Data from: Day/night upper thermal limits differ within Ectatomma ruidum ant colonies

In the tropics, daily temperature fluctuations can pose physiological challenges for ectothermic organisms, and upper thermal limits may affect foraging activity over the course of the day. Variation in upper thermal limits can occur among and within species, and for social insects such as ants, within colonies. Within colonies, upper thermal limits may differ among individuals or change for an individual throughout the day. Daytime foragers of the Neotropical ant Ectatomma ruidum have higher critical thermal maxima (CTmax) than nocturnal foragers, but whether these differences occur among or within colonies was not previously known. We investigated the potential mechanisms accounting for day/night variation in CTmax of E. ruidum foragers by testing whether CTmax varied among or within colonies or due to individuals within colonies acclimating to changes in temperature over a short time scale (3 h). We found within- but not among-colony differences in CTmax on a diel cycle, and we found no evidence for among- or within-colony partitioning of foraging times by individual workers. Individuals did not acclimate to experimental manipulations of temperature, although additional experiments with more ecologically relevant temperature manipulations are needed to rule out this mechanism. In summary, we have shown that day/night differences in upper thermal limits can occur within ant colonies, but further investigation is needed to elucidate the mechanisms driving this variation.热带地区的每日温度波动可对外温动物（ectothermic organisms）造成生理胁迫，其高温耐受上限（upper thermal limits）亦可能影响一日内的觅食活动。高温耐受上限的差异可存在于物种间与物种内部；对于蚂蚁等社会性昆虫而言，这类差异还可存在于蚁群内部。在蚁群内部，不同个体间的高温耐受上限可能存在差异，单个个体的耐受上限也可能在一日内发生变化。新热带区蚂蚁Ectatomma ruidum的日间觅食工蚁，其临界热最大值（critical thermal maxima，CTmax）高于夜行觅食工蚁，但此前尚不明确该差异究竟存在于蚁群间还是蚁群内部。本研究围绕E. ruidum觅食工蚁的CTmax昼夜差异的潜在机制展开探究，通过检验CTmax是否存在蚁群间差异、蚁群内部差异，或是蚁群内个体是否会在短时间尺度（3小时）内适应温度变化，以此开展相关研究。研究结果显示，在昼夜周期内，CTmax仅存在蚁群内部的差异，而非蚁群间的差异；同时未发现证据表明工蚁个体在蚁群间或蚁群内部会按照觅食时间进行分工。个体并未对温度的实验操控产生适应，尽管仍需开展更多具备更高生态相关性的温度操控实验，方能排除这一适应机制的可能性。综上，本研究证实蚂蚁蚁群内部可存在高温耐受上限的昼夜差异，但仍需进一步研究以阐明驱动该差异的内在机制。