Assembly of species climate niches of coastal communities does not shift after invasion

Abstract

Question Do invasions by invasive plant species with contrasting trait profiles (Arctotheca calendula, Carpobrotus spp., Conyza bonariensis, and Opuntia dillenii) change the climatic niche of coastal plant communities?

Location Atlantic coastal habitats in Huelva (Spain).

Methods We identified the species composition of 216 paired (non-invaded and invaded) 10 × 10 m plots along the coast. For each species, we calculated its climatic niche based on the two main axis of a PCA constructed with nine climatic variables. We defined the community ensemble niche by the union of the overall climate niches of co-occurring species within a plot. We compared niche overlap metrics between non-invaded and invaded paired communities.

Results There was an almost complete overlap in the community ensemble niches between non-invaded and invaded plots for the four invaders. Plots invaded by Carpobrotus spp. presented the lowest niche stability and those invaded by A. calendula had the highest. Plots invaded by Carpobrotus spp. showed the highest values of niche unfilling and expansion. In contrast, plots invaded by O. dillenii exhibited the lowest niche unfilling. Species similarity between non-invaded and invaded plots was on average 58%. The community ensemble niches differed depending on the invasive species and were related to differences in community species similarity between non-invaded and invaded plots. Overall, there was a positive correlation between community species similarity and climatic niche stability, and a negative correlation between community difference in taxonomic richness and climatic niche stability.

Conclusions Species assemblages in coastal vegetation did not change their community ensemble climatic niches after invasion by plants with contrasted life forms. This pattern is likely the result of invasion which did not trigger major changes in species richness and composition, or alternatively, because the species that were locally displaced by invasion have been substituted by others with similar climatic requirements.