Ecological aspects of sex expression in subdioecious Schiedea globosa (Caryophyllaceae)

• Published in: American journal of botany 1991-09, Vol.78 (9), p.1280-1288
• Main Authors: Sakai, A.K. (University of California, Irvine, CA), Weller, S.G
• Format: Article
• Language: English
• Subjects: AFFECTATION DE RESSOURCES; ASIGNACION DE RECURSOS; Biological and medical sciences; Biology and morphogenesis of the reproductive apparatus. Photoperiodism, vernalisation; Botany; Capsules; CARYOPHYLLACEAE; Dioecy; ECOLOGIA VEGETAL; Ecology; Evolution; EXPRESION GENICA; EXPRESSION DES GENES; FACTEUR DU MILIEU; FACTORES AMBIENTALES; Fundamental and applied biological sciences. Psychology; GENETICA; GENETIQUE; HAWAI; HAWAII; Inbreeding; Inflorescences; INTERACCION GENOTIPO AMBIENTE; INTERACTION GENOTYPE ENVIRONNEMENT; Liability; Male animals; Mortality; Ovules; PHYTOECOLOGIE; Plant growth; Plant physiology and development; Plant reproduction; Plants; Pollen; Resource allocation; SEXE; SEXO; Vegetative and sexual reproduction, floral biology, fructification
• ISSN: 0002-9122; 1537-2197
• DOI: 10.1002/j.1537-2197.1991.tb11420.x

The importance of ecological factors such as sex lability, spatial segregation, and resource allocation in the evolution of dioecy were examined in Schiedea globosa. S. globosa is a subdioecious species with equal numbers of plants possessing strictly male or female function and a small proportion of hermaphrodites. The propensity for labile sex expression was under both environmental and genetic control; some plants with male function became hermaphroditic (by producing female flowers) under better growing conditions in the field and in the greenhouse. There was some spatial segregation of the sexes. Because of sex lability, more hermaphrodites than males occurred on moister slopes. Although there were not measurable sex-related differences in mortality within or between two flowering seasons, more females than males and hermaphrodites occurred at the bottom of slopes. Males and females produced the same number of ramets and inflorescences, but females had a greater number of flowers per inflorescence. Males and females had the same number of ovules (vestigial in males), but females had larger ovules and longer stigmas. Hermaphrodites and males had the same amount of pollen per flower despite the production of fruit by the hermaphrodites. In hermaphrodites, there was no apparent tradeoff within flowers between pollen production and ovule production. These results indicate that spatial segregation, sex lability, and environmental conditions influence allocation patterns of S. globosa, and in combination with high inbreeding depression and selfing rates, may promote the further evolution of dioecy in S. globosa