Heterostyly in Turnera trioniflora, a Roadside Weed of the Amazon Basin1

Heterostyly in Tarnera trioniflor'a is associated with both self-incompatibility and within-morph incompatibility, a trait not usually associated with weedy species. This breeding system is discussed in terms of the potential of evolving locally adapted highly competitive genotypes, and the advantages for a high level of genetic heterogeneity in tropical weedy plants. Turnera trioniflora, Sims, is a native weed common in the Amazon Basin. Since it is tolerant of sandy soils and regenerates quickly after rough cutting, it is most frequently found along roadsides or in heavily disturbed areas such as urban fields or rights-of-way. It will begin to flower 10-12 weeks after germination or within two weeks after severe pruning. A single plant may have up to 20 new flowers each day and continues to produce flowers for many months, or even years if it is cut and allowed to regrow in the absence of competition from larger neighboring weeds. In the wild, a flower opens about 07:30 hrs and wilts by early afternoon. Any individual flower lasts only one day, whether it has been pollinated or not.