Reconstructing the origin of Helianthus deserticola: Survival and selection on the desert floor

B.L. Gross, D.L. Kane, C. Lexer, F. Ludwig, D.R. Rosenthal, L.A. Donovan, L.H. Rieseberg

Research output: Contribution to journalArticleAcademicpeer-review

62 Citations (Scopus)


The diploid hybrid species Helianthus deserticola inhabits the desert floor, an extreme environment relative to its parental species Helianthus annuus and Helianthus petiolaris. Adaptation to the desert floor may have occurred via selection acting on transgressive, or extreme, traits in early hybrids between the parental species. We explored this possibility through a field experiment in the hybrid species' native habitat using H. deserticola, H. annuus, H. petiolaris, and two populations of early-generation (BC2) hybrids between the parental species, which served as proxies for the ancestral genotype of the ancient hybrid species. Character expression was evaluated for each genotypic class. Helianthus deserticola was negatively transgressive for stem diameter, leaf area, and flowering date, and the latter two traits are likely to be advantageous in a desert environment. The BC 2 hybrids contained a range of variation that overlapped these transgressive trait means, and an analysis of phenotypic selection revealed that some of the selective pressures on leaf size and flowering date, but not stem diameter, would move the BC2 population toward the H. deserticola phenotype. Thus, H. deserticola may have originated from habitat-mediated directional selection acting on hybrids between H. annuus and H. petiolaris in a desert environment.
Original languageEnglish
Pages (from-to)145-156
JournalAmerican Naturalist
Issue number2
Publication statusPublished - 2004


  • boron toxicity tolerance
  • hybrid speciation
  • mediterranean populations
  • transgressive segregation
  • aquilegia-pubescens
  • water-stress
  • asteraceae
  • evolution
  • ancient
  • plants

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