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

理解是什么推动了各种动物形态的进化是进化生物学中一个悬而未决的关键问题。该研究项目将调查海洋蜗牛的生活和化石群体的生命之树，以及它们的外壳形状在地质时期发生的变化。蜗牛壳是生物有效防御捕食者的一个标志性例子。蜗牛是海洋中最多样化的无脊椎动物，有超过30,000种已知的现存物种和无数的化石；它们外壳形态的多样性同样令人印象深刻。它们丰富的化石记录显示，从大约1.6亿年前的中生代中期开始，贝壳特征发生了转变。当时，当恐龙在陆地上繁衍生息的时候，鱼类和螃蟹在海洋中变得越来越多样化，它们粉碎贝壳的能力也越来越强。因此，贝壳形状的变化被假设为对捕食增加的进化反应。如果捕食压力确实是贝壳形状进化过程中的一个重要驱动因素，那么在中生代中期之后，防御能力较强的形式将普遍占主导地位。研究人员将从化石和现存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体的起源时间；这些结果将用于研究中生代壳的形状轨迹。这项研究的结果将发表在同行评议的期刊和公众可以广泛访问的科学博客上。将制作大量的壳图像并在网上提供，包括科学传播网站。此外，高中生和大学生将在他们的第一次科学体验中得到指导。所研究的特定海螺类群Vetigastropoda的成员（包括鲍鱼、锁眼帽贝、顶壳等）在壳的高度和盘绕程度上有很大的差异。更短和更少卷曲的外壳是特殊的特点，可以提供机械阻力，防止外壳破碎。本研究将验证以下假设：(1)壳的形态空间受到捕食者选择压力的限制，(2)壳的形状轨迹趋向于更短和更少的螺旋形状。假设检验将通过将壳形态数据添加到从高通量序列数据推断的分子系统发育中来完成。这些化石数据将为估计植物腹足类动物系统发育的分化时间提供依据，并为不同性状进化模式的比较提供依据。

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.