The across-shore distribution of arthropods in two Uruguayan sandy beach–dune​ systems with contrasting morphodynamics was investigated. A deconstructive analysis was performed to describe faunal changes from the dunes to the shoreline. The Habitat Safety Hypothesis (HSH), which states that sandy beach supralittoral species are more abundant in the backshore of reflective beaches than in dissipative ones, was assessed. A hypothesis that predicts more diverse and abundant supralittoral and dune insects and arachnids in dissipative beaches was also tested. Sampling was performed simultaneously in both beaches with pitfall traps that were kept active for 24 h at three transects that included 17 sampling levels. The reflective beach presented significantly higher elevation, sand temperature, grain size and sorting, and lower sediment compaction and moisture than the dissipative one. Total abundance of arthropods was significantly higher in the reflective beach, supporting the HSH. However, the deconstructive analysis revealed different patterns in the across-shore distribution, diversity and abundance among taxa. Crustaceans, coleopterans and dipterans exhibited higher abundance in the backshore of the reflective beach, whereas acarines were more abundant in the dunes of the dissipative beach. Ants were similarly abundant in the dunes of both beach types. Species diversity did not differ between beaches and was higher in the dunes than in the backshore. The higher abundance observed in the backshore of the reflective beach supports the HSH, reinforcing the idea that the backshore of reflective beaches can be a safer zone not only for beach crustaceans inhabiting this beach fringe, but also for some insects (coleopterans and dipterans). Other arthropods (acarines) inhabiting the dunes were more abundant in the dissipative beach. The similar abundance of ants found in both beaches suggests that dunes offer suitable microhabitats for them, overriding the effects of beach morphodynamic factors.

研究了两个乌拉圭沙滩-沙丘系统中节肢动物的跨岸分布，它们的形态动力学存在差异。进行了解构分析，以描述从沙丘到海岸线的动物群变化。栖息地安全假说（HSH）被评估，该假说说沙滩上的滨海物种在反射性海滩的后部比耗散性海滩的丰富。还测试了一个假设，该假设可预测耗散海滩中更多种类的，丰富的沙丘上和沙丘昆虫和蜘蛛纲动物。在两个海滩上同时进行了采样，使用了陷阱陷阱，陷阱在三个包含17个采样级别的样带中保持活动24小时。反光海滩的海拔，沙温，粒度和分类明显更高，并且比耗散性更低的泥沙压实度和水分含量。在反射海滩上，节肢动物的总丰度明显更高，这支持了HSH。然而，解构分析揭示了分类单元之间跨岸分布，多样性和丰度的不同模式。甲壳类，鞘翅类和双翅类动物在反光海滩的后滩表现出较高的丰度，而耗散海滩的沙丘中的螨类则更为丰富。在这两种海滩类型的沙丘中，蚂蚁也同样丰富。海滩之间的物种多样性没有差异，沙丘中的物种多样性高于后海地区。在反光海滩的后方观察到的较高的丰度支持了HSH，加强了这样的想法，即反射性海滩的后部不仅对于居住在该海滩边缘的海滩甲壳类动物，而且对于某些昆虫（鞘翅目和双翅类动物）来说都是一个更安全的区域。在耗散的海滩上，居住在沙丘上的其他节肢动物（凤尾鱼）更为丰富。在两个海滩上发现的类似数量的蚂蚁表明，沙丘为它们提供了合适的微生境，从而超越了海滩形态动力学因素的影响。