Variation in flowering phenology characteristics in the North American dandelion Taraxacum officinale (Asteraceae). (Plant Ecology 02:00 PM, Saturday, April 5, 2003 Brewer/Frost Science 142 Dr. Cadance A. Lowell-Presiding).

Collier, Matthew H. ; Rogstad, Steven H.

2:00

We investigated the hypothesis that. dandelion (Taraxacum officinale Weber, sensu lato; Asteraceae) clones differ in their floral stage timing characteristics under a constant set of environmental conditions. To test this hypothesis, plants representing nine different dandelion clones (identified by DNA fingerprinting) were grown in groups of five (N = 45) in a growth chamber for a period of eight months, with chamber settings similar to environmental conditions at peak dandelion flowering time for their population sites. Five flowering phenology parameters were monitored daily for a total of 301 buds developing during this time: 1) time to bud; 2) time to inflorescence (i.e., anthesis); 3) time to re-closure of inflorescence; 4) time to fruit (full re-opening of the inflorescence); and 5) total flowering time. Significant differences in mean time to inflorescence, mean time to re-closure, mean time to fruit, and mean total flowering time were revealed among some dandelion clones (ANOVA, P d*0.05). No differences in mean number of buds per plant (P = 0.0852) or mean time to bud (P = 0.8240) were detected among the nine clones. These results suggest that some differences in floral stage timing may largely be determined by variation in genotypes that have different responses to uniform environmental conditions among dandelion clones, rather than exclusively by phenotypic plastic responses affected by micro-environmental factors. These differences may have potential fitness effects. Further research is needed to determine if such clonal differences are observed under a broader range of uniform environmental conditions.

MATTHEW H. COLLIER (1), [email protected], AND STEVEN H. ROGSTAD (2) [email protected], (1) WITTENBERG UNIVERSITY, DEPT OF BIOLOGY, PO BOX 720, SPRINGFIELD OH 45501-0720 AND -(2) UNIVERSITY OF CINCINNATI