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

热带森林包括多样性的栖息地，这导致了植物的专门化。在秘鲁亚马逊的伊基托斯附近，营养贫乏的白色沙林紧邻营养丰富的粘土森林，每个森林都有独特的栖息地专业树组成。为什么会出现栖息地专门化？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创造了强大的选择压力。因此，没有进化出高水平的抗草食动物防御的物种在白色沙林中处于劣势，被草食动物排除在外。为了测试草食动物是否在白沙植物中选择更理想的抗草食动物防御，我们比较了来自6个属的33个物种的国防投资，其中包括几对在系统发育上相互独立的白沙和粘土专家。此外，我们还建立了相互移植实验，以控制草食动物的存在，并直接测试草食动物在多大程度上保持了两个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著影响，这将提出一种新的方式来影响植物的进化：由于非生物因素而使栖息地边界变得尖锐，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.