The circadian clock controls daily activities at the cellular and organismic level, allowing an organism to anticipate incoming stresses and to use resources accordingly. The circadian clock has therefore been considered a fitness trait in multiple organisms. However, the mechanism of how circadian clock variation influences organismal reproductive fitness is still not well understood. Here we describe habitat-specific clock variation (HSCV) of asexual reproduction in Neurospora discreta, a species that is adapted to 2 different habitats, under or above tree bark. African (AF) N. discreta strains, whose habitat is above the tree bark in light-dark (LD) conditions, display a higher rhythmicity index compared with North American (NA) strains, whose habitat is under the tree bark in constant dark (DD). Although AF-type strains demonstrated an overall fitness advantage under LD and DD conditions, NA-type strains exhibit a habitat-specific fitness advantage in DD over the LD condition. In addition, we show that allelic variation of the clock-controlled gene, Ubiquinol cytochrome c oxidoreductase (NEUDI_158280), plays a role in HSCV by modulating cellular reactive oxygen species levels. Our results demonstrate a mechanism by which local adaptation involving circadian clock regulation influences reproductive fitness.

昼夜节律时钟控制着细胞和生物体的日常活动，使生物体能够预料到即将来临的压力并相应地利用资源。因此，生物钟已被认为是多种生物的适应性特征。然而，关于昼夜节律变化如何影响机体生殖适应性的机制仍然不甚了解。在这里，我们描述了神经孢子虫（Neurospora discreta）中无性繁殖的特定于栖息地的时钟变化（HSCV），该物种适应于树皮以下或上方的两个不同的栖息地。非洲（AF）离散虫在北美地区（NA）的树种在恒定黑暗（DD）下，其光亮指数（LD）比在树皮下栖息的树种具有更高的节奏指数。尽管AF型菌株在LD和DD条件下显示出整体适应性优势，但NA型菌株在DD条件下在LD条件下显示出特定于栖息地的适应性优势。此外，我们显示时钟控制基因泛醇细胞色素c氧化还原酶（NEUDI_158280）的等位基因变异通过调节细胞活性氧水平在HSCV中发挥作用。我们的结果证明了一种机制，其中涉及昼夜节律调节的局部适应影响生殖适应性。