The Theory of Ecological Communities. Monographs in Population Biology 57, Mark Vellend, Princeton University Press, Princeton, NJ, USA (2016). 248 pp., $49.95, ISBN: 9780691164847 (Hardback), 9781400883790 (eBook)

A productive concept, or “theory” in ecological jargon, trikes just the right balance between abstract universality nd specific applicability. Too abstract, and ecologists will gnore it as too aloof; too specific, and it will not cross ub-disciplinary boundaries and fade away. Darwin’s Thery of Natural Selection fits this bill, as does MacArthur Wilson’s Island Biogeography. Will Vellend’s Theory of cological Communities become one of these few just-theight-level-of-abstraction-theories? It will not, as Vellend dmits right away, as he considers “only” what he calls horizontal communities” (such as guilds, vegetation, and xcluding consumer-resource interactions, mutualist netorks, and food webs). Yet, his ambition is to offer a igh-level unification of the processes in such communities, ontaining all existing theories as special cases. Four higherevel processes are all it takes to describe the ecology of orizontal communities, Vellend claims, and those are modlled on the highly successful four higher-level processes of opulation genetics: selection, drift, speciation (mutation in enetics) and dispersal (gene flow). A substantial part of this book is devoted to convincing he reader that such a high-level approach is useful. To do o, Vellend runs through the “history of ideas in commuity ecology” and dwells on the importance of theory for eneralising ecological understanding (including some pracical modelling in R, much too short to be of any use). hile these first 100 pages are offering little new to the racticing ecologist, they culminate in a list that repreents the essence of the usefulness of Vellend’s high-level pproach: a four-page table of theories, concepts and effects xplained through the four above-mentioned processes or heir interplay. The Janzen–Connell effect as well as the ntermediate-disturbance hypothesis is essentially selectionriven, Island Biogeography a mixture of drift and dispersal,