Orchis patens Desf.: seed morphology of an endangered Mediterranean orchid

Abstract

The loss of orchid habitats has increased the investment on orchid conservation efforts to reduce the risk of extinction of rare species. In northwestern Italy, orchids are among the most threatened of all plant groups in the region, but little is known about the biology of most of the less abundant taxa. In this study, we used light and scanning electron microscopy to characterize the morphology of the seeds of the threatened Orchis patens Desf., a declining species present in semi-natural habitats. We found a marked positive relationship between seed size and embryo size that may be not restricted to O. patens but also occur in other orchid species. The comparative analysis of the observed seed traits revealed hidden morphological affinities at the reproductive level among O. patens and the three subspecies of O. mascula, showing the potential of this approach to test the taxonomic relationships among the different taxa included in the genus Orchis.

Keywords:

• Rare species
• reproductive biology
• orchid taxonomy
• microscopy

Acknowledgments

The experimental work for this study has been performed within the doctoral research project of J. Calevo (PhD School in Biology and Applied Biotechnologies, University of Turin). We are really thankful to Prof. Kingsley Dixon for the kind revision and suggestions, and to Mrs. Laura Negretti for SEM analysis.