Role of intraspecific competition in mass seeding and senescence in Polymnia canadensis, a primarily monocarpic species

Mass seeding and senescence in 2-year population cycles previously were documented in the primarily monocarpic species Polymnia canadensis. In the present study, small individuals of this species died in competition with large ones in field trials. These results suggested that intraspecific competition followed by synchronous semelparity in a dominant age-class could result in mass flowering and senescence and thus could play a role in population cycling in P. canadensis. It was also found in some trials that other environmental factors such as drought could eliminate small individuals, perhaps sometimes in interaction with competition.