Pamela K. Diggle


Department of Ecology and Evolutionary Biology

University of Colorado


Plant Morphology and Evolution

My research focuses on the combined effects of genotype, environment, and ontogenetic history on the development and evolutionary diversification of plant phenotypes. I am particularly interested in the role of developmental plasticity in morphological diversification and intra-individual variation among metamers (what I have termed architectural effects) as the raw materials for the evolution of floral specialization.

Current research projects include:

Developmental plasticity, architectural effects and the evolution of andromonoecy. Andromonoecy is a reproductive system in which plants bear both hermaphroditic and male flowers. The evolution of this reproductive system has frustrated biologists since Darwin described it as a "great and curious blunder in dame nature." A key to understanding the origin and diversification of this reproductive system has been to examine the evolution of flowers within the context of the whole organism. Both positional variation in developmental potential among flowers, and phenotypic plasticity in response to fruit set have played key roles.

Architectural effects and the evolution of floral size dimorphism. In the vast majority of species that bear unisexual flowers, there is some sort of floral dimorphism, often in size, associated with the different flower types. Much of the extensive literature on this topic is focused on constructing and testing adaptive hypotheses for sexual size dimorphism between male and female (or male and hermaphroditic) flowers. In collaboration with Jill Miller (Amherst College), I am examining an alternative hypothesis that the common perception of size differences among flower types is due to "architectural effects," variation inherent to the production of repeated units within axes.

Evolution of fruit size in Solanum. Within Solanum fruit size varies tremendously. We are using a candidate gene approach to examine the evolutionary diversification of fruit size within two small clades, sections Lasiocarpa and Acanthopohora.

Floral Assembly Rules, a NSF-NESCent Working Group. With Charles Fenster (University of Maryland) and Scott Armbruster (University of Alaska) I have organized a working group to examine the evolution sequence for the assembly of complex floral morphology. We have assembled experts in several fields pertaining to floral biology, including genetics, development, ecological function, systematics, and evolution. Together, we are working to define a research agenda for considering floral evolution from a multivariate perspective and to promote the flower as a model system for understanding the evolution of complex traits.