Data from: Heritabilities of directional asymmetry in the fore- and hindlimbs of rabbit fetuses

Directional asymmetry (DA), where at the population level symmetry differs from zero, has been reported in a wide range of traits and taxa, even for traits in which symmetry is expected to be the target of selection such as limbs or wings. In invertebrates, DA has been suggested to be non-adaptive. In vertebrates, there has been a wealth of research linking morphological asymmetry to behavioural lateralisation. On the other hand, the prenatal expression of DA and evidences for quantitative genetic variation for asymmetry may suggest it is not solely induced by differences in mechanic loading between sides. We estimate quantitative genetic variation of fetal limb asymmetry in a large dataset of rabbits. Our results showed a low but highly significant level of DA that is partially under genetic control for all traits, with forelimbs displaying higher levels of asymmetry. Genetic correlations were positive within limbs, but negative across bones of fore and hind limbs. Environmental correlations were positive for all, but smaller across fore and hind limbs. We discuss our results in light of the existence and maintenance of DA in locomotory traits.

定向不对称（Directional asymmetry，DA）指种群水平上对称性偏离零值的现象，该现象已在众多性状与生物类群中被报道，即便在四肢、翅膀这类对称性本应作为选择靶标的性状中亦是如此。在无脊椎动物中，定向不对称被认为是非适应性的；而在脊椎动物中，已有大量研究将形态不对称与行为偏侧化联系起来。另一方面，定向不对称的产前表达以及不对称性存在数量遗传变异的证据，或许表明其并非仅由两侧机械负荷差异所诱导。本研究基于大型家兔数据集，对胎儿四肢不对称性的数量遗传变异进行了评估。研究结果显示，所有性状的定向不对称程度虽低但极显著，且部分受遗传调控，其中前肢的不对称水平更高。四肢内部的遗传相关呈正相关，而前肢与后肢的骨骼间遗传相关则为负相关；所有性状的环境相关均为正相关，但前肢与后肢间的环境相关程度更低。本研究结合运动性状中定向不对称的存在与维持机制，对研究结果展开了讨论。