Species – body weight relationships

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

2. Biogeographicdistributions of invertebrate body sizes (Makarieva et al. 2005)

3. Worlddistribution of largest land vertebrates Mammals: Phytophagesintropical regions Predatorsathigherlatitudes Birds: In tropical regions Reptiles and Amphibians: In tropical regions

4. Sizedistributions as a statisticalartefact Ifverylargespecies form always a small part of thetotal fauna high latitude regions will have a lowchance of containglargespecies. Ifevolutioncreateslarger and smallerspecieswithsimilarprobabilityspeciesrich regions will have a higherchance of containinglargebiodiedspecies. Thelatitudinal gradient causeshigherdiversityintropical regions. Beforeinterpretingecologicalpatterns and processinterms of ecologicalmechanisms we have to pureexcludestatisticalexplanations!

5. A random sample model to test for statisticalartefacts At high latitudesthereare less large and less smallbodiedspringtailspeciesthanexpectedjust by chance.. Atlowlatitudesthesenumbers do not deviatefrom random expectation

6. Statisticalartefact Ecologicalpattern

7. Diversity and body size Lord Robert May (1936- Extinction rate Speciation rate z = -2.0 ln (Population size) Species richness Body size – species richness relationship in metazoa ln (Body size) Body size 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 Metabolic theory predicts • This hypothesis assumes that • either smaller sized species have a higher speciation rate or • larger sized species have a higher extinction rate Evolutionary speed should be higher in smaller bodied species of the same population sizes. Evolutionary speed is higher in small populations.

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

9. Species – body weight relationships Adult mammal female body weight

10. 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

11. Today’s reading Body size and abundance: www.biology.usu.edu/labsites/ernestlab/PDFs/White_etal_2007.pdf 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. 2006. Consumer-resource body-size relationships in natural food webs. Ecology  87: 2411 - 2417.pdf