Latitudinal Gradients, Natural Selection, and Variation in N:P Stoichiometry in Plankton: A Test of the Growth Rate Hypothesis

Elser 9527322动物的元素组成(“化学计量学”)在不同物种之间有何不同？身体元素组成的差异可能会如何影响食物网的功能？该项目将检验这样一种假设，即不同物种在营养物质氮(N)和磷(P)的身体化学计量比上的差异反映了不同物种特定生长速度的差异。据预测，快速生长的生物体内必须有高浓度的核糖体。核糖体是富含磷(低N：P)的细胞结构，负责蛋白质合成和生长。因此，与生长较慢的物种相比，快速生长的生物体内的N：P比率预计会更低。我们将通过研究高纬度和中纬度浮游动物物种的元素和生化组成以及身体生长率来验证这一假设。假设沿着纬度梯度的自然选择是为了在类似的浮游物种中选择不同的生长速度。我们将研究一个参数的生态和进化决定因素，动物N：P化学计量比，这可能是影响湖泊和海洋生态系统食物网的关键因素。

Elser 9527322 How does elemental composition ("stoichiometry") of animals vary among species? How might differences in body elemental composition affect how food webs function? This project will test the hypothesis that differences among species in body stoichiometry of the nutrients nitrogen (N) and phosphorus (P) reflect differences among species in specific growth rate. It is predicted that rapidly growing organisms must have high ribosome concentrations in their bodies. Ribosomes are P-rich (low N:P) cellular structures responsible for protein synthesis and thus growth. Therefore, rapidly growing organisms are predicted to have lower N:P ratios in their bodies that slower growing species. We will test this hypothesis by studying elemental and biochemical composition and body growth rates of zooplankton species at high latitudes vs. mid-latitudes. Natural selection along latitudinal gradients is hypothesized to select for differing growth rates among similar planktonic species. We will study ecological and evolutionary determinants of a parameter, animal N:P stoichiometry, that is likely to be a key factor influencing food webs of lake and ocean ecosystems.