DISSERTATION RESEARCH: Integrative research in gastropods: Phylogeny and shell shape evolution

了解是什么驱动了不同动物形态的进化，是进化生物学中一个基本上没有答案的关键问题。该研究项目将调查海洋蜗牛的生活和化石群体的生命树，以及它们的外壳形状在地质时期发生的变化。蜗牛壳是生物体有效防御捕食者的标志性例子。有超过30，000个被描述的活物种和无数的化石，蜗牛是海洋中最多样化的无脊椎动物群体;它们的外壳形式的多样性同样令人印象深刻。它们丰富的化石记录显示，大约1.6亿年前的中生代中期开始，贝壳特征发生了转变。当时，恐龙在陆地上繁衍生息，而海洋中的鱼类和螃蟹则不断增加，它们的破碎能力也越来越强。因此，假设贝壳形状的变化是对捕食增加的进化反应。如果捕食压力确实是一个重要的驱动力，在外壳形状的演变，一个更好的防御形式的普遍优势，预计在中生代中期之后。研究人员将从化石和活物种的大量贝壳中收集数据，以推断它们之间的关系，并估计不同形状的蜗牛群的起源时间;这些结果将用于研究中生代期间贝壳形状的轨迹。这项研究的结果将发表在同行评议的期刊和科学博客上，公众可以广泛访问。将制作大量贝壳图像并在网上提供，包括科学传播网站。此外，高中和本科生将在他们的第一次科学经验的指导。研究中的海蜗牛的特定类群Vetigastropoda的成员（包括鲍鱼、匙孔帽贝、顶壳和其他）在壳高度和盘绕水平方面存在很大差异。较短和较少盘绕的壳体是可以提供对壳体破碎的机械阻力的特殊特征。本研究将验证以下假设：（1）在捕食者选择压力的作用下，贝壳的形态空间变得更加有限;（2）贝壳形状的轨迹趋向于更短和更少的螺旋形。假设检验将通过将壳形态学数据添加到从高通量序列数据推断的分子遗传学中来完成。这些化石数据将为估计岩腹足类进化过程中的分歧时间和比较不同的性状进化模型提供依据。

Understanding what drives the evolution of diverse animal forms is a largely unanswered key question in evolutionary biology. This research project will investigate the tree of life of living and fossil groups of marine snails, and the changes that happened in the shape of their shells through geological time. Snail shells are an iconic example of an organisms' effective defense against predators. With more than 30,000 described living species and countless fossils, snails are the most diverse group of invertebrate animals in the oceans; the diversity of their shell forms being equally impressive. Their rich fossil record shows a transition of shell features starting in the middle of the Mesozoic Era, around 160 million years ago. At that time, while dinosaurs thrived on land, fishes and crabs with increasing capacity of crushing shells were diversifying in the oceans. Changes in shell shape are thus hypothesized to be an evolutionary response to increased predation. If predation pressure was indeed an important driver during the evolution of shell shape, a general dominance of better-defended forms would be expected after the mid-Mesozoic. The researchers will gather data from an ample set of shells from fossil and living species to infer how they are related to each other and to estimate the times of origin of snail groups with different shapes; these results will be used to investigate the trajectory of the shell shape during the Mesozoic. Results from this research will be published in peer-reviewed journals and science blogs broadly accessible to the public. A large number of shell images will be produced and made available online, including websites for science communication. In addition, high school and undergraduate students will be mentored in their first experience in science. The members of Vetigastropoda, the specific group of marine snails under study (including abalone, key-hole limpets, top-shells and others), present great variation in shell height and level of coiling. Shorter and less coiled shells are particular features that could offer mechanical resistance against shell crushing. This study will test the hypotheses that: (1) the morphospace of shells became more restricted in response to predator selective pressure, and (2) the trajectory of shell shape trended towards shorter and less spired forms. Hypothesis testing will be accomplished by adding shell morphological data to a molecular phylogeny inferred from high-throughput sequence data. The fossil data will provide the basis for estimating divergence times in the phylogeny of vetigastropods, and for the comparison among distinct models of trait evolution.