Genecological studies of Urtica dioica L, II. Patterns of variation at Wicken Fen, Cambridgeshire, England.
An extreme genetic variant of U. dioica possessing few stinging hairs, tall, unbranched growth form, long, narrow leaves and late flowering is described from Wicken Fen. Evidence from plants grown from seed of this variant sown in a transect across the fen showed that there was significant gene flow into the fen by seed and pollen transport. Patterns of variability in adults did not suggest that natural selection was acting in the short term but historical factors were potentially important since the plant is a long-lived perennial.