Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Tracing floral adaptations from ecology to molecules

Key Points

  • The study of floral evolution provides a simple system to investigate the link between environmental adaptation, phenotypic determination and genetic change.

  • The methods of molecular genetics offer powerful comparative tools for unravelling the evolution of floral adaptations.

  • Flower colour is a simple phenotype with well-characterized pathways of biochemical and molecular determination, which greatly facilitates comparative analysis.

  • The morning glory genus Ipomoea is well suited to comparative molecular research on floral evolution owing to the great range of floral phenotypes that have arisen in the genus in the past 30 million years.

  • Differences in floral colour among Ipomoea species seem to be largely the result of shifts in gene expression rather than the result of changes in enzymatic genes.

  • Over longer periods of evolutionary time (≥50 million years) gene duplication has been the source of important new innovations in the flavonoid biosynthesis.

  • Transposons are an important source of allelic diversity in flavonoid genes in Ipomoea species.

  • Ecological research with Ipomoea provides a direct link between phenotypic selection and the environment by showing that bumblebee pollinators discriminate between pigmented and white floral morphs, leading to asymmetries in genetic transmission that should favour white genes when they are expressed at low frequency.

  • The study of floral adaptation at all levels of biological organization requires mixing historical inference with direct experimentation.


Flowers have long fascinated humans. The scientific study of floral biology unifies many diverse areas of research, ranging from systematics to ecology, and from genetics to molecular biology. Despite this unity, few plant species offer the experimental versatility to encompass all levels of biological investigation in a single system. An exception is the morning glory genus Ipomoea, in which a broad picture of floral evolution, ranging from ecology to molecular biology, is emerging.

Your institute does not have access to this article

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Between species and within species floral variation in Ipomoea.
Figure 2: Flavonoid biosynthetic pathway.
Figure 3: Differential patterns of expression of flavonoid genes in the petals of Ipomoea species.
Figure 4: Chalcone synthase gene family tree.
Figure 5: Transposon variation in chalcone synthase D sequences from Ipomoea purpurea and Ipomoea nil.


  1. Correns, C. Mendel's law concerning the behavior of progeny of varietal hybrids. Berichte der Deutschen Botanischen Gesellschaft 18, 158–168 (1900).

    Google Scholar 

  2. de Vries, H. Concerning the law of segregation of hybrids. Comptes Rendus de l'Academie des Sciences 130, 845–847 (1900).

    Google Scholar 

  3. Watson, J. D. & Crick, F. C. Genetical implications of the structure of deoxyribonucleic acid. Nature 171, 964 (1953).

    CAS  Article  Google Scholar 

  4. Daborn, P. J. et al. A single P450 allele associated with insecticide resistance in Drosophila. Science 297, 2253–2256 (2002).

    CAS  Article  Google Scholar 

  5. Bradshaw, A. D. & McNeilly, T. Evolution and Pollution (Arnold, London, 1981).

    Google Scholar 

  6. Steinberg, M. H. Disorders of Hemoglobin (Cambridge Univ. Press, UK, 2001).

    Google Scholar 

  7. Watt, W. Adaptation, Constraint, and Neutrality: Mechanistic Case Studies with Butterflies and their General Implications (Cambridge Univ. Press, Cambridge, in the press).

  8. Yokoyama, S. Molecular evolution of vertebrate visual pigments. Prog. Retin. Eye Res. 19, 385–419 (2000).

    CAS  Article  Google Scholar 

  9. Doebley, J. & Lukens, L. Transcriptional regulators and the evolution of plant form. Plant Cell 10, 1075–1082 (1998).

    CAS  Article  Google Scholar 

  10. Wang, R. L., Stec, J., Hey, L., Lukens, L. & Doebley, J. The limits of selection during maize domestication. Nature 398, 236–239 (1999).

    CAS  Article  Google Scholar 

  11. Clark, A. Limits to Prediction of Phenotypes from Knowledge of Genotypes 205–222 (Plenum, New York, 2000).

    Google Scholar 

  12. Clegg, M. T. & Durbin, M. L. Flower color variation: a model for the experimental study of evolution. Proc. Natl Acad. Sci. USA 97, 7016–7023 (2000). A summary of genetic and molecular studies on flower colour evolution in Ipomoea . This paper makes a case for why flower colour is a good model for the study of evolution and phenotypic adaptation.

    CAS  Article  Google Scholar 

  13. Beldade, P. & Brakefield, P. M. The genetics and evo–devo of butterfly wing patterns. Nature Rev. Genet. 3, 442–452 (2002).

