Ecological partitioning among parapatric cryptic species

Geographic range differences among species may result from differences in their physiological tolerances. In the intertidal zone, marine and terrestrial environments intersect to create a unique habitat, across which physiological tolerance strongly influences range. Traits to cope with environmental extremes are particularly important here because many species live near their physiological limits and environmental gradients can be steep. The snail Melampus bidentatus occurs in coastal salt marshes in the western Atlantic and the Gulf of Mexico. We used sequence data from one mitochondrial (COI) and two nuclear markers (histone H3 and a mitochondrial carrier protein, MCP) to identify three cryptic species within this broad-ranging nominal species, two of which have partially overlapping geographic ranges. High genetic diversity, low population structure, and high levels of migration within these two overlapping species suggest that historical range limitations do not entirely expla...物种间地理分布范围的差异，可能源于其生理耐受能力的不同。潮间带（intertidal zone）是海洋与陆地环境交汇形成的独特生境，在此区域内生理耐受能力对物种分布范围的影响极为显著。由于多数物种生存于其生理耐受极限附近，且环境梯度往往较为陡峭，因此应对极端环境的相关性状在此显得尤为关键。双齿嗜蜗牛（Melampus bidentatus）分布于西大西洋沿岸盐沼及墨西哥湾海域。我们依托1个线粒体（COI）基因标记与2个核标记（组蛋白H3及线粒体载体蛋白MCP）的序列数据，在这一分布广泛的名义物种中鉴定出3个隐存种，其中2个隐存种的地理分布范围存在部分重叠。这两个分布重叠的隐存种具有较高的遗传多样性、较低的种群遗传结构分化以及高水平的种群迁移，表明历史上的分布范围限制并未完全解释……