Department of Biology, Indiana University, Bloomington, IN, USA.
J Evol Biol. 2021 Aug;34(8):1326-1332. doi: 10.1111/jeb.13877. Epub 2021 Jun 18.
An organism's fitness depends strongly on its age and size at maturation. Although the evolutionary forces acting on these critical life history traits have been heavily scrutinized, the developmental mechanisms underpinning intraspecific variation in adult size and development time remain much less well-understood. Using RNA interference, I here show that the highly conserved sex-determination gene doublesex (dsx) mediates sexual size dimorphism (SSD) in the gazelle dung beetle Digitonthophagus gazella. Because doublesex undergoes sex-specific splicing and sex-limited isoforms regulate different target genes, this suggests that dsx contributes to the resolution of intralocus sexual conflict in body size. However, these results contrast with previous studies demonstrating that dsx does not affect body size or SSD in Drosophila. This indicates that intraspecific body size variation is underlain by contrasting developmental mechanisms in different insect lineages. Furthermore, although male D. gazella have a longer development time than females, sexual bimaturism was not affected by dsx expression knockdown. In addition, and in contrast to secondary sexual morphology, dsx did not significantly affect nutritional plasticity in life history. Taken together, these findings indicate that dsx signalling contributes to intraspecific life history variation but that dsx's function in mediating sexual dimorphism in life history differs among traits and species. More generally, these findings suggest that genes ancestrally tasked with sex determination have been co-opted into the developmental regulation of life history traits and may represent an underappreciated mechanism of life history evolution.
生物体的适合度强烈依赖于其成熟时的年龄和体型。尽管作用于这些关键生命史特征的进化力量受到了广泛关注，但支持成年体型和发育时间种内变异的发育机制仍知之甚少。我在这里通过 RNA 干扰发现，高度保守的性别决定基因 doublesex（dsx）介导了瞪羚蜣螂 Digitonthophagus gazella 的性二型（SSD）。由于 doublesex 经历性别特异性剪接，性别限制的同工型调节不同的靶基因，这表明 dsx 有助于解决体型上的种内性冲突。然而，这些结果与先前的研究形成对比，表明 dsx 不会影响果蝇的体型或 SSD。这表明，不同昆虫谱系中存在不同的发育机制，导致了种内体型变异。此外，尽管雄性 D. gazella 的发育时间比雌性长，但 dsx 表达敲低并不影响性双态性。此外，与次生性形态不同，dsx 对生活史中的营养可塑性没有显著影响。综上所述，这些发现表明 dsx 信号参与了种内生活史变异，但 dsx 在介导生活史性二型方面的功能在不同性状和物种之间存在差异。更普遍地说，这些发现表明，最初负责性别决定的基因已被共同用于生活史特征的发育调控，可能代表了一种被低估的生活史进化机制。
