Lovas-Kiss Ádám, Vincze Orsolya, Kleyheeg Erik, Sramkó Gábor, Laczkó Levente, Fekete Réka, Molnár V Attila, Green Andy J
Wetland Ecology Research Group Department of Tisza Research MTA Centre for Ecological Research-DRI Debrecen Hungary.
Evolutionary Ecology Group Hungarian, Department of Biology and Ecology Babeş-Bolyai University Cluj Napoca Romania.
Ecol Evol. 2020 Jan 15;10(3):1413-1424. doi: 10.1002/ece3.5997. eCollection 2020 Feb.
Field studies have shown that waterbirds, especially members of the Anatidae family, are major vectors of dispersal by endozoochory for a broad range of plants lacking a fleshy fruit, yet whose propagules can survive gut passage. Widely adopted dispersal syndromes ignore this dispersal mechanism, and we currently have little understanding of what traits determine the potential of angiosperms for endozoochory by waterbirds. Results from previous experimental studies have been inconsistent as to how seed traits affect seed survival and retention time in the gut and have failed to control for the influence of plant phylogeny. Using 13 angiosperm species from aquatic and terrestrial habitats representing nine families, we examined the effects of seed size, shape, and hardness on the proportion of seeds surviving gut passage through mallards () and their retention time within the gut. We compiled a molecular phylogeny for these species and controlled for the nonindependence of taxa due to common descent in our analyses. Intact seeds from all 13 species were egested, but seed survival was strongly determined by phylogeny and by partial effects of seed mass and hardness (wet load): species with seeds harder than expected from their size, and smaller than expected from their loading, had greater survival. Once phylogeny was controlled for, a positive partial effect of seed roundness on seed survival was also revealed. Species with seeds harder than expected from their size had a longer mean retention time, a result retained after controlling for phylogeny. Our study is the first to demonstrate that seed shape and phylogeny are important predictors of seed survival in the avian gut. Our results demonstrate that the importance of controlling simultaneously for multiple traits and relating single traits (e.g., seed size) alone to seed survival or retention time is not a reliable way to detect important patterns, especially when phylogenetic effects are ignored.
野外研究表明，水鸟，特别是鸭科成员，是许多缺乏肉质果实但繁殖体能够在肠道中存活的植物通过内吞传播进行扩散的主要媒介。广泛采用的扩散综合征忽略了这种扩散机制，而且我们目前对决定被子植物通过水鸟进行内吞传播潜力的特征了解甚少。以往实验研究的结果在种子特征如何影响种子在肠道中的存活和保留时间方面并不一致，并且未能控制植物系统发育的影响。我们使用来自九个科的13种水生和陆生栖息地的被子植物物种，研究了种子大小、形状和硬度对通过绿头鸭肠道的种子存活比例及其在肠道内保留时间的影响。我们为这些物种编制了分子系统发育图谱，并在分析中控制了由于共同祖先导致的分类群非独立性。所有13个物种的完整种子都被排出，但种子存活强烈取决于系统发育以及种子质量和硬度（湿负荷）的部分影响：种子比根据其大小预期的更硬且比根据其负荷预期的更小的物种，具有更高的存活率。一旦控制了系统发育，种子圆度对种子存活的正向部分影响也被揭示出来。种子比根据其大小预期的更硬的物种平均保留时间更长，在控制了系统发育后这一结果仍然成立。我们的研究首次证明种子形状和系统发育是鸟类肠道中种子存活的重要预测因素。我们的结果表明，同时控制多个特征并仅将单个特征（例如种子大小）与种子存活或保留时间相关联，不是检测重要模式的可靠方法，特别是当系统发育效应被忽略时。
