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Avian community ecology: Patterns of co-occurrence, nestedness, and morphology.

机译：鸟类群落生态学：共生，嵌套和形态的模式。

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A central tenet of the competition paradigm is that community structure is governed by deterministic rules. The competition paradigm pervades nearly all subdisciplines and extends to the broadest, deepest questions in ecology. To determine whether patterns of co-occurrence, nestedness, and morphology in avian communities are consistent with a competition hypothesis, I use null models to compare observed patterns to patterns expected in the absence of competition.; I use presence-absence matrices of birds in three archipelagoes to test whether species exhibit exclusive distributions. Congeneric birds co-occur significantly less frequently than predicted in two archipelagoes, consistent with a competition hypothesis. However, when examined separately, most genera do not exhibit patterns that differ from random expectations. Furthermore, species differences in habitat preference and barriers to dispersal within archipelagoes are two alternate hypotheses that can explain many exclusive patterns and are supported by available data. Distributional evidence alone does not implicate competition. I argue that the range of conditions under which competition is likely to generate exclusive distributions across islands is narrow.; Although nested patterns are viewed as the converse of competitive exclusion, meta-analyses of presence-absence matrices simultaneously support the ubiquity of exclusive distributions and indicate that most ecological systems are nested. I show why these apparently contradictory patterns are not mutually exclusive. Patterns of nestedness can result from multiple processes; without understanding mechanisms, nestedness analysis is unlikely to prove useful for conservation.; I study algorithms that randomize presence-absence matrices. Two commonly used algorithms generate biased statistical distributions and should be abandoned.; I test for community-wide character displacement in wing length and talon size among Accipiter hawks. I also assess whether subspecific variation in wing length is predictable from community composition. I find limited evidence of community-wide character displacement for wing length, but talon size, which relates directly to resource use, shows larger minimum and more equal size ratios than predicted. I find no evidence of competitively driven change in wing length. These findings demonstrate the importance of examining traits directly related to function. I cannot determine whether community-wide character displacement of talon size results from ecological character displacement, species assortment, or both.
机译：竞争范式的中心原则是，社区结构由确定性规则支配。竞争范式几乎遍及所有子学科，并延伸到生态学中最广泛，最深入的问题。为了确定鸟类群落中共生，嵌套和形态的模式是否与竞争假设一致，我使用空模型将观察到的模式与在没有竞争的情况下预期的模式进行比较。我使用三个群岛中鸟类的不在场矩阵来测试物种是否表现出排他性分布。与竞争假设相一致，同属鸟类的发生频率明显低于两个群岛中的预测发生频率。但是，当单独检查时，大多数属都不会表现出与随机预期不同的模式。此外，物种在栖息地偏好方面的差异以及在群岛内扩散的障碍是两个可以替代的假设，它们可以解释许多排他性模式，并得到现有数据的支持。仅分发证据并不意味着竞争。我认为，竞争可能在整个岛屿上产生独家分布的条件范围很窄。尽管嵌套模式被视为竞争排斥的反面，但存在-不存在矩阵的荟萃分析同时支持了唯一分布的普遍性，并表明大多数生态系统都是嵌套的。我展示了为什么这些看似矛盾的模式不是互斥的。嵌套模式可以由多个过程产生；如果不了解机制，嵌套分析就不可能证明对保护有用。我研究随机化存在矩阵的算法。两种常用的算法会产生有偏差的统计分布，应将其丢弃。我测试了Accipiter鹰的机翼长度和爪数在社区范围内的角色位移。我还评估了机翼长度的亚种变异是否可从群落组成中预测到。我发现有限的证据表明整个机翼的字符长度发生位移，但与资源使用直接相关的爪子尺寸却显示出比预期更大的最小尺寸比率和更相等的尺寸比率。我没有发现机翼长度竞争性改变的证据。这些发现证明了检查与功能直接相关的特征的重要性。我无法确定整个社区范围内爪大小的性格位移是否是由于生态性格位移，物种分类或两者导致的。

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