Assembly patterns of mixed-species avian flocks in the Andes

The relative contribution of deterministic and stochastic processes in the assembly of biotic communities is a central issue of controversy in community ecology. However, several studies have shown patterns of species segregation that are consistent with the hypothesis that deterministic factors such as competition and niche-partitioning structure species assemblages in animal communities. Community assembly provides a theoretical framework for understanding these processes, but it has been seldom applied to social aggregations within communities. In this research we assessed patterns of non-randomness in Andean mixed-species flocks using three assembly models: (a) co-occurrence patterns (b) guild proportionality; and (c) constant body-size ratios using data from 221 species of resident and Neotropical migrant birds participating in 311 mixed-species flocks at 13 regions distributed in Venezuela, Colombia, Ecuador, and Peru. Significant assembly patterns for mixed-species flocks based o...确定性过程与随机过程在生物群落构建中的相对贡献，是群落生态学领域长期存在的核心争议议题。不过，已有多项研究揭示了物种分隔格局，该格局与“竞争、生态位分化等确定性因素可塑造动物群落的物种组合”这一假说相符。群落构建理论为理解此类过程提供了理论框架，但该理论极少被应用于群落内社会聚集群体的相关研究。本研究采用三类群落构建模型，对安第斯山鸟类混群的非随机格局进行评估，具体模型包括：(a) 共现格局；(b) 功能群比例；(c) 恒定体型比。研究所用数据来自分布于委内瑞拉、哥伦比亚、厄瓜多尔及秘鲁的13个研究区域内的311个混群，涉及221种留鸟与新热带区迁徙鸟类。