Taxonomic revision of Geranium subsect. Tuberosa (Boiss.) Yeo (Geraniaceae)

Geranium subsect. Tuberosa (Geraniaceae) consists of seven species. The highest diversity of the group is located between Turkey and Iran, where six taxa grow. Other species reach Western Europe and northwestern Africa, and central Asia. In contrast to the current literature, we consider G. linearilobum subsp. transversale and G. tuberosum subsp. linearifolium to be synonyms of G. linearilobum and G. tuberosum, respectively. A univariate morphometric study revealed some valuable quantitative characters useful for the identification of these species. Micromorphological features of pollen, seeds, and mericarps are investigated by SEM. A new key is provided, as well as new and detailed descriptions. Geranium kotschyi subsp. kotschyi, G. macrostylum and G. tuberaria are here illustrated for the first time. One neotype and eight lectotypes are designated, and distribution maps are presented.