Yale School of Forestry and Environmental Studies, New Haven, Connecticut, 06511, USA.
Department of Plant Ecology, Bayreuth Center for Ecology and Environmental Research, University of Bayreuth, Bayreuth, 95440, Germany.
Ecology. 2020 Nov;101(11):e03151. doi: 10.1002/ecy.3151. Epub 2020 Sep 22.
In tropical forests, insect herbivores exert significant pressure on plant populations. Adaptation to such pressure is hypothesized to be a driver of high tropical diversity, but direct evidence for local adaptation to herbivory in tropical forests is sparse. At the same time, herbivore pressure has been hypothesized to increase with rainfall in the tropics, which could lead to differences among sites in the degree of local adaptation. To assess the presence of local adaptation and its interaction with rainfall, we compared herbivore damage on seedlings of local vs. nonlocal populations at sites differing in moisture availability in a reciprocal transplant experiment spanning a rainfall gradient in Panama. For 13 native tree species, seeds collected from multiple populations along the rainfall gradient were germinated in a shadehouse and then transplanted to experimental sites within the species range. We tracked the proportion of seedlings attacked over 1.5 yr and quantified the percentage of leaf area damaged at the end of the study. Seedlings originating from local populations were less likely to be attacked and experienced lower amounts of herbivore damage than those from nonlocal populations, but only on the wetter end of the rainfall gradient. However, overall herbivore damage was higher at the drier site compared to wetter sites, contrary to expectation. Taken together, these findings support the idea that herbivory can result in local adaptation within tropical tree species; however, the likelihood of local adaptation varies among sites because of environmentally driven differences in investment in defense or herbivore specialization or both.
在热带森林中，昆虫食草动物对植物种群施加了巨大的压力。人们假设这种压力是热带地区高生物多样性的驱动因素之一，但在热带森林中，对食草动物的适应性的直接证据却很少。同时，人们假设食草动物的压力随着热带地区降雨量的增加而增加，这可能导致不同地点对本地适应性的适应程度存在差异。为了评估本地适应性的存在及其与降雨量的相互作用，我们在巴拿马的一个降雨量梯度上进行了一个互惠移植实验，比较了在水分供应不同的地点，来自本地和非本地种群的幼苗受到食草动物损害的情况。对于 13 种本地树种，我们从沿着降雨量梯度的多个种群中收集种子，在遮荫棚中发芽，然后将其移植到物种分布范围内的实验地点。我们追踪了 1.5 年的幼苗被攻击的比例，并在研究结束时量化了叶片受损的百分比。与来自非本地种群的幼苗相比，来自本地种群的幼苗受到攻击的可能性较小，受到的食草动物损害也较小，但这种情况仅出现在降雨量梯度的较湿端。然而，与预期相反的是，与较湿地点相比，较干燥地点的总体食草动物损害更高。总的来说，这些发现支持了食草动物会导致热带树种产生本地适应性的观点；然而，由于环境驱动的防御投资或食草动物专业化或两者的差异，本地适应性的可能性在不同地点存在差异。
