Out of Colchis: The Colonization of Europe by Primula vulgaris Huds. (Primulaceae)

In the cold periods of Quaternary climatic fluctuations, many temperate species underwent severe range contractions, and their survival during these periods was associated with climatically more favorable regions, so-called glacial refugia, from which subsequent range expansions took place. In this regard, the relative roles of the Southern (“main”), Northern (i.e., cryptic northern), and Eastern European (e.g., Colchis) refugia in shaping the evolutionary history of European temperate plants should be evaluated. In this study, we investigated the phylogeographic structure of Primula vulgaris, a European mesophilous species, by comparing DNA sequences derived from the nuclear (nrITS) and the plastid (trnL-trnF and rpl32-trnL) genomes of specimens covering the entire distribution range of the species. The variability in flower morphology was also studied on an area-wide scale with geometric morphometry. Our results clearly show the importance of the northern and eastern refugia (the Carpathian Basin and Colchis) as sources of genetic variation among European mesophilous plant species. Primula vulgaris spread initially from the Colchis refugium westwards, and a proportion of the colonists survived during the last glacial period in the Carpathian Basin, which may have served as a secondary center of diversity from which all Europe was subsequently populated.