Monotropa hypopitys L., Yellow Bird’s-nest, is the only European species in the family Monotropaceae (Fl. Europaea), although some authors include it within either the Pyrolaceae or the Ericaceae.
Synonym: Hypopitys monotropa Crantz.
It is considered to have two subspecies (Stace 1997), but morphology is not always reliable and only a handful of specimens in the U.K. have had their chromosome number checked to date.
- ssp. hypophegea (Wallr.) Holmboe which is glabrous and has a chromosome number 2n = 16 (Stace 2010).
- ssp. hypopitys, which has pubescent stamens, carpels and petals; 2n = 48 (Stace 2010).
Monotropa hypopitys is a saprophytic plant with no chlorophyll. Its flowering stems above ground are whitish in colour and up to 30cm tall.
Monotropa hypopiitys in flower (left) and fruit (right)
Photography: A.J. Lockton
Widespread throughout the British Isles, but increasingly rare towards the north and west. Absent from the Isle of Man, the Scillies, and the Northern and Western Isles. It occurs throughout the Northern Hemisphere, being widespread but thinly scattered in North America, Europe and Asia. In America it is known as Indian Pipe or Pinesap and sometimes listed as a different subspecies: photographs of it on American web sites often show plants with a reddish tinge, which does not seem to occur in British plants.
- Origin: native. It was first recorded by Robert Plot at Stokenchurch in 1677 (Clarke 1900), although he mentions earlier records by John Goodyer (1592-1664), which must pre-date this.
- Rarity: not quite a Nationally Scarce species in Britain, being recorded in 103 hectads in the New Atlas (Preston et al. 2002). In Ireland and Scotland it would certainly count as a rare plant.
- Threat: its status in the JNCC Red List (Cheffings & Farrell 2005) is ‘endangered’ - an assessment based on the Change Index, which shows it to be declining in Britain. Rumsey, in the New Atlas, also describes it as having suffered a prolonged decline.
- Conservation: several county recorders have listed it as an axiophyte, but it is not quite obvious which BAP habitats it occurs in. It is debatable whether it really warrants such a status, and more research is needed.
Monotropa contains no chlorophyll, and was until recently thought to be saprophytic (deriving nutrients from decaying leaf litter) but recent research shows that it is actually epiparasitic, using Tricholoma fungi to extract nutrients from living trees in its vicinity (Leake et al. 2004). It is usually found in woods or in scrub. Rumsey (in the New Atlas, op. cit.) describes it as most frequent under Beech and Hazel on calcareous soils, and under pines on more acid substrates. It is sometimes also found in dune slacks, where it is associated with Creeping Willow, Salix repens. It is not listed by Rodwell (1991-2000) as a component of any NVC community. The maps show that in the past it was strongly associated with limestone and chalk soils in the south of England, but that seems a less obvious association in the more recent data. It is a rather transient plant, sometimes appearing in large numbers (hundreds of flowering spikes) at a site, only to disappear within a few years. Sometimes it is found in secondary woodland. It is a lowland plant - the maximum recorded altitude is 395 m, at Buxton, Derbyshire.
The Maps Scheme, which divides records into five date classes (rather than the two used in the Change Index), shows no obvious change in its range. Whether there is any decline in abundance within its range is more difficult to assess. The Change Index works on the assumption that plants stay in the same place and that recording effort in the more distant past was less than recently. But neither of these may hold true for Monotropa, so an accurate assessment of any change in its abundance requires a different method of calculation. This is one of the outcomes we hope to achieve with the Threatened Plants Project. It would be interesting to study how long populations tend to persist in one place, and whether it is likely to recur there. Its disappearance from sites might be due to competition from other species or from depletion of nutrients - or some other cause. No studies seem to have been undertaken on its vegetation communities and specific niche - e.g. how often it is found in ancient woodland or recent scrub.
- Leake J. R., Mckendrick S. L., Bidartondo M. & Read D. J. 2004. Symbiotic germination and development of the myco-heterotroph Monotropa hypopitys in nature and its requirement for locally distributed Tricholoma spp. New Phytologist 163, 405-423.