Fire reduces parasite load in a Mediterranean lizard

Abstract

Wildfires are a natural disturbance in many ecosystems. However, their effect on biotic interactions has been poorly studied. Fire consumes the vegetation and the litter layer where many parasites spend part of their life cycles. We hypothesize that wildfires reduce habitat availability for parasites with consequent potential benefits for hosts. We tested this for the lizard Psammodromus algirus and its ectoparasites in a Mediterranean ecosystem. We predicted that lizards in recently burned areas would have lower parasite load (cleaning effect) than those in unburned areas and that this phenomenon implies that lizards spending their entire lives in postfire conditions experience a lower level of parasitism than those living in unburned areas. We compared the ectoparasite load of lizards between eight paired burned/unburned sites, including recent (less than 1 year postfire) and older fires (2–4 years). We found that lizards' ectoparasites prevalence was drastically reduced in recently burned areas. Likewise, lizards in older burned areas showed less evidence of past parasitic infections. Fire disrupted the host–parasite interaction, providing the opportunity for lizards to avoid the negative effects of ectoparasites. Our results suggest that wildfires probably fulfil a role in controlling vector-borne diseases and pathogens, and highlight ecological effects of wildfires that have been overlooked.

Resilience of reptiles to megafires

“…Although P. algirus is considered a fast colonizer of disturbed habitats (Márquez‐Ferrando et al, 2009) and it can even benefit from post‐fire environments (e.g., lower parasitic load; Álvarez‐Ruiz et al, 2021), in this study it showed no evidence of neither post‐fire colonization from unburnt (no spatial pattern) nor in situ recovery of the abundance during the 4 years after the megafires (Figure 2). This slow recovery could suggest that some plots had suboptimal environmental conditions for reptiles after the megafires.…”

Do natural catastrophic events and exceptional climatic conditions also affect parasites?

“…Considering the impact on ecosystems, fires consume not only the vegetation but also affect the upper soil layer where many parasites spend part of their life cycle, thus reducing habitat availability, with consequent potential benefits for the hosts (Álvarez-Ruiz et al ., 2021 ). As reviewed by Scasta ( 2015 ), North American studies have illustrated how fires altered the micro-habitat of ticks and reduced the density of larvae, nymphs and adults (Scifres et al ., 1988 ; Mather et al ., 1993 ; Stafford et al ., 1998 ; Cully, 1999 ).…”

Fire as a driver and mediator of predator–prey interactions

“…The global fire season lengthened by an average of 18.7% between 1979 and 2013 (Jolly et al ., 2015), and catastrophic fires have recently impacted large areas in Brazil, Australia, the USA and many other locations (Kganyago & Shikwambana, 2020; Nolan et al ., 2020). Potential consequences of altered fire regimes include vegetation state transitions (Dwomoh & Wimberly, 2017), increased extinction risk (Jones et al ., 2016; Kelly et al ., 2020), exotic species invasions (Reilly et al ., 2020), changes in animal behaviour, physiology and health (Stawski et al ., 2016; Álvarez‐Ruiz et al ., 2021; Kay et al ., 2021), and altered species interactions (Geary et al ., 2018; Smith, 2018). Shifts in fire regimes that strengthen the effects of predators are particularly concerning because the combined impacts of these two processes could push some prey species towards local or complete extinction (Brooker & Brooker, 1994; Leahy et al ., 2015; Whitehead et al ., 2018).…”