The spectacular diversity of insect male genitalia, and their relative insensitivity to the environment, have long puzzled evolutionary biologists and taxonomists. We asked whether the unusual evolvability of male genitalia could be associated with low morphological integration of genitalic traits, by comparison with male somatic traits and female traits. We also asked whether this pattern was robust to variation in resource availability during development, which affects adult condition. To address these questions, we manipulated larval diet quality in a split-brood design and compared levels of integration of male and female genitalic and somatic traits in the neriid fly, Telostylinus angusticollis. We found that male genitalic traits were substantially less integrated than male somatic traits, and less integrated than female genitalic traits. Female genitalic traits were also less integrated than female somatic traits, but the difference was less pronounced than in males. However, integration of male genitalic traits was negatively condition-dependent, with high-condition males exhibiting lower trait integration than low-condition males. Finally, genitalic traits exhibited lower larval diet × family interactions than somatic traits. These results could help explain the unusually high evolvability of male genitalic traits in insects.

中文翻译：

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表型整合的条件依赖性和类蝇中生殖器性状的演变。

昆虫雄性生殖器的惊人多样性及其对环境的相对敏感性一直困扰着进化生物学家和分类学家。我们询问男性生殖器异常的进化能力是否可能与男性躯体性状和女性性状的低形态整合有关。我们还询问这种模式是否对开发过程中资源可用性的变化具有鲁棒性，从而影响成年条件。为了解决这些问题，我们采用分裂育种设计来控制幼虫的饮食质量，并比较了神经节蝇Telostylinus angusticollis中男性和女性生殖器和躯体性状的整合水平。我们发现男性生殖器性状的整合程度远低于男性躯体性状，而整合度低于女性生殖器性状。女性的生殖器性状也没有女性的躯体性状综合，但是这种差异不如男性明显。然而，男性生殖器性状的整合是负性的条件依赖性，高条件男性的性状整合度比低条件男性低。最后，生殖器性状表现出比体细胞性状低的幼虫饮食×家庭相互作用。这些结果可能有助于解释昆虫中男性生殖器性状异常高的进化能力。生殖器性状的幼虫饮食和家庭间相互作用比躯体性状低。这些结果可能有助于解释昆虫中男性生殖器性状异常高的进化能力。生殖器性状的幼虫饮食×家庭间相互作用比躯体性状低。这些结果可能有助于解释昆虫中男性生殖器性状异常高的进化能力。