Functional diversity is increasingly recognized as an important contributor to ecosystem processes, and maximizing diversity within plant communities has become a key goal in the restoration of degraded habitats. One method used in restoration efforts aiming to increase functional diversity is to employ propagules from ecologically disparate populations as a proxy for functional differences. However, the assumptions underlying these methods are challenged by the fact that the degree of trait variation within and between populations of the same species is not clear. In the present study we investigated functional trait variation at the genotype and population levels in five high-priority native forb species for restoration use in the Colorado Plateau in order to address the following questions: 1) are traits considerably different between populations and 2) how much of the variation in traits is attributed to differences between genotypes? To answer these questions, we employed micropropagation techniques to clone genotypes from three populations of each species and measured four functional traits after growing them for 8 weeks in ex vitro conditions. We used mixed-effect models to evaluate trait differences between populations and the contribution of genotype to trait variation.
Results/Conclusions
Our study found that the ability of population to predict differences in functional traits varied with species. Specific leaf area, leaf circularity, and leaf dry matter content differed considerably between populations in two out of the five species we investigated while root mass fraction was different between populations in three of the five species. The amount of variation explained by differences among genotypes was contingent on both the species and trait, with intraclass correlation coefficient (ICC) ratios of between genotype to within genotype variance ranging from 0.02 to 0.74. Variation in leaf dry matter content and leaf circularity were most strongly influenced by genotype (average ICC = 0.46 and 0.51, respectively) while the influence of genotype on specific leaf area and root mass fraction was noticeably lower (average ICC = 0.27 and 0.30). Our results illustrate that functional trait variation within species can be driven by population, genotype, or both, and that these relationships are contingent on both species identity and trait. These findings suggest that mixing disparate populations may not always result in functionally diverse restorations. Preliminary trait surveys may help identify populations that differ significantly in important traits likely to provide increased ecosystem functioning through trait complementarity.