Bidens frondosa L. (Asteraceae) in the Republic of Mordovia (Russia)

Resumo

Bidens frondosa L. populations are studied in the Republic of Mordovia. The density of individuals of invasive species is high and it fluctuates on average from 78 to 202 individuals per 1 m². A comparison of the seed mass, the number of seeds per calathidium, the seed germination, and the area of torus of calathidium of alien B. frondosa with those for native B. tripartita L. is carried out. Seed germination of B. tripartita (on average from 32.3 to 41.7% depending on conditions of germination) is considerably higher than that for B. frondosa (from 1.7 to 8.0% depending on conditions of germination and the sites of seeds harvesting). The number of seeds per calathidium and seed mass are higher in population of native species. Invasive activity of B. frondosa is explained by a more rapid development during ontogeny, but it is not explained by features of the reproductive biology of this alien species.