Laboratoire de Morphologie Fonctionnelle et Evolutive, Institut de Chimie (B6c), Université de Liège, B-4000 Liège, Belgium.
BMC Evol Biol. 2011 Mar 30;11:82. doi: 10.1186/1471-2148-11-82.
Quantitative studies of the variation of disparity during ontogeny exhibited by the radiation of coral reef fishes are lacking. Such studies dealing with the variation of disparity, i.e. the diversity of organic form, over ontogeny could be a first step in detecting evolutionary mechanisms in these fishes. The damselfishes (Pomacentridae) have a bipartite life-cycle, as do the majority of demersal coral reef fishes. During their pelagic dispersion phase, all larvae feed on planktonic prey. On the other hand, juveniles and adults associated with the coral reef environment show a higher diversity of diets. Using geometric morphometrics, we study the ontogenetic dynamic of shape disparity of different head skeletal units (neurocranium, suspensorium and opercle, mandible and premaxilla) in this fish family. We expected that larvae of different species might be relatively similar in shapes. Alternatively, specialization may become notable even in the juvenile and adult phase.
The disparity levels increase significantly throughout ontogeny for each skeletal unit. At settlement, all larval shapes are already species-specific. Damselfishes show high levels of ontogenetic allometry during their post-settlement growth. The divergence of allometric patterns largely explains the changes in patterns and levels of shape disparity over ontogeny. The rate of shape change and the length of ontogenetic trajectories seem to be less variable among species. We also show that the high levels of shape disparity at the adult stage are correlated to a higher level of ecological and functional diversity in this stage.
Diversification throughout ontogeny of damselfishes results from the interaction among several developmental novelties enhancing disparity. The bipartite life-cycle of damselfishes exemplifies a case where the variation of environmental factors, i.e. the transition from the more homogeneous oceanic environment to the coral reef offering a wide range of feeding habits, promotes increasing shape disparity of the head skeleton over the ontogeny of fishes.
缺乏有关珊瑚礁鱼类辐射过程中视差变化的定量研究。这些研究涉及变异性（即有机形态的多样性）在个体发育过程中的变化，可能是检测这些鱼类进化机制的第一步。雀鲷科（Pomacentridae）鱼类具有二分体生活史，与大多数底栖珊瑚礁鱼类一样。在它们的浮游分散阶段，所有幼虫都以浮游猎物为食。另一方面，与珊瑚礁环境相关的幼鱼和成年鱼表现出更多样化的饮食。我们使用几何形态测量学研究了这个鱼类家族中不同头部骨骼单元（脑颅、悬器、鳃盖、下颌和前颌骨）的形状变异性的个体发育动态。我们预计不同物种的幼虫在形状上可能相对相似。或者，专业化甚至在幼鱼和成年阶段都可能变得明显。
每个骨骼单元的变异性水平在整个个体发育过程中都显著增加。在定居时，所有幼鱼的形状已经具有物种特异性。雀鲷科鱼类在其定居后生长过程中表现出高水平的个体发育异速生长。分异模式的分歧在很大程度上解释了个体发育过程中形状变异性模式和水平的变化。形状变化的速度和个体发育轨迹的长度在物种间似乎变化较小。我们还表明，成年阶段的高形状变异性与该阶段更高水平的生态和功能多样性相关。
雀鲷科鱼类在个体发育过程中的多样化是由几种发育创新相互作用增强变异性的结果。雀鲷科鱼类的二分体生活史是一个环境因素变化的例子，即从更均匀的海洋环境向提供广泛饮食习惯的珊瑚礁的过渡，促进了鱼类头部骨骼在个体发育过程中形状变异性的增加。
