Gambling on grandchildren: do aphids hedge their bets?

所有的生物都生活在一个不确定的世界里，面对这种变异，它们必须为后代的生存做好准备。为了确保至少有一些后代存活下来繁衍后代，母亲们可以采取几种策略。(I)悲观情绪：母亲们可能会投入比正常情况下更多的资源，以防日子不好过。(2)可塑性：母亲可根据当时的环境条件为后代提供改变表型的能力。(3)套期保值(或风险扩散)：母亲可能会产生具有各种表型的后代，希望至少其中一些后代能存活下来繁殖。赌注对冲的概念在其后代出现在不同季节的生物体中得到了大量支持：在这种情况下，非直觉的结果是，增加一个后代的变异性可以减少他们未来成功的差异，从而有利于适应能力，并导致可遗传的赌注对冲行为在种群中传播。这一迷人的解释也适用于其后代在一个季节内经历不可预测的空间变化的生物体。然而，这种代内押注套期保值实际上很难演变。世代之间更好的对冲之所以有效，是因为某一表型的后代都经历了相同的环境。世代内较好的对冲只在非常小的种群中起作用，因为环境和表型之间没有相关性。蚜虫被宣传为一代内押注对冲的经典例子。当蚜虫母亲产生无翅后代时，她们会给它们提供统一数量的卵巢孔(生殖投资)，因为它们的环境是可预测的(与母亲生活的植物相同)。然而，当母亲生下有翅膀的后代时，这些后代必须飞到一个不可预测的环境中，这就给了他们不同的繁殖潜力。我的目的是证明，这只能在比对冲更好的世代内考虑，并且只有在具有不同繁殖潜力的后代也有不同的扩散倾向和扩散距离的情况下，才能受到自然选择的青睐。通过这种方式，表型和环境之间的相关性被创造出来，满足了更好的对冲作为对异质性的适应性反应的假设。更好地了解蚜虫的套期保值将为我们提供更清晰的信息，使我们了解在不断变化的、极其多变的环境中生存的最佳策略。这可能会指导气候变化中的虫害防治策略，甚至可能建议在面对不可预测和资源有限的未来时使用人力资源的最佳策略。

All organisms live in an uncertain world, and must prepare their offspring for survival in the face of this variation. In order to ensure that at least some offspring survive to reproduce, several tactics are available to mothers. (i) Pessimism: mothers may invest more resources than are normally required, just in case times are hard. (ii) Plasticity: mothers may provide offspring with the ability to change phenotype according to the prevailing environmental conditions. (iii) Bet hedging (or risk spreading): mothers may produce offspring with a variety of phenotypes, in the hopes that at least some of them survive to reproduce. The concept of bet hedging has received a great deal of support in organisms whose offspring emerge in different seasons: in this scenario, the non-intuitive outcome is that increasing the variability of ones offspring can reduce the variance in their future success, thus benefitting fitness and causing heritable bet hedging behaviour to spread through populations. This glamorous explanation has also been applied to organisms whose offspring experience unpredictable spatial variation within a season. However, such WITHIN generation bet hedging is actually very difficult to evolve. Between generation bet hedging works because offspring of a certain phenotype all experience the same environment. Within generation bet hedging only works in VERY small populations, because there is no correlation between environment and phenotype. Aphids have been promoted as a classic example of within-generation bet hedging. When aphid mothers produce unwinged offspring, they give them a uniform number of ovarioles (reproductive investment) because their environment is predictable (the same plant on which the mother lives). However, when mothers make winged offspring, who must fly away into an unpredictable environment, they give them variable reproductive potential. I aim to demonstrate that this can only be considered within generation bet hedging, and can only be favoured by natural selection, if offspring with different reproductive potential also have different dispersal propensities and dispersal distances. In this way, a correlation between phenotype and environment is created that satisfies the assumption of bet hedging as an adaptive response to heterogeneity. A better understanding of bet hedging in aphids will provide us with clearer information on optimal tactics for living in a changing, and extremely variable, environment. This may guide tactics for pest control in a changing climate, and may even suggest optimal tactics for human resource use in the face of an unpredictable and resource-limited future.