THE ECOLOGICAL IMPORTANCE OF CRUSTACEAN DIVERSITY

Crustaceans inhabit a wide variety of habitats, from the open ocean to ephemeral pools. Within these habitats, crustaceans play key roles as herbivores, detritivores, and predators, and interact with competitors ranging from conspecifics to other crustaceans to diverse assemblages of invertebrates. As with most communities and ecosystems, efforts to understand the impacts of crustacean community diversity on ecosystem functioning began with studying species richness and relative abundance and have progressed to quantifying multiple continuous functional traits. This shift has resulted in more direct tests of how environmental conditions and changing anthropogenic stressors shape community composition, and how functional diversity allows species to make complementary contributions to control of algae, nutrient cycling, and provision of food to higher trophic levels. Greater focus on the role of functional traits in communities has also led ecologists to think about the macroevolutionary origins of functional differences within and among crustacean lineages and the ways that evolutionary histories might predict contemporary community functioning. There is also increasing evidence that rapid genetic and phenotypic divergence within species can affect ecological function at a finer scale of biodiversity that will be important for adaptive responses to global change. In this chapter, we review evidence for the effects of genetic, taxonomic, and functional or phenotypic diversity within and among crustacean taxa on the food web structure and functioning of aquatic communities. We end by outlining emerging methods for measuring these integrated facets of biodiversity and emerging questions about ecological and evolutionary components of resilience in rapidly changing ecosystems.