Abstract

Insectivorous birds reach their highest diversity in the tropics and represent a striking variety of morphological and behavioral specializations for foraging, yet explanations for these patterns are inadequate because of both our limited understanding of the drivers of ecological diversification within and among clades and of coexistence mechanisms in particular. Here we synthesize recent information on Neotropical insectivorous birds, including their diversity, evolutionary ages and locations of origin, phylogenies, and both competitive and predator–prey species interactions. We propose a novel evolutionary hypothesis for the origin and coexistence of the phenotypic diversity of insectivore foraging morphologies in species-rich communities, based on their extraordinary food-resource specializations. Specifically, we develop the Biotic Challenge Hypothesis to explain the evolution of these specializations, and we provide preliminary evidence in support of this hypothesis based on a synopsis of both Neotropical insectivore specializations by family and arthropod antipredator adaptations by category. We argue that, from the perspective of tropical insectivorous birds, and particularly in the most species-rich, mainland Neotropical communities, the environment is an arthropod desert. Coexistence with all of the other insectivores requires feeding specialization to compete exploitatively and diffusely against evolutionarily diverse species and far less frequently against sister species. The arthropod desert arises primarily because of (1) the tactical diversity of arthropod predators as insectivore competitors and (2) the evolutionary arms races involving arthropod predators with their prey, which render many arthropods inaccessible to most insectivorous predators. Our idea provides an explicit mechanism for pervasive, diffuse tropical interspecific competition, for evolutionary specialization, and for positive feedback on speciation rates at low latitudes, thereby generating new predictions and insights into tropical life histories and the Latitudinal Diversity Gradient. Other recent ideas concerning the coexistence of Neotropical insectivores, including positive species interactions within mixed species flocks, are recognized and evaluated. We discuss ways to test predictions resulting from the new view of communities developed here, including a case study of diet specialization by Costa Rican tyrannid flycatchers. Our synthesis of the origin and nature of Neotropical insectivore communities injects new life into the “zombie” idea that evolution works differently in the species-rich tropics.

中文翻译：

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新热带地区的食虫鸟类：物种丰富的社区中的生态辐射，专业化和共存

摘要

食虫鸟类在热带地区达到最高的多样性，代表了觅食的形态学和行为学专业领域的惊人变化，但是由于我们对进化枝内部和进化枝之间的生态多样化驱动力以及共存机制的了解有限，因此无法对这些模式进行解释。特定。在这里，我们综合了有关新热带食虫鸟的最新信息，包括它们的多样性，进化年龄和起源位置，系统发育以及竞争性和捕食者与猎物之间的相互作用。我们基于物种非凡的食物资源专业化提出食虫食性觅食形态表型多样性的起源和共存的新的进化假设。特别，我们开发了生物挑战假说来解释这些专业的演变，并基于按族群划分的新热带食虫动物专业和按节肢动物反捕食者改编的概要提供了支持这一假说的初步证据。我们认为，从热带食虫鸟类的角度来看，尤其是在物种最丰富的大陆新热带大陆社区中，环境是一种节肢动物沙漠。与所有其他食虫动物共存需要饲料专门化以与进化上多样化的物种进行竞争性地扩散和竞争，而与姐妹物种的竞争则很少。节肢动物沙漠的产生主要是由于（1）节肢动物食虫动物作为食虫动物竞争者的战术多样性，以及（2）涉及节肢动物食肉动物及其猎物的进化军备竞赛，这使得大多数节肢动物食虫动物无法进入节肢动物。我们的想法为广泛的，分散的热带种间竞争，进化的专业化以及低纬度物种形成率的积极反馈提供了一个明确的机制，从而为热带生活史和纬度多样性梯度提供了新的预测和见识。有关新热带食虫动物并存的其他最新观点，包括混合物种群内的积极物种相互作用，也得到了认可和评估。我们讨论了测试根据此处开发的社区新观点得出的预测的方法，包括哥斯达黎加暴君捕蝇器对饮食专门化的案例研究。我们对新热带食虫动物群落的起源和性质的综合研究为“僵尸”思想注入了新的活力，这种思想在物种丰富的热带地区进化作用不同。