Ezoe H
Department of Natural Science, Osaka Women's University, Daisen-cho 2-1, Sakai, 590-0035, Japan.
J Theor Biol. 1998 Feb 7;190(3):287-93. doi: 10.1006/jtbi.1997.0553.
The evolutionary stable (ESS) dispersal range for annual plants is studied in a stable environment when there is a trade -off between seed survivability and dispersal range via seed size. Larger seed size is more beneficial in the competition for safe sites, but likely to be dispersed a shorter distance and to suffer competition among siblings. Previously Hamilton & May found that dispersal can be adaptive in a stable environment to reduce competition among sibs, but they assumed that dispersers were likely to enter all the patches equally-this is not suitable for many terrestrial plants with limited dispersal range. In this article I discuss the evolution of dispersal range for wind dispersed seeds when dispersal range is tightly coupled with seed size. I assume that the density of dispersed seed follows a two-dimensional normal distribution function, with variance decreasing with seed size. Due to the trade-off between the seed number and the survivability of a seedling offspring, there is a seed size &wtilde; that maximizes the product of the two quantities. This is the optimal seed size when size-dependent dispersal is neglected. The ESS seed size considering the size-dependent dispersal w* is also calculated by neglecting the effect of spatial clumping of relatives. Under the environment unfavorable for seed dispersal, the ESS seed size w* can be much smaller than the optimal seed size &wtilde;, but there is a lower limit for the ESS dispersal range even in the extremely sticky environment. Even if the dependency of seed survivability on the seed size is so weak that the cost of long-range dispersal is small, the ESS seed dispersal range cannot become very large. These results are confirmed by individual-based computer simulations with more realistic assumptions considering spatial clumping of non-sib relatives.Copyright 1998 Academic Press Limited
在稳定环境中，当种子生存能力与通过种子大小决定的扩散范围之间存在权衡时，对一年生植物的进化稳定（ESS）扩散范围进行了研究。较大的种子大小在安全地点的竞争中更具优势，但可能传播较短的距离，并在同胞之间遭受竞争。此前，汉密尔顿和梅发现，在稳定环境中扩散可以适应减少同胞之间的竞争，但他们假设扩散者可能平等地进入所有斑块——这不适用于许多扩散范围有限的陆生植物。在本文中，我讨论了风传播种子的扩散范围的进化，此时扩散范围与种子大小紧密相关。我假设扩散种子的密度遵循二维正态分布函数，方差随种子大小减小。由于种子数量与幼苗后代生存能力之间的权衡，存在一个种子大小&wtilde;，它使这两个数量的乘积最大化。这是忽略大小依赖性扩散时的最佳种子大小。考虑大小依赖性扩散w的ESS种子大小也通过忽略亲属空间聚集的影响来计算。在不利于种子扩散的环境中，ESS种子大小w可能比最佳种子大小&wtilde;小得多，但即使在极其粘性的环境中，ESS扩散范围也有下限。即使种子生存能力对种子大小的依赖性非常弱，以至于长距离扩散的成本很小，ESS种子扩散范围也不会变得非常大。这些结果通过基于个体的计算机模拟得到证实，该模拟考虑了非同胞亲属的空间聚集，假设更为现实。版权所有1998年学术出版社有限公司
