Trait differentiation between native and introduced populations of the invasive plant Sonchus oleraceus L. (Asteraceae)

Abstract

There is growing evidence that rapid adaptation to novel environments drives successful establishment and spread of invasive plant species. However, the mechanisms driving trait adaptation, such as selection pressure from novel climate niche envelopes, remain poorly tested at global scales. In this study, we investigated differences in 20 traits (relating to growth, resource acquisition, reproduction, phenology and defence) amongst 14 populations of the herbaceous plant Sonchus oleraceus L. (Asteraceae) across its native (Europe and North Africa) and introduced (Australia and New Zealand) ranges. We compared traits amongst populations grown under standard glasshouse conditions. Introduced S. oleraceus plants seemed to outperform native plants, i.e. possessing higher leaf and stem dry matter content, greater number of leaves and were taller at first flowering stage. Although introduced plants produced fewer seeds, they had a higher germination rate than native plants. We found strong evidence for adaptation along temperature and precipitation gradients for several traits (e.g. shoot height, biomass, leaf and stem dry matter contents increased with minimum temperatures, while germination rate decreased with annual precipitations and temperatures), which suggests that similar selective forces shape populations in both the native and invaded ranges. We detected significant shifts in the relationships (i.e. trade-offs) (i) between plant height and flowering time and (ii) between leaf-stem biomass and grain yield between native and introduced plants, indicating that invasion was associated with changes to life-history dynamics that may confer competitive advantages over native vegetation. Specifically, we found that, at first flowering, introduced plants tended to be taller than native ones and that investment in leaf and stem biomass was greater in introduced than in native plants for equivalent levels of grain yield. Our study has demonstrated that climatic conditions may drive rapid adaption to novel environments in invasive plant species.

Time‐traveling seeds reveal that plant regeneration and growth traits are responding to climate change

“…First, similar recent (Ollivier et al 2020) and classic often‐cited (Maron et al 2004) studies have provided valuable insights without maternal corrections. For example, Ollivier et al (2020) measured 20 plant traits (including germination, seed mass, seed number, plant height, and biomass) in Sonchus oleraceus in a glasshouse experiment, and then evaluated the effects of temperature and precipitation variables on each of the traits. In that study, seeds were collected over 2 yr from 14 populations in nine countries, stored in paper bags with silica gel, and then just sown directly for trait measurements.…”

“…Nevertheless, we are still confident in the validity of our experimental design. First, similar recent (Ollivier et al 2020) and classic often-cited (Maron et al 2004) studies have provided valuable insights without maternal corrections. For example, Ollivier et al (2020) measured 20 plant traits (including germination, seed mass, seed number, plant height, and biomass) in Sonchus oleraceus in a glasshouse experiment, and then evaluated the effects of temperature and precipitation variables on each of the traits.…”

Can rotations improve management of herbicide-resistant annual sowthistle (Sonchus oleraceus) and prickly lettuce (Lactuca serriola) in lentil production systems of southern Australia?

“…Mature weed plants in each plot were identified, and the number of capitula were recorded to generate an estimate of the average number of capitula per plant in each plot: if fewer than five plants were found in a plot, the number of capitula on each was recorded, and if more than five plants were identified, five were randomly selected from the plot for capitula counts. These numbers were multiplied by the number of plants per plot from the earlier posttreatment weed counts and an estimated average of 170 seeds per capitula based on the literature (Mobli et al 2020;Ollivier et al 2020). Due to low weed densities in 2018 at RS2, an extra weed density assessment was completed before presowing herbicide treatments in 2019.…”

Population genomics reveal multiple introductions and admixture of Sonchus oleraceus in Australia

“…More research is needed to determine the relative fitness advantages of admixed versus non-admixed genotypes of S. oleraceus in Australia over several generations (Cristescu, 2015). However, a recent study by Ollivier et al (2020) showed that S. oleraceus plants from S8). In other Asteraceae species that have become successful invaders, there is similar evidence of repeated introductions from different geographical areas (Eriksen et al, 2015;van Boheemen et al, 2017).…”

“…These human-mediated introductions are likely to have promoted admixture from multiple sources followed by recombination and selection for multiple traits in introduced Australian S. oleraceus plants (Ollivier et al, 2020).…”