Data from: Female ornamentation and the fecundity trade-off in a sex-role reversed pipefish

Sexual ornaments found only in females are a rare occurrence in nature. One explanation for this is that female ornaments are costly to produce and maintain and, therefore, females must trade-off resources related to reproduction to promote ornament expression. Here, we investigate whether a trade-off exists between female ornamentation and fecundity in the sex-role reversed, wide-bodied pipefish, Stigmatopora nigra. We measured two components of the disk-shaped, ventral-striped female ornament, body width and stripe thickness. After controlling for the influence of body size, we found no evidence of a cost of belly width or stripe thickness on female fecundity. Rather, females that have larger ornaments have higher fecundity and thus accurately advertise their reproductive value to males without incurring a cost to fecundity. We also investigated the relationship between female body size and egg size and found that larger females suffered a slight decrease in egg size and fecundity, although this decrease was independent of female ornamentation. More broadly, considered in light of similar findings in other taxa, lack of an apparent fecundity cost of ornamentation in female pipefish underscores the need to revisit theoretical assumptions concerning the evolution of female ornamentation.

仅雌性个体拥有的性装饰（sexual ornaments）在自然界中实属罕见。对此的一种主流解释为：雌性装饰的产生与维持需付出高昂成本，因此雌性必须在繁殖相关的资源分配上进行权衡，以支撑装饰结构的表达。本研究以性角色反转的宽体海龙（Stigmatopora nigra）为研究对象，旨在探究雌性装饰与繁殖力之间是否存在此类资源权衡关系。我们针对雌性个体盘状腹侧条纹装饰的两个特征参数进行了测量：体宽与条纹厚度。在控制个体体型的影响效应后，我们未发现腹纹宽度或条纹厚度对雌性繁殖力存在任何成本性负面影响。与之相反，装饰特征更显著的雌性个体繁殖力更高，能够在不损耗繁殖力的前提下，向雄性精准传递自身繁殖价值的信号。我们同时探究了雌性体型与卵粒大小之间的关联，结果发现体型更大的雌性个体其卵粒大小与繁殖力存在小幅下降，但该变化与雌性装饰特征并无关联。综合其他类群的同类研究结果来看，雌性海龙的装饰并未表现出明显的繁殖力成本，这一发现凸显了重新审视雌性装饰演化相关理论假设的必要性。