The importance of direct fitness for helpers in advanced insect societies

自私个体之间的合作和利他行为的演变长期以来一直困扰着生物学家。汉密尔顿·S的包容性健康理论解释说，帮助者在帮助繁育亲戚并通过他们帮助增加后代数量时，可以获得间接的健康益处。此外，群居哺乳动物和鸟类中的帮助者可以通过接管鸟巢或领地的繁殖位置或通过提高它们的育儿技能来获得直接的健康，这将使它们自己的后代受益。但是，这种直接的健身益处在蚂蚁等先进的社会社会中也很重要吗？工人的行为表明，他们是这样做的。许多蚂蚁物种的工蚁可以从未受精卵中繁殖出雄性蚂蚁，但通常不会在蚁后面前这样做。然而，在女王去世后，工蚁建立了社会和生殖等级秩序，只有最高级别的工蚁才会产卵。此外，在社会上占主导地位的工蚁避免了代价高昂的任务，如觅食和群体防御。这表明，员工的目标是保留获得直接健身的选项，但自私是否会带来回报，从来没有量化过。在这个项目中，我们将通过第一次估计野生群居昆虫种群中的工蚁直接适合度来填补我们对优势性理解的这一重要空白。为此，我们将通过野外普查和对雄性蚂蚁母体的遗传分析来确定工蚁群体中工蚁繁殖的丰度。此外，我们将通过受控繁殖实验和测量精子数量和存活率来确定工蜂和蜂后产生的雄性在健康特征上是否存在差异。最后，通过操纵群体组成，我们将检验工人的自私是否会对群体凝聚力和生产力造成代价。该项目建立在对粗毛虫的广泛先导研究的基础上。它从正在进行的关于包容性适合度和亲缘选择的价值的激烈讨论中获得了额外的现实性，并将导致对高级群居昆虫维持优势性的更全面的理解。

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.