A tenet of evolutionary theory is that phenotypic variation of a trait is inversely related to the intensity of stabilizing selection pressure. Among homologous bones, such as metapodials, a rudimentary, “nonfunctional” bone is expected to be more variable in length than nonrudimentary bones. This study compares variation and association in length among metapodials using 277 adult skeletons of Canis latrans. Canis latrans has a short, “functionless” first metacarpal (mc1) and “rudimentary, vestigial” first metatarsal (mt1). Results show that among the 10 metapodials, mt1 has the highest variation in length; other metapodials do not differ significantly from one another in their variation. Correlation coefficients for length of mc1 and mt1 with their ipsilateral metapodials 2‐5 are significantly lower than coefficients for all other ipsilateral pairs. The correlation coefficient between left and right mt1 is significantly the lowest among all bilateral pairs of metapodials. Results are interpreted as follows. Mt1's high variation and low association in length are the outcome of less intense stabilizing selection pressure compared with other metapodials. The nonsignificant difference for variation in length between mc1 and metapodials 2‐5 may be that mc1 is functional for development of a pollical dewclaw that helps restrain small prey.

中文翻译：

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Canis latrans 的基本的、“无功能的”第一后足：长度的变化和关联与更长的、有功能的后足

进化理论的一个原则是，性状的表型变异与稳定选择压力的强度成反比。在同种骨骼中，例如后足骨，一个基本的、“非功能性”的骨头预计比非基本的骨头在长度上更可变。本研究使用 277 具 Canis latrans 成年骨骼比较了后足动物的长度变化和关联。Canis latrans 有一个短的、“无功能的”第一掌骨 (mc1) 和“基本的、退化的”第一跖骨 (mt1)。结果表明，在 10 个后足中，mt1 的长度变化最大；其他metapodials在它们的变化上彼此没有显着差异。mc1 和 mt1 的长度与其同侧后足 2-5 的相关系数显着低于所有其他同侧对的系数。左右 mt1 之间的相关系数在所有双足后足对中显着最低。结果解释如下。与其他后足类相比，Mt1 的高变异和低关联是由于稳定选择压力较小的结果。mc1 和后足动物 2-5 之间长度变化的无显着差异可能是 mc1 对发育有助于抑制小型猎物的爪爪有功能。与其他后足动物相比，长度的高变异和低关联是稳定选择压力较小的结果。mc1 和后足动物 2-5 之间长度变化的无显着差异可能是 mc1 对发育有助于抑制小型猎物的爪爪有功能。与其他后足动物相比，长度的高变异和低关联是稳定选择压力较小的结果。mc1 和后足动物 2-5 之间长度变化的无显着差异可能是 mc1 对发育有助于抑制小型猎物的爪爪有功能。