Ranunculus auricomus L., Goldilocks Buttercup

Account Summary

Growth form and habitat preferences

Goldilocks Buttercup is a perennial with a short, stout rootstock and in Fermanagh it mainly occurs (or perhaps is most noticed) beneath hedges, especially on roadsides where its distinctive pale yellow flowers can be spotted even from a car. Less frequently it is found in quite deep shade in hazel woods on limestone, eg in the Screenagh River Glen. These are moist to fairly dry sites and R. auricomus appears to require moderately fertile, base-rich, generally calcareous soils. It really thrives when it is supplied with a good depth of rich leaf-mould in undisturbed corners of old woodland or under scrub in light to half-shade conditions.

R. auricomus avoids both very acid and very dry sites (Garrard & Streeter 1983) and it appears to be both a weak competitor and intolerant of grazing or cutting, tending to shun unshaded meadow grassland for these reasons (Salisbury 1942, p. 54; Sinker et al. 1985). R. auricomus also tends to be a lowland species in Britain and Ireland, although in some parts of Scotland at least, it can rarely be found on open moorland when it is protected from grazing by boulders, and it may also occur rarely on mountain ledges (R.A. Fitzgerald, in: Preston et al. 2002).

Further north, in the Nordic region of continental Europe, R. auricomus shows a very much wider habitat range than is observed in Britain and Ireland, appearing in much more open situations, eg in meadows and grazed pastures, in wetter littoral and riparian habitats with bare soil, in mountain snowbeds and on scree. It is also a weed in cultivated and disturbed ground in the more northern part of its species distribution. Another difference is that it appears indifferent to lime in these northern territories (Jonsell et al. 2001).

Overwintering (perennation) and phenology

The rootstock of R. auricomus overwinters with its bud at or just beneath the soil surface (ie it is a rosette-forming hemicryptophyte, or a buried geophyte). It begins growth in the very early spring, enabling it to flower a couple of weeks before R. bulbosus (Bulbous Buttercup) and several weeks earlier than all the other buttercups in Britain and Ireland. In a comparative study of the flowering behaviour of five buttercup species in central Germany, R. auricomus was first to flower and it had a five week flowering period (Steinbach & Gottsberger 1994).

British and Irish occurrence

R. auricomus is almost certainly an under-recorded species in Britain and Ireland and particularly so in the less-frequented corners of these islands, due to its early flowering season. This runs from March to May and peaks in April, so that it may be missed by 'summer botanists'. Despite their awareness of this, Webb & Scannell (Flora of Connemara and the Burren, 1983) regarded Goldilocks Buttercup as a rare species in W Ireland and it is generally considered that R. auricomus declines in frequency in Britain and Ireland as one goes northwards and westwards, a belief reinforced by the distribution shown in the New Atlas (Preston et al. 2002).

R. auricomus is frequent and widespread in England and to some extent at least it mirrors the distribution of chalk and limestone. In Wales, Scotland and Ireland, however, R. auricomus is very much more scattered and the mapped distribution in these areas does not reflect the calcareous geology. This is especially the case in Ireland where the distribution of the species is much better represented than was the case in the previous 1955-60 BSBI Atlas survey (Perring & Walters 1962, 1976; Preston et al. 2002, page 3).

Fermanagh occurrence

In Fermanagh, there were just 18 pre-1975 records for R. auricomus, but when RHN started looking for it around 1986, he found that it was very widespread, quite frequent and locally abundant. We now have over 250 records and the distribution map shows Goldilocks Buttercup present in 121 tetrads, 22.9% of those in the VC. Harron in his Flora of Lough Neagh (1986) made the very same discovery around Lough Neagh, where he considered R. auricomus present in greater abundance than anywhere else in Ulster (ie in the nine county Irish province).

Apomixis, an unusual breeding system producing an exceptional range of variation

R. auricomus is a facultative apomictic, ie in addition to the normal sexual process it displays pseudogamous agamospermy − which is a shorthand technical way of saying that it can set seed asexually, but only after pollination takes place (either by crossing or selfing). Despite the requirement for pollination, in the case of apomixis, no actual fertilisation takes place, yet seed is produced. For a simple introduction to this complex matter see Proctor et al. (1996), pp. 348-349, and for a more detailed explanation see Richards (1997a), p. 405 and pp. 411-420).

