Comparison of Variance in Quantitative Growth and Physiological Traits between Genets and Ramets Derived from an Invasive Weed, Spartium junceum (Fabaceae)

The ability to identify genetic regulation of quantitative traits is often complicated by environmentally induced variation. The purpose of this study was to determine if the variance in biomass and physiological traits is larger for populations of genetically distinct individuals (genets) compared with populations of genetically identical individuals (ramets) of the same species. Spartium junceum L. was used for this study because it is a weedy species, and variation in quantitative traits is important for its invasive characteristic. Several mean growth traits were significantly different between ramet and genet populations. The variance in biomass traits was higher for genet populations in 26 of 30 comparisons with ramet populations. In contrast, few mean physiological traits differed between ramet and genet populations, and trait variance was equal between the two population types in 23 out of 30 comparisons. Thus, even under uniform growth conditions in a greenhouse, environmental variance accounts for a large proportion of population variance in physiological traits. Environmental variance also accounted for ca. 33% of phenotypic variance in biomass traits. The results of this study have important implications for common garden and reaction norm studies of genetic determination of quantitative physiological traits.