Hybridization as a Stimulus for the Evolution of Invasiveness in Plants
Whitney, Kenneth D , Randell, Rebecca A , Rieseberg, Loren H. .
Hybridization, the introgression of herbivore resistance, and southward range expansion in the wild sunflower Helianthus annuus.
INSIGHTS into biological invasions may be gained by considering a related process, range expansion. We used a system of hybridizing sunflowers to examine how introgression may have influenced adaptation and range expansion. Previous work suggested that the sunflower Helianthus annuus has captured genetic material from the Texas endemic H. debilis and has recently colonized southern Texas (forming a subspecific taxon, H. annuus texanus). But did introgression of debilis genes drive colonization success in annuus, or was it just coincidence? We present new data documenting higher fitness in the hybrid lineage relative to the parental species, as well as data suggesting that a number of herbivore resistance traits have introgressed from debilis into annuus. Artificial annuus × debilis hybrids were then synthesized to mimic the ancestors of H. a. texanus, and were grown in a replicated field experiment. Natural selection favored plants with debilis-like resistance to seed midges and head-feeding Lepidoptera. These results suggest that introgression of herbivore resistance traits was important in the adaptation of H. annuus to central and southern Texas, and likely aided the southward range expansion of that lineage. In ongoing work, we are mapping quantitative trait loci (QTL) for these traits and assessing the extent to which advantageous alleles originated in H. debilis.
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1 - Rice University, Ecology and Evolutionary Biology, 6100 Main St., MS 170, Houston, Texas, 77005, USA
2 - Indiana University, Department of Biology, Jordan Hall, 1001 East Third Street, Bloomington, Indiana, 47405, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, August 2nd, 2006
Time: 11:00 AM