Abstract

The adoption of sub-dioecious and sub-monoecious sexual models is rare among angiosperms. In particular, the female-sterile reproductive systems – andromonoecy and androdioecy – are considered the rarest strategies, being known for about 4,000 angiosperm species which are approximately 1% of the total number. Despite the general rarity of femalesterile reproductive systems, even including particular cases such as gender disphasy, in the last twenty years a growing number of studies are emphasizing the occurrence of these strategies within the monocot order Liliales, where about 20% of the ca. 1600 species are known to be dioecious (i.e. the whole family Smilacaceae; Chamaelirium luteum – Melianthaceae), about 1% is known to show female-sterile systems (Colchicaceae: Wurmbea dioica; Colchicum stevenii; Melanthiaceae: Veratrum nigrum; Zigadenus paniculatus; Liliaceae: see over) and only 0.2% to show male-sterile systems (Chionographis). Accordingly, Liliales show an inverted proportion in occurrence of male-sterile and femalesterile systems, respect with other angiosperms, where gynomonoecy/gynodioecy is much more frequent than andromonoecy/androdiocey. Within Liliaceae, several species have been hitherto reported to be andromonoecious and/or androdioecious, like for instance Gagea spp. (incl. Lloydia) and Fritillaria camtschatcensis. The occurrence of male flowers is here documented also in Fritillaria involucrata (from Maritime Alps, SE France), Fritillaria messanensis (from Calabria, S Italy), Fritillaria montana (from several populations in central and southern Italy), Fritillaria persica (from Botanical Garden of Pisa University), Lilium bulbiferum subsp. croceum (from Tuscany, C Italy) and Tulipa sylvestris (from Emilia-Romagna). Increasingly frequent observations of female-sterile systems within the order, and particularly in Liliaceae, suggest they could have an evolutionary significance.