Bürli Sarah, Ensslin Andreas, Kempel Anne, Fischer Markus
Botanical Garden of the University of Bern Bern Switzerland.
Institute of Plant Sciences University of Bern Bern Switzerland.
Ecol Evol. 2023 Sep 5;13(9):e10482. doi: 10.1002/ece3.10482. eCollection 2023 Sep.
Rare plant species are suggested to be less resistant to herbivores than common species. Their lower apparency and the fact that they often live in isolated populations, resulting in fewer herbivore encounters, might have led to the evolution of reduced defences. Moreover, their frequent lower levels of genetic diversity compared with common species could negatively affect their resistance against enemies. However, the hypothesis that plant resistance depends on plant regional and local rarity, independently of habitat and competitive and growth strategy, lacks evidence. To test this hypothesis, we assessed the performance and preference of one belowground and three aboveground generalist invertebrate herbivores from different taxonomic groups as indicators of plant resistance. Herbivores were fed a total of 62 regionally and locally rare and common plant species from Switzerland. We accounted for differences in a plant's growth and competitive strategy and habitat resource availability. We found that regionally and locally rare and common plant species did not generally differ in their resistance to most generalist herbivores. However, one herbivore species even performed better and preferred locally and regionally common plant species over rarer ones, indicating that common species are not more resistant, but tend to be less resistant. We also found that all herbivore species consistently performed better on competitive and large plant species, although different herbivore species generally preferred and performed better on different plant species. The latter indicates that the use of generalist herbivores as indicators of plant-resistance levels can be misleading. Synthesis: Our results show that rare plant species are not inherently less resistant than common ones to herbivores. Instead, our results suggest that the ability of plants to allocate resources away from defence towards enhancing their competitive ability might have allowed plants to tolerate herbivory, and to become locally and regionally common.
稀有植物物种被认为比常见物种对食草动物的抵抗力更弱。它们较低的显眼程度以及它们通常生活在孤立种群中，导致与食草动物的接触较少，这可能导致了防御能力下降的进化。此外，与常见物种相比，它们的遗传多样性水平通常较低，这可能会对它们抵御敌人的能力产生负面影响。然而，植物抗性取决于植物在区域和局部的稀有程度，而与栖息地、竞争和生长策略无关这一假设缺乏证据。为了验证这一假设，我们评估了来自不同分类群的一种地下和三种地上广食性无脊椎食草动物的表现和偏好，以此作为植物抗性的指标。给食草动物喂食了来自瑞士的总共62种区域和局部稀有及常见的植物物种。我们考虑了植物生长和竞争策略以及栖息地资源可用性的差异。我们发现，区域和局部稀有及常见的植物物种对大多数广食性食草动物的抗性通常没有差异。然而，有一种食草动物物种在本地和区域常见植物物种上的表现甚至更好，并且更喜欢常见植物物种而非稀有植物物种，这表明常见物种并非更具抗性，而是往往抗性更弱。我们还发现，所有食草动物物种在具有竞争力的大型植物物种上的表现始终更好，尽管不同的食草动物物种通常更喜欢并在不同的植物物种上表现得更好。后者表明，将广食性食草动物用作植物抗性水平的指标可能会产生误导。总结：我们的结果表明，稀有植物物种对食草动物的抗性并非天生就比常见物种弱。相反，我们的结果表明，植物将资源从防御转向增强其竞争能力的能力可能使植物能够耐受食草作用，并在本地和区域变得常见。
