Spatial and temporal variation on fruit set in <i>Epipactis</i> thunbergii (Orchidaceae) from southern Korea

Abstract

ABSTRACT: Spatio-temporal variation in fruit set in orchids would affect long-term population viability and willinfluence genetic diversity over many generations. The aim of this study was to examine the breeding system ofthe nectariferous terrestrial orchid Epipactis thunbergii, to specifically determine levels of fruit set in terms oftime and space under natural conditions. We examined pollination under natural conditions and conducted handpollination experiments during a 2-year survey in four populations located along 1.5 km of coastal line in Jingui-ri (rual village) [Jeollanam-do (province), southern Korea]. We found that, over a 2-year period, levels of per-centage of fruit set were similar within patches of the four populations. By contrast, we detected significant dif-ferences in the percentage of fruit set among patches. We also found that plants with larger inflorescence sizeproduced significantly more fruits than plants with fewer flowers. Over a 2-year period, the percentage of fruitset for E. thunbergii was similar but low (14.1%) compared to that averaged for eighty-four rewarding species(37.1%). However, an increase in fruit set was achieved by hand-pollinations: artificial self-pollination (90.5−95.2%), artificial geitonogamy (94.7−95.0%), and cross-pollination (artificial xenogamy, 91.3−91.4%). Noemasculated flowers produced fruits and no automatic pollination was found in E. thunbergii. Our findings sug-gest that E. thunbergii is a self-compatible terrestrial orchid that depends on pollinators (insects) to achieve fruitset in natural habitats, and that local environmental conditions were similar over a period of 2 years in the studyarea. Our results also highlight the cryptic variation of fruit production in time, but more pronounced variabilityin space.