Phragmites clonal growth: invasion or stability?

Background/Question/Methods

Characteristics of clonal growth that are advantageous in invasive plants can also result in native plants’ ability to resist invasion. We compare the clonal architecture and diversity of an invasive lineage (introduced Phragmites) and a non-invasive lineage (native Phragmites) present in much of North America. This is the first stand scale diversity study with sample size and systematic spatial sampling scheme adequate for characterizing clonal structure in this important species. Our questions: 1) Does the structure and extent of clonal growth suggest that the potential for clonal growth contributes to the invasiveness of the introduced lineage? 2) Is clonal growth common in the native lineage, acting as a possible source of ecological resistance and resilience. Microsatellite markers were used to measure clonal sizes, architecture, and diversity within each lineage in stands within four marshes. 

Results/Conclusions

Measures of clonal diversity indicate that clonal growth is significantly greater in the stands of native lineage than in the introduced lineage. While lineage was a consistent predictor of clonal diversity relative ranking, the marsh location was a much stronger predictor of the absolute range of these values. Our results indicate an important role for clonal growth in native Phragmites’ space consolidation and could explain why the introduced lineage, with its stronger competitive traits, has not replaced the native where they co-occur. These results with regard to clone size, size distributions, singleton occurrence and clonal architecture provide some evidence for stand development that follows an Initial Genotypes Model.