Sánchez-Galván Ingrid R, Marcos-García María Ángeles, Galante Eduardo, Azeria Ermias T, Micó Estefanía
Centro Iberoamericano de la Biodiversidad (CIBIO), Universidad de Alicante, San Vicente del Raspeig, Spain.
Alberta Biodiversity Monitoring Institute, Science Centre, University of Alberta, Edmonton AB, Canada.
Environ Entomol. 2018 Apr 5;47(2):300-308. doi: 10.1093/ee/nvy008.
Tree hollows are complex microhabitats in which a variety of abiotic and biotic factors shape the community assembly of saproxylic insects. Detecting non-random species co-occurrence patterns is a fundamental goal in ecology in order to understand the assembly mechanisms of communities. We study association patterns of species of Coleoptera and Diptera (Syrphidae), belonging to different trophic guilds, on 72 tree hollows at a local and regional scale in three protected areas in Mediterranean forests using a fixed-fixed null model. Our matrix-level analysis shows a tendency for segregation in species association (species exclusion) at the regional and site levels. However, the high complexity of tree-hollow habitats, offering different resources for a more or less specialized fauna, makes it difficult to prove competition interactions. Indeed, pairwise analysis shows a dominance of non-random aggregation patterns (species coexistence) at the local and regional levels. Both aggregation and segregation of non-random patterns were more common among species from different trophic guilds than within the same guilds, with predators being a common denominator for a high percentage of the inter-guild pairs. Our results suggest that predation and facilitation interactions, together with habitat segregation, are the main factors shaping tree-hollow assemblages, while competition seems to be less important. We conclude that species interactions take an important part of the process of assemblage structuration and special attention should be paid to 'ecosystem engineers' and threatened species in the conservation of tree hollow assemblages.
树洞是复杂的微生境，其中各种非生物和生物因素塑造了蛀木昆虫的群落组成。检测非随机的物种共现模式是生态学的一个基本目标，以便了解群落的组装机制。我们使用固定-固定零模型，在地中海森林三个保护区的局部和区域尺度上，研究了72个树洞上属于不同营养类群的鞘翅目和双翅目（食蚜蝇科）物种的关联模式。我们的矩阵水平分析表明，在区域和地点水平上，物种关联存在隔离趋势（物种排斥）。然而，树洞栖息地的高度复杂性为或多或少特化的动物群提供了不同的资源，这使得难以证明竞争相互作用。事实上，成对分析表明，在局部和区域水平上，非随机聚集模式（物种共存）占主导地位。非随机模式的聚集和隔离在不同营养类群的物种之间比在同一类群内更为常见，捕食者是高比例类群间配对的一个共同因素。我们的结果表明，捕食和促进相互作用，以及栖息地隔离，是塑造树洞群落的主要因素，而竞争似乎不太重要。我们得出结论，物种相互作用在群落结构形成过程中起着重要作用，在保护树洞群落时应特别关注“生态系统工程师”和受威胁物种。
