Data from: Testing the depth-differentiation hypothesis in a deepwater octocoral

The depth-differentiation hypothesis proposes that the bathyal region is a source of genetic diversity and an area where there is a high rate of species formation. Genetic differentiation should thus occur over relatively small vertical distances, particularly along the upper continental slope (200–1000 m) where oceanography varies greatly over small differences in depth. To test whether genetic differentiation within deepwater octocorals is greater over vertical rather than geographical distances, Callogorgia delta was targeted. This species commonly occurs throughout the northern Gulf of Mexico at depths ranging from 400 to 900 m. We found significant genetic differentiation (FST = 0.042) across seven sites spanning 400 km of distance and 400 m of depth. A pattern of isolation by depth emerged, but geographical distance between sites may further limit gene flow. Water mass boundaries may serve to isolate populations across depth; however, adaptive divergence with depth is also a possible scenario. Microsatellite markers also revealed significant genetic differentiation (FST = 0.434) between C. delta and a closely related species, Callogorgia americana, demonstrating the utility of microsatellites in species delimitation of octocorals. Results provided support for the depth-differentiation hypothesis, strengthening the notion that factors covarying with depth serve as isolation mechanisms in deep-sea populations.深度分化假说（depth-differentiation hypothesis）提出，半深海带（bathyal region）是遗传多样性的源区，同时也是物种形成速率较高的区域。因此，遗传分化理应在相对较小的垂直距离内发生，尤其是在上大陆坡（200–1000米）区域——该区域的海洋学特征随深度的微小差异发生显著变化。为验证深水八放珊瑚（deepwater octocorals）的遗传分化是否在垂直距离上大于地理距离，本研究以Callogorgia delta为研究对象。该物种广泛分布于墨西哥湾北部海域，栖息深度范围为400至900米。研究团队在横跨400公里地理距离、400米垂直深度的7个采样点中，检测到了显著的遗传分化（FST = 0.042）。研究结果呈现出深度分化的模式，但采样点间的地理距离可能进一步限制了基因流。水团边界可能成为不同深度种群间的隔离屏障，但随深度发生的适应性分化也是一种潜在情形。微卫星标记（microsatellite markers）还显示，Callogorgia delta与近缘物种Callogorgia americana之间存在显著的遗传分化（FST = 0.434），证实了微卫星标记在八放珊瑚物种界定中的应用价值。本研究结果为深度分化假说提供了支持，进一步强化了"与深度协同变化的因素作为深海种群隔离机制"这一观点。