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（honest signaling）的终极成因始终是学界争论的核心议题，关于信号代价与遗传约束的相对重要性仍存在诸多未决问题。信号代价可令欺骗行为变得高昂到难以承受，而遗传约束则可能使欺骗完全无法实现。我们以黑毛蚁（Lasius niger）为研究对象，采用全同胞分析（full-sib analysis）与亲子回归（parent-offspring regression）方法开展研究：该物种的蚁后会分泌基于表皮碳氢化合物（cuticular hydrocarbon）的信息素，用以传递自身生育能力信号，并抑制工蜂的繁殖行为与攻击行为。我们发现多项证据表明，表皮碳氢化合物的合成与卵子发生（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3-甲基三十一烷（3-methylhentriacontane）与其他3-甲基烷烃（3-methylalkanes）与生育能力的遗传关联更为显著。这类遗传相关或许能在信号受到定向选择（directional selection）的情境下维持信号的诚实性，同时也解释了社会性昆虫中被认为广泛存在的、基于表皮碳氢化合物的生育信号使用现象。我们还观察到不同品级（caste）间的生育能力存在正向遗传相关：即生育能力最强的蚁后，其所培育的工蜂往往也具有更强的生育能力。本研究结果凸显，品级间的遗传相关可能会约束蚁后-工蜂二态性（queen-worker dimorphism）的演化进程，这意味着工蜂的繁殖行为有时或许并非经正向选择的适应性欺骗行为，而是一种非适应性的‘品级负荷（caste load）’。