As a further complication, the apomictic microspecies created are all at least tetraploid (Jonsell et al. 2001). As a result of its dual reproductive methods, R. auricomus is extremely variable in form, especially with regard to petal development. A very full treatment of the microspecies has recently appeared in Flora Nordica, 2 (in English), where a total of no less than 605 microspecies in the Nordic countries are described (Jonsell et al. 2001). The agamospecies have not yet been formally described within the British Isles, but Stace (1997) reckons at least 100 R. auricomus microspecies exist in these islands.

Flower variation

In Fermanagh, as elsewhere, plants of R. auricomus are sometimes found with five perfect petals as, eg in the Teemore district, but more frequently the petals are reduced in number, distorted in their development, or even in some cases totally absent. When the petals are much reduced or are completely absent, the sepals, which are usually greenish, may develop yellow colour and become shiny and petaloid, thus taking on the advertising role as insect attractants (Hutchinson 1972).

Pollination compared with related species

R. auricomus has either a cup-like nectary without a covering scale, or it has a small or abortive scale (Butcher 1961; Clapham et al. 1962). The flowers attract insect visitors, but in smaller numbers than most other terrestrial buttercup species. A study of five common buttercup species in central Germany found that while in its natural habitat R. flammula (Lesser Spearwort) attracted up to a mean of 35.7 insects per hour, R. auricomus achieved a mean of just 2.3 per hour. When cultivated in a garden bed R. auricomus was visited by ten species of insects (evenly divided between Diptera, Hymenoptera and Coleoptera), whereas R. acris (Meadow Buttercup), R. flammula, R. bulbosus (Bulbous Buttercup) and R. repens (Creeping Buttercup) had visits from 54, 41, 37 and 28 species, respectively. Thrips were the only insects observed collecting nectar from the Goldilocks Buttercup, while the other nine visiting species took only pollen. In its natural habitat, R. auricomus was visited only by Coleoptera at the very low rate quoted above (Steinbach & Gottsberger 1994).

Seed production

The present author does not know of any study of the reproductive capacity of R. auricomus (certainly nothing published in English).

Seed dispersal

Nordic studies of seed dispersal in their much wider range of habitats emphasised the role of human activities (eg transport of hay), for both local and long-distance microspecies movements (Jonsell et al. 2001). However, this is obviously irrelevant, or much less relevant, when the plant lives in woods and hedges rather than in meadows, as is the situation in most of Britain and Ireland. How does Goldilocks Buttercup get about? Does it have a dispersal mechanism at all? The seed (actually achenes) are described as, "very shortly pubescent" (Stace 1997), perhaps suggesting they might adhere to animal coats. Another project beckons!

Buried seed longevity

The survey of soil seed banks in W Europe found a total of 15 estimates , ten of which regarded R. auricomus seed as transient, two considered it long-term (ie persisting for at least 5 years), and three did not specify any duration (Thompson et al. 1997).

A call for basic ecological information

A careful but necessarily incomplete internet search failed to unearth any other information on the life history or ecology of this interesting species group. Perhaps if less research emphasis were placed on its genetics and reproductive strategy and a preliminary study initiated on the population biology, life-table and natural history of the species group, it might prove worth the effort.

European and World occurrence

In W & N Europe, R. auricomus s.l. is widespread everywhere except Spain and the Mediterranean mainland, where it becomes rare and scattered towards the south. It is absent from all Mediterranean islands except Corsica (Jalas & Suominen 1989, Map 1809). R. auricomus s.l. also occurs in N Asia, Alaska, NE Canada and Greenland (Jonsell et al. 2001).

Uses

Despite its attractive-sounding English common name, the species does not appear to have any folk-lore or use specifically associated with it. This is probably because the plant is too rare, or is seldom recognised.

Names

'Ranunculus' is derived from the Latin 'rana' meaning 'a frog', an allusion to the fact that so many members of the plant genus live in or near water, the habitat of frogs (Johnson & Smith 1946). The Latin specific epithet 'auricomus' is a combination of 'aurum' meaning 'gold' and 'coma', meaning 'hair of the head' or 'locks', and thus translates as 'with golden hair', presumably a poetic likening of the spring carpet of yellow flowers to a blonde head of hair (Gilbert-Carter 1964). The English common name 'Goldilocks' or 'Goldylocks' is a straightforward translation of its Latin specific name, first used by William How in his Phytologia britannica of 1650. An alternative name is 'Wood Crow-foot' (Britten & Holland 1886).

Threats

Removal of both hedges and small patches of woodland.

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