Phenotypic integration in plants

The interrelationships among phenotypic traits of plants has been of interest to plant evolutionary biologists for almost a century. Broadly defined, phenotypic integration refers to the correlations among traits within functional units (such as a flower). In this review, the classic research of Berg (1960) on the relationships among traits within floral modules, the dissociation of the floral module from the vegetative module are reviewed and advances in our understanding of these relationships is explored. Recent data on changes in integration of traits during development or across environments, as well as phylogenetic comparisons of integration, are highlighted. Common statistical approaches used to address these issues are briefly reviewed. In summary, it is argued that our understanding of the evolution of phenotypic integration will continue to advance as studies simultaneously examine the developmental, physiological and genetic mechanisms behind the genotype to phenotype map, and consider how selection acts on complex functional phenotypes.