Complex relationship between tunneling patterns and individual behaviors in termites

The nests built by social insects are complex group-level structures that emerge from interactions among individuals following simple behavioral rules. Nest patterns vary among species, and the theory of complex systems predicts that there is no simple one-to-one relationship between variations in collective patterns and variation in individual behaviors. Therefore, a species-by-species comparison of the actual building process is essential to understand the mechanism producing diverse nest patterns. Here we compare tunnel formation of three termite species, and reveal two mechanisms producing interspecific variation: in one, a common behavioral rule yields distinct patterns via parameter-tuning; in the other, distinct rules produce similar patterns. We found that two related species transport sand in the same way using mandibles but build tunnels with different degree of branching. The variation arises from different probabilities of choosing between two behavioral options at crowded tunnel faces: excavating the sidewall to make a new branch or waiting for clearance to extend the current tunnel. We further discovered that a third species independently evolved low-branched patterns using different building rules; namely a bucket-brigade that can excavate a crowded tunnel. Our findings emphasize the importance of direct comparative study of collective behaviors at both individual- and group-levels.

Methods
All data is collected through image analysis and video analysis. See the method section of the paper and readme.txt.

社会性昆虫构筑的巢穴是复杂的群体层级结构，其形成源于个体间遵循简单行为规则的协同交互。不同物种的巢穴模式存在显著差异，而复杂系统理论预测，集体模式的变异与个体行为的变异之间并不存在简单的一一对应关系。因此，针对实际构筑过程开展跨物种比较研究，是解析多样巢穴模式产生机制的必要前提。
本研究对3种白蚁的隧道构筑过程进行了比较分析，揭示了两种导致种间模式差异的核心机制：其一，同一通用行为规则可通过参数调节产生截然不同的巢穴模式；其二，不同的行为规则可产生相似的巢穴模式。
研究发现，两种亲缘关系较近的白蚁物种虽均通过颚部以相同方式搬运沙粒，但其构筑的隧道分支程度却存在显著差异。这种变异源于拥挤隧道端面处，个体在两种行为选项间的选择概率不同：要么开挖侧壁以开辟新分支，要么等待通道畅通后延伸当前隧道。
本研究进一步发现，第三种白蚁物种独立演化出了低分支的隧道构筑模式，其采用了不同的构筑规则——即一种可用于开挖拥挤隧道的桶链式（bucket-brigade）作业机制。
本研究结果凸显了同时从个体与群体层级开展集体行为直接比较研究的重要性。

研究方法
所有数据均通过图像分析与视频分析采集获取。详见论文的方法章节及readme.txt文件。