The genus Koenigia L. emend. Hedberg (Polygonaceae)

Pollen morphological studies revealed the occurrence of the characteristic spinulose pollen type of Koenigia not only in the three species earlier recognized in the genus (A" islandka, K. nepalensis and K. pilosd) but also in three additional species earlier treated under Polygonum , viz. K delicatula (Meisn.) Hara, K. forrestii (Diels) Mesicek & Soják, and A" nummularifolia (Meisn.) Mesicek & Soják. Further studies of flower morphology, fruit and petiole anatomy, basic chromosome number, etc., revealed additional similarities between those species, which led to a taxonomic revision of the genus Koenigia. This genus seems to be most closely related to Persicaria Mill, sections Cephalophilon (Meisn.) Gross and Echinocaulon (Meisn.) Gross, with Koenigia delicatula as a connecting link. There arc also interesting similarities with the genus Aconogonon (Meisn.) Rchb. Koenigia exemplifies the derivation from montane ancestors of a high mountain-dwelling genus displaying adaptive radiation to fit diverse alpine niches. Five species out of six are confined to high mountain areas in southeastern Asia, primarily in the Himalayas, whereas the sixth has spread to Arctic and alpine areas in the northern hemisphere and even penetrated to southern South America. The latter species shows progressive reduction in size in combination with adaptation to a very short summer under severe climatic conditions.