A forgotten habitat? Granite inselbergs conserve reptile diversity in fragmented agricultural landscapes

Abstract

1. Rocky outcrop ecosystems support unique biological communities, high levels of species endemism and are important in the conservation of biodiversity worldwide. Some rocky ecosystems occur in fragmented landscapes, and as such, play a key role in conserving reptile biodiversity in modified environments. 2. We present a case study of reptile diversity in granite landforms from south-eastern Australia, using a conceptual framework based on landscape ecology theory. We stratified inselbergs by landform and assessed the relevance of patch size, matrix, habitat complexity and hierarchy theories in explaining reptile responses. Regression modelling was used to relate species richness, abundance and diversity to theory and habitat variables. 3. We found all theories to be generally applicable in interpreting reptile responses in this system but certain habitat attributes needed to be measured carefully to accurately predict reptile responses. We found that reptile species richness and diversity were congruent with predictions of patch size (island biogeography theory) and habitat structure (complexity theory), although both concepts were confounded by landform. Matrix condition had a significant influence on reptile diversity with low predicted values in relictual landscapes. 4. At the outcrop patch-level, reptile diversity was negatively related to exotic grass cover, stem density, vegetation structure and grazing intensity, whereas native grass cover and total rock cover increased diversity. 5. Synthesis and applications. The conservation of rock-dwelling reptiles in fragmented agricultural landscapes worldwide can be guided by concepts based on landscape ecology and will involve strategic management of 'inselberg landscapes', by addressing issues relevant to both the outcrop and surrounding matrix. Thus, matrix (landscape-level) management should focus on maintaining maximum habitat heterogeneity, whereas outcrop (patch-level) management will require controlling grazing regimes, invasive weeds and woody regrowth, thereby maintaining solar infiltration levels necessary for reptile thermoregulation. © 2008 The Authors.