Mixed mating systems in Hawaiian Bidens (Asteraceae)

Abstract

Protandry and male sterility promote outcrossing, while self-compatibility and geitonogamy contribute to inbreeding. The combination of these floral mechanisms results in a mixed mating system in all species studied. Outcrossing rates of 15 populations of the 11 species ranged from 0.43-0.88, averaging 0.65. Apparent selfing rates of females ranged from 0-0.25 in 7 gynodioecious populations, suggesting that there is variation in the level of biparental inbreeding among populations. Presence of females increased the level of outcrossing by an average of 9% in gynodioecious populations. Efficiency of gynodioecy as an outcrossing mechanism largely depends on the current outcrossing rate of hermaphrodites, frequency of females, and extent of genetic substructuring in populations. On average, autogamy contributed 4%, geitonogamy contributed 24%, and consanguineous mating contributed 15% to the realized selfing rate (43%) in the hermaphrodites of these species. -from Authors