Biological Flora of the British Isles: Epipogium aphyllum Sw.

P>1. This account provides information on all aspects of the biology of Epipogium aphyllum Sw. that are relevant to understanding 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, response to biotic factors, responses to environment, structure and physiology, phenology, reproductive characteristics, herbivores and disease, history and conservation. 2. Epipogium aphyllum is a native mycoheterotrophic herb, with a British distribution that is restricted to a few beech and oak woodlands in the Chilterns and the Welsh Borders. Sightings are scarce, the majority of years passing with no observations in the British Isles. The species extends throughout temperate Eurasia, with concentrations of records in Scandinavia and the foothills of the Alps. 3. Epipogium aphyllum is most commonly found growing in the deep shade of dense woodland; its achlorophyllous nature means that it is entirely dependent on its endomycorrhizal symbiont (Inocybe sp.) for nutrition. 4. The biology of reproduction is poorly understood. Sexual reproduction, both entomogamous and autogamous, appears inefficient, as fruiting plants are rare. Vegetative propagation can occur via bulbils attached to the underground stolons. 5. Both the occurrence and timing of flowering are highly unpredictable, the season extending from late May to early October. A wet winter followed by a warm summer is thought to trigger flowering. The rhizome can survive underground undetected for many years. 6. Epipogium aphyllum has repeatedly been described as Britain's rarest orchid. Sightings since its first English record in 1854 have been interrupted by periods of decades. A recent observation gap of more than two decades led to suggestions of extirpation, though this assumption has been challenged by statistical modelling and refuted by the discovery of a single depauperate flower on the Welsh Borders in 2009. Primary threats to this species already at the edge of its natural range include deforestation and degradation of its native broadleaf habitat, as well as trampling, herbivory and climate change. As a result, extirpation of the Ghost Orchid from Britain is still likely in the near future.