Faculty Research: Aquilegia

Quantitative Trait Locus Mapping

A major focus of my laboratory is to understand the genetic basis of adaptation, reproductive isolation, and species diversification. We have identified the evolution of floral nectar spurs as a key evolutionary innovation because they are highly correlated with increased rates of species diversification across a wide range of flowering plants (Hodges & Arnold 1995; Hodges ; Hodges). This finding continues to be one of the best examples of a single trait promoting species diversification in any group of organisms. Our hypothesis for why this occurs has been that fairly simple genetic changes may cause differences in nectar spurs. These differences in flowers then allow specialization to different pollinators which result in reproductively isolated groups, and hence, diversification. Thus, a major goal for my laboratory has been to determine the genetic architecture of floral differences between species with different specialized pollinators. To do this, we have been conducting a quantitative trait locus (QTL) mapping study of floral differences between Aquilegia formosa and A. pubescens. These species have very different floral forms and we have previously shown that they are primarily pollinated by different species (Fulton & Hodges 1999). We are currently conducting a quantitative trait locus (QTL) analysis of these floral traits using a large F2 population (Hodges et al. 2002). This research is funded by NSF.

Aquilegia formosa

/ Aquilegia pubescens

Phylogeny

Aquilegia is a prime example of a rapid radiation of species after the evolution of nectar spurs (Hodges & Arnold 1994, 1995). The genus is widespread with species in the mountainous regions of Europe, Asia and North America. The 70 or so described species vary tremendously in floral forms that correspond to differences in the types of pollinators that visit them. In addition, there is a great deal of ecological variation among the species with some occurring in moist, shady environments, some occurring in high altitude, rocky and exposed slopes, and still others along desert springs. In order to test whether shifts in floral morphology may cause this diversification, we are currently reconstructing the phylogeny for this genus using both single gene genealogies and AFLP markers. This project is being conducted by Justen Whittall, Ph.D. candidate.

Aquilegia canadensis

Aquilegia flavescens

Aquilegia coerulea ssp pinetorum

Aquilegia skinneri

phylogeny of Aquilegia and close relatives

Hybrid Zone Analyses

As another test of whether differences between species of Aquilegia in floral traits affects reproductive isolation, we are studying mating patterns in hybrid zones between Aquilegia formosa and A. pubescens in the Sierra Nevada Mountains of California. A. formosa occurs at lower elevations (6000-10,000 ft) and A. pubescens occurs at high elevations (10,000-13,000 ft). The floral morphology and habitats of these two species differ radically. A. formosa has red & yellow, short spurred, pendent flowers and occurs in moist, shady environments. A. pubescens has white or yellow, long spurred and erect flowers and occurs in rocky/gravel soils ;that are exposed. At mid elevations where these habitats come into close contact, natural hybrid zones form and a spectacular amount of floral variation is produced. Using microsatellite markers, we are identifying mating patterns in these zones to determine the reproductive fitness of hybrids and the two species. This project is being conducted by Ji Yang, Ph. D. candidate.

Examples of natural variation in a hybrid zone between A. Formosa and A. pubescens

Scott Hodges | Research | Publications | Curriculum Vitae

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