The role of biotic factors during plant establishment in novel communities assessed with an agent-based simulation model

Abstract

BackgroundEstablishment success of non-native species is not only influenced by environmental conditions, but also by interactions with local competitors and enemies. The magnitude of these biotic interactions is mediated by species traits that reflect competitive strength or defence mechanisms. Our aim was to investigate the importance of species traits for successful establishment of non-native species in a native community exhibiting biotic resistance in the form of competition and herbivory.MethodsWe developed a trait-based, individual-based simulation model tracking the survival of non-native plants in a native community. In the model, non-native plants are characterized by high or low values of competition and defence traits. Model scenarios included variation of initial number of non-natives, intensity of competitive interaction, density of herbivores and density as well as mixture of the native community.ResultsTraits related to competition had a much greater impact on survival of non-native species than traits related to defence. Survival rates of strong competitors never fell below 50% while survival of weak competitors averaged at about 10%. Weak competitors were also much more susceptible to competitive pressures such as community density, composition and competition intensity. Strong competitors responded negatively to changes in competition intensity, but hardly to composition or density of the native community. High initial numbers of non-native individuals decreased survival rate of strong competitors, but increased the survival rate of weak competitors. Survival under herbivore attack was only slightly higher for plants with high defensive ability than for those with low defensive ability. Surprisingly, though, herbivory increased survival of species classified as weak competitors.DiscussionHigh survival rates of strong non-native competitors relate to a higher probability of successful establishment than for weak competitors. However, the reduced survival of strong competitors at high initial numbers indicates a self-thinning effect, probably mediated by a strongly competitive milieu. For weak competitors, our model emphasizes positive effects of high propagule pressure known from field studies. General effects of herbivory or defence abilities on survival were not supported by our model. However, the positive effect of herbivory on survival of weak competitors indicated side effects of herbivory, such as weakening resident competitors. This might play an important role for establishment of non-natives in a new community.

Take me for a ride: Herbivores can facilitate plant reinvasions

“…In accordance with existing theory, we find that in many syndromes herbivores slow spreading speed, primarily through impacts on plant demography (Fagan et al, 2005; Fagan & Bishop, 2000; Holt & Barfield, 2009; Owen & Lewis, 2001; Radny & Meyer, 2018). Empirical evidence demonstrates that herbivores either consume plant tissue that subsequently decreases seed production (Foster & Ackerman, 2021; Hrafnkelsdottir et al, 2020; Miller et al, 2009; Schultz et al, 2017), or fully consume adult plants (Auberson‐Lavoie & Vellend, 2020; Kuijper et al, 2004; Rivest & Vellend, 2018), both which in turn slow spatial spread.…”

Trait-based modelling in ecology: lessons from two decades of research

“…This goal was particularly common among statistical models (Otfinowski et al, 2007;Herron et al, 2007;Küster et al, 2008). The individual-based models of plant invasion focused on understanding the invasion process incorporating, for instance, disturbance (Higgins and Richardson, 1998), or herbivory (Radny and Meyer, 2018). These models have different regional and taxonomic foci including pine trees in the southern hemisphere (Higgins and Richardson, 1998), exotic plants in North America (Otfinowski et al, 2007;Herron et al, 2007), invasion success in Germany (Küster et al, 2008), and establishment success as the combined effect of functional traits and biotic pressures (Radny and Meyer, 2018).…”

A hybrid model connecting regulatory interactions with stem cell divisions in the root

“…ABMs consist of autonomous 'agents' that dynamically interact and show responsive behaviour through a set of simple rules. ABMs have, for example, been used to simulate plant-herbivore interactions (Radny & Meyer, 2018). However, within the molecular plant biology field, these models are not widely used, despite their capacity to capture system-level behaviour.…”