Research

The marine diversity spectrum

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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 center dot 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 center dot 5 and -0 center dot 1. Slopes of -0 center dot 5 and -0 center dot 1 represent markedly different communities: a slope of -0 center dot 5 depicts a 10-fold reduction in diversity for every 100-fold increase in asymptotic mass; a slope of -0 center dot 1 depicts a 1 center dot 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.

body mass evolutionary process marine diversity Vertebrata Chordata Animalia (Animals Chordates Fish Nonhuman Vertebrates Vertebrates) - Pisces [85200] fish common 01500 Evolution 04500 Mathematical biology and statistical methods 07502 Ecology: environmental biology - General and methods 07508 Ecology: environmental biology - Animal 07512 Ecology: environmental biology - Oceanography 10515 Biophysics - Biocybernetics Computational Biology Ecology Environmental Sciences global empirical analysis mathematical and computer techniques mechanistic model mathematical and computer techniques Biodiversity Evolution and Adaptation Marine Ecology Models and Simulations ECOLOGY ZOOLOGY BODY-SIZE DISTRIBUTIONS METABOLIC-RATE FOOD WEBS NATURAL MORTALITY GLOBAL DIVERSITY MOLECULAR CLOCK REGIONAL SCALES CLIMATE-CHANGE FISH TEMPERATURE biodiversity community neutral theory power law size spectrum MARINE ecology