Differences between Pelargonium moniliforme (Geraniaceae) and the closely related P. vinaceum

A multidisciplinary study of living plants and herbarium specimens of what was hitherto known as Pelargonium moniliforme Drege ex Harv. (section Hoarea (Sweet) DC.) reveals two different taxa: P. moniliforme, which can reach a height of 400mm when in flower and P. vinaceum EM Marais, which only reaches a height of 180mm in exceptional cases. P. moniliforme also has larger flowers and longer hypanthia than P. vinaceum. The leaves of P. vinaceum are covered with short glandular hairs with appressed bristles along the margins, whereas those of P. moniliforme have long glandular hairs interspersed with soft patent hairs and with appressed or patent stiff hairs along the margins. P. moniliforme always has five fertile stamens, in contrast to the two to four in P. vinaceum. In addition, the taxa have different distributions and flowering times. P. moniliforme has a more southern distribution, in an area with an annual precipitation of 150–350mm, and flowers in September when leaves are still present. P. vinaceum occurs more to the north in an area with an annual rainfall of less than 150mm, and flowers in October and November after the leaves have died. Similarities in the flower and leaf morphology, leaf anatomy and karyology reveal a close relationship between the two species. Illustrations of the two species are provided as well as a combined map of the rainfall figures and the distributions of the two species.