Niche Diversification and Coexistence of Insect Herbivores along the Food Quality Axis: Do Grasshoppers Ride the Rails?

基于功能营养生态学的新进展，本研究解决了一个核心问题：食物质量和可获得性对确定共存的食草昆虫物种的数量、组成和相对丰度有多重要？对昆虫食草性能至关重要的初级营养质量（蛋白质和碳水化合物水平）在天然存在的食用植物中差异很大，物种对可变食物供应的反应也不同。通过控制饲养研究，对某些物种比其他物种更有利的营养条件进行精确预测，以预测物种的共存和相对丰度。蚱蜢是一种数量丰富、种类多样、功能重要、经济重要的食草昆虫，分布在大多数草原上。对于蛋白质：碳水化合物比例不同的食物，将确定支持最佳表现（“均衡饮食”）的营养摄入目标、次优饮食的表现以及普通蚱蜢调节营养摄入以实现均衡饮食的能力。由于天然食用植物的叶子质量对蚱蜢来说通常不是最优的，因此由此产生的分析框架将预测蚱蜢如何应对不断变化的环境和不理想的食物-典型情况。以营养为基础的理论预测蝗虫群落中物种丰度和共存模式的能力将在自然变化的条件下进行测试。

Based on new advances in functional nutritional ecology, this study addresses the central question: How important is food quality and availability for determining the number, composition and relative abundances of coexisting insect herbivore species? Primary nutritional quality (protein and carbohydrate levels) important to insect herbivore performance varies greatly in naturally occurring food plants, and species responses to variable food availability differ. Using controlled feeding studies, exact predictions about nutritional conditions that favor some species over others will be devised to predict coexistence and relative abundances of species. Research focuses on grasshoppers, which are abundant, diverse, functionally significant, and economically important insect herbivores found in most grassland. Nutritional intake targets supporting optimal performance ("balanced diets"), performance on suboptimal diets, and capacities of common grasshopper species to regulate nutritional intake to achieve balanced diets will be determined for food that varies in the ratio of protein:carbohydrate. Because leaf quality of naturally occurring food plants is not typically optimal to grasshoppers, the resulting analytical framework will predict how grasshoppers can respond to changing environments with suboptimal food - the typical situation. The ability of nutrition-based theory to predict patterns of species abundance and coexistence in grasshopper communities will be tested under naturally varying conditions.