Genetic and environmental contributions to multivariate morphological pattern in Puccinellia (Poaceae)

Abstract

The contributions of genetic and environmental variation to multivariate patterns in morphology were investigated in a comparative analysis of two samples of plants representing the Puccinellia nuttalliana complex (Poaceae). The first sample is a series of individuals (genotypes) collected live, vegetatively divided, and grown under controlled environmental conditions. Phenotypic variation in this sample, in individual characters and in multivariate factors, can be apportioned between genetic (among genotype) and environmental (among treatment) causes. The second sample consists of field-collected individuals from throughout the North American range of the complex. Variation in this sample, as in most field-collected samples, cannot be assigned directly to its underlying causes. Multivariate patterns in the two samples were analyzed by identical principal-components analyses of 48 morphological characters. The strongest factor identified by the greenhouse principal-components analysis correlates with the strongest of the field principal-components analysis; they are similar in character makeup, both reflecting spikelet size and plant scabrousness. These factors have a genetic component and no environmental component and appear to differentiate Puccinellia distans from the rest of the complex. The second strongest factor of the greenhouse principal-components analysis correlates with the second of the field principal-components analysis. These axes reflect general vegetative stature; they have genetic and plastic components. The overall analysis indicates that multivariate patterns in phenotype can reflect both genetic and environmental effects, in varying proportions; patterns of genetic affinity therefore may be difficult to dissociate from those reflecting plasticity.