The numbers of different floral organs that comprise an individual flower are thought to be among the most constant of all taxonomic characters in angiosperms, but developmental instability can occasionally lead to inconstancy of floral formula. I am studying the reproductive consequences of such instabilty in Phlox longifolia. Phlox longifolia is a native Colorado annual exhibiting reproductive organ canalization with a 5:5:5:3 floral formula (petals:sepals:anthers:carpels). This formula in highly conserved within the Phlox genus and also among most members of the Polemoniaceae family, which includes the genera Gilia, Ipomopsis, Linanthus, and Polemonium among others.

This formula remains relatively constant under normal conditions, but it is thought that factors such as environmental stress, inbreeding, and extensive hybridization can lead to developmental instability and a shift in the respective numbers of floral organs.  It is also believed that when these numbers do shift in Phlox species, there is significant correlation between petals and sepals and between anthers and carpels. That is, if instability causes the plant to produce a flower with more than 5 petals, it is highly likely that the same flower will also have more than 5 sepals.

This simple deviation from the normal floral formula has provoked several valid questions. What is causing the deviation? Is the deviation heritable or is it a somatic mutation? Can it be genetically isolated or mapped? Are there any negative/positive effects to having an abnormal number of flower parts? If so, is there a difference in effect between having MORE and having FEWER than normal parts? What is the overall level of instability? Can it be quantified? Is it the same in every population?

I am interested in finding answers to all of the above questions, but as far as dissertation work, I will focus mainly on the reproductive effects of floral formula inconstancy. That is, I am hoping to characterize the effects of various abnormal formulas on reproductive variables such as fruit set, seed set, and progeny fitness.  Also, since Phloxlongifolia has not been specifically studied in the past, I am hoping to establish standard baseline rates of autogamous and xenogamous pollination for the species.

These are the questions that I am interested in answering, and doing so will employ field observations, greenhouse breeding studies, and genetic mapping studies. The results should be applicable to the entire Polemoniaceae family and will hopefully bring to light the significance of stable floral development as it pertains to reproductive fitness.