Data from: Testing trade-offs and the dominance-impoverishment rule among ant communities

Aim: Ant communities are believed to be structured by competition, with dominant species competitively excluding subordinates (the dominance-impoverishment rule). However, a high number of seemingly similar species coexist, possibly due to interspecific trade-offs. Here, we examine the evidence for the dominance-impoverishment rule across a broad latitudinal gradient and explore whether trade-offs explain coexistence within and among ant communities. Location: 40 sites in 19 countries across Europe, western North America and northern South America. Taxon: Formicidae. Methods: We conducted 2-h baiting experiments at each site. Three dominance scores were calculated for each species at each site where it occurred. We then examined the relationship between ant dominance and diversity and tested for the generality of three trade-offs (dominance-discovery, dominance-thermal tolerance and dominance-generalism) within and among ant communities along with the possible effects of environmental variables on these trade-offs. Results: We found no support for the dominance-impoverishment rule. Instead, overall species richness at baits was positively correlated with the number of dominant species and exhibited a unimodal relationship with the relative abundance of dominant ants. Moreover, we found little consistent evidence for the three interspecific trade-offs. Main conclusion: Although total species richness at baits is positively correlated with species richness of dominant species and, to a point, increasing worker numbers of dominants, trade-offs among species do not appear to shape broad-scale patterns of coexistence among ants. Species richness declines only when the numbers of dominant workers are very high. Together, these results suggest that while trade-offs and the dominance impoverishment rule might promote coexistence or shape ant communities in some locations, the evidence for their being general across communities is scant.研究目的：学界普遍认为蚂蚁群落由竞争作用塑造，优势物种通过竞争排除从属物种（即优势种-贫瘠化法则（dominance-impoverishment rule））。然而，大量形态相似的物种能够实现共存，这一现象可能源于物种间的权衡策略。本研究旨在验证跨广泛纬度梯度下的优势种-贫瘠化法则是否成立，并探讨种间权衡能否解释蚂蚁群落内部及群落间的物种共存机制。 研究区域：覆盖欧洲、北美西部与南美北部的19个国家，共设置40个采样位点。 研究类群：蚁科（Formicidae）。 研究方法：在每个采样位点开展2小时的诱饵诱集实验。针对在该位点出现的每个蚁种，计算三种优势度得分。随后，我们分析了蚂蚁优势度与物种多样性之间的关联，检验了三种种间权衡（优势度-发现能力、优势度-热耐受性以及优势度-泛化性）在群落内部及群落间的普适性，同时探究了环境变量对这些权衡关系的潜在影响。 研究结果：未发现支持优势种-贫瘠化法则的证据。与之相反，诱饵样方中的总物种丰富度与优势物种数量呈正相关，且与优势蚂蚁的相对多度呈现单峰关系。此外，几乎未找到支撑上述三种种间权衡的一致性证据。 主要结论：尽管诱饵样方中的总物种丰富度与优势物种丰富度呈正相关，且在一定范围内，优势工蚁数量的增加会提升物种丰富度，但物种间的权衡似乎并未塑造蚂蚁群落跨大尺度的物种共存格局。仅当优势工蚁数量极高时，物种丰富度才会出现下降。综上，尽管种间权衡与优势种-贫瘠化法则或许能在局部区域促进物种共存或塑造蚂蚁群落结构，但相关证据在群落尺度上的普适性十分有限。