Meeting Abstract
The distribution of phenotypes observed in nature is shaped by interactions among intrinsic factors, such as the architecture of developmental pathways, and external factors, such as the the strength and direction of selection. Flower color offers a powerful system for understanding how developmental constraints affect natural variation given that the wide diversity of colors across angiosperms has evolved by modifications of just a handful of pigment pathways. In this talk I will review the relationship between the structure and regulation of pigment pathways and macroevolutionary patterns of color diversity. Studies across multiple taxa demonstrate that flower color intensity is highly labile and controlled by rapidly evolving transcriptional activators and repressors. By contrast, changes in floral hue can involve coordinated changes in multiple genes and in some cases, multiple pathways. Moreover, the order of these changes appears to be evolutionarily constrained, leading to gaps in the space of possible phenotypes. Although the exact mechanistic basis for these phenotypic gaps remains unclear, a combination of mathematical modeling and experimental manipulations offer a path for probing the boundaries of color space. Overall, these studies of pigmentation may provide a model for understanding how the molecular dynamics of developmental pathways divide the continuous space of possible phenotypes into discrete character states.
