School of Life and Environmental Sciences, University of Sydney, NSW 2006, Sydney, Australia.
School of Life and Environmental Sciences, Deakin University, Waurn Ponds, Vic 3125, Australia.
Sci Rep. 2017 Sep 12;7(1):11363. doi: 10.1038/s41598-017-11768-y.
The challenge of identifying the proximate causes and ecological consequences of phenotypic variation can be facilitated by studying traits that are usually but not always bilaterally symmetrical; deviations from symmetry likely reflect disrupted embryogenesis. Based on a 19-year mark-recapture study of >1300 slatey-grey snakes (Stegonotus cucullatus) in tropical Australia, and incubation of >700 eggs, we document developmental and ecological correlates of two morphological traits: asymmetry and fragmentation of head scales. Asymmetry was directional (more scales on the left side) and was higher in individuals with lower heterozygosity, but was not heritable. In contrast, fragmentation was heritable and was higher in females than males. Both scale asymmetry and fragmentation were increased by rapid embryogenesis but were not affected by hydric conditions during incubation. Snakes with asymmetry and fragmentation exhibited slightly lower survival and increased (sex-specific) movements, and females with more scale fragmentation produced smaller eggs. Counterintuitively, snakes with more asymmetry had higher growth rates (possibly reflecting trade-offs with other traits), and snakes with more fragmentation had fewer parasites (possibly due to lower feeding rates). Our data paint an unusually detailed picture of the complex genetic and environmental factors that, by disrupting early embryonic development, generate variations in morphology that have detectable correlations with ecological performance.
研究通常但不总是左右对称的特征可以帮助我们确定表型变异的近因和生态后果；对称性的偏差可能反映了胚胎发生的中断。基于对澳大利亚热带地区超过 1300 条石板灰色蛇（Stegonotus cucullatus）的 19 年标记-重捕研究和对超过 700 个卵的孵化，我们记录了两个形态特征的发育和生态相关性：头部鳞片的不对称和碎裂。不对称是定向的（左侧的鳞片更多），并且在杂合度较低的个体中更高，但没有遗传性。相比之下，碎裂是可遗传的，并且在雌性中比雄性更高。快速胚胎发生会增加鳞片的不对称和碎裂，但孵化期间的水分条件不会影响它们。具有不对称和碎裂的蛇的存活率略低，运动增加（具有性别特异性），鳞片碎裂较多的雌性产卵较小。违反直觉的是，具有更多不对称性的蛇具有更高的生长速度（可能反映了与其他特征的权衡），而具有更多碎裂的蛇寄生虫较少（可能由于进食率较低）。我们的数据描绘了一个异常详细的复杂遗传和环境因素的图片，这些因素通过破坏早期胚胎发育，产生了与生态表现有可检测相关性的形态变异。
