Data from: Plasticity in parental care: Interspecific competitor cues shape biparental cooperation in a burying beetle

Interspecific competition is an important evolutionary driver of many
species’ life histories and behaviours, arising wherever those species
come into conflict over limited resources. However, how such competition
shapes the plasticity of social behaviours within a species, such as
biparental care, remains less clear. The burying beetle Nicrophorus
vespilloides is an insect that exhibits biparental care, relying on small
vertebrate carcasses to breed on. Such carcasses are relatively rare and
highly valuable in nature, and so are competitively sought out by many
other species, including the bluebottle fly, Calliphora vomitoria. Despite
the close association and frequent rivalry between the two species, how
their interactions shape biparental care decisions in these beetles has
received little attention. We investigated how breeding success and
duration of male and female care change with the perceived risk of
interspecific competition by staging encounters between breeding pairs of
beetles and fly intruders. We presented breeding pairs with dead flies, at
varying times and densities, to assess changes in duration of care and
fitness outcomes. We used dead flies to ensure the beetles’ response was
driven solely by cues associated with flies, rather than direct
interaction or resource depletion. We found that the duration of both male
and female care was plastic to the presence of competitors, as both
increased their duration of care. However, these encounters also resulted
in increased breeding failures, with the strongest effects occurring when
encounters took place early in the breeding attempt. Our results
demonstrate parents’ behaviour was responsive to the perceived competitive
threat, but this plastic response is itself associated with increased
breeding failures, suggesting a trade-off between dealing with competitors
and completing other parental tasks.

种间竞争（interspecific competition）是诸多物种生活史与行为演化的重要驱动力，当不同物种因有限资源产生冲突时便会引发此类竞争。然而，这类竞争如何塑造单一物种内部社会行为的可塑性——例如双亲育幼（biparental care）——目前仍不甚明晰。埋葬甲（burying beetle）Nicrophorus vespilloides是一种展现双亲育幼行为的昆虫，其繁殖依赖小型脊椎动物尸体作为基质。这类尸体在自然环境中相对稀有且价值极高，因此会被包括丽蝇（Calliphora vomitoria）在内的诸多其他物种竞争性地搜寻与抢占。尽管这两个物种间存在紧密的生态关联与频繁的竞争对抗，但二者的互作如何塑造埋葬甲的双亲育幼决策，相关研究仍较为匮乏。本研究通过让埋葬甲的繁殖配对个体与丽蝇入侵者开展受控互作实验，探究了种间竞争感知风险对繁殖成功率以及雌雄亲代育幼时长的影响。我们在不同时间节点、以不同密度向繁殖配对体施加死蝇，以此评估育幼时长与适合度结果的变化。我们采用死蝇作为处理对象，以确保埋葬甲的行为反应仅由与蝇类相关的信号所驱动，而非源于直接互作或资源消耗。研究结果显示，雌雄亲代的育幼时长均会随竞争者的存在发生可塑性改变，二者均显著延长了育幼时长。然而，这类互作同时也会提升繁殖失败率，且该效应在繁殖早期开展互作时最为显著。本研究结果表明，亲代行为会响应其感知到的竞争威胁，但这种可塑性响应本身也伴随着繁殖失败率的上升，这暗示亲代在应对竞争者与完成其他育幼任务之间存在权衡（trade-off）。