Interspecific aggression may shape species distributions through competitive exclusion, resulting in spatial segregation, or facilitate sympatry as an adaptive mechanism for resource partitioning. Competitive exclusion results from asymmetric aggression of one species towards another, but if the aggressive relationship between species is symmetric, they may persist in sympatry. Interspecific aggression is widely cited as a mechanism for maintaining the distributional limits of tropical birds, but how it shapes the spatial dynamics of competing species that are sympatric over larger geographic areas is less clear. To address this issue, we conducted reciprocal playback experiments on two congeneric Antbirds — Thamnophilus atrinucha and T. doliatus — that occur in sympatry across a habitat matrix in Colombia to characterize their relationship as symmetrically or asymmetrically aggressive and analyzed point count data to assess the degree to which they occur sympatrically. We found weak evidence for competitive exclusion, with the larger T. doliatus responding asymmetrically to T. atrinucha, and the two species having a low co-detection rate during point counts. However, despite their 22% difference in body size, T. atrinucha still responded to T. doliatus playback in over half of our trials, and the two species co-occurred on nearly 25% of point counts, indicating that interspecific aggression does not drive complete spatial segregation. Our findings highlight how the degree to which one species can competitively exclude another may vary, especially across a dynamic landscape.

中文翻译：

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同属热带鸟类交感中的种间攻击

种间侵略可能通过竞争排斥来塑造物种分布，导致空间隔离，或促进同源性作为资源分配的适应性机制。竞争排斥是由一个物种对另一个物种的不对称攻击引起的，但如果物种之间的攻击关系是对称的，它们可能会持续存在同源性。种间攻击被广泛认为是维持热带鸟类分布限制的一种机制，但它如何塑造在更大地理区域上同域的竞争物种的空间动态尚不清楚。为了解决这个问题，我们对两种同类蚁鸟——Thamnophilus atrinucha 和 T. doliatus——在哥伦比亚的一个生境矩阵中出现，以将它们的关系描述为对称或不对称的侵略性，并分析了点计数数据，以评估它们出现的程度。我们发现竞争排斥的证据不足，较大的 T. doliatus 对 T. atrinucha 的反应不对称，并且这两个物种在点计数期间的共同检测率较低。然而，尽管它们的体型差异 22%，T. atrinucha 在我们超过一半的试验中仍然对 T. doliatus 播放有反应，并且这两个物种在近 25% 的点数上同时出现，表明种间攻击不会驱动完全的空间隔离。我们的研究结果强调了一个物种竞争性排除另一个物种的程度可能会有所不同，尤其是在动态景观中。