz-Guajardo JC, Roze D, Stone GN (2011)
Daily temporal structure in African savanna flower visitation networks and consequences for network sampling
Ecology, 92, 687-698.URL PMID:21608477 [本文引用: 1]
[8]
Bascompte J, Jordano P, Melián CJ, Olesen JM (2003)
The nested assembly of plant-animal mutualistic networks
Proceedings of the National Academy of Sciences, USA, 100, 9383-9387.[本文引用: 2]
[9]
Bascompte J, Jordano P, Olesen JM (2006)
Asymmetric coevolutionary networks facilitate biodiversity maintenance
Science, 312, 431-433.DOI:10.1126/science.1123412 URL PMID:16627742 [本文引用: 1]
The mutualistic interactions between plants and their pollinators or seed dispersers have played a major role in the maintenance of Earth's biodiversity. To investigate how coevolutionary interactions are shaped within species-rich communities, we characterized the architecture of an array of quantitative, mutualistic networks spanning a broad geographic range. These coevolutionary networks are highly asymmetric, so that if a plant species depends strongly on an animal species, the animal depends weakly on the plant. By using a simple dynamical model, we showed that asymmetries inherent in coevolutionary networks may enhance long-term coexistence and facilitate biodiversity maintenance.
[10]
Basilio AM, Medan D, Torretta JP, Bartoloni NJ (2006)
A year-long plant-pollinator network
Austral Ecology, 31, 975-983.[本文引用: 1]
[11]
Blüthgen N, Menzel F, Blüthgen N (2006)
Measuring specialization in species interaction networks
BMC Ecology, 6, 9.DOI:10.1186/1472-6785-6-9 URL PMID:16907983 [本文引用: 1]
BACKGROUND: Network analyses of plant-animal interactions hold valuable biological information. They are often used to quantify the degree of specialization between partners, but usually based on qualitative indices such as 'connectance' or number of links. These measures ignore interaction frequencies or sampling intensity, and strongly depend on network size. RESULTS: Here we introduce two quantitative indices using interaction frequencies to describe the degree of specialization, based on information theory. The first measure (d') describes the degree of interaction specialization at the species level, while the second measure (H2') characterizes the degree of specialization or partitioning among two parties in the entire network. Both indices are mathematically related and derived from Shannon entropy. The species-level index d' can be used to analyze variation within networks, while H2' as a network-level index is useful for comparisons across different interaction webs. Analyses of two published pollinator networks identified differences and features that have not been detected with previous approaches. For instance, plants and pollinators within a network differed in their average degree of specialization (weighted mean d'), and the correlation between specialization of pollinators and their relative abundance also differed between the webs. Rarefied sampling effort in both networks and null model simulations suggest that H2' is not affected by network size or sampling intensity. CONCLUSION: Quantitative analyses reflect properties of interaction networks more appropriately than previous qualitative attempts, and are robust against variation in sampling intensity, network size and symmetry. These measures will improve our understanding of patterns of specialization within and across networks from a broad spectrum of biological interactions.
[12]
Bosch J, González AMM, Rodrigo A, Navarro D (2009)
Plant-pollinator networks: adding the pollinator’s perspective
Ecology Letters, 12, 409-419.URL PMID:19379135 [本文引用: 2]
[13]
Burkle L, Irwin R (2009)
The importance of interannual variation and bottom-up nitrogen enrichment for plant-pollinator networks
Oikos, 118, 1816-1829.[本文引用: 1]
[14]
Burkle L, Alarcón R (2011)
The future of plant-pollinator diversity: understanding interaction networks across time, space, and global change
American Journal of Botany, 98, 528-538.URL PMID:21613144 [本文引用: 1]
[17]
Devoto M, Bailey S, Memmott J (2010)
The ‘night shift’: nocturnal pollen-transport networks in a boreal pine forest
Ecological Entomology, 36, 25-35.DOI:10.1111/een.2011.36.issue-1 URL [本文引用: 1]
[18]
Dorado J, Vázquez DP, Stevani EL, Chacoff NP (2011)
Rareness and specialization in plant-pollinator networks
Eco- logy, 92, 19-25.[本文引用: 1]
[19]
Du W (杜巍), Wang HX (王红侠), Wang XF (汪小凡) (2007)
Insect visitors and their behaviors in the typical herbaceous plant communities of the Shennongjia Mountains
Biodiversity Science (生物多样性), 15, 666-672. (in Chinese with English abstract)[本文引用: 1]
[20]
Dupont YL, Hansen DM, Olesen JM (2003)
Structure of a plant-flower-visitor network in the high-altitude sub-alpine desert of Tenerife, Canary Islands
Ecography, 26, 301-310.[本文引用: 1]
[21]
Dupont YL, Padrón B, Olesen JM, Petanidou T (2009)
Spatio-temporal variation in the structure of pollination networks
Oikos, 118, 1261-1269.[本文引用: 2]
[22]
Elberling H, Olesen M (1999)
The structure of a high latitude plant-flower visitor system: the dominance of flies
Ecography, 22, 314-323.[本文引用: 1]
[23]
Faegri K, van der Pijl L(1979) The Principles of Pollination Ecology, 3rd edn. Pergamon Press, Oxford.
