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Admixture increases performance of an invasive plant beyond first‐generation heterosis

Li, Yan, Stift, Marc, van Kleunen, Mark
Thejournal of ecology 2018 v.106 no.4 pp. 1595-1606
Erythranthe guttata, greenhouse experimentation, heterosis, inbreeding depression, introduced plants, invasive species, outcrossing, progeny, selfing, New Zealand, North America, Scotland
Through its potential to enhance progeny performance, admixture (between‐population crossing) may promote invasiveness of alien plants. The few studies that tested this idea found evidence for heterosis (positive effects of admixture) in the first generation (F₁), but have not considered further generations. In this paper, we test whether admixture benefits can be maintained in subsequent generations of an invasive plant. We follow up on a previous study, in which we made crosses between plants of Mimulus guttatus from native‐ (western North America) and invaded‐range populations (New Zealand and Scotland), and showed that admixture increases F₁ performance. Here, we performed further crosses to create non‐admixed progeny, F₁ progeny resulting from within‐ and between‐range admixture, and subsequent F₂ progeny both through outcrossing and through self‐fertilization. As heterosis, out‐ and inbreeding depression may depend on the environment, we assessed progeny performance under benign (well‐watered) and drought‐stress conditions in a greenhouse experiment. We found that non‐admixed progeny of M. guttatus were outperformed by admixed progeny (averaged across F₁ and F₂), particularly by progeny from between‐range admixture. However, the benefit of admixture was stronger in F₁ than in F₂ progeny, especially when the F₂ was produced by self‐fertilization. The benefit of admixture also depended on the range of origin and the test environment. Synthesis. Our findings indicate that increased performance of admixed F₁ progeny is partly maintained in the F₂ progeny. Admixture might thus significantly boost performance of an invasive plant across multiple generations.