Biology Department, Southern Connecticut State University. New Haven, CT, 06501, USA.
Biology Department, Southern Connecticut State University. New Haven, CT, 06501, USA.
Environ Pollut. 2022 Mar 1;296:118757. doi: 10.1016/j.envpol.2021.118757. Epub 2021 Dec 29.
Organisms that rely on aquatic habitats in roaded landscapes face a growing array of consequences from pollution, especially due to freshwater salinization. Critically, these consequences can vary from population to population depending on exposure histories and evolutionary responses. Prior studies using transplant and common garden experiments have found that aquatic-stage wood frogs (Rana sylvatica) from roadside populations are less fit in the wild and more sensitive to road salt than their counterparts from woodland populations away from roads. While this pattern is consistent with local maladaptation, unresolved insights into the timing and duration of these effects leave open the possibility that negative outcomes are countered during development. Here, we asked whether the survival disadvantage of roadside wood frogs is stage-specific, and whether this disadvantage reverses before metamorphosis. We used a common garden road salt exposure experiment and a field-based reciprocal transplant experiment to examine differences in survival across life-history stage and with respect to population type. In each experimental context, roadside embryos showed a survival disadvantage relative to woodland embryos, and this disadvantage was not reversed prior to metamorphosis. We also found that salt exposure delayed metamorphosis more strongly for roadside than woodland populations. Together, these results suggest that local maladaptation in aquatic-stage wood frogs is driven by embryonic sensitivity to salt and that roadside populations are further compromised by delayed developmental rates. Future studies should consider which embryonic traits fail to adapt to salt toxicity, and how those traits might correlate with terrestrial trait variation.
依赖道路景观中水生栖息地的生物面临着越来越多的污染后果，特别是由于淡水盐化。至关重要的是，这些后果因暴露史和进化反应而异，在不同种群之间存在差异。先前使用移植和共同花园实验的研究发现，来自路边种群的水生期林蛙（Rana sylvatica）在野外的适应性较差，对道路盐的敏感性高于来自远离道路的林地种群的同类。虽然这种模式与局部适应不良一致，但对于这些影响的时间和持续时间的见解仍未解决，这使得负面结果在发育过程中得到逆转的可能性仍然存在。在这里，我们想知道路边林蛙的生存劣势是否具有阶段性，以及这种劣势是否在变态之前逆转。我们使用了共同花园道路盐暴露实验和基于现场的互惠移植实验，以检查不同种群类型在整个生命史阶段的生存差异。在每种实验环境中，路边胚胎相对于林地胚胎表现出生存劣势，并且在变态之前这种劣势没有逆转。我们还发现，盐暴露使路边种群比林地种群的变态时间延迟得更厉害。综上所述，这些结果表明，水生期林蛙的局部适应不良是由胚胎对盐的敏感性引起的，而路边种群由于发育速度较慢而进一步受到损害。未来的研究应考虑哪些胚胎特征不能适应盐毒性，以及这些特征如何与陆地特征的变化相关。
