Cryptic species are a major challenge for morphologically based species identification. Molecular approaches to species delimitation can be a valuable tool to provide preliminary taxonomic hypotheses and significantly complements morphological taxonomy. In South America, the freshwater crabs of the genus Aegla have sparked much interest as they are key species in the often-endangered freshwater ecosystems and themselves are often considered endangered species. Morphological similarity among Aegla species is not always positively correlated with genetic relatedness and growing evidence suggests that several putative single taxa are actually assemblages of cryptic species. We coupled broad geographically sampling (Argentina, Brazil and Uruguay) with multilocus (COI, 16S and ANT) phylogenies to investigate the diversity of Aegla uruguayana. Our species delimitation analyses suggested that 19 aeglid populations form a well-supported clade, although individuals from 10 populations possibly represent a complex of cryptic species. The significant amount of cryptic diversity found in aeglids seem to rely on several factors, including habitat fragmentation, life history features, morphological stasis, convergent evolution and recent divergence. The search for new diagnostic characters and the description of the cryptic species that remain unnamed will probably be the next challenge for this unique group of crustaceans.

中文翻译：

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Entangled Aeglidae (Decapoda, Anomura)：神秘物种的额外证据

隐性物种是基于形态的物种识别的主要挑战。物种定界的分子方法可以成为提供初步分类学假设和显着补充形态分类学的宝贵工具。在南美洲，Aegla属的淡水蟹引起了极大的兴趣，因为它们是经常濒临灭绝的淡水生态系统中的关键物种，而且它们本身通常被认为是濒临灭绝的物种。Aegla物种之间的形态相似性并不总是与遗传相关性呈正相关，越来越多的证据表明，几个假定的单一分类群实际上是隐秘物种的组合。我们将广泛的地理抽样（阿根廷、巴西和乌拉圭）与多位点（COI, 16S和ANT ) 系统发育来调查Aegla uruguayana的多样性。我们的物种定界分析表明，19 个 aeglid 种群形成了一个得到充分支持的进化枝，尽管来自 10 个种群的个体可能代表了一个复杂的神秘物种。在 aeglids 中发现的大量隐秘多样性似乎依赖于几个因素，包括栖息地破碎化、生活史特征、形态停滞、趋同进化和最近的分歧。寻找新的诊断特征和描述仍未命名的神秘物种可能是这个独特的甲壳类动物群的下一个挑战。