The Deschampsia cespitosa (Poaceae) complex in Great Britain and Ireland

Abstract

The Deschampsia cespitosa complex in Great Britain and Ireland is shown to consist of three distinct species, one represented by three variants: (1) D. parviflora (Thuill.) P. de Beauvois, a shade tolerant diploid species with spikelets less than 3.5 mm, of heavy clay or flushed soils in ancient woodland, principally from East Inverness-shire and central Scotland southwards; (2) D. alpina (L.) Roemer and Schultes, a small, tetraploid, viviparous species, with hooded leaf-tips and brittle plantlets with appressed glumes and lemmas, of wet, open habitats at high altitudes in the Scottish Highlands and (rarely) in Ireland; (3) D. cespitosa (L.) P. de Beauvois, represented by three variants, (a) a seed-bearing diploid found primarily in peripheral coastal areas and islands in northern and western Scotland and on mountains in the central and northern Scottish Highlands and Teesdale, (b) a seed-bearing tetraploid which is the common cytotype of the species in unshaded and many woodland habitats from central Scotland southwards, (c) a viviparous tetraploid, which is a form of the seed-bearing tetraploid, found in the south-west Scottish Highlands, English Lake District and Snowdonia and is probably unique to Britain. Suspected viviparous triploid hybrids were found between diploid D. cespitosa and both D. alpina and tetraploid D. cespitosa.