Rice University Academy of Fellows, Rice University, Houston, TX, USA.
Department of Biosciences, Rice University, Houston, TX, USA.
J Anim Ecol. 2018 Mar;87(2):379-387. doi: 10.1111/1365-2656.12696. Epub 2017 Jun 22.
The success of social living can be explained, in part, by a group's ability to execute collective behaviours unachievable by solitary individuals. However, groups vary in their ability to execute these complex behaviours, often because they vary in their phenotypic composition. Group membership changes over time due to mortality or emigration, potentially leaving groups vulnerable to ecological challenges in times of flux. In some societies, the loss of important individuals (e.g. leaders, elites and queens) may have an especially detrimental effect on groups' ability to deal with these challenges. Here, we test whether the removal of queens in colonies of the acorn ant Temnothorax curvispinosus alters their ability to execute important collective behaviours and survive outbreaks of a generalist entomopathogen. We employed a split-colony design where one half of a colony was maintained with its queen, while the other half was separated from the queen. We then tested these subcolonies' performance in a series of collective behaviour assays and finally exposed colonies to the entomopathogenic fungus Metarhizium robertsii by exposing two individuals from the colony and then sealing them back into the nest. We found that queenright subcolonies outperformed their queenless counterparts in nearly all collective behaviours. Queenless subcolonies were also more vulnerable to mortality from disease. However, queenless groups that displayed more interactions with brood experienced greater survivorship, a trend not present in queenright subcolonies. Queenless subcolonies that engage in more brood interactions may have had more resources available to cope with two physiological challenges (ovarian development after queen loss and immune activation after pathogen exposure). Our results indicate that queen presence can play an integral role in colony behaviour, survivorship and their relationship. They also suggest that interactions between workers and brood are integral to colonies survival. Overall, a social group's history of social reorganization may have strong consequences on their collective behaviours and their vulnerability to disease outbreaks.
群居生活的成功可以部分归因于群体执行个体无法完成的集体行为的能力。然而，不同群体在执行这些复杂行为的能力上存在差异，这通常是因为它们在表型组成上存在差异。由于死亡或移民，群体成员会随时间发生变化，这可能使群体在动荡时期容易受到生态挑战的影响。在一些社会中，重要个体（如领袖、精英和蚁后）的丧失可能对群体应对这些挑战的能力产生特别不利的影响。在这里，我们测试了在橡实蚁 Temnothorax curvispinosus 的蚁群中移除蚁后是否会改变它们执行重要集体行为和应对广谱昆虫病原体爆发的能力。我们采用了分裂殖民地设计，其中一半殖民地保留蚁后，另一半与蚁后分离。然后，我们在一系列集体行为测试中测试这些亚殖民地的表现，最后通过暴露两个来自殖民地的个体并将它们密封回巢穴来使殖民地暴露于昆虫病原真菌绿僵菌中。我们发现，有蚁后的亚殖民地在几乎所有的集体行为中都表现优于没有蚁后的亚殖民地。没有蚁后的亚殖民地也更容易受到疾病导致的死亡。然而，与幼虫有更多互动的没有蚁后的群体具有更高的存活率，这种趋势在有蚁后的亚殖民地中并不存在。与幼虫有更多互动的没有蚁后的亚殖民地可能有更多的资源来应对两个生理挑战（蚁后丧失后的卵巢发育和病原体暴露后的免疫激活）。我们的结果表明，蚁后的存在可以在群体行为、存活率及其关系中发挥不可或缺的作用。它们还表明，工蚁和幼虫之间的相互作用对于蚁群的生存至关重要。总的来说，一个社会群体的社会重组历史可能对其集体行为及其对疾病爆发的脆弱性产生强烈影响。
