Ecological Implications of Body Size in Deep-Sea Gastropods

该项目的主要目标是在体型最优模型的背景下批判性地评估深海腹足类动物的体型趋势。体型的进化是一个重要的问题，它关系到群落结构和生物多样性的保护。深海底栖动物最明显和最普遍的特征是大多数物种的体型都很小。记录和解释深海中大小模式的许多尝试都集中在物种或整个动物群组成部分之间的变化上，并导致了相互矛盾和矛盾的结果。总的来说，人们没有认识到，研究大小作为对深海环境的适应，必须包括对物种内部的分析，使用标准化的大小测量来适应共同的生长阶段。此外，大多数研究没有采用适当的统计方法来证明或比较尺寸趋势。Sebens的海洋无脊椎动物体型最优模型为探索深海物种体型进化提供了一个有用的概念框架。它预测，在营养输入减少、食物摄取率降低和觅食成本增加的情况下，最佳体型应随深度而减小；但当更大的规模带来竞争优势时，它也允许在最优规模之上的进化。对8种深海腹足动物的初步分析表明，幼虫和成虫的体型都有随深度增加而增加的明显趋势。基于这一初步分析和Sebens的最优性模型，本项目将检验物种内部和物种之间存在尺寸深度趋势的假设。利用生态相似的单一分类学上一致的物种（Turridae）和协方差分析，该项目将测试四个具体的预测：1。该尺寸随物种深度的增加而增加，但尺寸-深度关系的斜率随深度的增加而减小。当物种沿着深度梯度相互替换时，这个尺寸会减小。3 .物种的大小会有一个纬度梯度，在高纬度地区发现的物种更大；高产量地区的尺寸深度回归将比低产量地区的回归具有更高的海拔。该项目将首次提供深海物种大小地理变化的准确分析，并将对我们对大小作为对深海环境的适应性反应的基本理解做出重大贡献。＊＊＊

9301687 REX The primary objective of this project is to critically evaluate size trends in deep-sea gastropods in the context of an optimality model of body size. The evolution of body size is a problem of fundamental interest, and one that has an important bearing on community structure and conservation of biodiversity. The most obvious and pervasive characteristic of the deep-sea benthos is the small size of most species. The numerous attempts to document and explain size patterns in the deep sea have focused on variation among species or whole faunal components, and have led to conflicting and contradictory results, In general, there has been a failure to recognize that studying size as an adaptation to the deep-sea environment must include analyses within species using measures of size that are standardized to common growth stages. Also, most studies have not applied appropriate statistical methods for either demonstrating or comparing size trends. Sebens' optimality model of body size in marine invertebrates provides a useful conceptual framework for exploring the evolution of size in deep-sea species. It predicts that optimal body size should decrease with depth under circumstances where decreased nutrient input lowers food intake rates and increases costs of foraging; but it also allows for the evolution of size above the optimum when larger size confers a competitive advantage. A preliminary analysis within eight species of deep-sea gastropods reveals a clear trend for size to increase with depth in both larvae and adults. Based on this preliminary analysis and Sebens' optimality model, this project will test the hypothesis that there are within- and among- species components to size-depth trends. Using a single taxonomically coherent family of ecologically similar species (the Turridae) and the analysis of covariance, this project will test four specific predictions: 1. that size will increase with depth within species, but that the slopes of size-depth relations will decrease with depth, 2. that size will decrease among species as they replace one another along a depth gradient, 3. that there will be a latitudinal gradient in size, with larger species found at higher latitudes, and 4. that size-depth regressions in regions of higher production will have higher elevations than those in regions of low productions. This project will provide the first accurate analysis of geographic variation in size within deep-sea species, and will contribute significantly to our basic understanding of size as an adaptive response to the deep-sea environment. ***