A novel low salinity switch hypothesis is proposed to account for the speciation of an obligate estuarine (oligohaline) amphipod, Orchestia aestuarensis, from a closely-related one, Orchestia mediterranea, found in both estuarine and marine conditions (euryhaline). The underlying genetic mechanisms could involve: 1. A dimorphic allele, or linked set of alleles, carried by the euryhaline amphipod which controls the ability to breed in low salinity conditions in estuaries and which is selected for in these conditions, producing the oligohaline amphipod. 2. A genetically-assimilated gene or genes, controlling the ability to breed in low salinity conditions in estuaries, which is/are “switched on” by low salinity conditions. 3. Allopatric speciation from a euryhaline to an oligohaline amphipod species where low salinity conditions is the selective switch. It is possible that other estuarine, sibling, amphipod pairs have evolved by salinity switching. In the North Atlantic coastal region, this could include: Gammarus tigrinus/G. daiberi and G. salinus/G. zaddachi (Amphipoda, Gammaridae).

中文翻译：

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河口端足类动物：同胞物种低盐度转换假说

提出了一种新的低盐度转换假说，以解释在河口和海洋条件（广盐性）中发现的密切相关的 Orchestia mediterranea 的专性河口（寡盐）片脚类动物 Orchestia aestuarensis 的物种形成。潜在的遗传机制可能涉及： 1. 广盐性片脚类携带的双态等位基因或连锁等位基因组，其控制在河口低盐度条件下繁殖的能力，并在这些条件下被选择，产生寡盐性片脚类动物。2. 一个或多个基因同化基因，控制在河口低盐度条件下繁殖的能力，低盐度条件“开启”。3. 从广盐性到低盐度片脚类物种的异域物种形成，其中低盐度条件是选择性开关。其他河口、兄弟姐妹、片脚类动物可能是通过盐度转换进化而来的。在北大西洋沿海地区，这可能包括： Gammarus tigrinus/G. daiberi 和 G. salinus/G. zaddachi（端足类，Gammaridae）。