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Remote oceanic islands lie at the brink of complex biotic and abiotic interactions and throughout the Earth’s climatic cycles, have represented important refugia for marine populations, shaping current biodiversity patterns. A species’ dispersal ability additionally interacts with environmental conditions to determine its distribution patterns, yet the underlying mechanisms of such interaction remain largely unexplored. Marine benthic invertebrates display a wide array of dispersal mechanisms, and their well-preserved fossiliferous deposits offer valuable insights on past distribution patterns. Macaronesian Archipelagos exhibit some of the most remarkable fossil outcrops of the Atlantic Ocean, and due to their geological dynamism, the varying degree of isolation and their wide latitudinal gradient, they represent a valuable system for investigating Pleistocenic geographical range expansions. Within this rich fossil record, bivalves are by far the best represented. To understand the influence of biological and ecological factors in determining biogeographic patterns, a checklist of recent and late Pleistocene shallowwater marine bivalves from the Azores Archipelagos was compiled. Such work raised the number of known extant bivalve species to 143, rendering the Azores comparable in species number to other archipelagos in the north-east Atlantic. Moreover, preliminary analyses on such dataset suggest that strikingly different species abundance patterns occur between insular and continental settings, calling for directed investigations upon the processes underlying such disparities. Secondly, I analyzed population genetic structures throughout Macaronesia of two differently dispersing bivalve mollusks: Cardita calyculata (Linnaeus, 1758) and Ervilia castanea (Montagu, 1803). The different population structures retrieved demonstrate the significant role of dispersal in either promoting species diversification or selecting for specific traits enabling the species to withstand constant environmental pressure, such patterns potentially being also dependent upon the species’ habitat and its variation across different timescales. The processes generating such patterns are hereby discussed to provide a valuable insight and reference to unravel the evolutionary and biogeographic patterns behind benthic marine biodiversity.