XVI International Botanical Congess

A nested breeding design and common garden experiment examined the effects of population density on components of natural selection via maternal function on floral traits in wild radish (Brassicaceae). 19 paternal sibships (2700 seeds) were replicated in 3 densities, 20 life history and floral traits were recorded. Maternal fitness was estimated as fecundity and as yield (fecundity x mean seed mass). Phenotypic selection gradient analyses were conducted in each density. These analyses accounted for over 98% of the variance in fitness, but floral traits were rarely significantly associated with fitness. The strength of selection on some traits differed among densities, but did not tend to increase with density. The ability to detect significant narrow-sense hertability of floral traits was often density specific.