Keck Science Department, Pitzer College, Claremont, CA 91711, USA.
Physics and Astronomy Department, Pomona College, Claremont, CA 91711, USA.
Integr Comp Biol. 2020 Oct 1;60(4):919-924. doi: 10.1093/icb/icaa117.
Our article describes the explosive seed dispersal of the Hura crepitans fruit. Through high-speed video analysis of an exploding fruit, we observe that the seeds fly with backspin as opposed to topspin, which was previously assumed. Backspin orients seeds to minimize drag during flight and consequently increases dispersal distance. The seeds' dispersal distance is estimated by using results from the seeds of Ruellia ciliatiflora, which are similarly shaped but ∼10 times smaller than those of H. crepitans. We note that the effects of lowering drag on the dispersal distance are more pronounced at higher speeds. We also see that the effect of launch height on the dispersal distance of the seeds becomes less consequential at higher launch speeds. We conclude that the increased dispersal distance due to flying with backspin should improve fitness in colonizing new habitats or escaping disease or predation and that comparisons of the seed dispersal mechanisms across species within the Euphorbiaceae and Acanthaceae might help reveal the adaptive significance of this behavior.
我们的文章描述了霍拉·克里帕坦斯果实的爆炸式种子散布。通过对一个爆炸果实的高速视频分析，我们观察到种子呈反向旋转（backspin）而非之前假设的上旋（topspin）飞行。反向旋转使种子在飞行过程中最小化阻力，从而增加了散布距离。通过与形状相似但大小约为霍拉·克里帕坦斯果实的 10 倍的瑞香科植物瑞香的种子的结果进行比较，我们估算了种子的散布距离。我们注意到，在较高速度下，降低阻力对散布距离的影响更为显著。我们还发现，随着发射速度的提高，发射高度对种子散布距离的影响变得不那么重要。我们得出结论，由于反向旋转飞行而增加的散布距离应该有助于提高在新栖息地中定居或逃避疾病或捕食的适应性，并且在大戟科和爵床科内比较不同物种的种子散布机制可能有助于揭示这种行为的适应意义。
