| Summary: | ABSTRACT The distributional patterns of 13 species of Diaptomus Westwood, 1836 were analyzed using the panbiogeographical method of track analysis. Locality records were compiled from the literature and mapped for the construction of individual tracks for each species. These tracks were superimposed to find the generalized tracks. Four generalized tracks were found: (1) Siberia, Central Europe, and Iceland; (2) Northern Italy, southern France, central Spain, northern Algeria, and northern Morocco; (3) Southern France, central Spain, and northern Morocco; (4) Southern Italy, Sicily, and Albania. Five biogeographic nodes were found: (A) Southwestern Iberia, (B) Southeastern Iberia, (C) Central Iberia, (D) Cantabria, at the intersections of generalized tracks 2 and 3; and (E) Italian Peninsula Islands, at the intersection of generalized tracks 2 and 4. The main massing of the species of Diaptomus studied is located in the Iberian peninsula, where six of the species do occur. A model based on the fragmentation and differentiation of already widespread ancestors during the late Mesozoic and early Cenozoic, related to the opening the North Atlantic Ocean and the formation of the Mediterranean Sea, is proposed as a most parsimonious explanation for the observed patterns of geographic vicariance.
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