This paper explores shape disparity in the sulcus acusticus of saccular otolith using geometric morphometric methods in selected Gerreidae species. First, multivariate linear regressions between size (CS-log-transformed) and shape were implemented to uncover allometry in the variation of the sulcus acusticus at three levels: intraspecific, intrageneric, and interspecific. Second, we assessed species disparity to investigate if differences in disparity are associated with three biologically contrasting ecological or historical processes within the family. Specifically, we asked: (1) How has disparity changed as a result of an ecological shift from marine to freshwater habitat? (2) How has disparity changed in genera with increasing taxonomic richness? and (3) How did a vicariant event across the Panama isthmus changed disparity in a pair of sister species? Our results indicate that the disparity of the sulcus acusticus shape of the single freshwater species (Eugerres mexicanus) is in the middle of the range of values of the 17 marine species compared. This suggests that the change to a freshwater environment did not influence the variability of the sulcus acusticus. In the taxonomic comparisons, as expected, disparity is lowest in the monotypic Deckertichthys, while it increases with species number in Diapterus. In the vicariant pair, the Pacific basin species (Diapterus brevirostris) has a disparity value almost twice the value than in the Atlantic taxon (D. rhombeus). It remains to be investigated if the same disparity patterns documented here are associated to marine-freshwater ecological shifts and vicariant events in other fish families.

中文翻译：

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一种几何形态测量方法，用于测量 Gerreidae (Teleostei: Perciformes) 中矢状沟的差异

本文使用几何形态测量方法在选定的 Gerreidae 物种中探索了囊状耳石的耳沟形状差异。首先，实施了大小（CS-log 转换）和形状之间的多元线性回归，以揭示三个水平上耳沟变异的异速生长：种内、属内和种间。其次，我们评估了物种差异，以研究差异的差异是否与家庭内三个在生物学上形成对比的生态或历史过程有关。具体来说，我们问：(1) 由于生态从海洋栖息地到淡水栖息地的转变，差异如何变化？(2) 随着分类丰富度的增加，属间差异如何变化？(3) 跨巴拿马地峡的一次替代事件如何改变一对姐妹物种的差异？我们的结果表明，单一淡水物种（Eugerres mexicanus）的耳沟形状差异处于所比较的 17 种海洋物种的值范围的中间。这表明淡水环境的变化不会影响耳沟的变异性。在分类比较中，正如预期的那样，单型 Deckertichthys 的差异最小，而 Diapterus 的差异随着物种数量的增加而增加。在副神对中，太平洋盆地物种 (Diapterus brevirostris) 的差异值几乎是大西洋分类群 (D. rhombeus) 的两倍。此处记录的相同差异模式是否与其他鱼类家族的海洋-淡水生态变化和替代事件有关，还有待调查。