    CAS  Article  Google Scholar 

  14. Austin, D. F. & Huaman, Z. A synopsis of Ipomoea (Convolvulaceae) in the Americas. Taxon 45, 3–38 (1996).

    Article  Google Scholar 

  15. McDonald, J. A. & Mabry, T. J. Phylogenetic systematics of new-world Ipomoea (Convolvulaceae) based on chloroplast DNA restriction site variation. Plant Syst. Evol. 180, 243–259 (1992).

    CAS  Article  Google Scholar 

  16. Manos, P. S., Miller, R. E. & Wilkin, P. Phylogenetic analysis of Ipomoea, Argyreia, Stictocardia, and Turbina suggests a generalized model of morphological evolution in morning glories. Syst. Bot. 26, 585–602 (2001).

    Google Scholar 

  17. Miller, R. E., Rausher, M. D. & Manos, P. S. Phylogenetic systematics of Ipomoea (Convolvulaceae) based on ITS and waxy sequences. Syst. Bot. 24, 209–227 (1999). A thorough study using sequence data from both ribosomal internal transcribed spacer (ITS) and a single-copy gene (Waxy) to elucidate the phylogenetics of Ipomoea . Work by this group should lead to a better understanding of the relationships in the genus Ipomoea.

    Article  Google Scholar 

  18. Iida, S., Hoshino, A., Johzuka-Hisatomi, Y., Habu, Y. & Inagaki, Y. in Molecular Strategies in Biological Evolution Vol. 870 265–274 (Annals of the New York Academy of Sciences, New York, 1999). A summary of what is known about transposable elements in two species of Ipomoea and the role of such elements in generating new phenotypic traits.

    Google Scholar 

  19. Imai, Y. The genetics of Pharbitis purpurea. J. Coll. Agric. Imperial Univ. Tokyo 9, 119–122 (1927).

    Google Scholar 

  20. Imai, Y. Analysis of flower colour in Pharbitis nil. J. Genet. 24, 203–224 (1931).

    Article  Google Scholar 

  21. Imai, Y. Linkage studies in Pharbitis nil. Genetica 16, 467–475 (1934).

    Article  Google Scholar 

  22. Barker, E. E. Heredity studies in the morning glory (Ipomoea purpurea L. Roth.) Bull. Cornell Univ. Agric. Experiment Station 392, 121–154 (1917).

    Google Scholar 

  23. Glover, D. E., Durbin, M. L., Huttley, G. A. & Clegg, M. T. Genetic diversity in the common morning glory. Plant Spec. Biol. 11, 41–50 (1996).

    Article  Google Scholar 

  24. Brown, B. A. & Clegg, M. T. Influence of flower color polymorphism on genetic transmission in a natural population of the common morning glory, Ipomoea purpurea. Evolution 38, 796–803 (1984).

    Article  Google Scholar 

  25. Ennos, R. A. & Clegg, M. T. Flower color variation in the morning glory, Ipomoea purpurea. J. Hered. 74, 247–250 (1983).

    Article  Google Scholar 

  26. Schoen, D. J. & Clegg, M. T. The influence of flower color on outcrossing rate and male reproductive success in Ipomoea purpurea. Evolution 39, 1242–1249 (1985).

    Article  Google Scholar 

  27. Epperson, B. K. & Clegg, M. T. Frequency-dependent variation for outcrossing rate among flower-color morphs of Ipomoea purpurea. Evolution 41, 1302–1311 (1987).

    Article  Google Scholar 

  28. Rausher, M. D. & Fry, J. D. Effects of a locus affecting floral pigmentation in Ipomoea purpurea on female fitness components. Genetics 134, 1237–1247 (1993).

    CAS  PubMed  PubMed Central  Google Scholar 

  29. Fisher, R. A. Average excess and average effect of a gene substitution. Ann. Eugen. 11, 53–63 (1941).

    Article  Google Scholar 

  30. Holsinger, K. E. Pollination Biology and the Evolution of Mating Systems in Flowering Plants 107–149 (Plenum, New York, 1996).

    Google Scholar 

  31. Rausher, M. D., Augustine, D. & Vanderkooi, A. Absence of pollen discounting in a genotype of Ipomoea purpurea exhibiting increased selfing. Evolution 47, 1688–1695 (1993).

