Manipulation of cytosine methylation does not remove latitudinal clines in two invasive goldenrod species in Central Europe

Exploring the complex pre-adaptations of invasive plants to anthropogenic disturbance: a call for integration of archaeobotanical approaches

Pre-adaptation to anthropogenic disturbance is broadly considered key for plant invasion success. Nevertheless, empirical evidence remains scarce and fragmentary, given the multifaceted nature of anthropogenic disturbance itself and the complexity of other evolutionary forces shaping the (epi)-genomes of recent native and invasive plant populations. Here, we review and critically revisit the existing theory and empirical evidence in the field of evolutionary ecology and highlight novel integrative research avenues that work at the interface with archaeology to solve open questions. The approaches suggested so far focus on contemporary plant populations, although their genomes have rapidly changed since their initial introduction in response to numerous selective and stochastic forces. We elaborate that a role of pre-adaptation to anthropogenic disturbance in plant invasion success should thus additionally be validated based on the analyses of archaeobotanical remains. Such materials, in the light of detailed knowledge on past human societies could highlight fine-scale differences in the type and timing of past disturbances. We propose a combination of archaeobotanical, ancient DNA and morphometric analyses of plant macro- and microremains to assess past community composition, and species' functional traits to unravel the timing of adaptation processes, their drivers and their long-term consequences for invasive species. Although such methodologies have proven to be feasible for numerous crop plants, they have not been yet applied to wild invasive species, which opens a wide array of insights into their evolution.

Water temperature and chlorophyll a density drive the genetic and epigenetic variation of Vallisneria natans across a subtropical freshwater lake

Plant genetic diversity differs in habitat's oscillations, especially species distributed under heterogeneous environmental conditions. Freshwater ecosystems are vulnerable to biotic and abiotic impacts, which affect the genetic and epigenetic variations in aquatic plants. The extent of environmental heterogeneous attributes can be examined based on genetic and epigenetic variations. Such variations under environmental gradient can provide evidence for understanding the correlations between rapid environmental changes and species evolution. In this study, we performed amplified fragment polymorphism length and methylated-sensitive amplified polymorphism analysis to depict the genetic and epigenetic variations of Vallisneria natans in a subtropical lake. Results showed that this species maintained a relatively high genetic diversity (mean H E = 0.320, I = 0.474, PPL = 85.93%) and epigenetic variation (mean eH E = 0.282, eI = 0.428, ePPL = 83.91%). Water body temperature and chlorophyll a density were positively correlated to the genetic and epigenetic variations. The clonal generates of V. natans depicted a relative high methylation level and shew ancestral scenario between the genet and the second clonal generation. These findings revealed that species diversity is unevenly distributed under environmental heterogeneity, even at a fine geographic scale. Environmental characteristics in relation to temperature and chlorophyll a should be considered in the analysis of the genetic and epigenetic variations. Additionally, epigenetic variations between genets and ramets should be considered with caution when applied to analysis of other aquatic species.

Cytogeography of Naturalized Solidago canadensis Populations in Europe

Autopolyploidization has driven the successful invasion of Solidago canadensis in East Asia. However, it was believed that only diploid S. canadensis invaded Europe, whereas polyploids never did. Here, molecular identification, ploidy level, and morphological traits of ten S. canadensis populations collected in Europe were compared with previously identified S. canadensis populations from other continents and S. altissima populations. Furthermore, the ploidy-driven geographical differentiation pattern of S. canadensis in different continents was investigated. All ten European populations were identified as S. canadensis with five diploid and five hexaploid populations. Significant differences in morphological traits existed among diploids and polyploids (tetraploids and hexaploids), rather than between polyploids from different introduced ranges and between S. altissima and polyploidy S. canadensis. The invasive hexaploids and diploids had few differences in latitudinal distributions in Europe, which was similar to the native range but different from a distinct climate-niche differentiation in Asia. This may be attributed to the bigger difference in climate between Asia and Europe and North America. The morphological and molecular evidences proved the invasion of polyploid S. canadensis in Europe and suggest that S. altissima may be merged into a complex of S. canadensis species. Our study may be concluded that geographical and ecological niche differentiation of an invasive plant driven by ploidy depends on the degree of difference in the environmental factors between the introduced and native range, which provides new insight into the invasive mechanism.

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

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.

The Genomic Processes of Biological Invasions: From Invasive Species to Cancer Metastases and Back Again

The concept of invasion is useful across a broad range of contexts, spanning from the fine scale landscape of cancer tumors up to the broader landscape of ecosystems. Invasion biology provides extraordinary opportunities for studying the mechanistic basis of contemporary evolution at the molecular level. Although the field of invasion genetics was established in ecology and evolution more than 50 years ago, there is still a limited understanding of how genomic level processes translate into invasive phenotypes across different taxa in response to complex environmental conditions. This is largely because the study of most invasive species is limited by information about complex genome level processes. We lack good reference genomes for most species. Rigorous studies to examine genomic processes are generally too costly. On the contrary, cancer studies are fortified with extensive resources for studying genome level dynamics and the interactions among genetic and non-genetic mechanisms. Extensive analysis of primary tumors and metastatic samples have revealed the importance of several genomic mechanisms including higher mutation rates, specific types of mutations, aneuploidy or whole genome doubling and non-genetic effects. Metastatic sites can be directly compared to primary tumor cell counterparts. At the same time, clonal dynamics shape the genomics and evolution of metastatic cancers. Clonal diversity varies by cancer type, and the tumors’ donor and recipient tissues. Still, the cancer research community has been unable to identify any common events that provide a universal predictor of “metastatic potential” which parallels findings in evolutionary ecology. Instead, invasion in cancer studies depends strongly on context, including order of events and clonal composition. The detailed studies of the behavior of a variety of human cancers promises to inform our understanding of genome level dynamics in the diversity of invasive species and provide novel insights for management.