Wu, Carrie A. , Campbell, Diane R. .
The spatial genetic structure of cytoplasmic and nuclear markers in a natural Ipomopsis (Polemoniaceae) hybrid zone.
Spatial variation in natural selection may play an important role in determining the genetic structure of hybridizing populations. Previous studies have found that F1 hybrids between naturally hybridizing Ipomopsis aggregata and I. tenuituba in central Colorado differ in fitness depending on both genotype and environment: hybrids had higher survival when I. aggregata was the maternal parent, except in the center of the hybrid zone where both hybrid types had high survival. Here we developed both maternally- (cpDNA PCR-RFLP) and biparentally-inherited (nuclear AFLP) species-diagnostic markers to characterize the spatial genetic structure of the natural Ipomopsis hybrid zone, and tested the prediction that the majority of natural hybrids have I. aggregata cytoplasm, except perhaps in areas near the center of the hybrid zone. Analyses of 342 individuals from across the hybrid zone indicate that cytoplasmic gene flow is bidirectional, but contrary to expectation, most plants in the hybrid zone have I. tenuituba cytoplasm. This cytotype distribution is consistent with a hybrid zone in historical transition, with I. aggregata nuclear genes advancing into the contact zone. Further, nuclear data show a much more gradual cline that is consistent with morphological patterns across the hybrid populations. A mixture of environment- and pollinator-mediated selection may contribute to the current genetic structure of this hybrid system.
1 - University of California, Irvine, Department of Ecology and Evolution, 321 Steinhaus Hall, UCI, Irvine, California, 92697, USA
Presentation Type: Paper
Location: Peruvian (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 9:15 AM