    Article  Google Scholar 

  32. Chang, S. M. & Rausher, M. D. The role of inbreeding depression in maintaining the mixed mating system of the common morning glory, Ipomoea purpurea. Evolution 53, 1366–1376 (1999).

    Article  Google Scholar 

  33. Mojonnier, L. E. & Rausher, M. D. A floral color polymorphism in the common morning glory (Ipomoea purpurea): the effects of overdominance in seed size. Evolution 51, 608–614 (1997).

    PubMed  Google Scholar 

  34. Durbin, M. L., McCaig, B. & Clegg, M. T. Molecular evolution of the chalcone synthase multigene family in the morning glory genome. Plant Mol. Biol. 42, 79–92 (2000).

    CAS  Article  Google Scholar 

  35. Inagaki, Y. et al. Genomic organization of the genes encoding dihydroflavonol 4- reductase for flower pigmentation in the Japanese and common morning glories. Gene 226, 181–188 (1999).

    CAS  Article  Google Scholar 

  36. Durbin, M. L., Lundy, K. E., Morrell, P. E., Torres–Martinez, C. L. & Clegg, M. T. Genes that determine flower color: the role of regulatory changes in the evolution of phenotypic adaptations. Mol. Phyl. Evol. (2003).

  37. Quattrocchio, F., Wing, J. F., van der Woude, K., Mol, J. N. M. & Koes, R. Analysis of bHLH and MYB domain proteins: species-specific regulatory differences are caused by divergent evolution of target anthocyanin genes. Plant J. 13, 475–488 (1998).

    CAS  Article  Google Scholar 

  38. Quattrocchio, F. et al. Molecular analysis of the anthocyanin2 gene of petunia and its role in the evolution of flower color. Plant Cell 11, 1433–1444 (1999).

    CAS  Article  Google Scholar 

  39. Spelt, C., Quattrocchio, F., Mol, J. N. M. & Koes, R. anthocyanin1 of petunia encodes a basic helix-loop-helix protein that directly activates transcription of structural anthocyanin genes. Plant Cell 12, 1619–1631 (2000).

    CAS  Article  Google Scholar 

  40. Spelt, C., Quattrocchio, F., Mol, J. & Koes, R. ANTHOCYANIN1 of petunia controls pigment synthesis, vacuolar pH, and seed coat development by genetically distinct mechanisms. Plant Cell 14, 2121–2135 (2002).

    CAS  Article  Google Scholar 

  41. Mol, J., Grotewold, E. & Koes, R. How genes paint flowers and seeds. Trends Plant Sci. 3, 212–217 (1998). A synopsis of the work on regulation of the flavonoid pathway in several diverse species. The authors do an excellent job of comparing and contrasting what is known about regulation of the flavonoid pathway with a goal of identifying common mechanisms.

    Article  Google Scholar 

  42. Koes, R. E., Spelt, C. E., Mol, J. N. M. & Gerats, A. G. M. The chalcone synthase multigene family of Petunia hybrida (V30): sequence homology, chromosomal localization and evolutionary aspects. Plant Mol. Biol. 10, 159–169 (1987).

    CAS  Article  Google Scholar 

  43. Stafford, H. A. Flavonoid evolution: an enzymatic approach. Plant Physiol. 96, 680–685 (1991).

    CAS  Article  Google Scholar 

  44. Koes, R., Quattrocchio, F. & Mol, J. The flavonoid biosynthetic pathway in plants: function and evolution. BioEssays 16, 123–132 (1993).

    Article  Google Scholar 

  45. Kidwell, M. G. & Lisch, D. R. Perspective: transposable elements, parasitic DNA, and genome evolution. Evolution 55, 1–24 (2001). A thorough analysis of the role of transposable elements in the evolution of genomes and the creation of new traits.

    CAS  Article  Google Scholar 

  46. McClintock, B. The origin and behavior of mutable loci in maize. Proc. Natl Acad. Sci. USA 36, 344–355 (1950).

    CAS  Article  Google Scholar 

  47. Habu, Y., Hisatomi, Y. & Iida, S. Molecular characterization of the mutable flaked allele for flower variegation in the common morning glory. Plant J. 16, 371–376 (1998).

    CAS  Article  Google Scholar 

  48. Durbin, M. L., Denton, A. L. & Clegg, M. T. Dynamics of mobile element activity in chalcone synthase loci in the common morning glory (Ipomoea purpurea). Proc. Natl Acad. Sci. USA 98, 5084–5089 (2001).

