The new diversity: management gains through insights into the functional diversity of communities

Summary 1.  Biodiversity is being lost in our rapidly changing world. Most studies that examine biodiversity measure species richness, but loss of functional diversity (FD) – defined as the trait variation or dispersion in an assemblage – is equally important. FD is useful for management actions focused on ecosystem services or functions, especially when ecosystem function is ambiguously defined, or there are multiple functions of interest. Because FD is often a multivariate measure of species differences, it has additional relevance given that we seldom have a complete understanding of how traits translate to function. 2.  This Special Profile includes six papers that examine how management activities or policy could benefit from consideration of the functional contributions of species. When focused on species richness, management activities may unintentionally reduce FD, with detrimental consequences for ecosystem services or stability. For example, two of the studies included in this Special Profile show that grassland management (e.g. mowing or grazing) can result in loss of FD, which may result in an unintended loss of ecosystem services. 3.  A third paper reviews how species extinction and environmental change can negatively affect FD and, potentially, ecosystem function. At the individual species level, invasions offer insight into the importance of species traits. The fourth paper in this Special Profile describes how an invader is successful because of unique trait values, underlining the importance of examining FD when considering management options. In another paper, eutrophication is shown to drastically affect lichen functional groups (some decreasing and some increasing) with a minor effect on overall richness. The final paper demonstrates that the ability of aquatic plants to maintain biomass production in changing environments is determined by their complementary contributions to productivity. These complementary contributions to ecosystem function –especially given that they are more important in fluctuating environments – need to be included in evaluations of diversity. 4.   Synthesis and applications . As FD is increasingly assessed in applied studies, it will call into question how we measure diversity and evaluate management success. It is clear that species richness cannot be the only measure considered. Given that environmental change and management activities can reduce FD as well as the number of species, management goals and criteria for success need to include FD.