Phenotypic developmental modularity in living and extinct fishes

生物和化石形式的进化研究得益于古生物学和进化发育生物学(EVO-DEVO)之间的联系。新生物学家和古生物学家现在都认为成年生物是发育稳定机制和发育不稳定机制之间复杂相互作用的结果。在稳定性过程中，表型模块化因其在复杂解剖系统进化中的重要性而备受关注。在模块化的各种定义中，模块可以被定义为作为相对独立的开发单元的交互元素的网络。个体发育过程中高度整合的大小和形状变化被认为是底层模块单位(如人类头骨和四肢)作用的结果。另一种个体发育变化对应于软骨化(软骨形成)和骨化(骨形成)的序列，可以用(1)元素首次出现的时间，(2)形态单位内的相对时间和(3)形态单位内系列元素之间的形成方向来描述。骨化方向已被用来识别表型发育模块。在鱼类的骨骼中只发现了几个模块(例如背鳍和肛鳍之间的相似性)。将从外部(大小和形状)和内部(软骨化和骨化序列)三个水平上研究活鱼和化石鱼颅后元素(脊柱和鳍支撑)的表型模块化：(1)个体发育过程中的整合；(2)个体发育与环境的整合；(3)个体发育与系统发育的整合。换句话说，我们将解决关于发育模块的三个基本问题：(1)它们是如何在鱼的早期生命阶段形成的？(2)它们是否受到环境因素或压力的影响？(3)我们能追踪它们的进化吗？这项研究计划将有助于理解鱼类的发育机制，这些机制过去是，现在仍然是鱼类进化的原因，鱼类是现存脊椎动物中最多样化的一类。

Research on the evolution of living and fossil forms has benefited from the linkage between paleontology and evolutionary developmental biology (evo-devo). Both, neontologists and paleontologists are now viewing adult organism as the result of complex interactions among developmental stability mechanisms and developmental instability. Among the stability processes, phenotypic modularity has been given much attention because of its importance in the evolution of complex anatomical systems. Among the various definitions of modularity, a module could be defined as a network of interacting elements behaving as relatively independent units of development. Highly integrated changes in size and shape during ontogeny have been identified as the result of the action of underlying modular units (e.g., human skull and limbs). Another type of ontogenetic change corresponds to sequences of chondrification (cartilage formation) and ossification (bone formation) that can be described in terms of (1) the time of first appearance of an element, (2) the relative timing within morphological units and (3) the direction of formation among serial elements within morphological units. Direction of ossification has been used to identify phenotypic developmental modules. Only a few modules have been identified in the skeleton of fishes (e.g., the similarity between the dorsal and anal fins). Phenotypic modularity of postcranial elements (vertebral column and fin supports) in living and fossil fishes will be investigated externally (size and shape) and internally (chondrification and ossification sequences) at three levels: (1) integration during ontogeny, (2) integration between ontogeny and environment, and (3) integration between ontogeny and phylogeny. In other words, we will be addressing three fundamental questions about developmental modules: (1) How do they form during the early life stages of a fish?; (2) Are they influenced by environmental factors or stresses?; and (3) Can we track down their evolution? This research program will help to understand developmental mechanisms that have been and are still responsible for the evolution of fishes, the most diversified group of living backboned animals.