The Relative Effects of Resources and Genetics on Reproductive Success in the Rare Kachina Daisy, Erigeron kachinensis (Asteraceae)

In a previous study, Erigeron kachinensis, the Kachina daisy, was found to have low percentage seed set because of low fertilization rates of ovules (ca. 48%) and high abortion rates of developing seeds (ca. 56%). Therefore, we initiated field and greenhouse experiments to determine which of several factors were responsible for the observed low production of filled seeds in this species. Unmanipulated plants in the greenhouse, under pollinator exclosures, demonstrated that E. kachinensis requires an animal vector for successful pollination. Geitonogamous field and greenhouse crosses produced almost no viable seed (<1%), demonstrating that the species is self‐incompatible. The species appears to exhibit a homomorphic sporophytic type incompatibility system, as found in other composites that may be responsible for the observed low levels of ovule fertilization. Although plants exhibited developmental asymmetries both vegetatively and reproductively under resource stress, resource availability did not affect abortion rates of developing seeds. Resource availability did affect the number of flower heads produced. Seed abortion was significantly decreased when pollen came from a different population. Seed set is likely limited by the species’ inability to find compatible mates because of its self‐incompatibility system and recessive lethals exposed during sexual recombination in its small populations.