Data from: Two-module organization of the mandible in the yellow-necked mouse: a comparison of two different morphometric approaches

Mandibles of yellow-necked mouse (Apodemus flavicollis) were used to explore modularity. We tested a biological hypothesis that two separate modules (alveolar region and ascending ramus) can be recognized within the mandible. As a second research goal, we compared two different morphometric procedures under the assumption that methodological approaches that use either geometric or traditional morphometric techniques should give similar results. Besides confirmation of the predicted hypothesis of modularity, the application of both approaches revealed that: 1) Modularity was somewhat more evident when it was analyzed on the asymmetric (fluctuating asymmetry, FA) than on the symmetric (individual variation) component of variation; 2) There is correspondence in the patterns of individual variation and FA, which indicates that integration of mandibular traits among individuals is primarily due to direct developmental interactions and 3) Allometry does not obscure the hypothesized modularity for individual variation or for FA. In addition, traditional morphometric method allowed us to check if allometry influenced each module to the same extent, and to conclude that the ascending ramus is more heavily influenced by general size than the alveolar region. In studies of modularity, differences in methods can lead to discrepancies in the results, and therefore some caution is required when comparing findings from different investigations. The substantial agreement between our results provides evidence that, when considering two-module organization of the mouse mandible, direct comparison among studies that use the methods applied herein is, in great part, reliable.本研究以黄颈姬鼠（Apodemus flavicollis）的下颌骨为研究对象，探讨其模块化特征。我们验证了一项生物学假说：下颌骨可划分为两个独立的模块——牙槽区（alveolar region）与下颌升支（ascending ramus）。本研究的第二项目标是对比两种不同的形态测量学方法：我们假设采用几何形态测量（geometric morphometric）技术与传统形态测量（traditional morphometric）技术的研究方法应当得到相似的结果。除验证了预设的模块化假说外，两种方法的应用还揭示了以下结论：1）相较于变异的对称组分（个体变异，individual variation），当基于不对称组分（波动不对称，fluctuating asymmetry, FA）进行分析时，模块化特征更为显著；2）个体变异与波动不对称的模式存在对应关系，这表明个体间下颌骨性状的整合主要源于直接的发育相互作用；3）异速生长（allometry）并未掩盖针对个体变异或波动不对称的预设模块化特征。此外，传统形态测量方法使我们得以验证异速生长对两个模块的影响程度是否一致，并得出结论：下颌升支相较牙槽区受整体大小的影响更为显著。在模块化研究中，方法的差异可能导致研究结果出现分歧，因此在对比不同研究的结论时需保持谨慎。本研究结果间的高度一致性表明，在探讨小鼠下颌骨的双模块结构时，采用本文所述方法的各项研究之间的直接对比在很大程度上是可靠的。