Traces of Genetic but Not Epigenetic Adaptation in the Invasive Goldenrod Solidago canadensis Despite the Absence of Population Structure

Abstract

Biological invasions may result from multiple introductions, which might compensate for reduced gene pools caused by bottleneck events, but could also dilute adaptive processes. A previous common-garden experiment showed heritable latitudinal clines in fitness-related traits in the invasive goldenrod Solidago canadensis in Central Europe. These latitudinal clines remained stable even in plants chemically treated with zebularine to reduce epigenetic variation. However, despite the heritability of traits investigated, genetic isolation-by-distance was non-significant. Utilizing the same specimens, we applied a molecular analysis of (epi)genetic differentiation with standard and methylation-sensitive (MSAP) AFLPs. We tested whether this variation was spatially structured among populations and whether zebularine had altered epigenetic variation. Additionally, we used genome scans to mine for putative outlier loci susceptible to selection processes in the invaded range. Despite the absence of isolation-by-distance, we found spatial genetic neighborhoods among populations and two AFLP clusters differentiating northern and southern Solidago populations. Genetic and epigenetic diversity were significantly correlated, but not linked to phenotypic variation. Hence, no spatial epigenetic patterns were detected along the latitudinal gradient sampled. Applying genome-scan approaches (BAYESCAN, BAYESCENV, RDA, and LFMM), we found 51 genetic and epigenetic loci putatively responding to selection. One of these genetic loci was significantly more frequent in populations at the northern range. Also, one epigenetic locus was more frequent in populations in the southern range, but this pattern was lost under zebularine treatment. Our results point to some genetic, but not epigenetic adaptation processes along a large-scale latitudinal gradient of S. canadensis in its invasive range.

Multiple Introductions and Distinct Genetic Groups of Canada Goldenrod (Solidago canadensis) in China Revealed by Genomic Single-Nucleotide Polymorphisms

“…Largely congruent with previous studies, we found no significant population structure of invasive S. canadensis (Figure 1 and Table S2) [41,42]. Meanwhile, we found that most sympatric (i.e., distributed at the same locality) individuals belonged to different genetic groups in China (Figure 1).…”

“…Given that S. canadensis is highly self-incompatible, the absence of mixed genotypes highlights the important role of clonal reproduction in the survival and spread of S. canadensis, as observed in field experiments [27,28,43]. As for the relatively higher N e (which can be translated into relatively higher genetic diversity) observed in Group 1 when the founder effect began, one possible explanation could be the presence of genetic adaptation during its colonization in Europe, as reported recently by Eckert et al [42].…”

Involvement of Dynamic Adjustment of ABA, Proline and Sugar Levels in Rhizomes in Effective Acclimation of Solidago gigantea to Contrasting Weather and Soil Conditions in the Country of Invasion

“…Czortek et al [40] also concluded that both local soil properties and functional diversity affect the performance of S. canadensis in its invasive range in central Europe. On the other hand, Eckert et al [41] pointed to some genetic, but not epigenetic adaptation processes of this species in its invasive range. Therefore, future studies on Solidago in central Europe should more strongly emphasize local and site-specific conditions and their impact on epigenetic variation.…”