[本文引用: 2]
[24]
Fang Q, Huang SQ (2012)
Relative stability of core groups in pollination networks in a biodiversity hotspot over four years
PLoS ONE, 7, e32663.DOI:10.1371/journal.pone.0032663 URL PMID:22412902 [本文引用: 1]
Plants and their pollinators form pollination networks integral to the evolution and persistence of species in communities. Previous studies suggest that pollination network structure remains nested while network composition is highly dynamic. However, little is known about temporal variation in the structure and function of plant-pollinator networks, especially in species-rich communities where the strength of pollinator competition is predicted to be high. Here we quantify temporal variation of pollination networks over four consecutive years in an alpine meadow in the Hengduan Mountains biodiversity hotspot in China. We found that ranked positions and idiosyncratic temperatures of both plants and pollinators were more conservative between consecutive years than in non-consecutive years. Although network compositions exhibited high turnover, generalized core groups--decomposed by a k-core algorithm--were much more stable than peripheral groups. Given the high rate of turnover observed, we suggest that identical plants and pollinators that persist for at least two successive years sustain pollination services at the community level. Our data do not support theoretical predictions of a high proportion of specialized links within species-rich communities. Plants were relatively specialized, exhibiting less variability in pollinator composition at pollinator functional group level than at the species level. Both specialized and generalized plants experienced narrow variation in functional pollinator groups. The dynamic nature of pollination networks in the alpine meadow demonstrates the potential for networks to mitigate the effects of fluctuations in species composition in a high biodiversity area.
[25]
Fenster CB, Armbruster WS, Wilson P, Dudash MR, Thomson JD (2004)
Pollination syndromes and floral specialization
Annual Review of Ecology, Evolution, and Systematics, 35, 375-403.[本文引用: 2]
[26]
Forup ML, Memmott J (2005)
The restoration of plant-pollinator interactions in Hay meadows
Restoration Ecology, 13, 265-274.[本文引用: 1]
[27]
Forup ML, Henson KSE, Craze PG, Memmott J (2007)
The restoration of ecological interactions: plant-pollinator networks on ancient and restored heathlands
Journal of Applied Ecology, 45, 742-752.[本文引用: 1]
[28]
Fründ J, Linsenmair KE, Blüthgen N (2010)
Pollinator diversity and specialization in relation to flower diversity
Oikos, 119, 1581-1590.[本文引用: 1]
[29]
Gong YB, Huang SQ (2009)
Floral symmetry: pollinator-mediated stabilizing selection on flower size in bilateral species
Proceedings of the Royal Society B: Biological Sciences, 276, 4013-4020.DOI:10.1098/rspb.2009.1254 URL PMID:19710062 [本文引用: 1]
Pollinator-mediated stabilizing selection (PMSS) has been proposed as the driver of the evolutionary shift from radial to bilateral symmetry of flowers. Studies have shown that variation in flower size is lower in bilateral than in radial species, but whether bilateral flowers experience more stabilizing selection pressures by employing fewer, more specialized pollinators than radial flowers remains unclear. To test the PMSS hypothesis, we investigate plant-pollinator interactions from a whole community in an alpine meadow in Hengduan Mountains, China, to examine: (i) variance in flower size and level of ecological generalization (pollinator diversity calculated using functional groups) in 14 bilateral and 13 radial species and (ii) the role pollinator diversity played in explaining the difference of variance in flower size between bilateral and radial species. Our data showed that bilateral species had less variance in flower size and were visited by fewer pollinator groups. Pollinator diversity accounted for up to 40 per cent of the difference in variance in flower size between bilateral and radial species. The mediator effect of pollinator diversity on the relationship between floral symmetry and variance in flower size in the community is consistent with the PMSS hypothesis.
