Preventing Extinction of the Critically Endangered Dactylorhiza incarnata subsp. ochroleuca in Britain Using Symbiotic Seedlings for Reintroduction

Abstract

The yellow early marsh-orchid (Dactylorhiza incarnata subsp. ochroleuca) is critically endangered in the UK. Reintroduction of this threatened orchid to former haunts that have been restored is a long-term objective of this study. Identifying germination-specific mycorrhizal fungus lineages from closely related species is used as a method due to the extremely small number of plants left in the wild. A putative orchid mycorrhizal fungus of the family Tulasnellaceae, isolated from Dactylorhiza praetermissa, supported in vitro seed germination to produce reintroduction-ready seedlings. Reintroduced symbiotic seedlings survived over the winter months in the flooded reintroduction site (RS). The comparative soil analysis for key nutrients before reintroduction showed that phosphorus content in the RS is very low compared to the soil collected from the wild site (WS) where the last viable population exists. On the other hand, C:N ratio in the soil at the WS and RS were not significantly different. To our knowledge, this is the first-ever report on the reintroduction of symbiotic seedlings of a threatened orchid back to the wild in the UK.

Fungal Community Composition at the Last Remaining Wild Site of Yellow Early Marsh Orchid (Dactylorhiza incarnata ssp. ochroleuca)

“…Sebacinales, which are a crucial group of OMFs, have been found to be widely distributed in most landscapes, although they are affected by changes in land use [ 26 , 27 , 28 ]. Our analysis supports these findings by revealing the presence of Sebacinales in the majority of the wild site plots.…”

“…In the spring of 2021, the last remaining wild site of the yellow early marsh orchid ( D. incarnata ssp. ochroleuca ), in Suffolk, Britain [ 27 ], was visited for data collection. The site was visually surveyed to identify the presence of orchids and subsequently divided into 20 rectangular plots of equal size ( Figure 1 b).…”

“…ochroleuca ( Wüstnei ex Boll ) P.F.Hunt & Summerh ) [ 21 ]. The last remaining population in Britain was found on a protected fen habitat in Suffolk [ 27 ], meaning that this orchid is on the brink of extinction. As part of a pilot study, symbiotic seedlings were successfully produced and translocated to a newly identified site near the wild location, aiming to explore the feasibility of conservation translocation for this taxon [ 27 ].…”

“…The last remaining population in Britain was found on a protected fen habitat in Suffolk [ 27 ], meaning that this orchid is on the brink of extinction. As part of a pilot study, symbiotic seedlings were successfully produced and translocated to a newly identified site near the wild location, aiming to explore the feasibility of conservation translocation for this taxon [ 27 ]. Despite facing unexpected challenges such as year-long flooding and an unusually hot and dry summer in 2022, a 10% recovery rate was achieved, with the translocated plants still thriving at the new site [ 27 ].…”

“…As part of a pilot study, symbiotic seedlings were successfully produced and translocated to a newly identified site near the wild location, aiming to explore the feasibility of conservation translocation for this taxon [ 27 ]. Despite facing unexpected challenges such as year-long flooding and an unusually hot and dry summer in 2022, a 10% recovery rate was achieved, with the translocated plants still thriving at the new site [ 27 ]. The senility of the remaining population has hindered natural seedling recruitment, and annual fluctuations in orchid numbers at the wild site further emphasise the need for future reinforcement.…”