GYNODIOECY IN <i>NEPETA GONTSCHAROVII</i> (LAMIACEAE)

Abstract

Gynodioecy is described for the first time in Nepeta gontscharovii, an endemic herbaceous polycarpic plant from the Hissar Darvaz mountains (Tajikistan). N. gontscharovii forms the flowers of two types: perfect and pistillate, on different plants. Both types of flowers are median zygomorphic, tetracyclic, and heteromeric: pentameric in the perianth, tetrameric in the androecium, and dimeric in the gynoecium. The stamens in pistillate flowers have transformed into staminodes. We have observed that the values of the vast majority of the studied morphological traits in perfect flowers are larger than in the pistillate ones. Three criteria have been identified which allow to distinguish reliably the flowers of different sexual forms: the size of flowers and their parts, the ratio of the length of corolla tube and calyx, and the position of anthers. The perfect flowers are characterized by pronounced protandry. According to the determined pollen/ovules ratio (from 1286 to 1657), N. gontscharovii is to be considered as a facultative xenogamous species. Females were rare (6.6%) in the studied population. We discuss the presence and distribution of gynodioecy within the genus Nepeta and section Macronepeta and its adaptive significance for the N. gontscharovii population.