Gradient analysis of macropod distribution in open forest and woodland of eastern Australia



Macropod communities are most diverse in eastern Australia. Patterns of macropod abundance along environmental gradients were examined from data collected on transects located in open forest, woodland, and pasture close to forest or woodland, throughout eastern Australia from latitudes 18–33??S. Nine species of macropod were recorded on the transects. Classification of the species by their abundance on transects grouped species in accordance with the latitudinal extent of their complete ranges. Three important environmental gradients were identified from 20 environmental variables measured at each transect: a climate–human influence gradient, contrasting heavily populated, temperate areas with sparsely populated, tropical/xeric areas; an elevation gradient, contrasting high, cold, sparsely vegetated areas with low, densely vegetated areas; and a physical–vegetation gradient, contrasting steep, rocky, densely vegetated areas with flat, sparsely vegetated areas. Most species showed significant variation in abundance across these gradients. Patterns of ecological separation of the species along the gradients are examined and discussed. Total macropod abundance, richness and diversity showed a unimodal pattern along the climate-human influence gradient, with low levels at the gradient’s extremes and high levels mid-way along the gradient. This pattern of richness and diversity is consistent with both productivity and structural diversity hypotheses. Abundance, richness and diversity varied linearly along the elevation and physical-vegetation gradients, with values increasing as elevation and slope increased. Variation in macropod abundance, richness and diversity along the physical–vegetation gradient may be related to shelter availability.