Department of Botany, University of Hawai'i at Mānoa, 3190 Maile Way, Room 101, Honolulu, Hawai'i, 96822, USA.
Ecology. 2017 Dec;98(12):3011-3021. doi: 10.1002/ecy.2031.
Plant-herbivore interactions have been predicted to play a fundamental role in plant invasions, although support for this assertion from previous research is mixed. While plants may escape from specialist herbivores in their introduced ranges, herbivory from generalists is common. Tolerance traits may allow non-native plants to mitigate the negative consequences of generalist herbivory that they cannot avoid in their introduced range. Here we address whether tolerance to herbivory, quantified as survival and compensatory growth, is associated with plant invasion success in Hawaii and investigate traits that may enhance tolerance in seedlings, the life stage most susceptible to herbivory. In a greenhouse experiment, we measured seedling tolerance to simulated herbivory through mechanical damage (50% leaf removal) of 16 non-native woody plant species differing in invasion status (invasive vs. non-invasive). Seedlings were grown for 2 weeks following damage and analyzed for biomass to determine whether damaged plants could fully compensate for the lost leaf tissue. Over 99% of all seedlings survived defoliation. Although species varied significantly in their levels of compensation, there was no consistent difference between invasive and non-invasive species. Seedlings of 11 species undercompensated and remained substantially smaller than control seedlings 2 weeks after damage; four species were close to compensating, while one species overcompensated. Across species, compensation was positively associated with an increased investment in potential storage reserves, specifically cotyledons and roots, suggesting that these organs provide resources that help seedlings re-grow following damage. Our results add to a growing consensus that pre-damage growth patterns determine tolerance to damage, even in young seedlings which have relatively low biomass. The lack of higher tolerance in highly invasive species may suggest that invaders overcome herbivory barriers to invasion in other ways, such as resistance traits, or that herbivory does not play an important role in the seedling invasion dynamics of these woody species in Hawaii.
植物-食草动物的相互作用被预测在植物入侵中起着基础性作用，尽管之前的研究对这一说法的支持并不一致。虽然植物在引入的范围内可能会逃避专食性食草动物，但广食性食草动物的存在是很常见的。耐受性特征可能使非本地植物减轻它们在引入范围内无法避免的广食性食草动物的负面影响。在这里，我们研究了在夏威夷，对食草动物的耐受性（以存活率和补偿性生长来量化）是否与植物入侵的成功有关，并研究了在幼苗阶段可能增强耐受性的特征，幼苗阶段最容易受到食草动物的影响。在温室实验中，我们通过模拟机械损伤（去除 50%的叶片）来测量 16 种不同入侵状态（入侵和非入侵）的非本地木本植物幼苗的耐受性。在损伤后，幼苗生长了 2 周，并对生物量进行了分析，以确定受损植物是否可以完全补偿失去的叶片组织。超过 99%的幼苗在去叶后存活下来。尽管物种之间在补偿水平上有显著差异，但入侵和非入侵物种之间没有一致的差异。11 种物种的幼苗补偿不足，在损伤后 2 周仍明显小于对照幼苗；4 种物种接近补偿，而 1 种物种过度补偿。在物种间，补偿与潜在储存储备（特别是子叶和根）的增加投资呈正相关，这表明这些器官提供了帮助幼苗在受损后重新生长的资源。我们的结果增加了一个共识，即损伤前的生长模式决定了对损伤的耐受性，即使是在生物量相对较低的幼苗中也是如此。高度入侵性物种没有更高的耐受性可能表明，入侵物种通过其他方式克服了入侵的食草动物障碍，例如抗性特征，或者食草动物在这些夏威夷木本物种的幼苗入侵动态中并不起重要作用。