[30]
Gong YB, Huang SQ (2011)
Temporal stability of pollinator preference in an alpine plant community and its implications for the evolution of floral traits
Oecologia, 166, 671-680.DOI:10.1007/s00442-011-1910-7 URL PMID:21253770 [本文引用: 1]
A traditional view of diverse floral traits is that they reflect differences in foraging preferences of pollinators. The role of pollinators in the evolution of floral traits has been questioned recently by broad community surveys, especially studies concerning variation in pollinator assemblages and visitation frequency, which suggest a diminished role of pollinators in floral evolution. Here, we investigate the relationships between six categories of floral traits of 29 species and 10 pollinator functional groups in an alpine meadow in the Hengduan Mountains of China, over three consecutive years. Simpson's diversity index was used to estimate the level of pollinator generalization of each plant species by considering both pollinator groups and their relative visitation frequencies. Multivariate analyses indicated that eight of the ten pollinator groups showed constant preferences for at least two floral traits, leading to a relatively stable level of ecological generalization for most floral traits (two out of three categories), despite the fact that the level of generalization of the entire community varied across years. Shape preferences of butterflies, honeybees and beeflies varied such that open flowers exhibited a lower level of ecological generalization in 2007 than closed flowers, in contrast with the other 2 years. These results suggest that temporally stabilized preferences of diverse pollinators may contribute to the evolution of specialized versus generalized floral traits; however, their role may be moderated by variation in community structure, including both the composition and abundance of plants and pollinators.
[31]
Gómez JM, Perfectti F, Jordano P (2011)
The functional consequences of mutualistic network architecture
PLoS ONE, 6, e16143.DOI:10.1371/journal.pone.0016143 URL PMID:21283583 [本文引用: 1]
The architecture and properties of many complex networks play a significant role in the functioning of the systems they describe. Recently, complex network theory has been applied to ecological entities, like food webs or mutualistic plant-animal interactions. Unfortunately, we still lack an accurate view of the relationship between the architecture and functioning of ecological networks. In this study we explore this link by building individual-based pollination networks from eight Erysimum mediohispanicum (Brassicaceae) populations. In these individual-based networks, each individual plant in a population was considered a node, and was connected by means of undirected links to conspecifics sharing pollinators. The architecture of these unipartite networks was described by means of nestedness, connectivity and transitivity. Network functioning was estimated by quantifying the performance of the population described by each network as the number of per-capita juvenile plants produced per population. We found a consistent relationship between the topology of the networks and their functioning, since variation across populations in the average per-capita production of juvenile plants was positively and significantly related with network nestedness, connectivity and clustering. Subtle changes in the composition of diverse pollinator assemblages can drive major consequences for plant population performance and local persistence through modifications in the structure of the inter-plant pollination networks.
[32]
Grant V, Grant KA (1965) Flower Pollination in the Phlox Family. Columbia University Press, New York.
[33]
Herrera CM (1988)
Variation in mutualisms: the spatiotemporal mosaic of a pollinator assemblage
Biological Journal of the Linnean Society, 35, 95-125.[本文引用: 1]
[34]
Huang SQ (黄双全) (2007)
Studies on plant-pollinator interaction and its significances
Biodiversity Science (生物多样性), 15, 569-575. (in Chinese with English abstract)[本文引用: 1]
[35]
Huang SQ (黄双全), Guo YH (郭友好) (2000)
New advances in pollination biology and the studies in China
Chinese Science Bulletin (科学通报), 16, 1441-1447. (in Chinese)[本文引用: 1]
[36]
Jordano P, Bascompte J, Olesen JM (2003)
Invariant properties in coevolutionary networks of plant-animal interactions
Ecology Letters, 6, 69-81.[本文引用: 3]
[37]
Kaiser-Bunbury CN, Muff S, Memmott J, Müller CB, Caflisch A (2010)
The robustness of pollination networks to the loss of species and interactions: a quantitative approach incorporating pollinator behaviour
Ecology Letters, 13, 442-452.DOI:10.1111/j.1461-0248.2009.01437.x URL PMID:20100244 [本文引用: 1]
Species extinctions pose serious threats to the functioning of ecological communities worldwide. We used two qualitative and quantitative pollination networks to simulate extinction patterns following three removal scenarios: random removal and systematic removal of the strongest and weakest interactors. We accounted for pollinator behaviour by including potential links into temporal snapshots (12 consecutive 2-week networks) to reflect mutualists' ability to 'switch' interaction partners (re-wiring). Qualitative data suggested a linear or slower than linear secondary extinction while quantitative data showed sigmoidal decline of plant interaction strength upon removal of the strongest interactor. Temporal snapshots indicated greater stability of re-wired networks over static systems. Tolerance of generalized networks to species extinctions was high in the random removal scenario, with an increase in network stability if species formed new interactions. Anthropogenic disturbance, however, that promote the extinction of the strongest interactors might induce a sudden collapse of pollination networks.
