title: The marine diversity spectrum.
abstract: Distributions of species body sizes within a taxonomic group, for example, mammals, are widely studied and important because they help illuminate the evolutionary processes that produced these distributions. Distributions of the sizes of species within an assemblage delineated by geography instead of taxonomy (all the species in a region regardless of clade) are much less studied but are equally important and will illuminate a different set of ecological and evolutionary processes. We develop and test a mechanistic model of how diversity varies with body mass in marine ecosystems. The model predicts the form of the 'diversity spectrum', which quantifies the distribution of species' asymptotic body masses, is a species analogue of the classic size spectrum of individuals, and which we have found to be a new and widely applicable description of diversity patterns. The marine diversity spectrum is predicted to be approximately linear across an asymptotic mass range spanning seven orders of magnitude. Slope -0.5 is predicted for the global marine diversity spectrum for all combined pelagic zones of continental shelf seas, and slopes for large regions are predicted to lie between -0.5 and -0.1. Slopes of -0.5 and -0.1 represent markedly different communities: a slope of -0.5 depicts a 10-fold reduction in diversity for every 100-fold increase in asymptotic mass; a slope of -0.1 depicts a 1.6-fold reduction. Steeper slopes are predicted for larger or colder regions, meaning fewer large species per small species for such regions. Predictions were largely validated by a global empirical analysis. Results explain for the first time a new and widespread phenomenon of biodiversity. Results have implications for estimating numbers of species of small asymptotic mass, where taxonomic inventories are far from complete. Results show that the relationship between diversity and body mass can be explained from the dependence of predation behaviour, dispersal, and life history on body mass, and a neutral assumption about speciation and extinction.
authors.affiliation: Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, SL5 7PY, UK.|Laboratory of Populations, Rockefeller University, 1230 York Ave, New York, NY, 10065, USA.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Reuman
authors.affiliation: Technical University of Denmark, Charlottenlund Slot, DK-2920, Charlottenlund, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Gislason
authors.affiliation: Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, Suffolk, NR33 OHT, UK.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Barnes
authors.affiliation: European Commission, Joint Research Centre, Institute for Environment and Sustainability, 21027, Ispra (VA), Italy.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Mélin
authors.affiliation: Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, Suffolk, NR33 OHT, UK.|School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Jennings
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology*; D044822:Biodiversity; D049628:Body Size; D017753:Ecosystem; D007448:Invertebrates / Q000502:physiology*; D008954:Models, Biological; D009792:Oceans and Seas; D013045:Species Specificity; D014714:Vertebrates / Q000502:physiology*
keywords: biodiversity; body mass; community; neutral theory; power law; size spectrum