Spatial and temporal unpredictability of colony size in Cliff Swallows across 30 years
Spatial and temporal unpredictability of colony size in Cliff Swallows across 30 years
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DOI：
10.1890/12-2001.1
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发表时间：
2013-11-01
影响因子：
6.1
通讯作者：
Roche, Erin A.
中科院分区：
文献类型：
--
作者：
Brown, Charles R.;Brown, Mary Bomberger;Roche, Erin A.
大多数殖民地繁殖的动物占据的群体大小从几对到数千个个体不等，但群体大小变化的原因在很大程度上是未知的。三个一般假设是：（1）群体大小的变化是通过与不同群体大小相关的适合度的空间和时间变化的波动选择来维持的;（2）群体的形成反映了栖息地的异质性，某些地点拥有的资源比其他地点支持更多的个体;和（3）个体评估当前殖民地居民在每个地点的存在或年度繁殖成功率，并优先聚集在高-质量网站。这些假设预测了不同地点和不同年份的菌落大小应该如何一致。我们研究了在内布拉斯加州西部30年期间，>200悬崖燕子（Petrochelidon pyrrhonota）的殖民地网站的殖民地大小的时间和空间变异。一个殖民地的基板类型，在研究区域的年人口规模，以及是否筑巢季节是相对温暖或凉爽，影响平均每年的殖民地规模。虽然一些崖燕殖民地网站举办常年大殖民地和其他常年小的，在大多数网站的殖民地规模的年间变化很高。年度菌落大小分布相对稳定，超过30年，并提供长期的方向变化的菌落大小的证据。唯一的生态特征，是密切相关的悬崖燕子殖民地的大小在一个网站是类型的筑巢基板，桥梁往往有更大的殖民地，更频繁地被占用比其他基板。一些网站显示，每年的变化与鸟类的基础上，他们的选择殖民地的存在或成功的同种的殖民地大小一致，但许多网站不符合预期的模式，如果殖民性是一个副产品的传统聚集。在30年的研究中，悬崖燕子的群体大小在时间和空间上都是不可预测的。解释大小变异的三个假设中的每一个都可能适用于某些地点，但菌落大小变异性的模式最支持这样的假设：对群体大小的波动选择维持了大小差异很大的菌落。
Most colonially breeding animals occupy colonies that range in size from a few pairs to thousands of individuals, but the causes of colony size variation are largely unknown. Three general hypotheses are: (1) that variation in colony size is maintained by fluctuating selection via spatial and temporal changes in fitness associated with different colony sizes; (2) that colony formation reflects heterogeneity in habitat, with some sites having resources to support more individuals than others; and (3) that individuals assess the presence or annual reproductive success of current colony residents at each site and aggregate preferentially at high-quality sites. These hypotheses make predictions about how consistent colony size should be across sites and among years. We examined temporal and spatial variability of colony size for >200 Cliff Swallow (Petrochelidon pyrrhonota) colony sites in western Nebraska across a 30-year period. A colony's substrate type, annual population size in the study area, and whether the nesting season was relatively warm or cool, influenced average annual colony size. While some Cliff Swallow colony sites hosted perennially large colonies and others perennially small ones, between-year variability in colony size at most sites was high. Annual colony size distributions were relatively stable over 30 years and provided no evidence for long-term directional changes in colony size. The only ecological characteristic that was strongly associated with Cliff Swallow colony size at a site was the type of nesting substrate, with bridges tending to have larger colonies and being more frequently occupied than other substrates. Some sites showed annual changes in colony size consistent with the birds' basing their choice of colony on the presence or success of conspecifics, but many sites did not conform to a pattern expected if coloniality is a by-product of traditional aggregation. Colony size in Cliff Swallows was temporally and spatially unpredictable when viewed across the 30 years of this study. Each of the three hypotheses to explain size variation may have applied at certain sites, but the pattern of colony size variability leant the most support to the hypothesis that fluctuating selection on group size maintains colonies of widely different sizes.