[38]
Lázaro A, Nielsen A, Totland Ø (2010)
Factors related to the inter-annual variation in plants’ pollination generalization levels within a community
Oikos, 119, 825-834.[本文引用: 1]
[39]
Llandres AL, De Mas E, Rodríguez-Gironés MA (2011)
Response of pollinators to the tradeoff between resource acquisition and predator avoidance
Oikos, 121, 687-696.[本文引用: 1]
[40]
Lopezaraiza-Mikel ME, Hayes RB, Whalley MR, Memmott J (2008)
The impact of an alien plant on a native plant- pollinator network: an experimental approach
Ecology Letters, 10, 539-550.DOI:10.1111/j.1461-0248.2007.01055.x URL PMID:17542933 [本文引用: 1]
Studies of pairwise interactions have shown that an alien plant can affect the pollination of a native plant, this effect being mediated by shared pollinators. Here we use a manipulative field experiment, to investigate the impact of the alien plant Impatiens glandulifera on an entire community of coflowering native plants. Visitation and pollen transport networks were constructed to compare replicated I. glandulifera invaded and I. glandulifera removal plots. Invaded plots had significantly higher visitor species richness, visitor abundance and flower visitation. However, the pollen transport networks were dominated by alien pollen grains in the invaded plots and consequently higher visitation may not translate in facilitation for pollination. The more generalized insects were more likely to visit the alien plant, and Hymenoptera and Hemiptera were more likely to visit the alien than Coleoptera. Our data indicate that generalized native pollinators can provide a pathway of integration for alien plants into native visitation systems.
[41]
Memmott J, Waser NM, Price MV (2004)
Tolerance of pollination networks to species extinctions
Proceedings of the Royal Society B: Biological Sciences, 271, 2605-2611.DOI:10.1098/rspb.2004.2909 URL PMID:15615687 [本文引用: 1]
Mutually beneficial interactions between flowering plants and animal pollinators represent a critical 'ecosystem service' under threat of anthropogenic extinction. We explored probable patterns of extinction in two large networks of plants and flower visitors by simulating the removal of pollinators and consequent loss of the plants that depend upon them for reproduction. For each network, we removed pollinators at random, systematically from least-linked (most specialized) to most-linked (most generalized), and systematically from most- to least-linked. Plant species diversity declined most rapidly with preferential removal of the most-linked pollinators, but declines were no worse than linear. This relative tolerance to extinction derives from redundancy in pollinators per plant and from nested topology of the networks. Tolerance in pollination networks contrasts with catastrophic declines reported from standard food webs. The discrepancy may be a result of the method used: previous studies removed species from multiple trophic levels based only on their linkage, whereas our preferential removal of pollinators reflects their greater risk of extinction relative to that of plants. In both pollination networks, the most-linked pollinators were bumble-bees and some solitary bees. These animals should receive special attention in efforts to conserve temperate pollination systems.
