Biological Flora of the British Isles: Neottia ovata

Summary This account presents information on all aspects of the biology of Neottia ovata (L.) Bluff & Fingerh. (Common Twayblade; Listera ovata (L.) R. Br.) that are relevant to an understanding of its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles : distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, reproductive characteristics, herbivores, history and conservation. Neottia ovata is one of the commonest orchids in the British Isles. It occupies a wide range of habitats from lowlands to mountains and from wet to dry sites: deciduous broadleaved and mixed woodland, forest edges, calcareous grassland and scrub, hedgerows, dry meadows, pastures, sand dunes, fens, floodplains and some anthropogenic sites. Neottia ovata is a perennial herb whose populations are maintained predominantly by sexual reproduction, as vegetative spread is limited. The main perennating organ is a horizontal rhizome that produces a new internode every year. The numerous adventitious roots are mainly colonized by Basidiomycota from Sebacinales (Clade B) but also by several other fungal groups. Dormancy, that is the failure of above‐ground parts to appear in a growing season, followed by reappearance of full‐sized photosynthetic plants in subsequent seasons, has been occasionally observed and typically lasts for one, or sometimes 2 years. The species flowers from early May to the beginning of July, or August at higher altitudes. The flowers of the genus Neottia possess a sensitive rostellum that releases a viscid fluid when it is touched, gluing the pollinia to the pollinator. N. ovata is pollinated mainly by three insect groups: ichneumonids, sawflies and beetles. The mean fraction of flowers setting fruit is c . 40%, but it depends on weather conditions: in rainy weather, it decreases to 10%, and in warm, dry weather, it can increase to 100%. Spontaneous autogamy is rare (1% of flowers). Neottia ovata is classified as a species of Least Concern in Great Britain. Although it appears well adapted to countryside changes, thanks to its wide habitat range, the species has vanished from almost 30% of its historical sites in Britain and Ireland. Agricultural activities are mainly responsible for losses of N. ovata sites in the lowlands.