Data from: The genetics of primary and secondary sexual character trade-offs in a horned beetle

When structures compete for shared resources, this may lead to acquisition and allocation trade-offs so that the enlargement of one structure occurs at the expense of another. Among the studies of morphological trade-offs, their importance has been demonstrated primarily through experimental manipulations and comparative analyses. Relatively, a few studies have investigated the underlying genetic basis of phenotypic patterns. Here, we use a half-sibling breeding design to determine the genetic underpinnings of the phenotypic trade-off between head horns and the male copulatory organ or aedeagus that has been found in the dung beetle Onthophagus taurus. Instead of the predicted negative genetic covariance among characters that trade-off, we find positive genetic covariance between absolute horn and aedeagus length and zero genetic covariance between relative horn and aedeagus length. Therefore, although the genetic covariance between absolute horn and aedeagus length would constrain the independent evolution of primary and secondary sexual characters in this population, there was no evidence of a trade-off. We discuss alternative hypotheses for the observed patterns of genetic correlation between traits that compete for resources and the implications that these have for selection and the evolution of such traits.

当不同生物结构竞争共享资源时，往往会引发资源获取与分配层面的权衡效应，即某一结构的发育增大往往以另一结构的发育为代价。在形态权衡的相关研究中，这类效应的重要性主要通过实验操控与比较分析得到验证；相对而言，仅有少数研究探讨了表型格局背后的遗传基础。本研究采用半同胞育种设计（half-sibling breeding design），旨在解析粪蜣螂物种金牛座嗡蜣螂（Onthophagus taurus）头部角突与雄性交配器官阳茎（aedeagus）之间表型权衡的遗传机制。本研究未观测到权衡性状间预期的负向遗传协方差，反而发现绝对角长与阳茎长度之间存在正向遗传协方差，而相对角长与阳茎长度之间的遗传协方差为零。因此，尽管绝对角长与阳茎长度间的遗传协方差会限制该种群中第一性征与第二性征的独立演化，但本研究未发现存在权衡效应的证据。最后，我们针对资源竞争性状间观测到的遗传相关格局，讨论了多种备选假说，并阐释了这些格局对性状选择与演化的潜在影响。