CIESM atlas of exotic species in the Mediterranean Sea. Vol. 4. Macrophytes.

This volume by two prominent French phycologists (Verlaque and Boudouresque) and their two collaborators (Ruitton and Mineur) provides fascinating insight into the state of exotic macroalgal species in the Mediterranean Sea. The authors are to be commended for such a useful and authoritative work. This monograph follows on from three previous volumes on fishes, molluscs and crustaceans sponsored by the Mediterranean Science Commission. Although the other volumes might not be of particular interest to phycologists, collectively they provide a comprehensive resource for marine ecologists and environmental managers throughout the Mediterranean Sea and adjoining regions. These exotic macrophytes of the Mediterranean Sea have a long and colourful history. With 120 aliens, this may be the flora presenting the greatest number of exotic species. It may be the only water body where the account of an invasive alga [i.e. Caulerpa taxifolia (M. Vahl) C. Agardh] reads like a mystery novel replete with controversy, coverups and government inaction (Meinesz 1999). The current volume provides a more useful, if less colourful, contribution to phycology. While the book provides an important reference work for phycologists, it was also written with the more general biologist in mind. Thus, there are opening sections comprising an introduction (seven pages); a general account of algal taxonomy, cell biology and phylogeny that is put into a larger context of the ‘Tree of Life’ (13 pages), and a glossary of algal terms (eight pages). In the space of a couple of pages, the authors summarise modes of species introduction, some useful ecological theory and cogent conservation issues. The main part of the book is an extensive list and account of the 118 taxa of rhodophyte (74 species), phaeophyte (23 species) and chlorophyte (21 species) introduced seaweeds, plus one flowering plant, Halophila stipulacea (Forsskål) Ascherson, exotic for the Mediterranean Sea. There is also a supplementary list of exotic species from adjacent coasts in the Atlantic Ocean that have not yet made their way into the Mediterranean Sea. Each species is assessed from the perspective of geographic origin and its potential as an invasive species. The authors rightfully distinguish between the merely exotic and those that are truly invasive, with the latter being 10% of the total (i.e. 12 species). Regardless, the impact of these invasions and of the additional species that might become invasive highlights why nonphycologists should find this work an important resource. The entry for each species is given in a well-organised and consistent format. The information includes the following: illustrations, major synonymy, historical misidentifications, short descriptions, distinguishing characters, biology/ecology/habitat, literature-based distribution, map, mode of introduction, establishment success, importance to humans and key references. All this this is squeezed into two pages for each taxon. The literature accounts for distributions seem comprehensive, with references to validate generalised distributions for the world (available in more detail in Guiry & Guiry 2015) and specific distributions in the Mediterranean Sea. The maps are particularly informative and give point distributions as well as areas of generalised distributions where a species might be expected (i.e. frequent) and areas where it is infrequent (as ‘unfrequent’) or suspected. Such maps make this a superb resource for anyone doing floristic or ecological research in that they can quickly establish if a suspected exotic species is now well outside its previous known range. If I have any complaint, it is that many of the images are little more than thumbnails. My interest in this book lies in the fact that the Mediterranean provides a fascinating model system for studying species diversity and historical biogeography. With 10% of the flora now represented by exotic species, it also becomes a natural experiment for how alien species become integrated into species-rich biotas. As the introduction points out, the flora is among the most diverse from a global perspective and has about 1300 native species comprising 12% of the world’s seaweeds in a system with only 0.8% of the area of the world’s oceans. The latter is clearly an understatement of the habitat extent, as compared to much of the rest of the world ocean, the Mediterranean has a much greater coastline relative to its size (over 40,000 DOI: 10.2216/5501br02 2016 International Phycological Society Phycologia Volume 55 (1), 105–106 Published 25 January 2016