During my postdoctoral fellowship at Indiana University, I investigated the evolutionary changes that have taken place in a hybrid swarm of annual sunflowers over its lifetime.  This fifty-five year old population of Helianthus annuus and H. bolanderi represents a unique opportunity to study a proposed case of rapid diploid hybrid speciation.  I performed controlled crosses among plants grown from wild-collected seed in order to determine if earlier predictions of diploid hybrid speciation in the population could be substantiated. Helianthus annuus crossed as easily with intermediate plants as with conspecific plants and progeny from these crosses had high pollen fertility (a sign of chromosomal compatibility of the parents), while H. bolanderi was isolated from both of the other groups.  Thus it does not appear that intermediates have formed a hybrid species.  Rather, they appear to have the same fertility type (chromosomal and/or genic) as H. annuus.  Analysis of karotypes is still in progress.
    Additionally, I was able to compare the current molecular and morphological makeup of the population with morphological data from the hybrid zone in the 1940s and 1950s, which allowed me to draw conclusions about the outcome of hybridization.  It appears that interspecific gene flow and possibly competition from the more common H. annuus could be leading to the local extinction of H. bolanderi (Carney, Gardner and Rieseberg In Review).
    Finally, I performed a reciprocal transplant study of the parental species and hybrids in the hybrid zone.  This should allow me to determine the role habitat plays in structuring the hybrid zone and assess the fitness of hybrids and parental individuals across the available habitats.