Data from: Genetic constraints on dishonesty and caste dimorphism in an ant

The ultimate causes of honest signaling remain a subject of debate, with questions remaining over the relative importance of costs and constraints. Signal costs may make dishonesty prohibitively expensive, while genetic constraints could make it impossible. We investigated honest signaling using full-sib analysis and parent-offspring regression in the ant Lasius niger, in which queens produce a cuticular hydrocarbon-based pheromone that signals fertility and inhibits worker reproduction and aggression. We found multiple lines of evidence that cuticular hydrocarbon production is genetically correlated with oogenesis and that the queen pheromone 3-methylhentriacontane and other 3-methylalkanes have strong genetic links with fertility relative to other cuticular hydrocarbons. These genetic correlations may maintain honesty in the face of directional selection on signaling and explain the putatively widespread use of cuticular hydrocarbons in fertility signaling across the social insects. We also found evidence for a positive genetic correlation for fertility between the castes; that is, the most fertile queens produced especially fertile workers. These results highlight that intercaste genetic correlations could constrain the evolution of queen-worker dimorphism, such that worker reproduction may sometimes reflect a nonadaptive “caste load” rather than positively selected cheating.诚实信号传递的终极成因至今仍是学界争论的焦点，关于成本与限制因素的相对重要性仍存在诸多未解疑问。信号成本可令欺骗行为的代价高到难以承受，而遗传限制则可能使欺骗完全无法实现。本研究以黑毛蚁（Lasius niger）为实验对象，采用全同胞分析（full-sib analysis）与亲子回归（parent-offspring regression）方法探究诚实信号传递机制：该蚁类的蚁后会分泌基于表皮碳氢化合物（cuticular hydrocarbon）的信息素（pheromone），用以传递自身产卵力信号，并抑制工蚁的繁殖行为与攻击行为。本研究获得多项证据表明，表皮碳氢化合物的产生与卵子发生（oogenesis）存在遗传相关性；且相较于其他表皮碳氢化合物，蚁后信息素成分3-甲基三十一烷（3-methylhentriacontane）与其他3-甲基烷烃（3-methylalkanes）与产卵力的遗传关联更为显著。这类遗传相关性可在信号传递受到定向选择（directional selection）的压力下维持信号的诚实性，同时也解释了为何表皮碳氢化合物据推测在社会性昆虫（social insects）的产卵力信号传递中被广泛应用。此外，本研究还发现不同品级（caste）间的产卵力存在正向遗传相关性：即产卵力最强的蚁后，其产下的工蚁繁殖能力也尤为突出。本研究结果表明，品级间的遗传相关性可能会限制蚁后与工蚁的形态二态性（dimorphism）演化，因此工蚁的繁殖行为有时可能反映的是一种非适应性的“品级负荷（caste load）”，而非受正向选择青睐的欺骗行为。