School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA.
U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado, USA.
Ecology. 2022 Dec;103(12):e3837. doi: 10.1002/ecy.3837. Epub 2022 Sep 30.
Root hemiparasitic plants both compete with and extract resources from host plants. By reducing the abundance of dominant plants and releasing subordinates from competitive exclusion, they can have an outsized impact on plant communities. Most research on the ecological role of hemiparasites is manipulative and focuses on a small number of hemiparasitic taxa. Here, we ask whether patterns in natural plant communities match the expectation that hemiparasites affect the structure of plant communities. Our data were collected on 129 national park units spanning the continental United States. The most common hemiparasite genera were Pedicularis, Castilleja, Krameria, and Comandra. We used null models and linear mixed models to determine whether hemiparasites were associated with changes in community richness and evenness. Hemiparasite presence did not affect community metrics. Hemiparasite abundance was positively associated with increasing evenness of herbaceous species, but not with species richness. The associations that we observed on a continental scale are consistent with evidence that the impacts of root hemiparasitic plants on evenness can be substantial and abundance dependent but that effects on richness are less pronounced. Hemiparasites mediate competitive exclusion in communities to facilitate species coexistence and merit consideration of inclusion in ecological theories of coexistence.
根半寄生植物与宿主植物既竞争又争夺资源。通过减少优势植物的丰度和使从属植物免受竞争排斥，它们可以对植物群落产生巨大的影响。大多数对半寄生植物生态作用的研究都是操作性的，并且集中在少数几种半寄生类群上。在这里，我们想知道自然植物群落中的模式是否符合半寄生植物影响植物群落结构的预期。我们的数据是在美国大陆的 129 个国家公园单位收集的。最常见的半寄生植物属是Pedicularis、Castilleja、Krameria 和 Comandra。我们使用零模型和线性混合模型来确定半寄生植物是否与群落丰富度和均匀度的变化有关。半寄生植物的存在并不影响群落指标。半寄生植物的丰度与草本物种均匀度的增加呈正相关，但与物种丰富度无关。我们在大陆范围内观察到的关联与以下证据一致，即根半寄生植物对均匀度的影响可能是巨大的，并且与丰度有关，但对丰富度的影响则不那么明显。半寄生植物在群落中调节竞争排斥，以促进物种共存，值得在共存的生态理论中考虑将其包括在内。
