Latitudinal Gradients in Plant Palatability in Atlantic Coast Salt Marshes

0107604彭宁生态学家长期以来一直假设，食草动物的压力更大，植物防御系统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，但该问题的大规模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研究直接证明，南部沼泽植物比北方同类植物更不适合食草动物。目前的项目将检验这一假设，即这些群落中的食草动物压力在低纬度地区比在高纬度地区更大。食草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、观察食草动物的危害和食草动物的数量来评估。该项目的第二个目标将是确定这些植物是否需要气候或食草动物损害等线索来形成适口性的纬度差异，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，该项目将把植物适口性的纬度梯度研究带到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.