Interplays between Atta ants (Formicidae: Attini), soils and environmental properties in the Brazilian Neotropics: a preliminary assessment

ABSTRACT Leaf-cutting ants are the most important herbivore in the neotropics, represent active agents of pedobioturbation, and are regarded as ecosystem engineers. These ants have a wide variety of ecological functions, such as pollination, seed dispersal, and tree-growing control. Despite this importance, little is known on their distribution in relation to possible soil and environmental conditions that affect Atta ants occurrence. This study aimed to spatialize the main occurrences of Atta species in the Brazilian territory and evaluate the main environmental conditions driving ants species in the Brazilian tropical landscapes, at a preliminary basis. We compiled data of occurrence for 12 Atta species from Global Biodiversity Information Facility (GBIF) databases, and scientific literature (up to 2019) for each Atta species. To each point, we obtained the respective geoenvironmental data as soil properties, biome, geology, vegetation land use, and climate variables. From these data, possible zonalities of occurrence of 9/10 Atta species were discussed. We applied the principal components analysis (PCA) and Canonical Correspondence Analysis (CCA) to identify the environmental gradient and investigate the possible interplay between variables and species. Soil, vegetation, and land use attributes are the main drivers on the distribution of Atta at local scale where their evolutionary physiological and foraging adaptations allow them to nest and maintain the fungi culture. At broader scales, climatic attributes are key drivers of Atta distribution across Brazil, and also influence pedogenic processes. Our study demonstrates that species of Atta ants are not randomly dispersed in Brazil and are strongly associated with complex and diverse Brazilian landscapes. We remark that further studies on the distribution of leaf-cutting ants of the Atta genus in Brazil, as well as their evolutionary phylogenetics, are needed, based on larger database.

摘要：切叶蚁(Leaf-cutting ants)是新热带区最重要的草食性昆虫，既是活跃的土壤生物扰动因子，也被视为生态系统工程师。该类蚂蚁拥有多样的生态功能，包括传粉、种子传播以及林木生长调控。尽管其生态重要性突出，但目前学界对阿塔切叶蚁属(Atta)的分布与影响其出现的潜在土壤及环境条件的关联认知仍十分有限。本研究旨在初步完成巴西境内阿塔切叶蚁属主要物种的分布空间化制图，并解析驱动巴西热带景观中该类蚂蚁物种分布的核心环境条件。我们从全球生物多样性信息设施(GBIF)数据库及截至2019年的相关科学文献中，收集了12种阿塔切叶蚁的物种出现记录数据。针对每一条记录点位，我们获取了对应的地理环境数据，包括土壤属性、生物群区、地质条件、植被与土地利用类型以及气候变量。基于上述数据，我们探讨了10种阿塔切叶蚁中9种的潜在分布地带性。本研究采用主成分分析(PCA)与典范对应分析(CCA)，以识别环境梯度并探究变量与物种间的潜在相互作用。在局域尺度上，土壤、植被与土地利用属性是阿塔切叶蚁分布的核心驱动因子——这与其进化生理及觅食适应性使其能够筑巢并维持真菌培养体系密切相关。而在更大空间尺度上，气候属性是巴西境内阿塔切叶蚁分布的关键驱动因子，同时也会影响成土过程。本研究表明，巴西境内的阿塔切叶蚁物种并非随机分布，而是与复杂多样的巴西景观存在显著关联。我们指出，未来需基于更大规模的数据库，开展针对巴西境内阿塔切叶蚁属切叶蚁的分布及其进化系统发育学的深入研究。