Introduced populations of ragweed show as much evolutionary potential as native populations

Invasive species are a global economic and ecological problem. They also
offer an opportunity to understand evolutionary processes in a colonizing
context. The impacts of evolutionary factors, such as genetic variation,
on the invasion process are increasingly appreciated, but there remain
gaps in the empirical literature. The adaptive potential of populations
can be quantified using genetic variance–covariance matrices (G),
which encapsulate the heritable genetic variance in a population. Here, we
use a multivariate Bayesian approach to assess the adaptive potential of
invasive populations of ragweed (Ambrosia artemisiifolia), a serious
allergen and agricultural weed. We compared several aspects of genetic
architecture and the structure of G matrices between
three native and three introduced populations, based on phenotypic data
collected in a field common garden experiment. We found moderate
differences in the quantitative genetic architecture among populations,
but we did not find that introduced populations suffer from a limited
adaptive potential or increased genetic constraint compared with native
populations. Ragweed has an annual life history, is an obligate
outcrosser, and produces very large numbers of seeds and pollen grains.
These characteristics, combined with the significant additive genetic
variance documented here, suggest ragweed will be able to respond quickly
to selection pressures in both its native and introduced ranges.