Martin, Noland H. , Arnold, Michael .
Genetic Architecture of Reproductive Isolation in Louisiana Irises: Pollinator preferences.
Divergent pollinator preferences may be an important reproductive barrier between potentially hybridizing species of flowering plants. Here we describe regions of plant genomes that affect pollinator preferences for two species of Louisiana Irises, Iris brevicaulis and Iris fulva, and their F1 and first generation backcross hybrids. Iris brevicaulis and I. fulva possess a “bee-pollination syndrome” and “bird-pollination syndrome”, respectively. Hummingbirds and lepidopterans showed a significant preference for I. fulva and I. fulva-like backcrosses, while bumblebees (genus Bombus) generally preferred I. brevicaulis and F1 hybrids in experimental field conditions. Significantly, while all three pollen vectors showed preferences for one or the other pure-species parental type, these preferences were never sufficiently strong to exclude visitation to other hybrid or parental classes, indicating that hybrid zones between I. brevicaulis and I. fulva can be facilitated by pollinator behavior. Using a quantitative trait locus (QTL) mapping approach in reciprocal backcross populations, we examined the genetic architecture of loci that affected pollinator-mediated reproductive isolation in Louisiana Iris. We detected six and nine QTLs that significantly affected pollinator visitation rates in BCIb and BCIf mapping populations, respectively, with as many as three QTLs detected for each trait. By examining the direction of QTL effects, we were unable to detect a signature of selection causing divergence in pollinator preferences. However, some of the preference QTLs did overlap with floral trait QTLs detected in a separate study, supporting the hypothesis that some measure of pollinator fidelity and tight linkage might limit the breaking up of floral trait associations. Overall, this study reflects the role that quantitative genetic factors may play in determining the pattern of pollinator-mediated genetic exchange.
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Martin et al. 2008: Evolution 62: 740-752
1 - Texas State University, Department of Biology, 601 University Drive, San Marcos, Texas, 78666, USA
2 - University of Georgia, Department Genetics, Life Sciences Building, Athens, Georgia, 30602, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Wednesday, July 30th, 2008
Time: 4:45 PM