Interactive effects of fragmentation and keystone species loss on the structure of a tropical pollination network

授粉对人类福祉至关重要，对维持生物多样性至关重要。研究表明，植物和传粉媒介的大规模减少，凸显了人们对传粉服务面临风险的担忧；出现这个问题的部分原因是，植物栖息地越来越分散，成为传粉者可能无法到达的互不相连的斑块。然而，传粉者和他们的植物在一个共享的植物物种和传粉者的网络中是相互关联的，因此寄主和传粉者的功能具有冗余性。原生栖息地的破碎化和丧失与传粉者的减少有关，但根据理论模型，传粉网络的结构预计会使它们由于冗余而具有普遍的弹性。然而，如果许多传粉物种所依赖的植物物种（即“关键物种”）消失，传粉网可能会更加脆弱，导致网络突然崩溃。本研究将解决两个首要问题：(1)关键植物的减少和灭绝对更广泛的授粉网络有什么影响？(2)景观连通性和随之而来的更大的传粉者在斑块间的移动能否缓冲传粉网络，防止网络崩溃？这项研究本身促进了科学的进步，并对国家福利产生了影响，因为它对维持传粉媒介物种多样性有潜在的贡献。此外，这项工作将继续利用热带蜂鸟的魅力和多样性来传播保护授粉服务的重要性。此前由美国国家科学基金会资助的研究表明，蜂鸟传粉者的活动受到景观破碎化的强烈限制，这导致了一种常见的keystone森林草本植物（Heliconia tortuosa）的花粉限制和随后的再生失败。在网络崩溃假说下，减小的花蜜密度会限制花蜜资源的可用性，从而减少传粉者对花蜜碎片的访问，最终导致网络崩溃。在这种情况下，景观连通性将减少维持网络结构所需的最小Heliconia数量。在稳健网络假说下，即使一些植物和枢纽传粉者缺失或丰度较低，传粉者的行为可塑性也会赋予其对网络的抵抗力。将从孤立的和连接的森林片段中移除H. tortuosa，以确定该物种密度的改变是否会影响(a)蜂鸟运动，(b)植物繁殖和遗传多样性，以及(c)传粉网络结构。蜂鸟的运动将通过无线射频识别设备（RFID）来量化网络中所有种类的蜂鸟。这种方法可以以前所未有的时间分辨率（秒）和空间尺度观察整个蜂鸟传粉者群落。更广泛的影响将包括教育和外联工作，包括大量媒体报道；国际公民科学；符合下一代科学标准的教育游戏和学生驱动的数据收集；以及公共教育的努力。

Pollination is essential to human well-being, as well as fundamental to maintenance of biological diversity. Research showing large-scale declines of plants and pollinators highlights the concern that pollination services are at risk; the problem arises in part because plant habitat is increasingly fragmented into unconnected patches that pollinators may not be able to reach. However, the pollinators and their plants are interrelated in a network of shared plant species and pollinators and so the functions of hosts and pollinator have redundancy. Fragmentation and loss of native habitats is associated with pollinator declines, but according to theoretical models, the structure of pollination networks is expected to make them generally resilient to change because of the redundancy. However, if plant species that are depended upon by many pollinator species (i.e., "keystone species") are lost, pollination webs may be more vulnerable, resulting in sudden network collapse. This research will address two overarching questions: (1) What are the consequences of keystone plant decline and extinction to the broader pollination network? (2) Can landscape connectivity and consequent greater pollinator movement across patches buffer pollination networks against network collapse? The research itself promotes the progress of science and has implications for national welfare given its potential contributions to the maintenance of pollinator species diversity. Additionally, this work will continue to capitalize on the charisma and diversity of tropical hummingbirds to transmit ideas about the importance of the conservation of pollination services. Previous NSF-funded work has shown that the movement of hummingbird pollinators is strongly restricted by landscape fragmentation, which results in pollen limitation and subsequent regeneration failure in a common keystone forest herb (Heliconia tortuosa). Under the network collapse hypothesis, reduced H. tortuosa densities will limit nectar resource availability thereby decreasing pollinator visitation to fragments and resulting in eventual network collapse. In this instance, landscape connectivity will decrease the minimum number Heliconia required to maintain network structure. Under the robust network hypothesis, the behavioral plasticity of pollinators will confer resistance to the network, even if some plant and hub pollinators are missing or at low abundance. H. tortuosa will be removed from isolated and connected forest fragments to determine whether altered densities of this species affects (a) hummingbird movement, (b) plant reproduction and genetic diversity, and (c) the structure of the pollination network. Hummingbird movement will be quantified for all species in the network using Radio-Frequency Identification Devices (RFID). This method will enable observations of the entire hummingbird pollinator community at an unprecedented temporal resolution (seconds) and spatial scale. Broader impacts will include educational and outreach efforts that include substantial media coverage; international citizen science; educational games and student-driven data collection that meet Next Generation Science Standards; and public education efforts.