Floral traits and breeding system of the Mediterranean subendemic Serapias neglecta De Not. (Orchidaceae)

Understanding a species’ reproductive biology is crucial to identify intrinsic and ecological factors influencing its persistence. Limited data exists on the biology of Serapias neglecta De Not., a Mediterranean orchid facing local extinctions and declining trends in Northern Italy. This study investigates the species’ reproductive traits. We characterized the floral volatilome using Solvent-Free Microwave Extraction (SFME) followed by GC/MS, and analysed floral macro- and micro-morphology. We verified whether the species could perform spontaneous autogamy, then assessed self-compatibility through artificial pollinations followed by seed viability–germination tests. Data on plant visitor/pollinator interactions were collected in the field. The volatilome comprised 75 compounds, mainly saturated and unsaturated hydrocarbons, several of which are known components of sex pheromones in various arthropod species. The central labellum featured long trichomes with dome-like protuberances, and several classes of secondary metabolites were recorded. Although seeds from both autogamous and geitonogamous selfing treatments were viable and germinable, cross-pollination enhanced germination rates; high values of inbreeding depression were detected. No events of spontaneous autogamy occurred, but we observed cases of self-pollination triggered by animal activity. During our surveys, no hymenopterans were observed; beetles occasionally carried pollinia, while spiders mainly used the cavity as shelter, despite no evidence of direct pollination being found. In conclusion, S. neglecta likely attracts pollinators by combining shelter-mimicry with a diverse volatilome and morphological traits.