The existence of a trade-off between current and future reproduction is a fundamental prediction of life-history theory. Support for this prediction comes from brood size manipulations, showing that caring for enlarged broods often reduces the parent's future survival or fecundity. However, in many species, individuals must invest in competing for the resources required for future reproduction. Thus, a neglected aspect of this trade-off is that increased allocation to current reproduction may reduce an individual's future competitive ability. We tested this prediction in the burying beetle, Nicrophorus vespilloides, a species where parents care for their offspring and where there is fierce competition for resources used for breeding. We manipulated reproductive effort by providing females with either a small brood of 10 larvae or a large brood of 40 larvae and compared the ability of these females, and virgin females that had no prior access to a carcass, to compete for a second carcass against a virgin competitor. We found that increased allocation to current reproduction reduced future competitive ability, as females that had cared for a small brood were more successful when competing for a second carcass against a virgin competitor than females that had cared for a large brood. In addition, the costs of reproduction were offset by the benefits of feeding from the carcass during an initial breeding attempt, as females that had cared for a small brood were better competitors than virgin females that had no prior access to a carcass, whilst females that had cared for a large brood were similar in competitive ability to virgin females. Our results add to our understanding of the trade-off between current and future reproduction by showing that this trade-off can manifest through differences in future competitive ability and that direct benefits of reproduction can offset some of these costs.

中文翻译：

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增加对繁殖的分配会降低未来在埋葬甲虫中的竞争力

当前和未来繁殖之间的权衡的存在是生命史理论的基本预测。对这一预测的支持来自育雏大小操作，表明照顾扩大的育雏通常会降低父母未来的存活率或繁殖力。然而，在许多物种中，个体必须投资于竞争未来繁殖所需的资源。因此，这种权衡被忽视的一个方面是增加对当前再生产的分配可能会降低个人未来的竞争力。我们在埋葬甲虫 Nicrophorus vespilloides 中测试了这一预测，这是一种父母照顾后代并且对用于繁殖的资源进行激烈竞争的物种。我们通过向雌性提供 10 只幼虫的小窝或 40 只幼虫的大窝来操纵繁殖努力，并比较这些雌性和之前没有接触过尸体的处女雌性与雌性竞争第二个尸体的能力。处女竞争者。我们发现，增加对当前繁殖的分配会降低未来的竞争能力，因为照顾小雏鸟的雌性在与原始竞争者竞争第二只尸体时比照顾大雏鸟的雌性更成功。此外，繁殖的成本被最初繁殖尝试期间从尸体喂养的好处所抵消，因为照顾小窝的雌性比之前没有接触过尸体的处女雌性是更好的竞争者，而照顾过大窝的雌性在竞争能力方面与处女雌性相似。我们的研究结果表明，这种权衡可以通过未来竞争能力的差异体现出来，并且再生产的直接收益可以抵消其中的一些成本，从而加深了我们对当前和未来再生产之间权衡的理解。