RAPID: Testing macronutrient imbalance as a key factor limiting range expansion in herbivores

昆虫爆发在自然界是常见的，而蝗虫爆发由于其巨大的生态和农业影响而特别严重。偶尔，昆虫种群在广阔的地理范围内爆发，然后在几个月或几年内崩溃回较小的永久繁殖区。人口增长和下降的机制都没有得到很好的理解，但我们对人口下降的认识尤其贫乏。这是生物生物学和生态学的重大挑战，对人类社会具有重大影响。该研究项目将利用正在爆发的南美蝗虫（取消血吸虫）来检验一种假设，即取消血吸虫获得生长所需的最佳营养平衡的能力限制了它们在南美洲广大地区保持持续高种群的能力。蝗虫是全球粮食安全面临的重大挑战，其暴发造成80%至100%的作物损失。未来，通过与政府植物保护机构的合作，这项研究可以直接应用于改善生计、人类和环境健康以及全球粮食安全的战略。此外，该奖项将支持博士后和学生培训，以及跨文化交流。南美蝗虫（Schistocerca cancellata）正在经历60年来最大的数量激增，从阿根廷西北部的永久繁殖区扩展到阿根廷的大部分地区，并扩展到玻利维亚和巴拉圭，在这三个国家造成了全国性的紧急情况。初步数据支持的一种假设是，在其扩张区，cancellata无法获得足够高的碳水化合物：蛋白质比以最大化其适应性的食物。这种营养不良会导致扩张区内的人口减少。本项目将通过以下方式对碳水化合物不足假说进行验证：1)在不同植物常量营养元素中位比的场地上，评估野刺荆芥的植物常量营养元素含量和摄食行为；2)测定饲料中宏量营养素含量对野外平梭子鱼幼鱼生产性能的短期影响；3)在受控环境条件下，测定饲料中宏量营养素含量对实验室平梭子鱼生产性能的终生影响。这些实验将共同测试可能导致衰退区和入侵区蝗虫数量波动的机制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Insect outbreaks are common in nature and locust outbreaks are particularly dramatic due to their tremendous ecological and agricultural impacts. Occasionally, insect populations explode throughout broad geographic ranges, and then collapse back into their smaller permanent breeding zones within months or years. Neither the mechanisms of population expansions nor declines are well understood, but our knowledge of the declines is particularly poor. This is a major challenge in organismal biology and ecology, with significant implications for human society. This research project will take advantage of an ongoing outbreak of the South American locust (Schistocerca cancellata) to test the hypothesis that the ability for S. cancellata to attain a balance of nutrients optimal for growth limits their capacity to maintain persistent high populations over broad regions of South America. Locusts are a major challenge for food security globally, with outbreaks causing 80-100% crop losses. In the future, working collaboratively with government plant protection agencies, this research can be directly applied to strategies to improve livelihoods, human and environmental health, and global food security. Moreover, this award will support postdoctoral and student training, and cross-cultural exchange. The South American locust (Schistocerca cancellata) is experiencing its largest population upsurge in 60 years, expanding beyond its permanent breeding zone in northwest Argentina into a much larger part of Argentina and beyond into Bolivia and Paraguay, causing national emergencies in those three countries. One hypothesis for why S. cancellata do not persist at high densities in their invasion zone, which is supported by preliminary data, is that S. cancellata in their expansion zones are unable to obtain food of sufficiently high carbohydrate:protein ratio to maximize their fitness. This poor nutrition then leads to population decreases in their expansion zone. This carbohydrate insufficiency hypothesis will be tested in this project by: 1) assessing the plant macronutrient contents and feeding behavior of S. cancellata in the field at sites differing in median plant macronutrient ratios; 2) measuring the short-term effects of dietary macronutrient content on the performance of juvenile S. cancellata in the field, and 3) measuring the whole-lifetime effects of dietary macronutient content on the performance of S. cancellata in the lab under controlled environmental conditions. Together these experiments will test the mechanisms potentially responsible for fluctuations in locust populations in the recession and invasion zones.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.