Data from: Response of bluebunch wheatgrass to invasion: differences in competitive ability among invader-experienced and naïve populations

1. Invasive species may alter selective pressures on native plant
populations, and there is some evidence that competition with invasive
plants may lead to differences in competitive ability between populations
that have experienced invasion and those that have not. Previous results
have varied among species but also among populations of the same species.
2. We conducted a greenhouse experiment to determine whether there was
variation in traits, or in ability to tolerate or suppress an invasive
species, among populations of a common native grass that had different
histories of exposure to competition from an invasive species.
Specifically, we grew seeds of a native grass (Pseudoroegneria spicata)
collected from 14 wild populations (six from invaded populations and eight
from uninvaded populations) and a cultivar (Anatone) alone or in
competition with the invasive species (Centaurea stoebe) and measured
traits of both species during and at the end of a 100-day growing period.
3. Pseudoroegneria spicata seedlings from invader-experienced populations
had more leaves than invader-naïve populations, and juvenile plants from
experienced populations were less affected by competition with C. stoebe
than were plants from naïve populations. 4. There were significant
differences in traits among populations at the seedling and juvenile life
stages, and at both life stages, variation among populations was greater
than variation among experience types. 5. The most predictive traits of P.
spicata tolerance to competition were number of leaves (seedling and
juvenile stage), and total and root biomass (juvenile only). No traits
significantly predicted suppression of C. stoebe. 6. There was not a
significant relationship between a population’s suppression of C. stoebe
and its tolerance of competition. 7. Our results suggest that in P.
spicata, invasion selects for larger plants and traits that can influence
tolerance of competition. If land managers are interested in identifying
highly competitive seed sources for revegetation in invaded areas, both
population and invader-experience type should be considered. Since
tolerance and suppression do not appear to be related in P. spicata, seed
source selection should be driven by the element of competitive ability
(either tolerance or suppression) that is most important to project goals.