Bigger is not always better:: Conflicting selective pressures on seed size in Quercus ilex
Bigger is not always better:: Conflicting selective pressures on seed size in Quercus ilex
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DOI：
10.1111/j.0014-3820.2004.tb01574.x
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发表时间：
2004-01-01
期刊：
影响因子：
3.3
通讯作者：
Gómez, JM
中科院分区：
文献类型：
--
作者：
Gómez, JM
大多数关于后代大小的进化生态学的理论处理都假设每个后代的投资对后代适合度的简单而直接的影响。本文通过实验确定冬青栎种子质量与几个主要适合度组分之间的关系，估计生命周期早期作用于种子质量的表型选择，并发现从传播到建立的不同阶段之间可能发生的选择冲突。我发现了一个积极的影响橡子大小对大多数健身组件有关的幼苗建立。大尺寸增加发芽率和幼苗存活率，加速发芽时间，并增强幼苗生长。然而，也有一个直接的负面影响，橡子的大小对生存捕食，因为大橡子是非常喜欢的主要postdispersion种子捕食者在研究现场，野猪和木鼠。由于逃脱捕食的概率较低，在此分量上估计的大橡子的适合度显着低于小橡子的适合度。因此，种子大小影响健身在两个不同的方式，产生相反和冲突的选择力。这些研究结果表明，一般的假设，后代的健身是一个固定的种子大小的正函数需要重新考虑一些系统。冲突选择的存在可能解释了在某些植物物种中发生的最佳种子大小，而不会引起种子数量-大小的权衡。
Most theoretical treatments of the evolutionary ecology of offspring size assume a simple and direct effect of investment per offspring on offspring fitness. In this paper 1 experimentally determine the relationship between seed mass and several main fitness components of the oak Quercus ilex, to estimate phenotypic selection acting on seed mass during the early life cycle and to discover any potential selective conflicts occurring between different stages from dispersal to establishment. I found a positive effect of acorn size on most fitness components related to seedling establishment. Large size increased germination rate and seedling survival, accelerated germination timing, and enhanced seedling growth. Nevertheless, there was also a direct negative effect of acorn size on survival to predation, because large acorns were highly preferred by the main postdispersal seed predators at the study site, wild boars and wood mice. Because of the low probability of escape from predation, the fitness of large acorns estimated on this component was significantly lower than the fitness of smaller acorns. Therefore, seed size affected fitness in two different ways, yielding opposing and conflicting selective forces. These findings suggest that the general assumption that offspring fitness is a fixed positive function of seed size needs to be reconsidered for some systems. The existence of conflicting selection might explain the occurrence of an optimal seed size in some plant species without invoking a seed number-size trade-off.