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，必须让它们的后代在面对这种变异时为生存做好准备。为了确保至少有一些后代存活下来繁殖，母亲可以采取几种策略。(i)悲观主义：母亲们可能会投入比通常所需更多的资源，以防时势艰难。(ii)可塑性：母亲可以根据当时的环境条件为后代提供改变表型的能力。(iii)赌注对冲（或风险分散）：母亲可能会产生具有各种表型的后代，希望至少其中一些能够存活下来繁殖。赌注对冲的概念在后代出现在不同季节的生物体中得到了大量的支持：在这种情况下，非直观的结果是增加后代的变异性可以减少未来成功的方差，从而有利于适应性并导致可遗传的赌注对冲行为在种群中传播。这个迷人的解释也被应用到生物体中，这些生物体的后代在一个季节内经历了不可预测的空间变化。不过，这样的代客下注对冲其实很难演变。代际间的赌注对冲之所以有效，是因为某种表型的后代都经历了相同的环境。代内赌注对冲只在非常小的群体中起作用，因为环境和表型之间没有相关性。蚜虫已被推广为一代人内赌注对冲的经典例子。当蚜虫母亲产生无翅的后代时，它们会给它们相同数量的卵巢管（生殖投资），因为它们的环境是可预测的（母亲生活在同一种植物上）。然而，当母亲生下有翅膀的后代时，他们必须飞到一个不可预测的环境中，这给了他们可变的生殖潜力。我的目的是证明，这只能被认为是在一代赌注对冲，只能受到自然选择的青睐，如果后代具有不同的生殖潜力也有不同的传播倾向和传播距离。通过这种方式，表型和环境之间的相关性被创造出来，满足了赌注对冲作为对异质性的适应性反应的假设。更好地了解蚜虫的赌注对冲将为我们提供更清晰的信息，以了解在不断变化且极其多变的环境中生活的最佳策略。这可能会指导在气候变化中的虫害控制策略，甚至可能在面对不可预测和资源有限的未来时提出人力资源使用的最佳策略。

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.