Dissertation Research: The Macroevolutionary Consequences of a Neogastropod Adaptation

虽然进化生物学家已经将适应的研究正式化，但很少有研究既解释为什么一种特征是适应的，又如何影响一种血统的历史。研究生丽贝卡·普莱斯在她的导师大卫·雅布朗斯基博士的帮助下，在一项关于一组腹足类软体动物的化石和活物种的研究中解决了这个问题。新腹足类是一个理想的焦点分类群，因为它们具有高度的现代多样性，允许使用活动物来确定所述特征的功能意义，并且具有丰富的化石记录，可以直接观察地质时代的形态变化。被测试的假说涉及腹足类贝壳孔上的柱状褶皱，传统上被用作分类学特征，并可能起到适应的作用，例如，在身体缩回以躲避捕食者，或在肌肉附着中以提高运动速度。这种功能适应可能影响了片形虫科(新腹足目：软体动物)内不同亚系物种多样性的速度和模式。这个家族有丰富的化石记录，褶皱形态多样，根据初步的系统发育，曾多次失去和增加褶皱。学生将使用计算机断层扫描(芝加哥郊外的阿贡国家实验室提供的设备)来描绘3维图像，并对这个家族中约100个样本中描述柱状皱褶形态的一系列特征进行量化。为了测试柱状褶皱的适应性，并评估一些假设的功能，学生将(1)将褶皱形态的每个方面映射到进化树上，以确定它何时进化，(2)在海洋空间站对有褶皱和没有褶皱的贝壳进行一系列功能实验。这些实验旨在提高我们对形态和功能之间的相关性的理解，并将结果外推到系统发育上，以从功能上追踪1.3亿年的筋膜历史。

0073248Jablonski and PriceAlthough evolutionary biologists have formalized the study of adaptation, few studies explain both why a trait is adaptive and ho--w it affects a lineage's history. Graduate student Rebecca Price, assisted by her adviser Dr. David Jablonski, addresses this issue in a study of fossil and living species of a group of gastropod molluscs of the Fasciolariidae. The neogastropods are an ideal focal taxon because they have high modern diversity, permitting the use of living animals to determine the functional significance of the character in question, and a rich fossil record directly to observe morphological changes through geologic time. The hypotheses under test concern the columellar folds, or plications on a gastropod shell's aperture, that traditionally are used as taxonomic characters, and that may function as adaptations, for example in body retraction to avoid predators, or in muscle attachment to increase speed of movement. Such functional adaptations may have affected rates and patterns of species diversification in different sublineages within the Fasciolariidae (Neogastropoda: Mollusca). This family has a rich fossil record, a range of fold morphologies, and, according to a preliminary phylogeny, has lost and added folds repeatedly. The student will use computed tomography (facilities made available at Argonne National Laboratory outside Chicago) to depict in 3-dimensions and quantify a series of characters that describe columellar fold morphology in ca. 100 samples in this family. To test that columellar folds are adaptive, and to evaluate some hypothetical functions, the student will (1) map each aspect of fold morphology onto an evolutionary tree to determine when it evolved, and (2) conduct a series of functional experiments at a marine station on shells with and without folds. The experiments are designed to improve our understanding of correlations between morphology and function, with the results extrapolated back on the phylogeny to track the 130 million years of fasciolariid history in functional terms.