Data from: Periphyton density is similar on native and non-native plant species

Non-native plants increasingly dominate the vegetation in aquatic ecosystems and thrive in eutrophic conditions. In eutrophic conditions, submerged plants risk being overgrown by epiphytic algae; however, if non-native plants are less susceptible to periphyton than natives, this would contribute to their dominance. Non-native plants may differ from natives in their susceptibility to periphyton growth due to differences in nutrient release, allelopathy and architecture. Yet, there is mixed evidence for whether plants interact with periphyton growth through nutrient release and allelopathy, or whether plants are neutral so that only their architecture matters for periphyton growth.
We hypothesised that (1) non-native submerged vascular plants support lower periphyton density than native species, (2) native and non-native species are not neutral substrate for periphyton and interact with periphyton and (3) periphyton density increases with the plant structural complexity of plant species.
We conducted an experiment in a controlled climate chamber where we grew 11 aquatic plant species and an artificial plant analogue in monocultures in buckets. These buckets were inoculated with periphyton that was collected locally from plants and hard substrate. Of the 11 living species, seven are native to Europe and four are non-native. The periphyton density on these plants was quantified after five weeks.
We found that the periphyton density did not differ between non-native and native plants and was not related to plant complexity. Three living plant species supported lower periphyton densities than the artificial plant, one supported a higher periphyton density and the other plants supported similar densities. However, there was a strong negative correlation between plant growth and periphyton density.
We conclude that the periphyton density varies greatly among plant species, even when these were grown under similar conditions, but there was no indication that the interaction with periphyton differs between native and non-native plant species. Hence, non-native plants do not seem to benefit from reduced periphyton colonisation compared to native species. Instead, certain native and non-native species tolerate eutrophic conditions well and as a consequence, they seem to host less periphyton than less tolerant species.

外来植物日益主导水生生态系统的植被群落，并在富营养化环境中长势旺盛。在富营养化环境中，沉水植物面临被附生藻类覆盖的风险；但若外来植物相较于本土植物对周丛生物（periphyton）的易感程度更低，这将助力其占据群落优势。外来植物与本土植物对周丛生物生长的易感程度可能存在差异，这源于二者在营养释放、化感作用以及植株构型上的不同。然而，目前关于植物是否通过营养释放与化感作用影响周丛生物生长，亦或是仅通过植株构型发挥作用（即植物对周丛生物无额外影响），相关研究结论并不一致。
本研究提出以下假说：（1）外来沉水维管植物上的周丛生物密度低于本土物种；（2）本土与外来植物均并非周丛生物的中性基质，二者会与周丛生物产生相互作用；（3）周丛生物密度会随植物结构复杂度的提升而增加。
本研究在可控气候室中开展实验，将11种水生植物与1种人工植物类似物以单种方式种植于桶缸中。向桶缸内接种从本地植物及硬质基质上采集的周丛生物。11种活体植物中，7种为欧洲本土物种，4种为外来物种。培养5周后，定量测定各植物表面的周丛生物密度。
研究结果显示，外来植物与本土植物上的周丛生物密度并无显著差异，且周丛生物密度与植物结构复杂度并无关联。3种活体植物上的周丛生物密度低于人工植物，1种活体植物上的周丛生物密度更高，其余植物的周丛生物密度与人工植物相近。不过，植物生长状况与周丛生物密度之间存在显著负相关关系。
研究结论表明，即便在相同培养条件下，不同植物物种上的周丛生物密度仍存在显著差异，但并无证据显示本土与外来植物和周丛生物的相互作用存在区别。因此，相较于本土物种，外来植物并未因周丛生物定植量减少而获得竞争优势。相反，部分本土与外来物种对富营养化环境的耐受性较强，故而其表面的周丛生物密度相较于耐受性较弱的物种更低。