A mechanistic assessment of the relationship between gut morphology and endozoochorous seed dispersal by waterfowl

Many plants and invertebrates rely on internal transport by animals for long-distance dispersal. Their dispersal capacity is greatly influenced by interactions with the animal’s digestive tract. Omnivorous birds adjust their digestive tract morphology to seasonally variable diets. We performed feeding trials in waterfowl to unravel how changing organ size, in combination with seed size, affects dispersal potential. We subjected captive mallards to mimics of summer (animal-based), winter (plant-based) and intermediate diets, and analysed gut passage of seeds before and after the treatment (trials 1 and 2). To test the effect of gut morphology on seed digestion, we measured digestive organ size after euthanasia. Three hours before euthanasia, differently sized seeds were fed to test how seed size affects gut passage by determining their relative position in the digestive tract (trial 3).
Trials 1 and 2 showed that intact seed passage was lower in the plant-based than in the animal-based ...

诸多植物与无脊椎动物依赖动物体内运输实现长距离扩散。其扩散能力极大程度上受与动物消化道相互作用的影响。杂食性鸟类会根据季节性变化的饮食调整消化道形态。本研究以水禽为对象开展饲喂试验，旨在阐明器官尺寸变化与种子尺寸共同作用如何影响扩散潜力。我们将圈养的绿头鸭分别暴露于模拟夏季（以动物性食物为主）、冬季（以植物性食物为主）以及中间型的饮食环境中，并分别在处理前后分析种子的消化道通过率（试验1与试验2）。为探究消化道形态对种子消化的影响，我们在实验动物安乐死后测量了其消化器官的尺寸。在安乐死前三小时，我们向实验动物投喂不同尺寸的种子，通过测定其在消化道中的相对位置来探究种子尺寸对消化道通过率的影响（试验3）。试验1与试验2结果显示，以植物性食物为主的饮食组中，完整种子的通过率低于以动物性食物为主的饮食组……