Laboratory Speciation in Helianthus Evolves a Native Species

furball4paws

[furball4paws]

Laboratory Speciation in Helianthus Evolves a Native Species

DNA examination of five species of Helianthus (H. annuus, H. petiolarus fallax, H. anomalus, H. paradoxus, and H. deserticola) suggested that H. annuus and H. petiolarus fallax are the evolutionary parents of the other three species (Rieseberg 1993, 1995, 1993). All five species are self-incompatible and fertile. Typically, H. annuus (the ancestor of the commercial sunflower) and H. petiolarus fallax form hybrids that are almost fully sterile. However, the few fertile hybrids, when subjected to sib-matings and back crossing regimes yield a new species that is fully fertile and cannot cross with either of the parental species. This new species is virtually identical to H. anomalus. The produced species is genetically isolated from the parents by chromosomal barriers. "Under laboratory conditions these changes are repeatable across independent experiments" (Niklas, p.64). The laboratory derived H. anomalus readily crosses with the native H. anomalus. Results indicate that H. deserticola and H. paradoxus may also have arisen via hybridization of H. annuus and H. petiolarus fallax. These two species have different synthetic capabilities from the parents and live in sandier and drier soils. Hybrid speciation may be common in plants where hybrids often form (see Gilia sp., Grant, 1966, Stebbins, 1959, Arnold, 1995), but is presumed rare in animals where hybrids are less common (however, see the minnow Gila seminuda, Bellini, 1994). Experiments to confirm the evolutionary parents of H. deserticola and H. paradoxus have not been performed. 1. Based on nuclear and chloroplast DNA analysis results, the Theory of Evolution predicts that H. annuus and H. pertiolarus fallax are evolutionary ancestors of H. anomalus, H. deserticola and H. paradoxus. 2. Hybrids of H. annuus and H. petiolarus fallax subjected to different regimes (at least 3) of back crossing and sib-matings, all converged into a new plant species with "nearly identical gene combinations" (Rieseberg) as the native species H. anomalus. This confirms the natural evolutionary parents of H. anomalus as predicted.

References 1. Arnold, J and S.A. Hodges. 1995. Are Natural Hybrids Fit or Unfit Relative to Their Parents? Trends Ecol. Evol. 10:67-71. 2. Bullini, L. 1994. Origin and Evolution of Animals by Hybrid Animal Species. Trends Ecol. Evol. 9:422-6. 3. Futuyma, D.J. 1998. Evolutionary Biology. 3rd. Edition, Sinauer Associates Inc., Sunderland, MA. 4. Grant, V. 1966. The Origin of a New Species of Gilia in a Hybridization Experiment. Genetics 54:1189-99. 5. Niklas, K.J. 1997. The Evolutionary Biology of Plants. Univ. Chicago Press, Chicago, IL. 6. Rieseberg, L.H. 1995. The Role of Hybridization in Evolution: Old Wine in New Skins. Amer. J. Bot. 82:944-53. 7. Rieseberg, L.H., and N.C. Ellstrand. 1993. What Can Molecular and Morphological Markers Tell Us About Plant Hybridization? Crit. Rev. Plant Sci. 12:213-41. 8. Rieseberg, L.H., B. Sinervo, C.R. Linden, M. Ungerer and D.M. Arias. 1996. Role of Gene Interactions in Hybrid Speciation: Evidence from Ancient and Experimental Hybrids. Science 272:741-44.A

Nice, neat, repeatable and meets all scientific criteria for a definitive experiment.

[Southack]

Oh please. What part of ---> "Cross-breeding can not explain the origin of the first two species" <-- did you not comprehend?!

[furball4paws]

It's not about the origin of the first two species. Try again.

[Southack]

"It's not about the origin of the first two species. Try again."

Ah, but my point was about the origin...as well as about the relevance of your article to the Evolution/Creationist/Intelligent Design argument.

I made a categorical comment about your article. such comments are useful in evaluating the Big Picture.

For those who are more interested in the details of your article, naturally my broad comment wouldn't apply.

[furball4paws]

BTTT