Habitat effects and differences in the reproductive success of Orchis punctulata and Orchis purpurea (Orchidaceae)

Abstract

The pollination success of two nonrewarding orchids in two coarse habitats was examined. The comparative results of Orchispunctulata and O. purpurea showed a significant differentiation. The fruit set of O. purpurea was significantly greater compared to O.punctulata, whereas both species also had significantly higher fruit set in the grassland compared to the forest. Although the pollinationsuccess of O. purpurea was not significantly correlated with plant height, inflorescence size, or nearest neighbor distance, these factorswere found to be significantly correlated to the pollination success of O. punctulata. Among these factors, the nearest neighbor distancehad the highest impact on the pollination success of O. punctulata, whereas the respective effects to the individuals of O. purpureawere found to be nonsignificant. The results demonstrate that the distribution of O. punctulata at the edges of its range is not delimitedby factors related to its pollination effectiveness and that other factors, mostly related to the microsite conditions, might play a moresignificant role in the colonization of more western areas. Moreover, suitable management treatments that would increase the light levelswithin the forest sites studied may also increase the pollination success and the fruit production of the studied orchids.