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
(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.