Changes in the distribution and abundance of Himantoglossum hircinum (L.) Sprengel (Orchidaceae) over the last 100 years

I. Species are likely to be most sensitive to climate change at the geographic limits of their distribution. The behaviour of such populations may therefore be a predictor of the response of the species to global change. 2. The northern limit of the Lizard Orchid, Himantoglossum hircinum, occurs in England. where 16 populations are currently known. British records over the past 100 years are particularly accurate for this species and it was one of the first for which changes in distribution were linked to an amelioration of climate (Good 1936). 3. Early records were checked to confirm the rise in population number in the early part of the century. Analysis of more recent data showed that this was followed by a sharp decline and numbers have only been rising again over the last decade. The range expanded with the earlier increase in population number. but did not contract as populations were lost. 4. Data collected between 1977 and 1998 in the largest population allowed flowering probability and seed production to be correlated with rainfall during the growing season. Analysis of the resulting model showed that both observed rises in population number followed periods during which the seasons for vegetative growth had been wet. 5. Populations have become both larger and more persistent due to an increased interest in conservation. 6. Changes in the abundance of H. hircinum are likely to depend on other factors. including patterns of human activity. as well as on climate change.