Functional traits are phenotypic characteristics that contribute to fitness of individuals in dynamic and changing environments. In mammals, both categorical and continuous (e.g., quantitative) functional traits have been extensively utilized as proxies for diet, locomotion, and other aspects of species ecology, but there has been less focus on form and function of soft tissues. This is particularly true for the digestive system, which varies in size and complexity across Class Mammalia and plays a major role in the energetics of species. To guide more effective utilization of gastrointestinal (GI) morphology as a functional proxy in small mammal ecology, we examined how GI tracts (lengths and masses of four GI sections) varied within a population of deer mice (Peromyscus maniculatus) in the Southern Appalachian Mountains of North Carolina, United States. We collected samples of adult P. maniculatus monthly for 1 year and measured GI tracts to quantify variation with respect to seasonality and trophic level, providing insight into plasticity in this soft tissue trait over time. We found that season had a significant effect on the total length and wet mass of the GI tract, with January mice having the longest GI tracts and lengths being shortest in the summer. The relative shortening of the GI tract in summer corresponded with a partial trophic increase detected by stable isotope signatures. GI length and wet mass also were affected by reproduction, but males and females responded in sex-specific ways to demands of reproduction, with reproductively active males having shorter and lighter GI tracts than nonreproductively active males. Our study provides proof-of-concept for understanding population-level plasticity in a rarely collected soft tissue trait, which may also be complementary to standard craniodental measurements as a functional dietary proxy to understand mammalian ecology and community assembly.

中文翻译：

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手足鼠胃肠道的季节性和性别特异性变化

功能特征是有助于个体在动态和变化的环境中适应的表型特征。在哺乳动物中，分类和连续（例如数量）功能性状已被广泛用作饮食、运动和物种生态学其他方面的代理，但对软组织的形式和功能的关注较少。对于消化系统来说尤其如此，不同哺乳动物纲的消化系统的大小和复杂性各不相同，并且在物种的能量学中发挥着重要作用。为了指导更有效地利用胃肠道（GI）形态作为小型哺乳动物生态学的功能指标，我们研究了南阿巴拉契亚山脉的鹿鼠（Peromyscus maniculatus）群体中胃肠道（四个胃肠道部分的长度和质量）的变化北卡罗来纳州，美国。我们连续 1 年每月收集成年 P. maniculatus 样本，并测量胃肠道，以量化季节性和营养水平的变化，从而深入了解这种软组织特征随时间的可塑性。我们发现季节对胃肠道的总长度和湿质量有显着影响，一月份的小鼠胃肠道最长，而夏季的长度最短。夏季胃肠道的相对缩短与稳定同位素特征检测到的部分营养增加相对应。胃肠道长度和湿质量也受到生殖的影响，但雄性和雌性以性别特异性的方式对生殖需求做出反应，生殖活跃的雄性比非生殖活跃的雄性具有更短和更轻的胃肠道。