Historical biogeography of the lineage Atopochara trivolvis PECK 1941 (Cretaceous Charophyta)
Abstract The evolutionary species Atopochara trivolvis represents a unique case of a charophyte with a well-documented, long-lasting fossil record of biostratigraphical interest and a worldwide distribution. This provides an excellent basis for analysing the historical biogeography of this important species. The origin of the lineage is recorded in the Early Berriasian of Western Europe, where an archipelago-like palaeogeography would have favoured allopatric speciation and small-sized original biogeographic ranges. The species first reached Eastern Europe during the Valanginian and expanded to China during the Hauterivian. It expanded worldwide during the Barremian–Aptian, first colonizing North Africa and South America through the Guinea Corridor and subsequently reaching North America. The Barremian–Aptian worldwide expansion was probably facilitated by the monoecious nature of A. trivolvis, which allowed for long-distance animal dispersal, as is the case with extant Chara. An initial fragmentation in the biogeographic range of A. trivolvis can be detected in the Albian–Cenomanian, when the species displayed up to 5 different morphotypes in scattered localities of Eurasia and North America. During the Turonian sea-level highstand A. trivolvis became extinct also from most of these localities, while, in the Latest Cretaceous plesiomorphic populations of A. trivolvis ulanensis survived in Mongolia and Northern China. The species became completely extinct near the K/T boundary.