[42]
Moldenke AR, Lincon PG (1979)
Pollination ecology in montane Colorado: a community analysis
Phytologia, 42, 349-379.[本文引用: 1]
[43]
Olesen JM, Bascompte J, Dupont YL, Jordano P (2007)
The modularity of pollination networks
Proceedings of the National Academy of Sciences, USA, 104, 19891-19896.[本文引用: 1]
[44]
Olesen JM, Bascompte J, Elberling H, Jordano P (2008)
Temporal dynamics in a pollination network
Ecology, 89, 1573-1582.DOI:10.1890/07-0451.1 URL PMID:18589522 [本文引用: 1]
Despite a strong current interest in ecological networks, the bulk of studies are static descriptions of the structure of networks, and very few analyze their temporal dynamics. Yet, understanding network dynamics is important in order to relate network patterns to ecological processes. We studied the day-to-day dynamics of an arctic pollination interaction network over two consecutive seasons. First, we found that new species entering the network tend to interact with already well-connected species, although there are deviations from this trend due, for example, to morphological mismatching between plant and pollinator traits and nonoverlapping phenophases of plant and pollinator species. Thus, temporal dynamics provides a mechanistic explanation for previously reported network patterns such as the heterogeneous distribution of number of interactions across species. Second, we looked for the ecological properties most likely to be mediating this dynamical process and found that both abundance and phenophase length were important determinants of the number of links per species.
[45]
Olesen JM, Jordano P (2002)
Geographic patterns in plant- pollinator mutualistic networks
Ecology, 83, 2416-2424.[本文引用: 2]
[46]
Padrón B, Traveset A, Biedenweg T, Díaz D, Nogales M, Olesen JM (2009)
Impact of alien plant invaders on pollination networks in two Archipelagos
PLoS ONE, 4, e6275.DOI:10.1371/journal.pone.0006275 URL PMID:19609437 [本文引用: 1]
Mutualistic interactions between plants and animals promote integration of invasive species into native communities. In turn, the integrated invaders may alter existing patterns of mutualistic interactions. Here we simultaneously map in detail effects of invaders on parameters describing the topology of both plant-pollinator (bi-modal) and plant-plant (uni-modal) networks. We focus on the invader Opuntia spp., a cosmopolitan alien cactus. We compare two island systems: Tenerife (Canary Islands) and Menorca (Balearic Islands). Opuntia was found to modify the number of links between plants and pollinators, and was integrated into the new communities via the most generalist pollinators, but did not affect the general network pattern. The plant uni-modal networks showed disassortative linkage, i.e. species with many links tended to connect to species with few links. Thus, by linking to generalist natives, Opuntia remained peripheral to network topology, and this is probably why native network properties were not affected at least in one of the islands. We conclude that the network analytical approach is indeed a valuable tool to evaluate the effect of invaders on native communities.
[47]
Petanidou T, Kallimanis AS, Tzanopoulos J, Sgardelis SP, Pantis JD (2008)
Long-term observation of a pollination network: fluctuation in species and interactions, relative invariance of network structure and implications for estimates of specialization
Ecology Letters, 11, 564-575.DOI:10.1111/j.1461-0248.2008.01170.x URL PMID:18363716 [本文引用: 3]
We analysed the dynamics of a plant-pollinator interaction network of a scrub community surveyed over four consecutive years. Species composition within the annual networks showed high temporal variation. Temporal dynamics were also evident in the topology of the network, as interactions among plants and pollinators did not remain constant through time. This change involved both the number and the identity of interacting partners. Strikingly, few species and interactions were consistently present in all four annual plant-pollinator networks (53% of the plant species, 21% of the pollinator species and 4.9% of the interactions). The high turnover in species-to-species interactions was mainly the effect of species turnover (c. 70% in pairwise comparisons among years), and less the effect of species flexibility to interact with new partners (c. 30%). We conclude that specialization in plant-pollinator interactions might be highly overestimated when measured over short periods of time. This is because many plant or pollinator species appear as specialists in 1 year, but tend to be generalists or to interact with different partner species when observed in other years. The high temporal plasticity in species composition and interaction identity coupled with the low variation in network structure properties (e.g. degree centralization, connectance, nestedness, average distance and network diameter) imply (i) that tight and specialized coevolution might not be as important as previously suggested and (ii) that plant-pollinator interaction networks might be less prone to detrimental effects of disturbance than previously thought. We suggest that this may be due to the opportunistic nature of plant and animal species regarding the available partner resources they depend upon at any particular time.
