Latitudinal Gradients in Plant Palatability in Atlantic Coast Salt Marshes

长期以来，生态学家一直假设草食动物的压力更大，而植物的防御能力在热带地区比在高纬度地区发展得更好。尽管一些间接证据支持这些观点，但该问题的大地理范围阻碍了更直接研究的尝试。我最近在大西洋海岸盐沼的工作直接证明了南方沼泽植物对食草动物的吸引力不如北方同类植物。目前的项目将测试一个假设，即在这些群落中，草食动物的压力在低纬度地区比在高纬度地区更大。草食动物的压力将通过在每个地理区域的沼泽中种植“标准”植物并观察草食动物的损害以及草食动物的数量来评估。该项目的第二个目标是确定植物是否需要气候或草食损害等线索来发展适口性的纬度差异，或者这些差异是否是“预先编程”的。这些替代方案将通过在一个共同的温室中并排种植来自两个地理区域的植物来进行比较。通过克服困扰过去研究的几个后勤问题，该项目将为植物适口性的纬度梯度研究带来一个新的严谨和理解水平。

DEB-0107604 PenningsEcologists have long hypothesized that herbivore pressure is more intense and that plant defenses are better developed towards the tropics than at higher latitudes. Although some indirect evidence supports these ideas, the large geographic scale of the problem has hampered attempts at more direct studies. My recent work in Atlantic coast salt marshes directly demonstrated that southern marsh plants are less palatable to herbivores than are northern plants of the same species. The current project will test the hypothesis that herbivore pressure in these communities is greater at lower than at higher latitudes. Herbivore pressure will be assessed by planting "standard" plants into marshes in each geographic region and observing herbivore damage, and by herbivore counts. A second goal of the project will be to determine whether the plants require cues such as climate or herbivore damage in order to develop latitudinal differences in palatability, or whether these differences are "pre-programmed". These alternatives will be compared by growing plants from both geographic regions side by side in a common greenhouse. By overcoming several of the logistical problems that have plagued past studies, this project will bring a new level of rigor and understanding to the study of latitudinal gradients in plant palatability.