Data for ant dominance and bi-stability

This data set includes the per plant proportion of baits (out of 5) occupied by various species of ants. It also includes the distance of the plants to the central Azteca sericeasur nest.These data set is used to analyze a system of diffuse competition in an ant community in a tropical coffee landscape in southern Mexico. The community is constrained by space in that the dominant competitor (Azteca seriaceasur) has a limited range of influence within which it excludes most other species, but outside that range, the other species may all persist. We use a simple dynamic model in which variable A, the dominant competitor, competes strongly with variable S, the collection of all other species in the system, the latter acting as a single strong competitor in the context of diffuse competition. Two qualitatively distinct outcomes are expected depending on the strength of competition: 1) a simple monotonic increase in species richness as the distance from the Azteca nest increases or 2) a range of distance from the nest in which there is bi-stability (either A dominates or S dominates), bookended by critical transitions. Studying five specific nests in wet and dry seasons over a two-year period, we find evidence for the bi-stability situation. Implications for metacommunity structure are discussed.

本数据集统计了单株植物上5个诱饵中，各蚂蚁物种所占据的诱饵比例，同时收录了各植株与核心Azteca sericeasur蚁巢之间的距离。本数据集被用于解析墨西哥南部热带咖啡种植园景观中蚂蚁群落内的弥散竞争 (diffuse competition) 系统。该蚂蚁群落受空间约束：优势竞争者Azteca sericeasur的影响范围有限，在此范围内它会排斥绝大多数其他蚂蚁物种；而在其影响范围之外，其余物种均可存续。本研究采用一款简易动态模型：其中变量A代表优势竞争者，它与代表系统内所有其余蚂蚁物种集合的变量S存在强烈竞争关系；在弥散竞争的框架下，后者可被视为单一的强劲竞争者。根据竞争强度的不同，可得到两种性质迥异的预期结果：其一，随着与Azteca sericeasur蚁巢的距离增加，物种丰富度呈单调递增趋势；其二，在距蚁巢的某一段距离范围内存在双稳态 (bi-stability)——要么A占据主导，要么S占据主导，该范围两端以临界转变为界。本研究在两年周期内，于湿季与旱季对5个特定蚁巢展开调研，结果找到了支持双稳态情形的证据。本研究还探讨了该结果对集合群落 (metacommunity) 结构的启示意义。