The animal species–body size distribution of Marion Island

Abstract

Body size is one of the most significant features of animals. Not only is it correlated with many life history and ecological traits, but it also may influence the abundance of species within, and their membership of, assemblages. Understanding of the latter processes is frequently based on a comparison of model outcomes with the frequency of species of different body mass within natural assemblages. Consequently, the form of these frequency distributions has been much debated. Empirical data usually concern taxonomically delineated groups, such as classes or orders, whereas the processes ultimately apply to whole assemblages. Here, we report the most complete animal species-body size distribution to date for those free-living species breeding on sub-Antarctic Marion Island and using the terrestrial environment. Extending over 15 orders of magnitude of variation in body mass, this distribution is bimodal, with separate peaks for invertebrates and vertebrates. Under logarithmic transformation, the distribution for vertebrates is not significantly skewed, whereas that for invertebrates is right-skewed. Contrary to expectation based on a fractal or pseudofractal environmental structure, the decline in the richness of species at the smallest body sizes is a real effect and not a consequence of unrecorded species or of species introductions to the island. The scarcity of small species might well be a consequence of their large geographic ranges.

How Dispersal Limitation Shapes Species–Body Size Distributions in Local Communities

“…Our model can also explain multimodal species-body size distributions, such as the bimodal distribution found by Gaston et al (2001), who report different optima for vertebrates and invertebrates. So far, we assumed that all guilds could be related to a single reference guild by universal allometric scaling laws.…”

“…Most of the studies report a unimodal, rightskewed shape for the species-body size distribution in a community (Dial and Marzluff 1988;Blackburn and Gaston 1994;Brown 1995;Dixon et al 1995;Siemann et al 1996Siemann et al , 1999Gregory 1998;Osler and Beattie 1999;Bakker and Kelt 2000;Gaston and Blackburn 2000;Gomez and Espadaler 2000). Nevertheless, the optimum at intermediate body size is not always very pronounced, there is much variation in skewness, and bimodal shapes are also observed (Chown and Gaston 1997;Bakker and Kelt 2000;Gaston and Blackburn 2000;Gaston et al 2001). Early studies even suggested that the classes of the smallest body sizes are the most speciose, and they explained the observed optimum at intermediate body size by poor sampling of small species (Van Valen 1973;May 1978May , 1986see, however, Hutchinson and MacArthur 1959).…”

The long-term patterns of phytoplankton taxonomic size-structure and their sensitivity to perturbation: A Lake Kinneret case study

“…Then, more sophisticated mathematical tools, already developed in pattern recognition sciences to compare a pair of histograms (Chaa and Sriharib, 2002), should be applied if the phenomenon of TTSS rigidity can be proven in other ecosystems and will receive more attention. The TTSS, like the more often-studied NBS, seems to be very consistent (Kendall et al, 1997;Roy et al, 2000;Gaston et al, 2001;Smith et al, 2004). Largescale comparisons, generalizations, and theoretical discussions already exist in zoology (mainly, for terrestrial communities) (Gaston et al, 2001;Smith et al, 2004).…”

“…While BSS, and especially NBS, have gained much scientifi c attention in recent years, relatively few studies (e.g., Chislenko, 1981;Holling, 1992;Allen et al, 1999;Smith et al, 2004) addressed TTSS patterns. Nevertheless, large-scale comparisons of animal communities have already highlighted the existence of invariant taxonomic size-frequency distributions (Roy et al, 2000;Gaston et al, 2001;Smith et al, 2004). The species sizedistribution patterns observed for pelagic and benthic assemblages also seem to be rather stable, despite changes in community composition (Raffaelli et al, 2000;Havlicek and Carpenter, 2001).…”

Spatial and temporal variability across life's hierarchies in the terrestrial Antarctic

“…Assemblage properties that are the stuff of modern macroecological analyses have enjoyed less attention, despite the fact that these species-poor systems lend themselves to this kind of analysis. For example, Gaston et al (2001) provided the most complete animal species-body size frequency distribution for any system globally by compiling and analysing these data for the well-surveyed Marion Island. Likewise, although early work was concerned with food webs in the Antarctic, largely as a consequence of the International Biosphere Programme (Block 1984(Block , 1985, little subsequent work has taken place (though see Wall & Virginia 1999).…”