Physiological Determinants of Vertical Zonation in Congeneric Marine Invertebrates: Comparative Analysis of Species Replacement Along the Subtidal to Intertidal Gradient

生态学家和进化生物学家非常感兴趣的一个问题是，“为什么物种出现在某些栖息地，而不是在其他栖息地？”控制物种分布的一个基础是它们对环境中物理因素的耐受性，特别是环境温度。这一事实在岩质潮间带栖息地中表现得尤为明显：在从潮下区到潮间带的梯度中，热条件变化很大，沿着这一样带发现的一组物种也是如此。一属中的一种被同一属的近亲物种（同属）所取代是很常见的。本提案支持的研究考察了来自不同垂直位置的同系物之间的生理、生化和分子差异，以努力确定有助于解释分布模式变化的适应性差异。要研究的系统包括：(i)热休克反应，修复热损伤蛋白质的救援系统；（ii）对温度明显敏感的心脏功能；（iii）膜完整性，这是许多生理过程所必需的；（iv）神经功能，这在设定热耐受极限时可能很重要。要使用的技术包括各种各样的分子方法（基因测序和基因表达模式分析），生化方法（测量热损伤蛋白的水平）和生理分析（心脏功能和神经信号的产生率）。研究种类包括蜗牛属和瓷蟹（石蟹属）。这两组同系物分布在广泛的垂直和纬度范围内，因此是阐明温度适应机制的良好研究系统。对适应不同温度的同系物的研究，使人们能够特别清楚地了解适应性变化在建立环境最优和容忍极限方面的作用。通过确定建立热最佳和极限的潜在机制，可以以更明确的方式理解预测的全球变暖的影响。

A question of great interest to ecologists and evolutionary biologists is, "Why do species occur in certain habitats and not in others?" One basis for governing the distributions of species is their tolerance of physical factors in the environment, notably ambient temperature. This fact is illustrated especially clearly in rocky intertidal habitats: In the gradient from the subtidal region to the intertidal zone, thermal conditions vary sharply, as does the set of species found along this transect. It is common for one species of a genus to be replaced by a closely related species of the same genus (a congener). The studies supported by this proposal examine the physiological, biochemical and molecular differences among congeners from different vertical sites in an effort to identify adaptive differences that help to explain variation in distribution patterns. The systems to be studied include: (i) the heat-shock response, a rescue system for repairing heat-damaged proteins; (ii) heart function, which is markedly sensitive to temperature; (iii) membrane integrity, which is essential for many physiological processes, and (iv) nerve function, which may be of importance in setting thermal tolerance limits. Techniques to be used include a wide variety of molecular methods (sequencing of genes and analysis of gene expression patterns), biochemical approaches (measurement of levels of heat-damaged proteins) and physiological analyses (rates of heart function and generation of nerve signals). Study species include snails of the genus Tegula and porcelain crabs (genus Petrolisthes). Both sets of congeners occur over wide vertical and latitudinal ranges and thus are excellent study systems for elucidating mechanisms of adaptation to temperature. The study of congeners adapted to different temperatures allows a particularly clear picture to be developed of the role of adaptive change in establishing environmental optima and tolerance limits. By identifying the underlying mechanisms that establish thermal optima and limits, the effects of predicted global warming could be understood in a more definitive manner.