Taxonomic, phylogenetic and ecological diversity of <i>Niphargus</i> (Amphipoda: Crustacea) in the Hölloch cave system (Switzerland)

Groundwater belongs to the spatially most extensive, but least explored freshwater systems. On a global scale, the species richness of several subterranean invertebrate taxa parallels species richness found in surface waters, while on a local scale species richness hardly exceeds 20 species. This results in a high contribution of groundwater ecosystems to regional β- and γ-diversity, and to a smaller degree to α-diversity, and deserves focused attention. In general, more species are to be found in large cave systems. The second largest cave system in Europe is Hölloch in Switzerland. In this paper we revised the taxonomic, phylogenetic and ecological diversity of the amphipod community in the Hölloch cave system. While previous records listed five geographically widespread species of the genus <i>Niphargus</i> for this cave system, we could not confirm the presence of any of those species, but rather found three highly distinct species new to science. In this paper we describe <i>Niphargus styx</i> sp. nov., <i>Niphargus murimali</i> sp. nov., and <i>Niphargus muotae</i> sp. nov., and suggest that previous records from that cave were probably misidentifications. Although amphipod species richness in this cave system seems to be lower than previously thought in terms of absolute numbers, the cave retained its regional and international importance in terms of nature conservation for multiple reasons. First, all newly described species are probably endemic to this cave system. Second, they are phylogenetically distantly related and exhibit moderate to high phylogenetic diversity. Third, the species, as inferred from their functional morphology, are also ecologically highly divergent. Based on geographic distribution of their nearest relatives, we hypothesize that the cave system was most likely independently colonized from North, West and South and that the pre-adapted ancestors occupied different ecological niches within the system. http://zoobank.org/urn:lsid:zoobank.org:pub:A19309E5-C06B-4844-A4D8-7571F05F25C9地下水是全球范围内空间分布最广但研究程度最低的淡水生态系统。在全球尺度下，若干地下无脊椎动物类群的物种丰富度与地表水域相当，但在局地尺度上，其物种丰富度罕有超过20种的情况。这使得地下水生态系统对区域β多样性、γ多样性贡献显著，而对α多样性的贡献相对有限，因此值得重点关注。 通常而言，大型洞穴系统中可观测到的物种数量更多。欧洲第二大洞穴系统为瑞士的赫洛克（Hölloch）洞穴。本研究对该洞穴系统内的端足类(amphipod)群落的分类学、系统发育学及生态学多样性进行了系统修订。 既往研究记录该洞穴系统共分布有5种广布性的泥钩虾属(Niphargus)物种，但本研究未证实其中任何一种的存在，反而发现了3种特征极为独特的科学新物种。 本文正式描述了新种泥钩虾(Niphargus styx) sp. nov.、泥钩虾(Niphargus murimali) sp. nov.以及泥钩虾(Niphargus muotae) sp. nov.，并指出此前该洞穴的相关记录大概率为物种鉴定错误。 尽管该洞穴系统内的端足类物种丰富度绝对数值较此前认知更低，但出于多重原因，该洞穴在区域及全球自然保护层面仍保有重要价值。 其一，所有新描述的物种大概率为该洞穴系统所特有；其二，这些物种间系统发育关系较远，展现出中等至较高的系统发育多样性；其三，通过功能形态学推断，这些物种在生态学层面也存在显著分化。 基于其近缘类群的地理分布格局，本研究推测该洞穴系统极有可能分别从北方、西方和南方被独立定殖，且预先适应了相应环境的祖先占据了该系统内不同的生态位。 http://zoobank.org/urn:lsid:zoobank.org:pub:A19309E5-C06B-4844-A4D8-7571F05F25C9