SPACE-TIME EQUIVALENCE IN AUSTRALIAN QUATERNARY MAMMAL COMMUNITIES (Invited Presentation)

Mammal communities represent a collection of species found together at the one time and in the same place due to historical, environmental, and ecological factors. Communities at one instant in time will change in composition over space, at least in part, due to changes in environments associated with different altitudes, lithologies, latitudes, longitudes, and meterological conditions. Likewise, going back in time, mammal communities from one place will change in response to changing environmental conditions associated with global climatic trends, extinctions, speciations, and invasions and geological events such as weathering, geohydrology, tectonics, and volcanism. Changes in mammal communities can be quantified either at the taxonomic or the functional group level. The latter, particularly when employing ‘taxon-free’ variables, can allow for comparisons between communities differing radically taxonomically through space or time. Space and time can also be examined simultaneously. Here, we examine Pleistocene fossil communities of two well-sampled Australian sites, Naracoorte Caves in South Australia, and Tight Entrance Cave in Western Australia. We quantify communities using functional groups (body size, trophic, locomotion) in order to examine them in multidimensional space. Fossil communities from each sampled unit are more similar to its neighbours in ecospace than to communities more different in time, thus providing a linear relationship between time and community structure. Communities from modern natural protected areas were also examined in ecospace. Their spatial relationships can be described in a similar linear fashion, starting from the closest natural protected area to the fossil site and moving out, but only in certain directions. Nevertheless, a linear relationship between space and community structure can be constructed. Given that community structure is equivalent between the space and time relationships, a space-time equivalence for Australian Quaternary mammal communities can be constructed that is independent of community structure. This paper explores whether such space-time equivalence in faunal communities can be generalised, and discusses if such an equivalence is meaningful or even useful for understanding deep time community ecology processes.