First record of orchid subfossil seeds - The abundant occurrence of Epipactis palustris (L.) Crantz and Dactylorhiza spp. seeds in early Holocene sediments from Central Europe

Numerous subfossil seeds of Epipactis palustris (L.) Crantz, and Dactylorhiza spp. (D. incarnata/maculata complex) found in early Holocene sediments in northern Poland are the first record of orchid seeds in geological formations of any age and location. The macro- and micromorphological characters of the seeds were examined to determine their taxonomic affinity. The seeds were found among numerous macroremains of aquatic and terrestrial organisms, which are distinct in effective buoyancy, enabling air and water dispersal. The orchid populations developed in a floodplain meadow where summer inundation was probably among the main agents facilitating seed dispersal and deposition in lake sediments. We discuss potential environmental factors enabling the formation and preservation of the subfossil assemblages and suggest some technical issues among the reasons for the general poverty of orchid fossil data. Our data provide the first direct evidence for the early post-glacial establishment of populations of E. palustris and species of the D. incarnata/maculata complex in the northern part of Central Europe. (C) 2019 Elsevier B.V. All rights reserved.