Diversity and Evolution of Sexual Strategies in Silene: A Review

Abstract

The variety and evolution of reproductive strategies in plants have attracted the attention of scientists for a long time. The genus Silene has been the focus of several studies related to the diversity and evolution of sexual systems. This review will summarize the huge amount of knowledge on sexual strategies in Silene species. Hermaphroditism is the most frequent condition in Silene; however, there is a relatively high frequency of gynodioecy and dioecy compared to angiosperms and dicotyledons. In some gynodioecious species, gynomonoecious individuals are common, forming a gynodioecious-gynomonoecious sexual system that is rare among angiosperms. Dioecy has independently evolved in the two phylogenetically supported subgenera of Silene, with a probable origin down the “gynodioecious pathway.” Heterogametic sex chromosomes have made S. latifolia and other dioecious species of the genus important models for the evolution of sex determination. In Silene species, studies on sexual expression at the plant and population level suggest that it is highly variable. Sexual dimorphism in reproductive and vegetative characters of dioecious species showed patterns that generally fit those found in other species. Compared with other genera of angiosperms, Silene presents a unique opportunity to evaluate the evolution of the different sexual systems and sex chromosomes (being of the few angiosperm genera with female heterogamety), the maintenance of gynodioecious and gynodioecious-gynomonoecious sexual systems, and the evolutionary implications of sexual dimorphism.