Evidence of gynodioecy in Fuchsia arborescens (Onagraceae)

Abstract

Gynodioecy, the coexistence of hermaphrodite and female plants in the same population, could be an intermediate state in the evolution of the full separation of sexual functions (dioecy). Fuchsia arborescens has been reported as a hermaphrodite species, however here we demonstrate that it is gynodioecious in most of its range. We sampled populations of F. arborescens along their distribution gradient (~900 km) to: (1) measure floral morphometry in both floral morphs (2) estimate female frequency and (3) evaluate seed production in both floral morphs. We found that F. arborescens shows floral dimorphism, mainly given by the length of the floral tube and anthers, which are shorter in female flowers and lack pollen grains in most cases (95%). The northernmost population in Jalisco was completely hermaphrodite while in the others female frequency ranged between 35% and 58%. We also found that female plants consistently produce more mature seeds per fruit than hermaphrodites, supporting the resource reallocation hypothesis for gynodioecious species. Further studies are required on seed germination and seedling performance of both morphs, as well as the estimation of visitation rate in both floral morphs.