Institute of Grassland Science, Northeast Normal University and Key Laboratory for Vegetation Ecology, Ministry of Education, Changchun, 130024, China.
Institute of Grassland Science, Northeast Normal University and Key Laboratory for Vegetation Ecology, Ministry of Education, Changchun, 130024, China; Department of Biology, Changchun Normal University, Changchun, 130032, China; Department of Biology, Eastern Liaoning University, Dandong, 118003, China.
Environ Pollut. 2018 Nov;242(Pt B):1166-1175. doi: 10.1016/j.envpol.2018.07.128. Epub 2018 Aug 7.
Plants growing in heavy-metal-rich soils can accumulate metals into their nectar. Nectar chemical composition can alter foraging behavior of floral visitors (including pollinators and floral antagonists) and further affect plant reproductive fitness. The role of nectar heavy metals in deterring pollinators (e.g., shortening foraging time) has been recently studied, but their effects on plant reproduction via changes in behaviors of both pollinators and floral antagonists (e.g., nectar robbers) are less understood. We experimentally manipulated four nectar heavy metals (Zn, Cu, Ni, and Pb) in a native ornamental plant, Hosta ensata F. Maekawa, to investigate the effect of nectar metals on plant reproductive success. We also recorded nectar robbing as well as foraging time and visitation rate of pollinators to assess whether nectar metals could alter the behavior of antagonists and mutualists. Although metals in nectar had no significant direct effects on plant reproduction via hand-pollination, we detected their positive indirect effects on components of female fitness mediated by pollinators and nectar robbers. Matching effects on female plant fitness, nectar robbers responded negatively to the presence of metals in nectar, robbing metal-treated flowers less often. Pollinators spent less time foraging on metal-treated flowers, but their visitation rate to metal-treated flowers was significantly higher than to control flowers. Moreover, pollinators removed less nectar from flowers treated with metals. Our results provide the first direct evidence to date that heavy metals in nectar are capable of deterring nectar robbers and modifying pollinator foraging behavior to enhance plant reproductive fitness.
生长在富含重金属土壤中的植物可以将金属积累在花蜜中。花蜜的化学成分会改变访花者（包括传粉者和花敌）的觅食行为，并进一步影响植物的繁殖适应性。花蜜重金属对传粉者的威慑作用（例如，缩短觅食时间）最近已得到研究，但它们通过改变传粉者和花敌（例如花蜜掠夺者）的行为对植物繁殖的影响则知之甚少。我们在一种本地观赏植物萱草（Hosta ensata F. Maekawa）中实验性地操纵了四种花蜜重金属（Zn、Cu、Ni 和 Pb），以研究花蜜金属对植物繁殖成功的影响。我们还记录了花蜜掠夺以及传粉者的觅食时间和访问率，以评估花蜜金属是否可以改变敌害和互利者的行为。尽管花蜜中的金属通过人工授粉对植物繁殖没有直接的显著影响，但我们发现，通过传粉者和花蜜掠夺者，金属对雌性植物适应性的组成部分有正向的间接影响。在雌性植物适应性方面存在匹配效应，花蜜掠夺者对花蜜中存在的金属表现出负面反应，掠夺金属处理花朵的次数减少。传粉者在金属处理花朵上的觅食时间减少，但对金属处理花朵的访问率明显高于对照花朵。此外，传粉者从处理过金属的花朵中吸取的花蜜较少。我们的研究结果提供了迄今为止的第一个直接证据，证明花蜜中的重金属能够威慑花蜜掠夺者并改变传粉者的觅食行为，从而增强植物的繁殖适应性。
