Dissertation Research: Herbivory and the Evolution of Habitat Specialization in Amazonian White Sand and Clay Forests

热带森林包括多样化的栖息地，这导致了植物的专业化。在秘鲁亚马逊地区的伊基托斯附近，营养贫乏的白沙森林紧邻营养丰富的粘土森林，每片森林都拥有独特的栖息地专业树木组成。为什么会出现栖息地专业化？我们的假设是，贫瘠的土壤和食草动物的结合为白沙林中的植物防御产生了强大的选择压力。因此，尚未进化出高水平反食草动物防御能力的物种在白沙森林中处于不利地位，并被食草动物排除在外。为了测试食草动物是否在白沙植物中选择更高的最佳反食草动物防御能力，我们正在比较 6 个属的 33 个物种的防御投资，其中包括几个系统发育上独立的密切相关的白沙和粘土专家对。此外，我们还建立了一个相互移植实验来操纵食草动物的存在，并直接测试食草动物在何种程度上维持两种森林类型之间物种组成的低重叠。如果食草动物对栖息地专门化有显着影响，那么它将表明食草动物可能影响植物进化的新方式：通过非生物因素锐化栖息地边界，从而增加栖息地专门化的潜力。

Tropical forests include a diversity of habitats, which has lead to specialization inplants. Near Iquitos, in the Peruvian Amazon, nutrient-poor white sand forests are foundimmediately adjacent to nutrient-rich clay forests, each harboring a unique compositionof habitat specialist trees. Why does habitat specialization occur? Our hypothesis is thatthe combination of impoverished soils and herbivory creates strong selective pressure forplant defenses in white sand forest. Species that have not evolved high levels ofantiherbivore defense are therefore at a disadvantage in white sand forests and excludedby herbivores.To test whether herbivores select for higher optimal antiherbivore defense inwhite sand plants, we are comparing defense investment in 33 species from 6 genera thatinclude several phylogenetically independent pairs of closely-related white sand and clayspecialists. In addition, we have established a reciprocal transplant experiment tomanipulate the presence of herbivores and directly test to what degree herbivoresmaintain the low overlap in species composition between the two forest types. Ifherbivory has a significant effect on habitat specialization, it will suggest a new way thatherbivores may influence plant evolution: by sharpening habitat boundaries due to abioticfactors and thereby increasing the potential for habitat specialization.