Department of Zoology, University of Wisconsin, Madison, WI, 53706, USA.
Oecologia. 2012 Apr;168(4):1103-10. doi: 10.1007/s00442-011-2159-x. Epub 2011 Oct 18.
Soil-borne seed pathogens may play an important role in either hindering or facilitating the spread of invasive exotic plants. We examined whether the invasive shrub Lonicera maackii (Caprifoliaceae) affected fungi-mediated mortality of conspecific and native shrub seeds in a deciduous forest in eastern Missouri. Using a combination of L. maackii removal and fungicide treatments, we found no effect of L. maackii invasion on seed viability of the native Symphoricarpos orbiculatus (Caprifoliaceae) or Cornus drummondii (Cornaceae). In contrast, fungi were significant agents of L. maackii seed mortality in invaded habitats. Losses of L. maackii to soil fungi were also significant in invaded habitats where L. maackii had been removed, although the magnitude of the effect of fungi was lower, suggesting that changes in soil chemistry or microhabitat caused by L. maackii were responsible for affecting fungal seed pathogens. Our work suggests that apparent competition via soil pathogens is not an important factor contributing to impacts of L. maackii on native shrubs. Rather, we found that fungal seed pathogens have density-dependent effects on L. maackii seed survival. Therefore, while fungal pathogens may provide little biotic resistance to early invasion by L. maackii, our study illustrates that more work is needed to understand how changes in fungal pathogens during the course of an invasion contribute to the potential for restoration of invaded systems. More generally, our study suggests that increased rates of fungal pathogen attack may be realized by invasive plants, such as L. maackii, that change the chemical or physical environment of the habitats they invade.
土壤传播的种子病原体可能在阻碍或促进入侵外来植物的传播方面发挥重要作用。我们研究了入侵灌木忍冬（忍冬科）是否会影响落叶林中同种和本地灌木种子的真菌介导死亡率。通过忍冬去除和杀菌剂处理的组合，我们发现忍冬入侵对本地 Symphoricarpos orbiculatus（忍冬科）或 Cornus drummondii（山茱萸科）种子活力没有影响。相比之下，真菌是入侵生境中忍冬种子死亡的重要因素。在入侵生境中，即使忍冬已被去除，忍冬对土壤真菌的损失也很明显，尽管真菌的影响幅度较小，这表明忍冬引起的土壤化学或微生境变化是影响真菌种子病原体的原因。我们的工作表明，通过土壤病原体产生的明显竞争不是忍冬对本地灌木产生影响的重要因素。相反，我们发现真菌种子病原体对忍冬种子存活具有密度依赖性影响。因此，虽然真菌病原体对忍冬早期入侵提供的生物抗性可能较小，但我们的研究表明，需要进一步研究了解入侵过程中真菌病原体的变化如何有助于恢复入侵系统的潜力。更一般地说，我们的研究表明，改变它们入侵的栖息地的化学或物理环境的入侵植物，如忍冬，可能会受到更多真菌病原体攻击。
