School of Life Sciences, Arizona State University, Tempe, AZ, USA.
Sci Rep. 2021 Apr 15;11(1):8332. doi: 10.1038/s41598-021-87797-5.
The fitness consequences of cooperation can vary across an organism's lifespan. For non-kin groups, especially, social advantages must balance intrinsic costs of cooperating with non-relatives. In this study, we asked how challenging life history stages can promote stable, long-term alliances among unrelated ant queens. We reared single- and multi-queen colonies of the primary polygynous harvester ant, Pogonomyrmex californicus, from founding through the first ten months of colony growth, when groups face high mortality risks. We found that colonies founded by multiple, unrelated queens experienced significant survival and growth advantages that outlasted the colony founding period. Multi-queen colonies experienced lower mortality than single-queen colonies, and queens in groups experienced lower mortality than solitary queens. Further, multi-queen colonies produced workers at a faster rate than did single-queen colonies, even while experiencing lower per-queen worker production costs. Additionally, we characterized ontogenetic changes in the organization of labor, and observed increasing and decreasing task performance diversity by workers and queens, respectively, as colonies grew. This dynamic task allocation likely reflects a response to the changing role of queens as they are increasingly able to delegate risky and costly tasks to an expanding workforce. Faster worker production in multi-queen colonies may beneficially accelerate this behavioral transition from a vulnerable parent-offspring group to a stable, growing colony. These combined benefits of cooperation may facilitate the retention of multiple unrelated queens in mature colonies despite direct fitness costs, providing insight into the evolutionary drivers of stable associations between unrelated individuals.
合作的健康后果可能因生物体的寿命而异。对于非亲属群体来说，特别是社会优势必须平衡与非亲属合作的内在成本。在这项研究中，我们询问了生命史阶段的挑战性如何促进无关蚁后的稳定、长期联盟。我们从蚁群建立到生长的前十个月（此时群体面临高死亡率），单独饲养和多蚁后饲养主要多态性收获蚁 Pogonomyrmex californicus 的单蚁后和多蚁后蚁群。我们发现，由多个无关蚁后建立的蚁群经历了显著的生存和生长优势，这些优势持续到蚁群建立时期之后。多蚁后蚁群的死亡率低于单蚁后蚁群，而群体中的蚁后死亡率低于独居蚁后。此外，多蚁后蚁群的工蚁繁殖速度比单蚁后蚁群快，即使它们经历的每只蚁后工蚁生产成本较低。此外，我们还描述了劳动组织的个体发育变化，并观察到随着蚁群的生长，工蚁和蚁后分别表现出劳动任务多样性的增加和减少。这种动态的任务分配可能反映了蚁后角色的变化，因为它们越来越能够将风险和成本高的任务委托给不断扩大的劳动力。多蚁后蚁群中工蚁的快速繁殖可能有助于从脆弱的亲代-后代群体向稳定、成长的蚁群进行这种行为转变。合作的这些综合益处可能有助于在成熟蚁群中保留多个无关的蚁后，尽管存在直接的适合度成本，从而为无关个体之间稳定关联的进化驱动力提供了深入了解。
