The role of anthropogenic habitats as substitutes for natural habitats: a case study on Epipactis helleborine (L.) Crantz (Orchidaceae, Neottieae). Variations in size and nutrient composition of seeds

Natural and anthropogenic habitats differed greatly in terms of soil nutrients. Soil at the anthropogenic sites contained significantly lower concentrations of nitrogen (N) than those at the natural sites. Seeds of Epipactis helleborine were sampled from these two contrasting growth habitats and their size and nutrient composition were recorded. The 8 populations of E. helleborine were different in seed and embryo volumes, but there were no significant differences in seed width. Habitat type significantly influenced seed area: in the anthropogenic areas, seed area was greater than in the natural areas. Two distinct groups of populations were evident with regard to seed length. On the whole, the seeds and embryos of E. helleborine plants from populations in the natural habitats were larger than those in the anthropogenic habitats. Seeds of E. helleborine are reticulated but their reticulation pattern is variable. Seeds varied in N content, with most of the variation being attributable to seed size. The reduced seed weight of E. helleborine in anthropogenic habitats may result, in part, from its inability to adapt to the lower nutrient availability in soils of these habitats.