Luís González1, Yaiza Lechuga-Lago1, Alejandra Guisande-Collazo1, Gabriel Rosón2, Diego Pereiro2 and Pablo Souza-Alonso1,3
1Laboratory of Plant Ecophysiology, Department of Plant Biology and Soil Science. Faculty of Biology. University of Vigo, Vigo, Spain
2Physical Oceanography Group (Gofuvi), Department of Applied Physics. University of Vigo, Vigo, Spain
3Center for Functional Ecology – Science for People & the Planet. Department of Life Sciences. Faculty of Sciences and Technology. University of Coimbra. Coimbra, Portugal
Coastal habitats across the Mediterranean region are suffering an increasing anthropic pressure that allows the expansion of invasive alien plants (IAPs). The coastline represents an ecotone with high ecological pressure, dominated by environmental forces that continuously transform it. The ecosystem engineer Carpobrotus edulis represents a threat for habitat conservation, biodiversity preservation and the provision of ecosystem services becoming a highly targeted species for eradication along the Mediterranean basis.
The presence of C. edulis in the coastline implies that it becomes the first receptor of high loads of energy. However, the possibility of propagule immersion and dispersion has not yet been explored. With the aim of obtaining a better understanding of the mechanisms driving successful invasion and dispersive potential of C. edulis, we assessed the capacity of plant propagules to survive and grow after increasing periods of seawater immersion (up to 144h). We further simulated the potential advection of propagules through the combined use of an oceanic model (ROMS-AGRIF) with a particle-tracking model based on stochastic dispersal components and environmental variables.
Propagules, previously submerged in seawater, were planted and maintained under greenhouse conditions for 2 months. Fragment survival rate (100%) suggested high tolerance to salinity. In fact, an increase in plant and root length was generally observed and immersed fragments consistently accumulated more biomass than control fragments suggesting that immersion positively affected plant growth. After two months of growth, photosynthetic parameters (i.e. Fv’/Fm’, ΦNO, and ΦII) remained stable. In addition, osmolyte and pigment content did not show significant changes. Fragment viability and performance suggests potential viability after longer immersion periods. Based on the capacity to resist seawater immersion, our model forecasted that C. edulis propagules may travel variable distances (during the first 144h) maintaining their physiological viability. The model also indicated that short-scale circulation would be the dominant process for propagule transport; however, long-scale circulation may be successfully accomplished. In fact, the model indicated that propagules may travel long distances (250 km from the origin) in less than 6 days under optimal conditions. Although oceanic transport should be considered as a secondary dispersal pattern, it can also be responsible for long-distance movements, increasing the invasive potential of C. edulis.
Understanding plant dispersal mechanisms is fundamental to unravel IAPs ecology. Modeling transport processes, combined with the dynamics of introduction and expansion, contribute to a better understanding of the invasive mechanisms of C. edulis and, consequently, to identify coastal areas with potential risk of invasion and design preventive strategies to reduce its impact. Our model can also be extended to study the invasion other IAPs across coastal landscapes, alone or in conjunction with species distribution models. The context of current and future climate change scenario remarks the necessity for a better understanding of propagation, resistance and spatiotemporal dynamics of coastal population of IAPs.