PHENOTYPIC INTEGRATION AND PLASTIC CORRELATIONS IN PHLOX-DRUMMONDII (POLEMONIACEAE)

Clones from two populations of Phlox drummondii were grown in three di fferent nutrient environments to determine the extent to which the ove rall level and pattern of correlation among traits within an environme nt changes across environments. With one exception, the level of pheno typic correlation in both populations was the same across environments . Plants from Lexington, Texas exhibited a significantly lower level o f phenotypic correlation when grown at a high nutrient concentration. The two populations did not differ from one another in their levels of phenotypic correlation when compared within environments. The pattern of correlation was homogenous both within populations across environm ents and among populations within environments. Tests of a priori hypo theses regarding the associations among functionally or developmentall y related traits suggest that the correlations among traits are higher in traits that share a common function or developmental origin. We al so compared the level and pattern of plasticity correlations among pop ulations for three different components of the plastic response. We fo und that the level and pattern of plastic correlation for the average, linear, and nonlinear components of the plastic response did not diff er among the two populations. With only one exception, the relationshi ps among the plastic responses of different traits fit our model of fu nctional and developmental integration. The results from our analyses of phenotypic and plastic correlations support the hypothesis that pla stic correlations determine the extent to which phenotypic correlation s are environment-dependent.