The importance of direct fitness for helpers in advanced insect societies

自私个体之间合作和利他行为的进化长期以来一直困扰着生物学家。汉密尔顿的包容性适应性理论解释说，帮助者可以获得间接的适应性好处，当他们帮助繁殖亲属，并通过他们的帮助增加其后代的数量。此外，群居哺乳动物和鸟类中的帮手可以通过接管巢穴或领地中的繁殖位置或通过提高它们的育雏技能来获得直接的适应性，这随后会使它们自己的后代受益。但是，这种直接的适应性益处在先进的真社会主义社会（如蚂蚁）中也重要吗？工人的行为表明他们是。许多种类的工蚁可以从未受精的卵中产生雄性，但通常不会在女王面前这样做。然而，在女王死后，工蜂建立了社会和生殖等级秩序，只有最高等级的工蜂产卵。此外，社会主导的工人避免昂贵的任务，如觅食和殖民地防御。这表明，工人的目标是保留获得直接健身的选择，但自私是否有回报从未被量化。在这个项目中，我们将填补这个重要的空白，我们的理解eusociality的第一次估计工人直接健身在野生社会昆虫种群。要做到这一点，我们将确定丰富的工人繁殖的Temnothorax crassispinus蚂蚁殖民地的人口普查在外地和遗传分析的母性的男性。此外，我们将通过控制育种实验和测量精子数量和活力来确定工蜂和蜂后产生的雄性在健身性状上是否不同。最后，通过操纵群体的组成，我们将研究工人的自私是否有成本的群体凝聚力和生产力。该项目建立在T.厚棘的它从正在进行的关于包容性适应度和亲属选择的价值的热烈讨论中获得了额外的现实性，并将导致对高级社会性昆虫的真社会性维持的更完整的理解。

The evolution of cooperation and altruistic behavior among selfish individuals has long puzzled biologists. Hamilton s theory of inclusive fitness explains that helpers can gain indirect fitness benefits when they assist a breeding relative and through their help increase the number of its offspring. In addition, helpers in group-living mammals and birds can gain direct fitness through taking over the breeding position in the nest or territory or through improving their brood care skills, which later benefits their own offspring. But are such direct fitness benefits also important in advanced eusocial societies, such as ants? The behavior of workers suggests that they are. Workers of many ant species can produce males from unfertilized eggs, but usually refrain from doing so in the presence of the queen. After the death of the queen, however, workers establish social and reproductive rank orders and only the top-ranking workers lay eggs. Furthermore, socially dominant workers refrain from costly tasks, such as foraging and colony defense. This suggests that workers aim to retain the option of obtaining direct fitness, but whether selfishness pays off has never been quantified. In this project we will fill this important gap in our understanding of eusociality by for the first time estimating worker direct fitness in a wild social insect population. To do so we will determine the abundance of worker reproduction in colonies of Temnothorax crassispinus ants by censuses in the field and by genetic analyses of the maternity of males. In addition, we will determine whether worker-and queen-produced males differ in fitness traits through controlled breeding experiments and measuring sperm quantity and viability. Finally, through manipulation of colony composition we will examine whether worker selfishness has a cost for colony cohesiveness and productivity. The project builds on extensive pilot studies in T. crassispinus. It receives additional actuality from the ongoing heated discussion about the value of inclusive fitness and kin selection and will lead to a more complete understanding of the maintenance of eusociality in advanced social insects.