The seeds of invasion: enhanced germination in invasive European populations of black locust (Robinia pseudoacacia L.) compared to native American populations

Abstract

Local adaptation and the evolution of phenotypic plasticity may facilitate biological invasions. Both processes can enhance germination and seedling recruitment, which are crucial life-history traits for plants. The rate, timing and speed of germination have recently been documented as playing a major role during the invasion process. Black locust (Robinia pseudoacacia L.) is a North American tree, which has spread widely throughout Europe. A recent study demonstrated that a few populations are the source of European black locust. Thus, invasive populations can be compared to native ones in order to identify genetic-based phenotypic differentiation and the role of phenotypic plasticity can thereby be assessed.• A quantitative genetics experiment was performed to evaluate 13 juvenile traits of both native and invasive black locust populations (3000 seeds, 20 populations) subjected to three different thermal treatments (18 °C, 22 °C and 31 °C).• The results revealed European populations to have a higher germination rate than the native American populations (88% versus 60%), and even when genetic distance between populations was considered. Moreover, this trait showed lower plasticity to temperature in the invasive range than in the native one. Conversely, other studied traits showed high plasticity to temperature, but they responded in a similar way to temperature increase: the warmer the temperature, the higher the growth rate or germination traits values.• The demonstrated genetic differentiation between native and invasive populations testifies to a shift between ranges for the maximum germination percentage. This pattern could be due to human-mediated introduction of black locust.

Insect invasions track a tree invasion: Global distribution of black locust herbivores

“…Black locust exhibits a high genetic diversity in its native range (Mebrahtu & Hanover, 1989; Surles et al, 1989) as well as in China (Guo et al, 2022), but studies directly comparing the genetic composition between native and non‐native populations are still lacking. Bouteiller et al (2021) found differences in the phenotypic plasticity between native and non‐native (European) populations of black locust, with an increased germination rate in the European populations. Furthermore, numerous other studies investigated black locust in its non‐native range and found a generally high degree of phenotypic plasticity, also in comparison with other trees (e.g., Granata et al, 2020; Guo et al, 2018; Luo et al, 2016; Mantovani et al, 2014; Su et al, 2021; Xu et al, 2009).…”

From Seed to Seedling: Influence of Seed Geographic Provenance and Germination Treatments on Reproductive Material Represented by Seedlings of Robinia pseudoacacia

“…In forestry practice, it may also be sufficient to use a chemical method by immersing the seeds for 60 min in concentrated sulfuric acid, then washing the seeds in cold water and leaving them to dry at adjusted temperature [46]. Another successful method is by scarifying the seeds using manual abrasion sandpaper so that the seed coat is scratched [15,17,47].…”

“…Four treatments were applied. The first treatment referred to the mechanical scarification method, using abrasive sandpaper until the tegument was visibly damaged [17]. The second type of treatment (thermal treatment) involved water-soaked seeds at different temperatures [3,6]; seeds were soaked for 10 min in water at a temperature of 100 • C, 70 • C, and 40 • C. For the third treatment, seeds were soaked in biostimulator solution (Foliplant, 0.9%) for 10 min [21].…”

“…As R. pseudoacacia has multiple valuable uses, but also undesirable features, the species behavior is worth studying under varying environmental factors to estimate the geographical area potentially invaded by R. pseudoacacia in the perspective of planning its management and biodiversity regulation [17]. Correlated with black locust utility, the frequent use nowadays and its invasive spread, all stages starting with seed harvest to germination and further tree growth, must be considered.…”

Biotic resistance in a stochastic world: Do rodents act as a filter to alien tree invasion in pampean old fields?

“…According to Guidobono (pers comm) about 13% and 9.45% of G. triacanthos seeds collected from cow dungs and pots, respectively, germinated in laboratory conditions, while Marcora et al (2018) reported about 15% of seedling emergence, and Ferreras et al (2015) 20.2%. For R. pseudoacacia, Yuan et al (Yuan et al, 2013) reported an emergence rate of 29%, while Bouteiller et al (2021) reported higher values, 60% and 80% in its native range and in Europe, respectively. Each plot was divided into halves by a plastic mesh and was separately sowed by hand with 200 seeds of G. triacanthos (100 seed mass: approximately 17 g) on one side and 200 seeds of R. pseudoacacia (100 seed mass: approximately 2 g) on the other side.…”