Data from: Great cormorants reveal overlooked secondary dispersal of plants and invertebrates by piscivorous waterbirds

In wetland ecosystems, birds and fish are important dispersal vectors for plants and invertebrates, but the consequences of their interactions as vectors are unknown. Darwin suggested that piscivorous birds carry out secondary dispersal of seeds and invertebrates via predation on fish. We tested this hypothesis in the great cormorant (Phalacrocorax carbo L.). Cormorants regurgitate pellets daily, which we collected at seven European locations and examined for intact propagules. One-third of pellets contained at least one intact plant seed, with seeds from 16 families covering a broad range of freshwater, marine and terrestrial habitats. Of 21 plant species, only two have an endozoochory dispersal syndrome, compared to five for water and eight for unassisted dispersal syndromes. One-fifth of the pellets contained at least one intact propagule of aquatic invertebrates from seven taxa. Secondary dispersal by piscivorous birds may be vital to maintain connectivity in meta-populations and between river catchments, and in the movement of plants and invertebrates in response to climate change. Secondary dispersal pathways associated with complex food webs must be studied in detail if we are to understand species movements in a changing world.

在湿地生态系统中，鸟类与鱼类是植物及无脊椎动物的重要传播媒介，但二者作为传播媒介的交互作用所带来的生态后果仍未明确。达尔文曾提出，食鱼鸟类可通过捕食鱼类的方式，实现植物种子与无脊椎动物的二次传播。本研究以普通鸬鹚（Phalacrocorax carbo L.）为对象，对该假说进行了验证。普通鸬鹚每日会反吐食丸，我们在欧洲7处采样点收集了这些食丸，并对其中完整的繁殖体进行了检测。三分之一的食丸中至少含有1粒完整的植物种子，这些种子隶属于16个科，涵盖淡水、海洋与陆生多种生境类型。在所分析的21种植物中，仅2种具备内食传播（endozoochory）的传播策略，另有5种依赖水媒传播，8种为无辅助自主传播。五分之一的食丸中，至少含有1份来自7个分类群的水生无脊椎动物完整繁殖体。食鱼鸟类介导的二次传播，对于维持集合种群（meta-population）内部以及河流流域之间的连通性，以及响应气候变化的植物与无脊椎动物的迁移过程至关重要。若要理解气候变化背景下的物种迁移规律，我们需要对复杂食物网相关的二次传播路径开展深入研究。