Ranunculus reptans

Ranunculus reptans L. (Ranunculaceae)

Creeping spearwort, Glaisleun Ealaidheach

Status in Britain: ENDANGERED.

Status in Europe: Not threatened.

Plants which are referable to R. reptans are known from four localities in Britain: the gravelly shores of Ullswater and Loch of Strathbeg, where they have been recorded with R. x levenensis, the shore of Loch Leven, where they were almost certainly associated with the same hybrid, and Loch Awe, where they have recently been found on silty sand near the top of the shore. At the Loch of Strathbeg, it occurs on the gently-sloping shore in locally flushed, open vegetation of Eleocharis palustris in company with such species as Agrostis stolonifera, Caltha palustris, Juncus articulatus, J. bufonius, Mentha x verticillata, Persicaria amphibia, and the mosses Cratoneuron filicinum and Drepanocladus aduncus. At Loch Awe associated species include Juncus bulbosus, Littorella uniflora and Lobelia dortmanna.

This species is a stoloniferous perennial, which creeps and roots at the nodes. Flowers have been recorded from June to September. It is partially self‑compatible.

R. reptans appears to be a transient member of the British flora. It was collected at Ullswater in 1887 and from 1911 to 1917 and at Loch Leven in 1869, 1896 and 1935. It is currently known from Loch of Strathbeg, where it was collected in 1876, 1900 and 1989 and was still present in 1996, and from Loch Awe, where it was collected in 1992. Gornall (1987) suggests that it is introduced repeatedly by waterfowl migrating in autumn from Iceland, Scandinavia or northern Russia.

Plants of R. reptans hybridise with R. flammula and give rise to persistent populations of the hybrid R. x levenensis. The reason that R. reptans itself fails to survive is not clear, but Gibbs & Gornall (1976) have shown that it is less phenotypically plastic than the hybrid and may therefore be at a disadvantage on lake shores where the water‑level fluctuates. R. x levenensis has been recorded from sites in north‑east Scotland and northern Ireland where R. reptans has never been reliably recorded, but where it was presumably once present.

R. reptans has a circumpolar distribution, being widespread in the boreal zone and extending southwards in the mountains of Europe, Asia and North America. In Europe its main range is in Scandinavia and the north‑east, but it is found at scattered sites south to the Alps, central Italy and Bulgaria (Jalas & Suominen, 1989). There are records from Iceland (where it is common, for example, in shallow roadside pools), and Greenland. 

The distinction between R. reptans and the variable hybrid R. x levenensis is difficult and somewhat arbitrary. This account is based on specimens determined by R. J. Gornall and P. D. Sell. Further details of R. reptans at the Loch of Strathbeg are given in Birse (1997).

C. D. Preston, adapted from an account in Preston & Croft (1997).