Remembrance of things past: modelling the relationship between species' abundances in living communities and death assemblages
Thomas D. Olszewski*
Department of Geology and Geophysics and Interdisciplinary Research Program in Ecology and Evolutionary Biology, Texas A&M University, College Station, TX 77843, USA
Accumulations of dead skeletal material are a valuable archive of past ecological conditions. However, such assemblages are not equivalent to living communities because they mix the remains of multiple generations and are altered by post-mortem processes. The abundance of a species in a death assemblage can be quantitatively modelled by successively integrating the product of an influx time series and a post-mortem loss function (a decay function with a constant half-life). In such a model, temporal mixing increases expected absolute dead abundance relative to average influx as a linear function of half-life and increases variation in absolute dead abundance values as a square-root function of half-life. Because typical abundance distributions of ecological communities are logarithmically distributed, species' differences in preservational half-life would have to be very large to substantially alter species' abundance ranks (i.e. make rare species common or vice-versa). In addition, expected dead abundances increase at a faster rate than their range of variation with increased time averaging, predicting greater consistency in the relative abundance structure of death assemblages than their parent living community.
time averaging, death assemblage, fossil assemblage, convolution, moving average process
One contribution of 12 to a Special Feature on ‘Models in palaeontology’.
Received March 24, 2011.
Accepted May 16, 2011.
This journal is © 2011 The Royal Society