From ashes to adaptation: the impact of wildfires on the diet of Podarcis lusitanicus revealed by DNA metabarcoding

Abstract

Fire has long been recognized as an important ecological and evolutionary force in plant communities, but its influence on animals, particularly regarding predator-prey interactions, remains understudied. This study focuses on the impact of wildfires on the diet of Podarcis lusitanicus, a lizard species inhabiting a fire-prone region in the Iberian Peninsula. Faecal samples were collected from 12 distinct locations in Northern Portugal, at sites that burned in two distinct years (2016 and 2022), and in sites unburned since at least 2016. Podarcis lusitanicus is a generalist arthropod predator with dietary flexibility. Given the turnover of arthropod species after fire, it is expected to find variations in diet caused by different fire histories, especially between unburnt and recently burnt sites. Using DNA metabarcoding approach, employing high-throughput sequencing, the study revealed that while prey richness remained unaffected by wildfire regime, significant shifts occurred in diet composition between more recently burned and unburned areas, demonstrating a likely influence on prey availability after a more recent fire. Specifically, we found that differences in diet composition between these two fire regimes were due to the presence of Tapinoma ants and jumping spiders (Salticus scenicus) in unburned areas, while these were absent in areas burned in 2022. Interestingly, diets in unburned areas and areas burned in 2016 showed no significant differences, highlighting the lizards adaptability and the habitats resilience over time. Talitroides topitotum was found in dominance in both burnt areas, suggesting that this species may be fire tolerant. In addition, families such as Cicadellidae and Noctuidae were found to be more associated with more recently burned areas. The use of DNA metabarcoding in this study was essential to provide a more detailed and accurate view of predator-prey interactions in ecosystems susceptible to fire, providing a better understanding of changes in prey consumption in these environments.