Using cenograms to investigate gaps in mammalian body mass distributions in Australian mammals

Abstract

Body size distribution and cenogram analyses both use body weight distributions of mammalian species to describe structural patterns within communities. Using these methods it has been possible to correlate modern mammalian community structure and habitat. In turn these correlations have been used to infer palaeohabitat from analysis of the structure of extinct mammal communities. We used the cenogram method to construct the body size distribution of both contemporary and pre-European invasion lists of mammal taxa from 52 Australian national parks spanning all major environments. All modern Australian open environments showed a gap in body mass distribution. Historical open environments showed no distinct gap in body mass distribution but had significantly less medium-sized species than closed environments. Large, introduced mammalian predators have been shown to prefer medium-sized prey over large or small prey and to contribute significantly to the extinction of medium-sized species in open environments. Our results are consistent with previous studies which have found that mid-sized mammals are more extinction prone, and this has been suggested to be due to introduced cats and foxes, following the European colonization of Australia. Two methods complementary to cenograms are introduced in this study, which are useful to infer vegetation covertures of fossil localities.