Female advantage in gynodioecious plants: A meta-analysis focused on seed quality

In gynodioecious systems, female plants must counteract the selective disadvantage of not passing genes via pollen production, as hermaphrodites can. Theory predicts that females must produce more or better-quality seeds than hermaphrodites in order to be maintained within the same population. This female advantage has been widely measured and reported for seed number, but whether female advantage is gained through the production of better seeds remains relatively under-studied. Here, a meta-analysis approach was used to investigate whether females in gynodioecious species produce seeds of better quality than hermaphrodites (measured as seed mass, seed nutrient content, seed germinability and seedling survival and performance) in addition to achieving a larger seed production. In total, 50 studies were included, reporting traits for 34 gynodioecious species in 17 different families. Female advantage was significant for seed number and seed germination, but was not detected for seed mass, seed nutrient content or seedling performance. A female advantage in seed number was corroborated in this meta-analysis, which together with better seed germination, may explain maintenance of female plants within gynodioecious populations.