Effect of Seed Traits and Waterbird Species on the Dispersal Effectiveness of Wetland Plants

SIMPLE SUMMARY: Quantifying the effects of seed traits on waterbird-mediated seed dispersal effectiveness contributes to understanding wetland plant ecology and hence can be used for improving wetland conservation and restoration, especially in the global scenario of wetland degradation and destruction. Waterbirds, especially dabbling ducks, can effectively disperse wetland plant seeds through their guts (endozoochory). Here, we experimentally quantified the effects of seed traits (length and lignin) on retention time, retrieval, and germination of surviving seeds. The results showed that the germination rate of recovered seeds was higher than the controls, suggesting that endozoochory contributes to seed germination. Local seed dispersal was more efficient, and long-distance dispersal was possible. Furthermore, smaller seeds passed through the guts faster, and there was no significant effect of disperser species on germination. We concluded that waterbird-mediated endozoochory plays an important role in wetlands. ABSTRACT: Seed dispersal is an important ecological process in wetland ecosystems and helps maintain community structure and ecosystem biodiversity. Waterbird-mediated endozoochory is an effective and feasible dispersal mechanism for wetland plants; however, the influence of vectors and seed traits on this mechanism remains unclear. To investigate the effects of vector species and seed traits (length and lignin) on retention time, retrieval and germination of gut-surviving seeds, we fed Baikal teals (Anas formosa) and green-winged teals (Anas crecca) eight common plant seeds (Polygonum aviculare, Rumex dentatus, Polygonum orientale, Vallisneria natans, Ranunculus polii, Polygonum hydropiper, Carex cinerascen and Euphrasia pectinata) in the Shengjin Lake wetland (a Ramsar site). We collected fecal samples at intervals of 2–6 h for 36 h, and found that the percentage of recovered seeds differed significantly among teal and plant species (3%~30%); 94% of viable seeds were recovered within 12 h after feeding. Moreover, the germination rate of the recovered seeds (25%~56%) was higher than that of the control. The seed retention time was affected by seed lignin and disperser species; higher lignin made digestion difficult with higher retrieval. Smaller seeds passed through the guts but had no significant effect on recovered seeds. Seed length and disperser species showed no significant correlation with germination. These findings suggested endozoochory by dabbling ducks as an effective wetland seed dispersal mechanism.