No abstract

The capacity of organisms to change their sex has evolved independently in several plant and animal lineages. Sex change has been widely studied, but research approaches have differed for plants and animals, and conclusions have often been taxon-specific. Although sex allocation theory provides a unifying framework for the study of sex change, this unity has not always been appreciated, especially in the botanical literature. Here, we review sex change with regard to its representation in relation to taxonomy and other sexual systems, with regard to its suggested adaptive benefits, and to the role of taxon-specific body architecture, such as modularity and gonadal structure. We highlight differences and similarities between plants and animals and suggest promising lines of future research.

SummaryIn gynodioecious plants, females are predicted to produce more and/or better offspring than hermaphrodites in order to be maintained in the same population. In the field, the roots of both sexes are usually colonized by arbuscular mycorrhizal (AM) fungi. Transgenerational effects of mycorrhizal symbiosis are largely unknown, although theoretically expected.We examined the maternal and paternal effects of AM fungal symbiosis and host sex on seed production and posterior seedling performance in Geranium sylvaticum, a gynodioecious plant. We hand-pollinated cloned females and hermaphrodites in symbiosis with AM fungi or in nonmycorrhizal conditions and measured seed number and mass, and seedling survival and growth in a glasshouse experiment.Females produced more seeds than hermaphrodites, but the seeds did not germinate, survive or grow better. Mycorrhizal plants were larger, but did not produce more seeds than nonmycorrhizal plants. Transgenerational parental effects of AM fungi were verified in seedling performance. This is the first study to show transgenerational mycorrhiza-mediated parental effects in a gynodioecious species. Mycorrhizal symbiosis affects plant fitness mainly through female functions with enduring effects on the next generation.

The different resource demands on male and female plants of dioecious species can lead to secondary sexual dimorphisms. Male and female plants might also interact differently with antagonists and mutualists. We used a repeated measures natural experiment in five subpopulations to investigate secondary sexual dimorphism in Carica papaya including interactions with arbuscular mycorrhizal fungi. Male and female plants did not differ in size or growth rate, but male plants flowered earlier than female plants. We observed different patterns of root colonization by arbuscular mycorrhizal fungi in male and female plants of C. papaya. These differences between the sexes preceded the flowering of most female plants. Female plants were sensitive to changes in soil fertility and adjusted the extent of their root colonization by arbuscular mycorrhizal fungi accordingly. Overall, the different resource demands on male and female plants seem to modulate the interactions of C. papaya with arbuscular mycorrhizal fungi.