    CAS  Article  Google Scholar 

  49. Hoshino, A., Johzuka-Hisatomi, Y. & Iida, S. Gene duplication and mobile genetic elements in the morning glories. Gene 265, 1–10 (2001).

    CAS  Article  Google Scholar 

  50. Schemske, D. W. & Bradshaw, H. D. Pollinator preference and the evolution of floral traits in monkeyflowers (Mimulus). Proc. Natl Acad. Sci. USA 96, 11910–11915 (1999). The work in Mimulus provides further evidence of how pollinator preference can influence phenotype and the evolution of the genus.

    CAS  Article  Google Scholar 

  51. Barrier, M., Robichaux, R. H. & Purugganan, M. D. Accelerated regulatory gene evolution in an adaptive radiation. Proc. Natl Acad. Sci. USA 98, 10208–10213 (2001). This work shows that rapid evolution in regulatory genes is correlated with adaptive evolution.

    CAS  Article  Google Scholar 

  52. Glover, B. J. & Martin, C. The role of petal cell shape and pigmentation in pollination success in Antirrhinum majus. Heredity 80, 778–784 (1998).

    Article  Google Scholar 

  53. Comba, L. et al. The role of genes influencing the corolla in pollination of Antirrhinum majus. Plant Cell Environ. 23, 639–647 (2000).

    CAS  Article  Google Scholar 

  54. Martin, C., Prescott, A., Mackay, S., Bartlett, J. & Vrijlandt, E. Control of anthocyanin biosynthesis in flowers of Antirrhinum majus. Plant J. 1, 37–49 (1991).

    CAS  Article  Google Scholar 

  55. Epperson, B. K. & Clegg, M. T. Genetics of flower color polymorphism in the common morning glory (Ipomoea purpurea). J. Hered. 79, 64–68 (1988).

    Article  Google Scholar 

  56. Epperson, B. K. & Clegg, M. T. Unstable white flower color genes and their derivatives in the morning glory. J. Hered. 83, 405–409 (1992).

    Article  Google Scholar 

  57. Saitou, N. & Nei, M. The neighbor-joining method: a new method for reconstructing phylogenetic trees. Mol. Biol. Evol. 4, 406–425 (1987).

    CAS  Google Scholar 

  58. Tropf, S., Lanz, T., Rensing, S. A., Schroder, J. & Schroder, G. Evidence that stilbene synthases have developed from chalcone synthases several times in the course of evolution. J. Mol. Evol. 38, 610–618 (1994).

    CAS  Article  Google Scholar 

  59. Tropf, S., Karcher, B., Schroder, G. & Schroder, J. Reaction-mechanisms of homodimeric plant polyketide synthases (stilbene and chalcone synthase): a single active-site for the condensing reaction is sufficient for synthesis of stilbenes, chalcones, and 6′-deoxychalcones. J. Biol. Chem. 270, 7922–7928 (1995).

    CAS  Article  Google Scholar 

  60. Johzuka-Hisatomi, Y., Hoshino, A., Mori, T., Habu, Y. & Iida, S. Characterization of the chalcone synthase genes expressed in flowers of the common and Japanese morning glories. Genes Genet. Sys. 74, 141–147 (1999).

    CAS  Article  Google Scholar 

Download references


This research was partially supported by a grant from the Alfred P. Sloan Foundation.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Michael T. Clegg.

Related links

Related links


Burpee Seeds and Plants

Daniel F. Austin's home page

GRIN/NPGS species list

Kyushu University Molecular Population Genetics

NIBB Division of Gene Expression and Regulation I



The tube-like, proximal-most region of Ipomoea petals.


The expanded, distal-most region of Ipomoea petals.


Soluble glycoside pigments that produce the blue-to-red colour in flowers and other plant tissues.


Genes that alter the system of mating and the statistical rules of genetic transmission in populations. An example is a gene that increases the frequency of self-fertilization.


Situation in which the transmission of genes through pollen is reduced below a random expectation.


Phenotypic expression is greater in the heterozygote than in either homozygote. This can result in an increased fitness of the heterozygote and lead to the maintenance of both alleles in the population.


Responsible for several distinct and seemingly unrelated phenotypic effects.


The production of a group of aromatic compounds that includes many common pigments such as flavones and anthocyanins.


A segment of genetic material that is capable of changing its location in the genome of an organism.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Clegg, M., Durbin, M. Tracing floral adaptations from ecology to molecules. Nat Rev Genet 4, 206–215 (2003).

Download citation

  • Issue Date:

  • DOI:

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing