THE EVOLUTION AND ECOLOGY OF FLORAL MORPHOLOGY IN AQUILEGIA AND THE INFLUENCE OF HORTICULTURE ON ITS EMERGENCE AS A MODEL SYSTEM

The columbine genus Aquilegia has been grown as a garden ornamental for centuries. Because of its unusual floral shape with the sepals being petaloid and colorful and the petals forming slender nectar spurs, many collections were made and species have been available to scientists as well as horticulturalists. Given its widespread natural distribution throughout the northern hemisphere, this availability was essential for early studies establishing that species in the genus were often highly intercompatible and their hybrids could be established. This led to a number of studies showing the relatively simple genetic inheritance of many of the dramatic differences among flowers of various species. More recent work has established the phylogenetic relationships among most of the species and showing that the genus had a burst of diversification after evolving the distinctive nectar spurs. Other studies have shown that this burst of diversification was likely due to adaptation to different pollinators, especially in North America, with changes in flower color, orientation and spur length to match the preferences and tongue lengths of new pollinators. Further studies have dissected the genetic basis of some of these traits. Aquilegia has also been noteworthy for its contributions to our understanding of the evolution of floral organ identity and horticultural varieties have, and will continue, to aid in these efforts. Aquilegia has now been the subject of substantial effort to develop it as a new model genomic system with the establishment of a high-quality reference sequence, derived from a highly inbred horticultural line as well as other resources such as a functional assay to assess specific gene functions. These resources poise Aquilegia to continue to be at the forefront of plant evolutionary and ecological research. INTRODUCTION The columbine genus, Aquilegia, has long been admired and cultivated due to its striking floral shape and extensive range of floral colors. The common name “columbine” is derived from the Latin columba for dove as the inwardly curled nectar spurs being thought to resemble a cluster of doves while Aquilegia is derived from aquila for eagle with the same nectar spurs being thought to resemble an eagle’s claw. For centuries Aquilegia has been cultivated and mutant forms selected as illustrated in herbals and floras from at least the late 1500s. The earliest depiction of Aquilegia I have found is from 1592 by Fabio Colonna in his Phytobasanos (Fig. 1A), though he labels the drawing as Isopyrum. Other depictions include homeotic mutants, clearly selected for their increased numbers of colorful sepals and or petals (Fig. 1B,C). Similar forms are still available in the trade and are prized garden additions. While the beautiful flowers have attracted gardeners and horticulturalists for hundreds of years, Aquilegia has also played an important scientific role in our understanding of adaptation, speciation and floral development. Interestingly many of the traits that have attracted horticulturalists turn out to be the same traits of interest to many scientists studying ecology and evolutionary biology. Here I review a number of the findings regarding the evolution of floral traits in Aquilegia and their ecological context and the role this genus will likely play in many future studies. Proc. XXV Int. Eucarpia Symp. – Section Ornamentals