Reptile responses to fire across the western Mediterranean Basin.

Abstract

Effects of anthropogenic activities, including climate change, are modifying fire regimes, and the dynamic nature of these modifications requires identification of general patterns of organisms' responses to fire. This is a challenging task because of the high complexity of factors involved (including climate, geography, land use, and species-specific ecology). We aimed to describe the responses of the reptile community to fire across a range of environmental and fire-history conditions in the western Mediterranean Basin. We sampled 8 sites that spanned 4 Mediterranean countries. We recorded 6064 reptile sightings of 36 species in 1620 transects and modeled 3 community metrics (total number of individuals, species richness, and Shannon diversity) as responses to environmental and fire-history variables. Reptile community composition was also analyzed. Habitat type (natural vs. afforestation), fire age class (time since the last fire), rainfall, and temperature were important factors in explaining these metrics. The total number of individuals varied according to fire age class, reaching a peak at 15-40 years after the last fire. Species richness and Shannon diversity were more stable during postfire years. The 3 community metrics were higher under postfire conditions than in unburned forest plots. This pattern was particularly prevalent in afforested plots, indicating that the negative effect of fire on reptiles was lower than the negative effect of afforestation. Community composition varied by fire age class, indicating the existence of early- and late-successional species (xeric and saxicolous vs. mesic reptiles, respectively). Species richness was 46% higher in areas with a single fire age class relative to those with a mixture of fire age classes, which indicates pyrodiverse landscapes promoted reptile diversity. An expected shift to more frequent fires will bias fire age distribution toward a predominance of early stages, and this will be harmful to reptile communities.