Adaptive and non‐adaptive evolution of trait means and genetic trait correlations for herbivory resistance and performance in an invasive plant

Abstract

The EICA‐hypothesis predicts that invading plants adapt to their novel environment by evolving increased performance and reduced resistance in response to the release from natural enemies, and assumes a resource allocation tradeoff among both trait groups as mechanistic basis of this evolutionary change. Using the plant Silene latifolia as a study system, we tested these predictions by investigating whether 1) invasive populations evolved lower resistance and higher performance, 2) this evolutionary change is indeed adaptive, and 3) there is a negative genetic correlation between performance and resistance (i.e. a tradeoff) in native and introduced individuals. Moreover, we sampled eight native and eight invasive populations and determined their population co‐ancestry based on neutral SSR‐markers. We performed controlled crossings to produce five sib‐groups per population and exposed them to increased and reduced levels of enemy attack in a full‐factorial experiment to estimate performance and resistance. With these data, we performed trait‐by‐trait comparisons between ranges with ‘animal models’ that account for population co‐ancestry to quantify the amount of variance in traits explained by non‐adaptive versus adaptive evolution. Moreover, we tested for genetic correlations among performance and resistance traits within sib‐groups. We found significant reductions in resistance and increases in performance in invasive versus native populations, which could largely be attributed to adaptive evolution. While we detected a non‐significant trend towards negative genetic performance × resistance correlations in native populations, invasive populations exhibited both significant and non‐significant positive correlations. In summary, these results do not support a shift of performance and resistance trait values along a tradeoff line in response to enemy release, as predicted by EICA. They rather suggest that the independent evolution of both traits is not constrained by a tradeoff, and that various selective agents (including resource availability) interact in shaping both traits and in weakening negative genetic correlations in the invaded habitat.

Climate outweighs native vs. nonnative range‐effects for genetics and common garden performance of a cosmopolitan weed

“…, Schrieber et al. ). This exceptionally strong relationship may be related to (1) the large sample size, (2) the very strong differentiation among the populations in our particular performance traits, and (3) the high quality of our microsatellite data (in which >95% of all scored loci were homozygote, making genotyping unusually unambiguous).…”

“…, Schrieber et al. ). As such, we emphasize that correcting for co‐ancestry may considerably increase the reliability of native vs. nonnative comparisons and should be applied more frequently in future studies on phenotypic among‐population differentiation.…”

“…, Schrieber et al. ). The co‐ancestry coefficients were calculated with the R package RAFM 1.1 (Karhunen ) applying an F model that allows for admixture of evolutionary independent lineages following the approach of Karhunen and Ovaskainen ().…”

“…Thus, conservative tests for contemporary adaptive divergence should correct for non‐adaptive evolution, such as statistically accounting for co‐ancestry of populations (Schrieber et al. ), but this has not been done in the vast majority of studies on post‐introduction evolution.…”

(Re)appreciating the role of life history in eco‐evolutionary dynamics

“…The importance of life histories as central tenet in eco‐evolutionary interactions is further demonstrated by a collection of regular contributions to the journal. tested the hypothesis that different movement strategies (here migration versus sedentary strategies) are associated with different individual phenotypes in terms of life histories. In line with coexistence theory they found no net‐fitness benefits of migrating individuals but, in contrast, higher population growth in migrating populations due in response to the current local environmental conditions.…”