Gunji Megu, Taewcharoen Nuttakorn, Yamada Fumio, Sherratt Emma
Department of Life Sciences, Faculty of Life Sciences, Toyo University, Saitama 351-0007, Japan.
School of Biological Sciences, Faculty of Sciences, Engineering and Technology, University of Adelaide, Adelaide, South Australia 5005, Australia.
R Soc Open Sci. 2025 Jan 29;12(1):241813. doi: 10.1098/rsos.241813. eCollection 2025 Jan.
In mammalian vertebral columns, locomotive ability is expected to be an evolutionary driver of variation in the number of vertebrae; in species evolved to run fast or have a flexible vertebral column, they generally have limited numerical variation and low occurrence of malformed vertebrae to maintain their running performance. Although this hypothesis is supported among species sharing similar locomotive constraints (e.g. dorsomobile versus dorsostable species), whether it applies at the within-species level is unknown. We test this hypothesis using species of Leporidae (rabbits and hares) with different locomotive abilities: we examined the number of presacral vertebrae and the frequency of abnormalities in 504 specimens from 4 species, representing cursorial, saltatorial and generalist modes. Our results show that the cursorial leporids had the lowest numerical variability and fewest abnormalities within species, although this was not statistically different from saltatorial or generalist species. We also identified 11 conditions of vertebral abnormality previously unexplored and theorize that each may pose different degrees of locomotive impairment and effects on species' fitness. The lack of statistical support for the hypothesis at a finer phylogenetic level suggests further research is needed to understand whether numerical variability is under stabilizing selection or a developmental response to locomotive constraints in cursorial animals.
在哺乳动物的脊柱中，运动能力有望成为椎骨数量变异的进化驱动力；在进化为快速奔跑或拥有灵活脊柱的物种中，它们通常具有有限的数量变异和较低的脊椎畸形发生率，以维持其奔跑性能。尽管这一假设在具有相似运动限制的物种（如背动型与背稳定型物种）中得到了支持，但它是否适用于物种内部层面尚不清楚。我们使用具有不同运动能力的兔科物种（兔子和野兔）来检验这一假设：我们检查了来自4个物种的504个标本的骶前椎骨数量和异常频率，这些物种代表了奔跑、跳跃和一般运动模式。我们的结果表明，奔跑型兔科动物在物种内部具有最低的数量变异性和最少的异常情况，尽管这与跳跃型或一般运动型物种在统计学上没有差异。我们还识别出了11种以前未被探索的脊椎异常情况，并推测每种情况可能对运动能力造成不同程度的损害以及对物种适应性产生影响。在更精细的系统发育水平上缺乏对该假设的统计支持，这表明需要进一步研究以了解数量变异性是否处于稳定选择之下，或者是对奔跑动物运动限制的一种发育反应。
