Gastropods with different development modes respond differently to habitat fragmentation.

The role of the human-made structures in coastal ecosystems can determine the spatial distribution or patterns of spatial abundances of marine organisms. To contribute to the understanding of linkages between different components of habitats (i.e. natural and artificial structures), we explored the role of type of larval development (planktotrophic vs. non-planktotrophic) on patterns of spatial variation of gastropods on rocky shores, elucidating the possible responsibility of habitat fragmentation on their distribution. Obtained results suggest that habitat fragmentation affects differently the patterns of variability of species with different types of larval development. Namely, fragmentation caused by artificial structures mostly influence variability of species with non-planktotrophic development. Moreover, although abundance of the species with non-planktotrophic development varied at small spatial scales, suggesting that processes operating at this scale are likely the main drivers of their distribution, changes in species variability were not associated with differences in species abundance among habitats.

Invasion of Sargassum muticum in intertidal rockpools: patterns along the Atlantic Iberian Peninsula.

Spatial patterns of non-indigenous species show scale-dependent properties. Sargassum muticum is an invasive macroalga widely distributed along the Atlantic Iberian Peninsula. Despite being quite abundant from Norway to South Portugal, there is little information about its patterns of distribution, particularly at a large spatial scale (i.e. thousands of kilometres). Here, we examined the spatial variation in the invasion success of S. muticum from rockpools at multiple spatial scales using a hierarchical design. In addition, we analysed how the richness of native assemblages was related to its invasion success and how this relationship changed over different scales. Most of the variation in the invasion success was found at the smallest scales of pool and plot. Furthermore, the invasibility of native macroalgal assemblages was related to the native species richness, but causes that determined invasion success could not be separated from the effects provoked by the invader. Results suggest that small-scale (centimetres to metres) processes contribute considerably to the heterogeneity of S. muticum invasion success.