Sexual dimorphism is generally obvious in brachyurans and sexual dimorphism between species is of higher degree to allow separation of trophic niches compared to the lower intraspecific variations between sexes. Mud crab genus Scylla are distributed along Indo-West Pacific region, and species within this genus often exhibit overlapping niches and similar external morphologies. This study compared the intra- and interspecific sexual dimorphism patterns of three sympatric Scylla species from four distinct geographical locations along the equatorial region based on 24 morphometric characters. The consistency of sexual dimorphism patterns between locations was higher than between species. However, reproduction-related characters such as cheliped dimensions and abdomen width exhibited similar sexual dimorphism patterns across species. Discriminant function analysis based on the 23 morphometric ratios revealed the morphometric intraspecific divergence in all three Scylla species from Asajaya Mangrove Forest. The cause for this regional intraspecific differentiation of mud crabs from Asajaya Mangrove Forest remains unknown.

中文翻译：

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赤道地区泥蟹属Scylla性别二态性模式的种内和种间变异

短尾目动物的性二态性通常很明显，物种间的性二态性与两性之间较低的种内变异相比，允许分离营养生态位的程度更高。泥蟹属Scylla分布在印度-西太平洋地区，该属内的物种经常表现出重叠的生态位和相似的外部形态。本研究基于 24 个形态测量特征，比较了来自赤道地区四个不同地理位置的三种同域 Scylla 物种的种内和种间性二态性模式。地点之间的性别二态性模式的一致性高于物种之间。然而，与生殖相关的特征，如螯肢尺寸和腹部宽度，在物种间表现出相似的两性异形模式。基于 23 种形态测量比率的判别函数分析揭示了来自 Asajaya 红树林的所有三种 Scylla 物种的形态测量种内差异。Asajaya Mangrove Forest 泥蟹的这种区域种内分化的原因仍然未知。