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 01 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 ifpredation
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.