Abstract
Background: Field and common garden comparisons are commonly performed to test the rapid evolution of increased vigor in introduced plant populations. Latitudinal clines in phenotypic traits can obscure such evolutionary inferences, particularly when native or introduced populations are distributed across large geographic ranges. We tested whether the latitudinal clines influence the comparisons between introduced and native populations of Senecio vulgaris. We compared plant height, number of branches and number of capitula in the field in Europe and China, and in a common garden in Switzerland.Results: The Chinese introduced populations performed better than the European native populations in the field in terms of plant height and number of capitula, which was consistent with the prediction of the evolution of increased competitive ability (EICA) hypothesis. The Chinese populations exhibited more capitula than the European populations when the latitudinal cline was considered in the common garden comparison. When we compared the traits of the northeast Chinese, southwest Chinese and European populations in both the field and common garden, the northeast Chinese populations, at latitudes similar to those of the European populations, exhibited greater plant size and more capitula than the European populations in both the field and common garden. However, the southwest Chinese populations, at latitudes that are much lower than those of the European populations, did not perform better in terms of reproduction than the native populations.Conclusion: Latitudinal clines in phenotypic traits should be considered in field and common garden comparisons when introduced populations are geographically structured.
Rapid evolution of an invasive weed
