Body size and community structure in British Pleistocene mammals

This study explores patterns of body size variation in the ungulates and large carnivores of the British Middle and Late Pleistocene (ca. 750-10 kyr B.P.) and examines how communities were organised in terms of the body sizes of their members. Body size analysis has been carried out using estimated body mass data, produced through the application of allometric scaling equations. A high degree of estimate consistency was achieved within and between skeletal elements, indicating that the methods produce accurate representations of mass. The biostratigraphic scheme applied relates terrestrial deposits to the Oxygen Isotope Record of climatic change. Body mass data generally supports the coherence of the stratigraphic divisions utilised. The majority of species underwent significant mass variation during the study period, with size differences identified at the OI Stage and Sub-Stage level. Post-crania appear to be more suitable for mass estimation than teeth. Comparison of the mass records produced from dental and post-cranial remains indicates whether size change events had a genetic or ecophenotypic basis. The patterns of body size variation revealed have been related to palaeoenvironmental conditions. British Pleistocene ungulates generally underwent size change opposite to the predictions of Bergmann's rule, while carnivores maintained relatively constant body sizes across periods of temperature variation. Primary productivity and levels of seasonality appear to have been the major determinants of ungulate body size. Carnivore body sizes may be related to size variations in their prey and can also be influenced by vegetation conditions if predation levels are affected, although changes in dental proportions may also result. Analysis of community structure suggests that the body sizes of different guild members were not closely linked during the Pleistocene. Community body mass distributions predicted by competition theory have not been consistently identified. The mammal communities appear to be loose associations of species acting individualistically and responding in different ways to environmental challenges