Flowering dynamics in the trimorphic species of Lythrum salicaria L. (Lythraceae)

Flowering in the population of Lythrum salicaria in the Yavorivskiy district of Lviv region lasts for about 70 days from the end of June till the beginning of September. Flowering period of the long-styled individuals lasts 30 days, middle-styled indivi­duals – 32 days, and short-styled individuals – 26 days. In the studied population, the ratio of flowering plants of different morphs changes in time: flowering long-styled individuals prevail at the beginning of the population flowering, middle-styled indivi­duals – at the time of mass flowering and short-styled individuals – at the end of flowering period. The percentage of dominant flowering morph in each phase of the population flowering can reach about 70 %. The prevalence of the middle-styled morph during mass flowering and the longest flowering period seem to be the features responsible for maximal seed production of this morph and for the highest chance to be cross- and self-pollinated. Short flowering period of the short-styled morph and its prevalence at the end of the flowering in population could be regarded as the features enhancing autogamy and also is responsible for the lowest seed production. The differentiated flowering dynamics of the morphs is considered to be the mode which optimizes the legitimate pollination of each morph in the defined phases of the flowering period.