Morphology: how does it vary and what does it reveal about evolution? Ontogenetic and phylogenetic variation in extant brachiopod crura and loops

形态?它是如何变化的，它揭示了进化的什么？现存腕足动物足部和环的个体发育和系统发育变异摘要生物体形状是生物体潜在基因组成与环境相互作用的媒介。只有通过研究形状及其变化的方式和原因，进化生物学家才能开始理解潜在的基因/环境相互作用的产物。由于形状是已灭绝（不再存活）生物遗传信息的主要来源，古生物学家假设形状变化的边界与枝（进化实体）密切相关，这是基于等级的分类群的等级所暗示的。这种假设很少得到验证。该研究项目将测试现存腕足动物分类群的演化状态，腕足动物是古生物学上最重要的后生动物类群之一，其多样性和丰度已超过5亿年。大约95%的物种已经灭绝；由于有5%的小腹足类和terebratulide类腕足类现存（仍然存活），我们有一个难得的机会(1)在不同的等级水平上测试分子和形态系统发育，这是以前从未尝试过的；(2)比较物种内、物种间、不同生长阶段成虫的重要功能特征，主要是脚和环的大小和形状；(3)利用这一信息对足部和环部的成人和生长阶段进行定量比较，并将生长转变置于由形状和分子告知的进化背景中。如果古生物学家不能可靠地区分进化信息和明显具有误导性的形状变化，那么从观察到的变化中得出的进化解释从根本上来说是不可检验的。这项对现存腕足动物的研究结果可能对从任何已灭绝的后生动物群体的分类数据中得出的宏观进化解释产生深远的影响，揭示了与不加批判地接受未经检验的同源性假设（共享共同祖先的特征）相关的问题。利用简约和贝叶斯分析方法，对所有现存的鼠脚藻属和terebratuldine属的代表性物种，以及所有已经获得分子序列的现存terebratuldine属进行分析。在脚和环的生长变化将量化使用几何形状分析的三维图像，从微ct扫描获得的钙质lophore支持在活的腕足动物。利用外群分析方法，将生长性状极性与系统发育极性进行比较。树比较方法将用于评价定性和定量形态特征分布模式，并比较分子和形态分析的结果。还将进行全证据分析，并与单独来自形态学和单独来自分子序列数据的证据进行比较。虽然腕足类这个词并不像蛤或蜗牛那样家喻户晓，但腕足类动物为研究其寿命和谱系的形态变化提供了绝佳的机会，化石记录中保存了大量灭绝的物种多样性，而今天生活的物种多样性更小，更容易管理。该研究项目将通过加州大学戴维斯分校的进化生物学和古生物学课程为本科生和研究生的教育做出贡献，并将支持培训和指导一名女研究生和一名女博士后研究员。我们将利用机会与公众分享我们的研究成果在野餐日（加州大学戴维斯分校校园范围内的年度开放日）和探索科学中心（戴维斯市）。腕足动物的三维图像将在一个网站上完全开放，该网站是为了分享我们研究的视觉结果而创建的。我们开始对脊椎动物形态的发展和进化有了更复杂的了解，但我们对更多种类的海洋无脊椎动物的进化形态的了解远远落后。我们的研究将努力向公众介绍和解释一组海洋无脊椎动物迷人的古生物复杂性的一部分，并使公众参与关于进化本质的讨论：认识、描述和解释随时间的变化。

Morphology? how does it vary and what does it reveal about evolution? Ontogenetic and phylogenetic variation in extant brachiopod crura and loopsAbstract Organism shape is the medium through which the underlying genetic makeup of the organism interacts with the environment. Only by studying shape and how and why it varies, can evolutionary biologists begin to understand the product of underlying genes/environment interaction. Because shape is the primary source of heritable information from extinct (no longer living) organisms, paleontologists assume that the boundaries of shape variation correspond closely to clades (evolutionary entities), as implied by the hierarchy of rank-based taxa. This assumption is seldom tested. This research project will test the clade status of taxa recognized in extant Brachiopoda, one of the most paleontologically significant metazoan groups in terms of diversity and abundance for over half a billion years. Roughly 95% of species are extinct; with the 5% of rhynchonellide and terebratulide brachiopod species extant (still living), we have a rare opportunity (1) to test molecular and morphological phylogenies at different hierarchical levels, never before attempted for this clade; (2) to compare the size and shape of functionally significant features, primarily features called crura and loops, among adults within and among species, and across growth stages; (3) to use this information to produce quantitative comparisons among adults and growth stages in crura and loops, and place the growth transformations in an evolutionary context informed by both shape and molecules. If paleontologists cannot reliably distinguish evolutionarily informative from significantly misleading shape variation, evolutionary interpretations drawn from the observed variation are fundamentally untestable. The results of this study on living brachiopods can have profound implications for macroevolutionary interpretations derived from taxonomic data on any group of extinct metazoans, in revealing problems associated with uncritically accepting untested assumptions of homology (shared common ancestry of features). Analyses will be conducted on representative species of all living rhynchonellide and terebratulidine genera, and all lving terebratellidine genera for which molecular sequences have been made available, using parsimony and Bayesian analysis. Growth variation in crura and loops will be quantified using geometric shape analysis on 3D images obtained from microCT scans of calcareous lophophore supports in living brachiopods. Growth character polarity in crural and loop development will be compared with phylogenetic polarity using outgroup analysis. Tree comparison methods will be utilized to evaluate patterns of qualitative and quantitative morphological character distribution, and to compare results from molecular and morphological analyses. Total evidence analyses will also be conducted and compared with those derived from morphology alone and molecular sequence data alone. Although the word brachiopod is not a household word, as is clam or snail, brachiopods provide an excellent opportunity to study changes in morphology over lifespans and lineages, with enormous extinct diversity preserved in the fossil record and a smaller, more manageable diversity living today. This research project will contribute to the education of undergraduate and graduate students through coursework in evolutionary biology and paleontology at UC Davis, and will support the training and mentoring of a female graduate student and female post-doctoral researcher. We will take advantage of opportunities to share our research results with the public at Picnic Day (a UC Davis campus-wide annual open house) and the Explorit Science Center (City of Davis). Three-dimensional images of brachiopods will be fully accessible on a website created to share the visual results of our research. We are beginning to develop a more sophisticated understanding of the development and evolution of morphology in vertebrate animals, yet our understanding of evolutionary morphology across a much more diverse array of marine invertebrate animals lags well behind. Our research will strive to introduce and explain a portion of the fascinating paleobiological complexity of one group of marine invertebrates to the general public, and engage the public in discussions about the nature of evolution: recognizing, characterizing, and interpreting change over time.