Inter‐ and intraspecific competitive abilities are significant determinants of invasive success and the ecological impact of non‐native plants. We tested two major hypotheses on the competitive ability of invasive species using invasive (Taraxacum officinale) and native (T. platycarpum) dandelions: differential interspecific competitive ability between invasive and native species and the kin recognition of invasive species. We collected seeds from two field sites where the two dandelion species occurred nearby. Plants were grown alone, with kin (plants from the same maternal genotype) or strangers (plants from different populations) of the same species, or with different species in a growth chamber, and the performance at the early developmental stage between species and treatments was compared. The invasive dandelions outcompeted the native dandelions when competing against each other, although no difference between species was detected without competition or with intraspecific competition. Populations of native species responded to interspecific competition differently. The effect of kinship on plant performance differed between the tested populations in both species. A population produced more biomass than the other populations when grown with a stranger, and this trend was manifested more in native species. Our results support the hypothesis that invasive plants have better competitive ability than native plants, which potentially contributes to the establishment and the range expansion of T. officinale in the introduced range. Although kin recognition is expected to evolve in invasive species, the competitive ability of populations rather than kinship seems to affect plant growth of invasive T. officinale under intraspecific competition.

Invasive plant species have been hypothesized to possess a suite of traits associated with successful invasion into areas in which they are introduced (van Kleunen et al., 2010;Rejmánek & Richardson, 1996).For instance, invasive species often have functional traits that confer greater resource capture ability, such as larger specific leaf areas (SLA) and smaller root-to-shoot ratios (R/S ratios) (Ehrenfeld, 2003;Grotkopp & Rejmánek, 2007). These traits result in faster growth rates and higher reproductive outputs of invasive species than those

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