Data from: Anthropogenic changes in sodium affect neural and muscle development in butterflies

The development of organisms is changing drastically because of anthropogenic changes in once-limited nutrients. Although the importance of changing macronutrients, such as nitrogen and phosphorus, is well-established, it is less clear how anthropogenic changes in micronutrients will affect organismal development, potentially changing dynamics of selection. We use butterflies as a study system to test whether changes in sodium availability due to road salt runoff have significant effects on the development of sodium-limited traits, such as neural and muscle tissue. We first document how road salt runoff can elevate sodium concentrations in the tissue of some plant groups by 1.5–30 times. Using monarch butterflies reared on roadside- and prairie-collected milkweed, we then show that road salt runoff can result in increased muscle mass (in males) and neural investment (in females). Finally, we use an artificial diet manipulation in cabbage white butterflies to show that variation in sodium chloride per se positively affects male flight muscle and female brain size. Variation in sodium not only has different effects depending on sex, but also can have opposing effects on the same tissue: across both species, males increase investment in flight muscle with increasing sodium, whereas females show the opposite pattern. Taken together, our results show that anthropogenic changes in sodium availability can affect the development of traits in roadside-feeding herbivores. This research suggests that changing micronutrient availability could alter selection on foraging behavior for some roadside-developing invertebrates.由于人为活动导致原本受限的营养元素发生改变，生物体的发育正发生剧烈变化。尽管氮、磷等大量营养素（macronutrients）的改变所带来的影响已得到广泛证实，但人为活动引发的微量营养素（micronutrients）变化会如何影响生物体发育、进而可能改变进化选择动态，目前仍尚不明确。我们以蝴蝶作为研究系统，探究道路盐径流导致的有效钠含量变化，是否会对神经组织、肌肉组织这类钠限制型性状（sodium-limited traits）的发育产生显著影响。我们首先证实，道路盐径流可使部分植物类群的组织钠浓度升高1.5至30倍。随后，我们利用在路边及草原采集的马利筋上饲养的帝王蝶开展实验，结果表明道路盐径流可使雄性个体肌肉量提升、雌性个体的神经资源投入增加。最后，我们通过对菜粉蝶开展人工饲料调控实验，证实氯化钠含量变化本身即可正向影响雄性的飞行肌肉发育以及雌性的脑容量大小。钠含量的变化不仅会因性别不同产生差异化影响，还会对同一组织产生截然相反的作用：在两个蝶类物种中，雄性的飞行肌肉资源投入随钠含量升高而增加，而雌性则呈现完全相反的变化趋势。综合来看，我们的研究结果证实，人为活动导致的有效钠含量变化，会影响取食路边植物的植食性动物的性状发育。本研究还表明，微量营养素有效含量的改变，可能会改变部分路边生境无脊椎动物的觅食行为所承受的进化选择压力。