Biological Flora of the British Isles: Ophrys sphegodes

Abstract

Summary This account presents information on all aspects of the biology of Ophrys sphegodes Mill. that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characteristics, herbivores and disease, history and conservation. Native to Britain, O. sphegodes used to be more widely distributed throughout south‐eastern England, but is now mainly restricted to the counties of Dorset, East Sussex and Kent. It is widespread throughout the western parts of central and southern Europe, and is common in Spain, France and Italy. Further east, it occurs in Bulgaria and Greece, including most of the Mediterranean islands, and extends into southern Russia, Turkey and northern Iran. Ophrys sphegodes grows on calcareous, nutrient‐poor substrates and rarely under any shade. It is most common in ancient, heavily grazed grassland on chalk and Jurassic limestone, but it also occurs in disturbed habitats, horizontally oriented rock floors in limestone quarries, on old limestone quarry spoil heaps, and in lightly trampled calcareous grasslands on maritime cliffs. Ophrys sphegodes multiplies predominantly by sexual reproduction. Vegetative multiplication occasionally occurs through survival or splitting of the old tuber. In the UK, the species is almost exclusively pollinated by males of the solitary bee Andrena nigroaenea. Male bees are attracted by complex floral bouquets emitted by the flowers that strongly resemble pheromones produced by female A. nigroaenea. Fruit production is generally low, and in most populations, <15% of the flowers produce capsules. Ophrys sphegodes is reproductively isolated from other species in the genus by strong pre‐mating barriers, most notably temporal (differences in flowering time) and floral (different pollinators) isolation. In particular, differences in floral odour appear to underlie floral isolation. Nonetheless, several hybrids involving O. sphegodes have been described in Britain and elsewhere in Europe. The range of O. sphegodes in Britain declined dramatically in the twentieth century, leading to its extinction in twelve vice‐counties. Losses were mainly due to ploughing of grassland and changes in fertilizer and grazing regimes. Its range has increased somewhat in recent years. However, increases in spring temperature due to climate warming may seriously threaten the species in Britain by disrupting the close relationship between O. sphegodes flowering time and the phenology of flight of its prime pollinator, leading to reproductive failure.