Patterns of genetic variation among populations of Poa pratensis L. and Agrostis capillaris L. from Britain and Iceland.
Plants of A. capillaris (outbreeding) and P. pratensis (apomictic) from populations in England (Rothamsted), southern Iceland (Sámsstadir), northern Iceland (Akureyri) and 2 higher sites in Iceland (Gullfoss and Skálafell) were grown in spaced-plant trials in England (Reading) and Iceland (Korpa). Plants from the different populations differed significantly in most of the 19 growth and development characters studied. Univariate and multivariate analyses showed that the largest differences were between plants from different climatic areas, especially between British and Icelandic populations. There were smaller differences between populations that had received different fertilizer treatments over the previous 30 years. Genetic variation within populations was wide and similar for both species; the population × species interaction for the index of genetic variation was usually small, implying that environmental factors affected genetic variation more than the breeding system. In general, Icelandic populations varied more than British populations. Variation within populations was greater when they were grown in an alien environment than when grown in climatic conditions similar to those of their native habitat.