Larson Diane L, Larson Jennifer L, Symstad Amy J, Buhl Deborah A, Portman Zachary M
Northern Prairie Wildlife Research Center U.S. Geological Survey Hot Springs AR USA.
Department of Entomology University of Minnesota St. Paul MN US.
Ecol Evol. 2021 Mar 20;11(9):4750-4762. doi: 10.1002/ece3.7375. eCollection 2021 May.
Network analyses rarely include fitness components, such as germination, to tie invasive plants to population-level effects on the natives. We address this limitation in a previously studied network of flower visitors around a suite of native and invasive plants that includes an endemic plant at Badlands National Park, South Dakota, USA. coflowers with two abundant invasive plants, and , as well as a common congener, . Network analyses had suggested strong linkages between and and , with a weaker link to . We measured visitation, pollen deposited on stigmas, achene weight and germination over three field seasons (two for germination) in four populations (two in the final season) of and applied in situ pollen treatments to , adding pollen from other flowers on the same plant; flowers on other plants; , or ; open pollination; or excluding pollinators. Insect visitation to was not affected by floral abundance of any of the focal species. Most visitors were halictid bees; one of these () was the only identified species to visit all three years. Ninety-seven percent of pollen on collected stigmas was conspecific, but 22% of flowers had >1 grain of pollen on stigmas and 7% had >1 grain of pollen; <1% of flowers had pollen on stigmas. None of the pollen treatments produced significant differences in weight or germination of achenes. We conclude that, in contrast to the results of the network analysis, neither of the invasive species poses a threat, via heterospecific pollen deposition, to pollination of the endemic , and that its congener provides alternative pollen resources to its pollinators.
网络分析很少纳入适合度组成部分，如发芽率，来将入侵植物与对本地植物种群水平的影响联系起来。我们在美国南达科他州荒地国家公园，针对一组本地和入侵植物周围的传粉者网络（其中包括一种特有植物），解决了这一局限性。该特有植物与两种常见入侵植物以及一种同属常见植物共同开花。网络分析表明，该特有植物与两种入侵植物之间存在紧密联系，而与同属常见植物的联系较弱。我们在该特有植物的四个种群（最后一个季节为两个种群）中，经过三个野外季节（发芽率测量为两个季节）测量了访花情况、柱头上沉积的花粉、瘦果重量和发芽率，并对该特有植物进行了原位花粉处理，添加来自同一植株上其他花朵的花粉、其他该特有植物植株上的花朵的花粉、另一种入侵植物的花粉或同属常见植物的花粉；进行开放授粉；或排除传粉者。对该特有植物的昆虫访花不受任何目标物种花量的影响。大多数访花者是隧蜂；其中一种（某种隧蜂）是唯一在所有三年中都访花的已识别物种。收集的该特有植物柱头上97%的花粉是同种花粉，但22%的花朵柱头上有超过1粒该特有植物的花粉，7%的花朵柱头上有超过1粒其他物种花粉；不到1%的花朵柱头上有另一种入侵植物的花粉。没有一种花粉处理在该特有植物瘦果的重量或发芽率上产生显著差异。我们得出结论，与网络分析结果相反，这两种入侵物种都不会通过异种花粉沉积对该特有植物的授粉构成威胁，并且其同属植物为其传粉者提供了替代花粉资源。
