Ecological Characterisation and Invasive Potential of Salpichroa origanifolia in a Meso-hygrophilous Forest Ecosystem

Viola Alessandrini ¹, Iduna Arduini ¹

Department of Agriculture, Food and Environment, University of Pisa, 56124 Pisa, Italy ¹

The introduction of invasive alien species represents a significant threat to global biodiversity, altering species interactions and ecosystem processes. Following introduction into a new environment, only 10% of the alien species become invasive. The success of colonisation, stabilisation and subsequent invasive spread is contingent upon a range of factors, including the level of propagule pressure, the functional traits of invasive species, and specific characteristics of the recipient ecosystem. This study explores the invasion process of Salpichroa origanifolia (Lam.) Baill. in the San Bartolomeo Forest (Tuscany, Italy), focusing on the interplay of these three factors. This is the only documented instance of extensive colonisation in an Italian forest. To assess propagule pressure, we documented flowering periods, revealing an extended flowering season (April–October) with a summer regression. Field observations documented consumption of the fruits by birds, foxes and herbivores. We considered vegetative reproduction and light adaptability as functional traits. The species' vegetative reproduction was supported by morphologically distinct rhizomes, collected and classified in different classes. To evaluate light-related functional traits, we measured branch length, leaf area, and biomass under three light conditions in the forest. Results indicated longer branches in high-light environments and larger specific leaf area (SLA) in shade. Anatomical sections revealed shaded leaves exhibiting a less organised anatomical structure. These findings demonstrated a remarkable capacity for adaptation to diverse light conditions through a differentiated allocation of resources. The characteristics of the recipient ecosystem influenced invasion patterns and were defined by vegetation type and abiotic conditions (soil moisture). S. origanifolia was more frequent in Quercus-dominated forests, whereas invasion was reduced in Fraxinus-dominated forests with high soil moisture and undergrowth dominated by Carex spp. The findings demonstrate that S. origanifolia can adapt to diverse light conditions, exhibits high propagule pressure through prolonged flowering, and displays robust vegetative reproduction through a complex system of rhizomes. However, its reduced presence in Fraxinus-dominated forests suggests the influence of abiotic factors (e.g., soil moisture) and biotic competition with large-sized sedges. This highlights the importance of the interplay of the presented factors in shaping invasion dynamics.

Main author career stage: PhD student

Contribution type: Talk

First choice session: 2. Ecology

Second choice session: 2. Ecology