Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, 32611, USA.
Sci Rep. 2021 Jan 13;11(1):1019. doi: 10.1038/s41598-020-80185-5.
Positive ecological relationships, such as facilitation, are an important force in community organization. The effects of facilitative relationships can be strong enough to cause changes in the distributions of species and in many cases have evolved as a response to predation pressure, however, very little is known about this potential trend in vertebrate facilitative relationships. Predation is an important selective pressure that may strongly influence breeding site selection by nesting birds. The American Alligator (Alligator mississippiensis) facilitates a safer nesting location for wading birds (Ciconiiformes and Pelecaniformes) by deterring mammalian nest predators from breeding sites. However, alligators do not occur throughout the breeding range of most wading birds, and it is unclear whether alligator presence affects colony site selection. We predicted that nesting wading birds change colony site preferences when alligators are not present to serve as nest protectors. Within the northern fringe of alligator distribution we compared colony characteristics in locations where alligator presence was either likely or unlikely while controlling for availability of habitat. Wading birds preferred islands that were farther from the mainland and farther from landmasses > 5 ha when alligator presence was unlikely compared to when alligators were likely. These findings indicate that wading birds are seeking nesting locations that are less accessible to mammalian predators when alligators are not present, and that this requirement is relaxed when alligators are present. This study illustrates how a landscape-scale difference between realized and fundamental niche can result from a facilitative relationship in vertebrates.
积极的生态关系，如促进作用，是群落组织的重要力量。促进关系的影响可能非常强烈，足以导致物种分布的变化，在许多情况下，这种关系是作为对捕食压力的一种反应而进化的，然而，对于脊椎动物促进关系的这种潜在趋势，我们知之甚少。捕食是一种重要的选择压力，可能强烈影响筑巢鸟类的筑巢地点选择。美洲鳄（Alligator mississippiensis）通过阻止哺乳动物的巢捕食者在繁殖地筑巢，为涉水鸟类（鹳形目和鹈形目）提供更安全的筑巢地点。然而，鳄鱼并不是大多数涉水鸟类繁殖范围的全部，鳄鱼的存在是否会影响到繁殖地的选择尚不清楚。我们预测，当鳄鱼不在场充当巢保护者时，涉水鸟类会改变繁殖地的偏好。在鳄鱼分布的北部边缘，我们在考虑栖息地可用性的情况下，比较了鳄鱼存在的可能性或不可能的情况下的繁殖地特征。与鳄鱼可能存在的情况相比，当鳄鱼不太可能存在时，涉水鸟类更喜欢距离大陆更远且距离大于 5 公顷的岛屿作为繁殖地。这些发现表明，当鳄鱼不在场时，涉水鸟类正在寻找对哺乳动物捕食者来说不太容易进入的筑巢地点，而当鳄鱼在场时，这种要求会放宽。这项研究说明了在脊椎动物中，实现的生态位和基础生态位之间的景观尺度差异如何是由促进关系造成的。