[48]
Philipp M, Böcher J, Siegismund HR, Nielsen LR (2006)
Structure of a plant-pollinator network on a pahoehoe lava desert of the Gálapagos Islands
Ecography, 29, 531-540.[本文引用: 1]
[49]
Rezende EL, Lavabre JE, Guimarães PR, Jordano P, Basco- mpte J (2007)
Non-random coextinctions in phylogeneti- cally structured mutualistic networks
Nature, 448, 925-929.DOI:10.1038/nature05956 URL PMID:17713534 [本文引用: 1]
The interactions between plants and their animal pollinators and seed dispersers have moulded much of Earth's biodiversity. Recently, it has been shown that these mutually beneficial interactions form complex networks with a well-defined architecture that may contribute to biodiversity persistence. Little is known, however, about which ecological and evolutionary processes generate these network patterns. Here we use phylogenetic methods to show that the phylogenetic relationships of species predict the number of interactions they exhibit in more than one-third of the networks, and the identity of the species with which they interact in about half of the networks. As a consequence of the phylogenetic effects on interaction patterns, simulated extinction events tend to trigger coextinction cascades of related species. This results in a non-random pruning of the evolutionary tree and a more pronounced loss of taxonomic diversity than expected in the absence of a phylogenetic signal. Our results emphasize how the simultaneous consideration of phylogenetic information and network architecture can contribute to our understanding of the structure and fate of species-rich communities.
[50]
Robertson C (1928) Flowers and Insects: Lists of Visitors of Four Hundred and Fifty-Three Flowers. Carlinville, Illinois.
DOI:10.3390/insects10100318 URL PMID:31557963 [本文引用: 1]
A two-year study evaluated the effect of a flowering border of buckwheat Fagopyrum esculentum Moench on rates of egg parasitism, egg predation and adult parasitism on two squash bug species, Anasa tristis (DeGeer) and Anasa armigera Say, by comparing rates in squash fields with and without a flowering border. Furthermore, we evaluated whether there was an edge effect by comparing parasitism and predation rates in plots located in the corner of a squash field with plots located in the center of a squash field for fields with and without a flowering border. The egg parasitism rates were not affected by either treatment (flowering border or control) or plot location (edge or center). Anasa armigera egg masses only accounted for 4.3% of the total egg masses collected. The egg parasitism rates increased gradually throughout the season, peaking in the last week of August in 2017 at 45% for A. tristis egg masses. The most common egg parasitoid recovered was Gryon pennsylvanicum (Ashmead) followed by Ooencyrtus anasae (Ashmead). Adult parasitism was not affected by treatment, but A. tristis adult parasitism rates were higher in plots located on the edge of squash fields compared with plots located in the center of squash fields in 2016. Since adult parasitoid, Trichopoda pennipes (Fabricius) flies were observed visiting buckwheat flowers, future studies could explore the possibility that the flowering buckwheat may have a more impact on adult parasitism if there was a greater distance between fields with and without a flowering border.
[51]
Stang M, Klinkhamer PGL, van der Meijden E (2007)
Asymmetric specialization and extinction risk in plant-flower visitor webs: a matter of morphology or abundance?
Oecologia, 151, 442-453.DOI:10.1007/s00442-006-0585-y URL PMID:17080257 [本文引用: 1]
A recently discovered feature of plant-flower visitor webs is the asymmetric specialization of the interaction partners: specialized plants interact mainly with generalized flower visitors and specialized flower visitors mainly with generalized plants. Little is known about the factors leading to this asymmetry and their consequences for the extinction risk of species. Previous studies have proposed random interactions proportional to species abundance as an explanation. However, the simulation models used in these studies did not include potential biological constraints. In the present study, we tested the potential role of both morphological constraints and species abundance in promoting asymmetric specialization. We compared actual field data of a Mediterranean plant-flower visitor web with predictions of Monte Carlo simulations including different combinations of the potential factors structuring the web. Our simulations showed that both nectar-holder depth and abundance were able to produce asymmetry; but that the expected degree of asymmetry was stronger if based on both. Both factors can predict the number of interaction partners, but only nectar-holder depth was able to predict the degree of asymmetry of a certain species. What is more, without the size threshold the influence of abundance would disappear over time. Thus, asymmetric specialization seems to be the result of a size threshold and, only among the allowed interactions above this size threshold, a result of random interactions proportional to abundance. The simulations also showed that asymmetric specialization could not be the reason that the extinction risk of specialists and generalists is equalized, as suggested in the literature. In asymmetric webs specialists clearly had higher short-term extinction risks. In fact, primarily generalist visitors seem to profit from asymmetric specialization. In our web, specialists were less abundant than generalists. Therefore, including abundance in the simulation models increased the difference between specialists and generalists even more.
