The effect of pollen origin (self- and cross-pollination) on seed production and viability in <i>Ophrys</i> (Orchidaceae)

The pollination biology of the genus Ophrys has been extensively explored, primarily due to their utilisation of sexual deception to attract pollinators. Typically, members of this genus produce a low number of fruits per individual and are considered obligate crossers. However, instances of self-pollination in Ophrys are not uncommon, although the impact of pollen origin on seed production remains understudied. As a predominantly cross-pollinated genus we hypothesise that self-pollination in Ophrys has a negative effect on seed production. The results of the present work will support decision making for the conservation of the genus. We investigate the consequences of self- and cross-pollination on (a) empty seeds produced and (b) viability of sound seeds for three Ophrys species: Ophrys aesculapii, Ophrys ferrum-equinum, and Ophrys kotschyi native to the East Mediterranean region. Bagged individuals of these species were meticulously hand-pollinated with pollen sourced either from their own flowers or from neighbouring individuals. Significant differences were observed across all three species, both in terms of the number of empty seeds and the viability of the produced seeds, with significantly lower viability and higher number of empty seeds in seed collections from self-pollinated individuals. Despite being self-compatible, the three Ophrys species exhibited notable inbreeding depression, as evidenced by the outcomes of this study. Based on our results the implementation of controlled cross hand-pollination in wild population may contribute in the increase of the reproductive success of Ophrys spp. by increasing the quality and quantity of the produced seeds.