Swida amomum seed germination

Premise: Effective seed dispersal is essential in population dynamics of plant species. Swida amomum (Silky dogwood) exhibits a dispersal syndrome characteristic of autumn-ripening shrubs with fleshy fruits, where attached fruits are ingested and defecated by birds while fallen fruits are consumed by ground-foraging birds and mammals. Methods: We documented that fallen fruits of this shrub were consumed by two aquatic turtle species (Eastern painted turtle, Chrysemys picta and Red-eared slider, Trachemys scripta) and that their seeds were defecated. We compared germination success (percentage of seeds germinated) of defecated seeds, seeds collected from pond surface, and seeds removed from shrubs. Results: While four seed taxa were identified in fecal samples, seeds of S. amomum were the most frequent (93%) among samples and the most numerous (106 seeds) in any sample. Average proportion of fecal seeds germinated (85.99%) exceeded that of seeds from pond surface (82.76%) and from shrubs (60.24%), albeit the difference in germination success was insignificant. When analyzed using fecal samples from Painted turtles only, the difference in germination success between fecal seeds and those collected from pond or shrub became significant. Conclusions: Our findings represent the first report of S. amomum seeds being dispersed by turtle gut passage and suggest aquatic turtles could be an important part of a secondary seed dispersal process influencing woody plant community composition in temperate wetland ecosystems.

背景：有效种子传播（seed dispersal）对于植物物种的种群动态至关重要。偃伏梾木（Swida amomum，Silky dogwood）具有肉质果实秋熟灌木的传播综合征特征：悬挂于植株上的果实会被鸟类取食并随粪便排出，而掉落的果实则由地面觅食的鸟类和哺乳动物取食。
方法：本研究记录了该灌木的掉落果实被两种淡水龟类——东部锦龟（Chrysemys picta）和红耳滑龟（Trachemys scripta）取食，且其种子会随龟类粪便排出的现象。我们分别对经粪便排出的种子、池塘表面采集的种子以及从植株上移除的种子的萌发成功率（germination success，即萌发种子占比）进行了比较。
结果：尽管在粪便样本中共鉴定出4种植物种子，但偃伏梾木的种子在所有样本中出现频率最高（占比93%），且单一样本中种子数量最多（达106粒）。经粪便排出的种子平均萌发率（85.99%）高于池塘表面采集的种子（82.76%）以及植株上移除的种子（60.24%），不过该萌发成功率的差异并不显著。当仅使用东部锦龟的粪便样本进行分析时，经粪便排出的种子与池塘或植株上采集的种子之间的萌发成功率差异则达到显著水平。
结论：本研究结果首次报道了偃伏梾木的种子可通过龟类消化道进行传播，这表明淡水龟类可能是温带湿地生态系统中影响木本植物群落组成的次生种子传播过程中的重要一环。