Relationships between body-size, species abundance and diversity in marine benthic assemblages: facts or artefacts?
Warwick, R.M. and Clarke, K.R. (1996) Relationships between body-size, species abundance and diversity in marine benthic assemblages: facts or artefacts? Journal of Experimental Marine Biology and Ecology, 202 (1). pp. 63-71.
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Plots of the number of species against body size for a wide range of undisturbed macrobenthic assemblages on the European continental shelf have an approximately lognormal distribution, i.e. there are more species of intermediate size than of either larger or smaller sizes. The total abundance of all macrobenthic species combined also peaks at an intermediate size. The abundance of individual species in relation to their average body size has a pattern similar to that observed for terrestrial guilds of animals; high abundances are found in some intermediate sized species but do not tend to be found in small or large sized species. This does not appear to be a purely statistical consequence of the greater number of intermediate sized species in the assemblage. We show (as these plots imply) that for a given number of individuals there are fewer species of intermediate size but the possibility of sampling artefacts cannot be discounted here. Plots of the number of species per 100 individuals against body-size are J-shaped, the minimum of the curve corresponding to the size of animals for which retention on a 0.5 or 1 mm mesh sieve starts to become inefficient and juveniles will pass through while adults are retained. Thus the real number of species per 100 individuals at these small sizes will tend to be lower than the sample data suggest. At larger body sizes there is a more or less linear increase in the curve (on a log/log scale). This would be an inevitable consequence, in a sample of fixed areal cover (e.g. a 0.1 m2 grab), of patterns of spatial dispersion scaling with organism size. This problem is of fundamental importance for the sampling of biodiversity and could be examined by scale- stratified sampling and model simulations.
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|Copyright:||© 1996 Published by Elsevier B.V.|
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