Does pyrodiversity beget alpha, beta or gamma diversity? A case study using reptiles from semi-arid Australia
A common assumption in fire ecology and management is that landscapes with a greater diversity of fire-ages will support a greater diversity of animal species (i.e. ‘pyrodiversity begets biodiversity’). This assumption is based on the idea that landscapes with a more diverse fire history provide a greater array of post-fire habitats, leading to a greater number of species within the landscape. We assessed the hypothesis that pyrodiversity begets biodiversity by enhancing community differentiation (β diversity), resulting in increased landscape-scale richness (γ-diversity). We used reptiles as a case-study.
The Mallee region of south-eastern Australia.
We used a study design in which ‘whole’ fire mosaics (12.6 km2) were the unit of replication. Study landscapes (n = 28) were selected to represent a gradient in the diversity and extent of fire-age classes. We surveyed reptiles by using pitfall traps at 10 sites within each landscape (280 sites in total). Reptile data were used to characterize reptile assemblages at the landscape-scale in three ways: alpha (average within-site diversity), beta (between-site diversity) and gamma diversity (total diversity).
The diversity of fire-age classes had little influence on the alpha, beta or gamma diversity of reptile assemblages. The properties of fire mosaics that most influenced assemblages were the extent of structurally important fire-age classes. The extent of long-unburned vegetation increased beta diversity but reduced alpha diversity of the total reptile assemblage, essentially cancelling each other out at the landscape scale.
This study highlights the importance of considering multiple measures of diversity when exploring the influence of landscape properties on biodiversity, as ‘null’ results at the landscape scale (gamma diversity) can result from contrasting patterns in alpha and beta diversity. Using fire to create habitat mosaics, at the scale of this study, is unlikely to enhance the status of reptiles in the region.