Slijepčević Maja, Galis Frietson, Arntzen Jan W, Ivanović Ana
Institute for Biological Research "Siniša Stanković", University of Belgrade , Belgrade , Serbia.
Naturalis Biodiversity Center , Leiden , The Netherlands.
PeerJ. 2015 Nov 10;3:e1397. doi: 10.7717/peerj.1397. eCollection 2015.
We explored intraspecific variation in vertebral formulae, more specifically the variation in the number of thoracic vertebrae and frequencies of transitional sacral vertebrae in Triturus newts (Caudata: Salamandridae). Within salamandrid salamanders this monophyletic group shows the highest disparity in the number of thoracic vertebrae and considerable intraspecific variation in the number of thoracic vertebrae. Triturus species also differ in their ecological preferences, from predominantly terrestrial to largely aquatic. Following Geoffroy St. Hilaire's and Darwin's rule which states that structures with a large number of serially homologous repetitive elements are more variable than structures with smaller numbers, we hypothesized that the variation in vertebral formulae increases in more elongated species with a larger number of thoracic vertebrae. We furthermore hypothesized that the frequency of transitional vertebrae will be correlated with the variation in the number of thoracic vertebrae within the species. We also investigated potential effects of species hybridization on the vertebral formula. The proportion of individuals with a number of thoracic vertebrae different from the modal number and the range of variation in number of vertebrae significantly increased in species with a larger number of thoracic vertebrae. Contrary to our expectation, the frequencies of transitional vertebrae were not correlated with frequencies of change in the complete vertebrae number. The frequency of transitional sacral vertebra in hybrids did not significantly differ from that of the parental species. Such a pattern could be a result of selection pressure against transitional vertebrae and/or a bias towards the development of full vertebrae numbers. Although our data indicate relaxed selection for vertebral count changes in more elongated, aquatic species, more data on different selective pressures in species with different numbers of vertebrae in the two contrasting, terrestrial and aquatic environments are needed to test for causality.
我们探究了蝾螈（有尾目：蝾螈科）椎骨公式的种内变异，更具体地说是胸椎数量的变异以及过渡性骶椎的频率。在蝾螈科蝾螈中，这个单系类群在胸椎数量上表现出最高的差异，并且胸椎数量存在相当大的种内变异。蝾螈物种在生态偏好上也有所不同，从主要陆生到大部分水生。遵循杰弗里·圣伊莱尔和达尔文的规则，即具有大量连续同源重复元素的结构比具有较少此类元素的结构更具变异性，我们假设在胸椎数量较多的更细长物种中，椎骨公式的变异会增加。我们还假设过渡椎骨的频率将与物种内胸椎数量的变异相关。我们还研究了物种杂交对椎骨公式的潜在影响。胸椎数量不同于模式数量的个体比例以及椎骨数量的变异范围在胸椎数量较多的物种中显著增加。与我们的预期相反，过渡椎骨的频率与完整椎骨数量变化的频率不相关。杂种中过渡性骶椎的频率与亲本物种的频率没有显著差异。这种模式可能是对过渡椎骨的选择压力和/或对完整椎骨数量发育的偏向的结果。尽管我们的数据表明在更细长的水生物种中对椎骨数量变化的选择有所放松，但需要更多关于在陆地和水生这两种截然不同环境中具有不同椎骨数量的物种的不同选择压力的数据来检验因果关系。
