Environments with strong gradients in physical conditions, such as rocky intertidal, induce animal morphological strategies to face them. The gastropod Trophon geversianus inhabit within the intertidal and subtidal habitats of Patagonian rocky shores. Although there is a wide knowledge of the phenotypic differences of this species regarding habitats (i.e., intertidal/subtidal), little is known about the interaction between habitat and latitude. Here, we studied form variation (size and shape) by using 3D geometric morphometric of T. geversianus shells from alive gastropods and analyzed the phenotypic effect from micro-scale (habitat), macro-scale (latitude), and the interaction habitat-latitude (site). Lastly, we tested the classification accuracy of the shape variable for each predictor variable and a synthetic variable (from a cluster analysis). We found that habitats and sites had the greatest influence on shape variation. Moreover, we found that the largest shell sizes were more likely to be located in subtidal habitats. Also, the size differences between sites were not negligible. Finally, habitat demonstrated the highest classification accuracy for shape, even higher than genetically determined (sex) and synthetic variables. We found that the gastropods from the intertidal habitat presented a globular morph with shorter spire and larger relative size of the shell aperture, while subtidal gastropod showed an elongated morph, with smaller aperture and longer spire. We present evidence of the complexity of size and shape variation in T. geversianus, highlighting that site-dependence on shape variation must be considered in geometric morphometrics studies at a latitudinal scale.

物理条件具有强梯度的环境，例如岩石潮间带，促使动物形态策略面对它们。腹足动物Trophon geversianus栖息在巴塔哥尼亚岩石海岸的潮间带和潮下带栖息地。尽管对该物种在栖息地（即潮间带/潮下带）方面的表型差异有广泛的了解，但对栖息地和纬度之间的相互作用知之甚少。在这里，我们通过使用T. geversianus 的3D 几何形态测量研究了形态变化（大小和形状）活腹足动物的壳，并分析了微观尺度（栖息地）、宏观尺度（纬度）和栖息地-纬度（地点）相互作用的表型效应。最后，我们测试了每个预测变量和合成变量（来自聚类分析）的形状变量的分类准确性。我们发现栖息地和地点对形状变化的影响最大。此外，我们发现最大的贝壳尺寸更有可能位于潮下带栖息地。此外，站点之间的大小差异也不容忽视。最后，栖息地表现出最高的形状分类准确度，甚至高于基因决定的（性别）和合成变量。我们发现潮间带栖息地的腹足动物呈球状形态，尖顶较短，壳孔相对尺寸较大，而潮下腹足动物则表现出细长的形态，孔径更小，尖顶更长。我们提供了尺寸和形状变化复杂性的证据T. geversianus，强调在纬度尺度的几何形态测量学研究中必须考虑对形状变化的位置依赖性。