Data from: Evolution of increased intraspecific competitive ability following introduction: the importance of relatedness among genotypes.

1.A long‐standing explanation for invasion success is that invasive plants
could evolve to be more competitive following introduction. This evolution
of increased competitive ability (EICA) hypothesis, however, has seldom
been tested with regard to intraspecific competition. Given that plants
can display different responses to related and unrelated conspecifics, the
evolution of intraspecific competitive ability might be specific to
genotypes of different relatedness. 2.Here, we grew five native (South
American) and five introduced (North American) genotypes of the clonal
herbaceous invasive plant Alternanthera philoxeroides alone, with
aboveground competition from kin (the same genotype) or from one of two
types of strangers (another genotype from the same range or another
genotype from the other range). 3.When grown alone, introduced and native
genotypes produced similar total biomass and storage‐root biomass.
However, in response to intraspecific competition, introduced genotypes
showed increases in total biomass and stem length, and a decrease in
specific stem length, whereas native genotypes showed the opposite
pattern. When grown with kin instead of strangers, introduced genotypes
showed an increase in branch number, whereas native genotypes showed the
opposite. 4.Synthesis. Our study provided evidence for evolution of
increased intraspecific competitive responses in an invasive plant. We
also found, for the first time, that the interactions among kin were
likely to shift from competition towards facilitation following
introduction.