The Indian subcontinent houses a unique fauna of freshwater mussels. Tectonic and biogeographic reconstructions indicate that this fauna represents a derivative of Mesozoic Gondwanan biota and that it arrived in Asia on the Indian Plate, using this tectonic block as a ‘biotic ferry’. Though a preliminary integrative revision of the Indian Unionidae was published recently, the level of endemism and taxonomic richness of regional assemblages are unsatisfactorily known. Here, we revise the taxonomy of freshwater mussels from the Brahmaputra River basin based on a large DNA-sequence and morphological dataset that was sampled in Assam, north-eastern India. We managed to collect and sequence topotypes for nearly all nominal species described from the region, except for Lamellidens friersoni and Parreysia smaragdites. Our phylogenetic and morphology-based research reveals that the regional Unionidae assemblage contains nine species, belonging to a single subfamily, the Parreysiinae. Seven species and three genera (Balwantia, Pseudoscabies Bolotov, Sonowal, Kardong, Pasupuleti and Subba Rao gen. nov., and Assamnaia Bolotov, Sonowal, Kardong, Pasupuleti and Subba Rao gen. nov.) appear to be endemic to the region, indicating that the Brahmaputra River may represent an endemism hotspot of global significance. Our findings highlight that this region should be considered a high-priority area for freshwater conservation management.

中文翻译：

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在阿萨姆邦发现淡水贻贝（双壳纲：Unionidae）特有热点，并描述了两个新属


印度次大陆拥有独特的淡水贻贝动物群。构造和生物地理重建表明，该动物群代表中生代冈瓦纳生物群的衍生物，并通过印度板块到达亚洲，利用该构造块作为“生物渡口”。尽管最近发布了印度Unionidae的初步综合修订版，但区域组合的特有性水平和分类丰富度仍不能令人满意。在这里，我们根据在印度东北部阿萨姆邦采样的大型 DNA 序列和形态数据集，修订了雅鲁藏布江流域淡水贻贝的分类法。我们成功地收集并测序了该地区几乎所有名义物种的拓扑型，除了 Lamellidens friersoni 和 Parreysia smaragdites 之外。我们基于系统发育和形态学的研究表明，区域性的Unionidae组合包含九个物种，属于一个亚科——Parreysiinae。七个物种和三个属（Balwantia、Pseudoscabies Bolotov、Sonowal、Kardong、Pasupuleti 和 Subba Rao gen. nov.，以及 Assamnaia Bolotov、Sonowal、Kardong、Pasupuleti 和 Subba Rao gen. nov.）似乎是该地区特有的，表明雅鲁藏布江可能代表了具有全球意义的特有热点地区。我们的研究结果强调，该地区应被视为淡水保护管理的高度优先区域。