种壳厚度对鼠类种子扩散行为及种子命运的影响

种子扩散是植物更新和扩大分布区的一种重要途径。鼠类采取不同的种子扩散和贮藏策略，以应对食物短缺，同时也促进了植物种子扩散。为应对鼠类对植物种子的过度取食，种子进化出了一系列物理、化学等防御特征。其中种壳厚度作为一种物理防御策略，是影响鼠类贮藏行为和种子命运的关键因素。本研究拟通过去除天然栓皮栎（Quercus variabilis）种子的外壳，再在种仁外包被1、2、4、6不同层数的聚乙烯薄膜，模拟种壳厚度，准确控制种壳厚度。2020年10月—2021年1月，在四川都江堰森林生境中释放人工种壳包被的种子，研究人工种壳厚度对鼠类介导的种子扩散和命运的影响。结果表明：（1）鼠类优先扩散种壳较薄（1层薄膜包被）的人工种子；随着种壳厚度的增加，扩散速率逐渐降低，种壳最厚（6层薄膜包被）的种子扩散最慢（P < 0.001）；（2）鼠类喜好分散贮藏1层、2层薄膜包被的种子；当种壳厚度增加至包被4层、6层薄膜时，分散贮藏比例显著降低（P < 0.05）；（3）鼠类偏好集中贮藏4层薄膜包被的种子（P < 0.05）；（4）不同种壳厚度的种子扩散距离无显著差异（P > 0.05）；（5）种壳较薄（1层薄膜包被）的种子分散贮藏率在3 m范围内比例较高。采用聚乙烯薄膜包被是模拟种子外壳的可行方法，并可用于评估种壳厚度对鼠类种子贮藏行为和种子命运的影响等相关研究。

Effects of seed coat thickness on rodents' seed dispersal behavior and seed fate

Seed dispersal is an important strategy for seed regeneration and distribution expansion of plants. Rodents adopt different seed dispersal and hoarding strategies in response to food shortages, which also promote seed dispersal. Seeds have evolved a series of traits, such as physical and chemical defenses in response to overfeeding by rodents. Seed coat thickness, as a physical defense strategy, is a key factor affecting the hoarding behavior of rodents and seed fates. However, there is still a lack of effective methods to artificially simulate seed coat thickness. In this study, by removing the coat of natural Quercus variabilis seeds, and then wrapping the seed kernels with different layers of polyethylene plastic, we aimed to accurately control the artificial seed coat thickness of the seed coats. The effects of seed coat thickness on seed dispersal and seed fate of artificially simulated seeds were investigated in the forests of the Dujiangyan region, Sichuan Province of China, from October 2020 to January 2021. We found that:(1) rodents preferred to disperse artificial seeds with the thinner coat (covered with 1 layer of polyethylene film); with the increase of seed coat thickness, the seed removal rate gradually decreased; the seeds with the thickest coat (covered with 6 layers of polyethylene film) had the slowest removal rate (P < 0. 001); (2) Rodents preferred to scatter-hoard seeds with 1 and 2 layers of polyethylene film. When the coat thickness increases to 4 and 6 layers of polyethylene film, the proportion of scatter-hoarded was significantly reduced (P < 0. 05); (3) Rodents preferred to larder-hoard seeds with 4 layers of film, compared to seeds covered with the other layers of polyethylene film (P < 0. 05); (4) There was no significant difference in seed dispersal distance among seeds with different seed coat thickness (P > 0. 05); (5) Seeds with thinner coat thickness (1 layer of film) had a higher proportion of scatter-hoarding within 3 m. The use of polyethylene film wrapping is a feasible method for simulating the seed coat, and could be used to evaluate the impact of the thickness of the seed coat on the hoarded behavior of rodent seeds and the fate of seeds.