Alien plant colonisation and community homogenisation: cause or consequence? A test in coastal dunes

Abstract

Evidence of the effects of alien plant colonisation on plant communities is often hindered by the fact that similar patterns in community composition can arise through a variety of processes. The objective of this study is to determine whether changes in species composition in coastal dune communities depend on the colonisation of a neophyte plant, Oenothera stucchii, or on concurrent processes that favour its colonisation. We hypothesised two scenarios: 1) a direct impact of O. stucchii on colonised communities, leading to displacement of native species; or 2) no direct impact of O. stucchii, i.e. the species colonises plant communities by exploiting disturbances that lead to the rearrangement of plant communities. We used the species-habitat network approach to identify potential drivers of changes in species composition, assuming that changes in the structure of the species-habitat network depend on the nature of the driving process. We demonstrated that changes in species composition in plant communities were due to species rearrangement, with colonised communities characterised by more homogeneous composition of species. We suggest that changes in plant communities may not depend on colonisation by O. stucchii per se, but on concomitant processes that affect coastal dune communities while promoting colonisation by O. stucchii.

Keywords:

• Alien species
• coastal dunes
• community homogenisation
• disturbance
• Oenothera stucchii
• species-habitat network

Acknowledgements

We thank Dr. Lucia Santoianni and Dr. Maria Carla de Francesco for supporting fieldwork activity.

Author contributions

All authors contributed to the study design and data collection. Analysis was performed by E.F. The first draft of the manuscript was written by E.F., and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Data availability

The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

E.F. and G.B. were supported by the Ca’ Foscari University of Venice, MUR and the European LIFE project LIFE16 IT/NAT/000589 REDUNE (E.F. and G.B.). F.P.T and A.S. were partially supported by LIFE CALLIOPE NAT/IT/000565 and INTERREG V-A IT-HR CBC Programme – ‘Strategic’ project: ‘CoAStal and marine waters integrated monitoring systems for ecosystems proteCtion AnD management’ (CASCADE – ID: 10255941).