The role of intraspecific crop-weed hybridization in the evolution of weediness and invasiveness: cultivated and weedy radish (Raphanus sativusL.) as a case study

Abstract

PREMISECrop-wild/weed hybrids usually exhibit intermediate and maladapted phenotypes compared to their parents; however, hybridization has sometimes been associated with increased fitness, potentially leading to enhanced weediness and invasiveness. Since the ecological context and maternal genetic effects may affect hybrid fitness, they could influence the evolutionary outcomes of hybridization. Here, we evaluated the evolutionary potential of reciprocal early-generation crop-weed hybrids using intraspecific weedy and cultivated radish (Raphanus sativusL.) as a model system.METHODSUsing experimental hybridization and common garden experiments under field conditions, we assessed the differences in time to flowering, survival to maturity, plant biomass and reproductive components between reciprocal crop-weed hybrids and their parents, under two contrasting ecological conditions, agrestal (wheat cultivation, fertilization, weeding) and ruderal (human-disturbed uncultivated area) over two years.RESULTSCrop, weeds and reciprocal hybrids overlapped -at least partially-during the flowering period, indicating a high probability of gene flow. Reciprocal hybrids survived to maturity at rates at least as successful as their parents and showed higher plant biomass and fecundity, which resulted in higher fitness compared to their parents in both contrasting environments, without any differences associated with the direction of the hybridization.CONCLUSIONSIntraspecific crop-weed hybridization, regardless of the cross direction, has the potential to promote weediness and invasiveness in the invasive feralR. sativusweed both agrestal and ruderal environments, increasing the chances of the introgression of crop alleles into weed populations. This is the first report of intraspecific crop-weed hybridization inR. sativus.

Admixture with cultivated sunflower likely facilitated establishment and spread of wild sunflower (H. annuus) in Argentina

“…Admixture between wild and cultivated individuals may increase invasiveness by distinct non-mutually-exclusive genetic mechanisms including adaptive introgression of large effect loci (e.g., those conferring herbicide resistance; Le Corre et al, 2020; Presotto et al, 2023), transgressive segregation (Campbell et al, 2006; Hedge et al, 2006), and hybrid vigor (Bock et al, 2018; Vercellino et al, 2023b). In our study, most of the genomic divergence between invasives and their native source populations is explained by alleles introduced from cultivars, suggesting that introgression is, at least partially, adaptive.…”