[52]
Stang M, Klinkhamer PGL, Waser NM, Stang I, van der Meijden E (2009)
Size-specific interaction patterns and size matching in a plant-pollinator interaction web
Annals of Botany, 103, 1459-1469.DOI:10.1093/aob/mcp027 URL PMID:19228701 [本文引用: 1]
BACKGROUND AND AIMS: Many recent studies show that plant-pollinator interaction webs exhibit consistent structural features such as long-tailed distributions of the degree of generalization, nestedness of interactions and asymmetric interaction dependencies. Recognition of these shared features has led to a variety of mechanistic attempts at explanation. Here it is hypothesized that beside size thresholds and species abundances, the frequency distribution of sizes (nectar depths and proboscis lengths) will play a key role in determining observed interaction patterns. METHODS: To test the influence of size distributions, a new network parameter is introduced: the degree of size matching between nectar depth and proboscis length. The observed degree of size matching in a Spanish plant-pollinator web was compared with the expected degree based on joint probability distributions, integrating size thresholds and abundance, and taking the sampling method into account. KEY RESULTS: Nectar depths and proboscis lengths both exhibited right-skewed frequency distributions across species and individuals. Species-based size matching was equally close for plants, independent of nectar depth, but differed significantly for pollinators of dissimilar proboscis length. The observed patterns were predicted well by a model considering size distributions across species. Observed size matching was closer when relative abundances of species were included, especially for flowers with openly accessible nectar and pollinators with long proboscises, but was predicted somewhat less successfully by the model that included abundances. CONCLUSIONS: The results suggest that in addition to size thresholds and species abundances, size distributions are important for understanding interaction patterns in plant-pollinator webs. It is likely that the understanding will be improved further by characterizing for entire communities how nectar production of flowers and energetic requirements of pollinators covary with size, and how sampling methods influence the observed interaction patterns.
[53]
Stogatz SH (2001)
Exploring complex networks
Nature, 410, 268-276.DOI:10.1038/35065725 URL PMID:11258382 [本文引用: 1]
The study of networks pervades all of science, from neurobiology to statistical physics. The most basic issues are structural: how does one characterize the wiring diagram of a food web or the Internet or the metabolic network of the bacterium Escherichia coli? Are there any unifying principles underlying their topology? From the perspective of nonlinear dynamics, we would also like to understand how an enormous network of interacting dynamical systems-be they neurons, power stations or lasers-will behave collectively, given their individual dynamics and coupling architecture. Researchers are only now beginning to unravel the structure and dynamics of complex networks.
[54]
Vázquez DP, Aizen MA (2004)
Asymmetric specialization: a pervasive feature of plant-pollinator interaction
Ecology, 85, 1251-1257.[本文引用: 1]
[55]
Vázquez DP, Blüthgen N, Cagnolo L, Chacoff NP (2009)
Uniting pattern and process in plant-animal mutualistic networks: a review
Annals of Botany, 103, 1445-1457.DOI:10.1093/aob/mcp057 URL PMID:19304996 [本文引用: 4]
BACKGROUND: Ecologists and evolutionary biologists are becoming increasingly interested in networks as a framework to study plant-animal mutualisms within their ecological context. Although such focus on networks has brought about important insights into the structure of these interactions, relatively little is still known about the mechanisms behind these patterns. SCOPE: The aim in this paper is to offer an overview of the mechanisms influencing the structure of plant-animal mutualistic networks. A brief summary is presented of the salient network patterns, the potential mechanisms are discussed and the studies that have evaluated them are reviewed. This review shows that researchers of plant-animal mutualisms have made substantial progress in the understanding of the processes behind the patterns observed in mutualistic networks. At the same time, we are still far from a thorough, integrative mechanistic understanding. We close with specific suggestions for directions of future research, which include developing methods to evaluate the relative importance of mechanisms influencing network patterns and focusing research efforts on selected representative study systems throughout the world.
[56]
Vázquez DP, Melián CJ, Williams NM, Blüthgen N, Krasnov BR, Poulin R (2007)
Species abundance and asymmetric interaction strength in ecological networks
Oikos, 116, 1120-1127.[本文引用: 1]
[57]
Waser NM, Chittka L, Price MV, Williams NM, Ollerton J (1996)
Generalization in pollination systems, and why it matters
Ecology, 77, 1043-1060.[本文引用: 2]
[58]
Waser NM, Ollerton J (2006) Plant-Pollinator Interactions: from Specialization to Generalization. University of Chicago Press, Chicago.
[本文引用: 1]
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