Data from: Intergenerational trade-off for water may induce a mother-offspring conflict in favour of embryos in a viviparous snake

Parent-offspring conflicts are likely to occur when resources are limiting either at pre- or postnatal stages due to intergenerational trade-offs over resources. Current theory posits that such conflicts may influence the evolution of parental allocation as well as reproductive modes. While energy allocation to the offspring has received considerable attention, the distribution of water – another potentially limited vital resource to both the mother and offspring – and the resulting outcomes remain grossly understudied. Here, we explored the intergenerational trade-off related to water resources in the viviparous aspic viper (Vipera aspis) by examining the effects of water deprivation on female physiology (body mass, haematocrit, and osmolality), water transfer to developing embryos, and reproductive performance. As a result of water deprivation, females became dehydrated, with the effects more pronounced in pregnant compared to non-reproductive females. Among pregnant females, the impacts of water deprivation on water balance were correlated with fecundity. In contrast, water deprivation had no effect on water transfer to the offspring or on reproductive performance. Our results demonstrate that, under water-constraining conditions, female water balance is compromised in favour of the developing embryos, highlighting a significant intergenerational trade-off for water. Although ectothermic reptiles are particularly tolerant in water balance perturbations, our results suggest that, like energy, water can be a conflicting resource between mother and offspring. Parent-offspring conflict over water should therefore be further investigated to better understand reproductive modes and reproductive trade-offs in terrestrial organisms.

当产前或产后阶段出现资源限制且代际间存在资源权衡时，亲子冲突（parent-offspring conflicts）极易发生。现有理论认为，此类冲突或可影响亲本资源分配策略以及繁殖模式的演化。尽管学界针对向子代分配能量的研究已获得大量关注，但水分作为母体与子代均依赖的潜在限制性关键资源，其分配模式及由此产生的后果，目前仍远未得到充分研究。本研究以胎生欧蝰（Vipera aspis）为对象，探讨了与水资源相关的代际权衡问题，通过分析水分剥夺对雌性个体生理指标（体重、血细胞比容(haematocrit)、渗透压(osmolality)）、向发育中胚胎的水分转移以及繁殖性能的影响展开研究。结果显示，水分剥夺会导致雌性个体脱水，且该效应在怀孕雌性中的表现较非繁殖雌性更为显著。在怀孕雌性中，水分剥夺对其水平衡的影响与其繁殖力呈显著相关。与之相反，水分剥夺并未对子代的水分转移过程或繁殖性能产生显著影响。本研究结果表明，在水资源受限的条件下，雌性个体的水平衡会以自身受损为代价，优先保障发育中的胚胎，这凸显了水分方面存在的重要代际权衡。尽管外温性爬行动物对水平衡紊乱的耐受性普遍较强，但本研究结果显示，与能量一样，水分同样可成为母体与子代间存在冲突的限制性资源。因此，针对水分介导的亲子冲突开展进一步研究，有助于我们更深入地理解陆地生物的繁殖模式及繁殖权衡策略。