Couchoux Christelle, Field Jeremy
Centre for Ecology & Conservation, University of Exeter, Penryn campus, Penryn, Cornwall, TR10 9FE UK.
Behav Ecol Sociobiol. 2019;73(3):36. doi: 10.1007/s00265-019-2646-3. Epub 2019 Feb 25.
Maternal effects should be especially likely when mothers actively provision offspring with resources that influence offspring phenotype. In cooperatively breeding and eusocial taxa, there is potential for parents to strategically manipulate offspring phenotype in their own interests. Social insect queens are nearly always larger than their worker offspring, and queens could benefit by producing small daughter workers in several ways. If queens use aggression to dominate or coerce workers, a queen producing small workers might minimize potential conflict or competition from her offspring. In addition, because of the trade-off between the number of workers she is able to produce and their individual size, a queen may produce small workers to optimize colony work effort. In this study, we investigate why queens of the primitively eusocial paper wasp limit the size of their workers. We created queen-worker size mismatches by cross-fostering queens between nests. We then tested whether the queen-worker size difference affects worker foraging and reproductive effort, or the amount of aggression in the group. Some of our results were consistent with the idea that queens limit worker size strategically: small workers were no less successful foragers, so that producing a larger number of smaller workers may overall increase queen fitness. We found that queens were less likely to attack large workers, perhaps because attempting to coerce large workers is riskier. However, larger workers did not forage less, did not invest more in ovarian development, and were not more aggressive themselves. There was therefore little evidence overall that queens limit conflict by producing smaller workers.
In social animals, parents might manipulate phenotypic traits of their offspring in their own interests. In paper wasps (), the first offspring produced are smaller than the queen and become workers: instead of founding their own nests, they stay and help their mother to rear new queens and males. We investigated whether queens could benefit by producing small daughter workers by using cross-fostering to create size mismatches between queens and their offspring. We then recorded foraging activity, reproductive effort, and aggression on nests. Queens were less likely to attack larger workers, but overall, there was limited evidence of size-based queen-worker conflict. However, because small workers were no less successful foragers, producing a larger number of smaller workers may optimize colony work effort.
当母亲主动为后代提供影响其表型的资源时，母体效应应该尤其显著。在合作繁殖和群居性类群中，父母有可能出于自身利益而策略性地操纵后代的表型。社会性昆虫的蚁后几乎总是比它们的工蚁后代体型更大，蚁后通过产下体型小的雌性工蚁可能会在几个方面受益。如果蚁后利用攻击性来支配或胁迫工蚁，那么产下体型小的工蚁的蚁后可能会将来自其后代的潜在冲突或竞争降至最低。此外，由于在她能够产生的工蚁数量与其个体大小之间存在权衡，蚁后可能会产下体型小的工蚁以优化蚁群的工作效率。在本研究中，我们探究了为什么原始群居性胡蜂的蚁后会限制其工蚁的体型。我们通过在巢穴间交叉寄养蚁后制造了蚁后与工蚁的体型不匹配。然后我们测试了蚁后与工蚁的体型差异是否会影响工蚁的觅食和繁殖努力，或者群体中的攻击量。我们的一些结果与蚁后策略性地限制工蚁体型这一观点一致：体型小的工蚁在觅食方面同样成功，因此产下数量更多的体型较小的工蚁总体上可能会提高蚁后的适应性。我们发现蚁后攻击体型大的工蚁的可能性较小，也许是因为试图胁迫体型大的工蚁风险更大。然而，体型大的工蚁觅食并不更少，在卵巢发育上投入也不多，而且它们自身也并不更具攻击性。因此，总体上几乎没有证据表明蚁后通过产下体型较小的工蚁来限制冲突。
在群居动物中，父母可能会出于自身利益操纵其后代的表型特征。在胡蜂中，第一批产生的后代比蚁后体型小并成为工蚁：它们不是建立自己的巢穴，而是留下来帮助它们的母亲养育新的蚁后和雄蜂。我们通过交叉寄养以在蚁后与其后代之间制造体型不匹配，来研究蚁后产下体型小的雌性工蚁是否能从中受益。然后我们记录了巢穴上的觅食活动、繁殖努力和攻击行为。蚁后攻击体型较大的工蚁的可能性较小，但总体而言，基于体型的蚁后与工蚁冲突的证据有限。然而，由于体型小的工蚁在觅食方面同样成功，产下数量更多的体型较小的工蚁可能会优化蚁群的工作效率。
