Species – body weight relationships Trichoplax adhaerens Loxodonta africana Balaenoptera musculus Neotrombicula autumnalis Goliathus regius

Biogeographic distributions of invertebrate body sizes (Makarieva et al. 2005)

World distribution of largest land vertebrates Mammals: Phytophages in tropical regions Predators at higher latitudes Birds: In tropical regions Reptiles and Amphibians: In tropical regions

Size distributions as a statistical artefact The latitudinal gradient causes higher diversity in tropical regions. If very large species form always a small part of the total fauna high latitude regions will have a low chance of containg large species. If evolution creates larger and smaller species with similar probability species rich regions will have a higher chance of containing large biodied species. Before interpreting ecological patterns and process in terms of ecological mechanisms we have to pure exclude statistical explanations!

A random sample model to test for statistical artefacts At high latitudes there are less large and less small bodied springtail species than expected just by chance.. At low latitudes these numbers do not deviate from random expectation

Statistical artefactEcological pattern

Body size Species richness Lord Robert May (1936- Body size – species richness relationship in metazoa z = -2.0 Smaller sized organisms should be species richer. The species richness – body size relationship was assumed to be approximately a power function with a slope of z = -2 This hypothesis assumes that either smaller sized species have a higher speciation rate or larger sized species have a higher extinction rate ln (Body size) ln (Population size) Speciation rate Extinction rate Metabolic theory predicts Evolutionary speed should be higher in smaller bodied species of the same population sizes. Evolutionary speed is higher in small populations. Diversity and body size

Species richness – taxon body size relationship Overall species richness – body size relationship Data from Orme et al. (2002) z = -0.5 Speciation driven

Species – body weight relationships Adult mammal female body weight

Passive diffusion model (McKinney 1990) Body size evolution is a random walk on log transformed values There is a lower reflecting or absorbing boundary Right skew should be most pronounced in small bodied taxa Right skew should decrease with increasing species richness

Today’s reading Body size and abundance: Brose U., Jonsson T., Berlow E. L., Warren P., Banasek-Richter C., Bersier L.-F., Blanchard J. L., Brey T., Carpenter S. R., Blandenier M. - F. C., Cushing L., Dawah1 H. A., Dell1 T., Edwards F., Harper-Smith S., Jacob U., Ledger M. E., Martinez N. D., Memmott J., Mintenbeck K., Pinnegar J. K., Rall B. C., Rayner T. S, Reuman D. C., Ruess R., Ulrich W., Williams R. J., Woodward G., Cohen J. E Consumer-resource body-size relationships in natural food webs. Ecology 87: pdfpdf