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.

当产前或产后阶段存在资源限制时，由于资源的代际权衡（intergenerational trade-off），亲子冲突（parent-offspring conflict）极易发生。当前理论认为，此类冲突或会影响亲本资源分配（parental allocation）策略以及生殖模式的演化。尽管针对后代的能量分配已受到广泛关注，但水分作为对母体与子代均至关重要且可能受限的另一类关键资源，其分配模式及由此产生的后果仍未得到充分研究。本研究以胎生阿斯佩蝰（Vipera aspis）为研究对象，通过探究水分剥夺对母体生理指标（体重、血细胞比容（haematocrit）、渗透压（osmolality））、向发育中胚胎的水分转运以及繁殖性能的影响，剖析了其与水资源相关的代际权衡。水分剥夺会导致母体出现脱水现象，且妊娠个体的脱水症状相较于非繁殖雌性更为显著。在妊娠母体中，水分剥夺对其水分平衡的影响与繁殖力呈显著相关。与之相反，水分剥夺并未对子代的水分转运或繁殖性能产生影响。本研究结果表明，在水资源受限的条件下，母体会牺牲自身水分平衡以保障发育中胚胎的供水需求，这凸显了水资源方面存在的重要代际权衡。尽管外温性爬行动物对水分平衡紊乱具有较强的耐受能力，但本研究结果显示，与能量类似，水分同样可能成为母体与子代间的冲突性资源。因此，未来需进一步针对水分相关的亲子冲突展开研究，以更深入地理解陆生生物的生殖模式与生殖权衡机制。