Morris Douglas W
Centre for Northern Studies, Department of Biology, School of Forestry, Lakehead University, Thunder Bay, Ontario, P7B 5E1, CANADA.
Evolution. 1992 Dec;46(6):1848-1861. doi: 10.1111/j.1558-5646.1992.tb01173.x.
The most productive litter size (five) was not as common as expected in a free-living population of white-footed mice. I evaluated four competing hypotheses that can explain this pattern. Reproductive costs and annual variation in recruitment appear to be insufficient explanations for the empirical distribution of litter size. Optimal investment of reproductive resources that vary among parents is supported by some tests, but not by all. The abundance of litters less than the apparent optimum is at least partially explained by asymmetric survival in large litters (the cliff-edge hypothesis). Hypotheses that explain the empirical distribution of brood size are not mutually exclusive. Several mechanisms can act alone, or interact, to create an average brood size less than that which appears to produce the greatest number of descendants.
在白足鼠的自由生活种群中，最高产的窝仔数（五只）并不像预期的那样常见。我评估了四种相互竞争的假设，这些假设可以解释这种模式。生殖成本和每年招募数量的变化似乎不足以解释窝仔数的实际分布情况。一些测试支持了不同亲本之间生殖资源的最优投资，但并非所有测试都支持。小于明显最优窝仔数的窝仔数量较多，这至少部分可以用大窝仔中不对称的存活率来解释（悬崖边缘假设）。解释窝仔数实际分布的假设并非相互排斥。几种机制可以单独起作用，或相互作用，从而产生一个平均窝仔数，该平均窝仔数小于似乎能产生最多后代的窝仔数。
