Phenotypic plasticity in sympatric diploid and autotetraploid Dactylis glomerata

It is often supposed that increased heterozygosity of autopolyploids provid es a greater stability of phenotypic expression compared with related diplo ids and, hence, a greater ability to survive in marginal diploid environmen ts or the ability to colonize new environments. The aim of this study was t o compare the phenotypic plasticity of fitness-related characters in diploi d and derivative autotetraploid Dactylis glomerata from genotypes sampled i n their zone of natural sympatric occurrence in northern Spain. To achieve this aim, nine genotypes were grown in a range of controlled environments. We found no evidence for consistent differences in plasticity between diplo ids and related tetraploids. We did find, however, consistent differences b etween diploids and tetraploids in the mean values of the set of examined f itness-related characters. Such differences could be critical for the maint enance and evolutionary success of polyploids.