Opposed elevational variation in prevalence and intensity of endoparasites and their vectors in a lizard

Abstract

Studying the causes of parasite geographic distribution is relevant to understand ecological and evolutionary processes that affect host populations as well as for species conservation. Temperature is one of the most important environmental variables affecting parasite distribution, as raising temperatures positively affect development, reproduction, and rate of transmission of both endo- and ectoparasites. In this context, it is generally accepted that, in mountains, parasite abundance decreases with elevation. However, empirical evidence on this topic is limited. In the present study, we analyzed the elevational variation of hemoparasites and ectoparasites of a lizard, Psammodromus algirus, along a 2,200-m elevational gradient in Sierra Nevada (SE Spain). As predicted, ectoparasite (mites, ticks, mosquitoes, and sandflies) abundance decreased with elevation. However, hemoparasite prevalence and intensity in the lizard augmented with altitude, showing a pattern contrary to their vectors (mites). We suggest that tolerance to hemoparasites may increase with elevation as a consequence of lizards at high altitudes taking advantage of increased body condition and food availability, and reduced oxidative stress. Moreover, lizards could have been selected for higher resistance against hemoparasites at lowlands (where higher rates of replication are expected), thus reducing hemoparasite prevalence and load. Our findings imply that, in a scenario of climate warming, populations of lizards at high elevation may face increased abundance of ectoparasites, accompanied with strong negative effects.

Habitat type influences parasite load in Algerian Psammodromus (Psammodromus algirus) lizards

“…Prevalence and intensity of hemoparasites was higher in the lowland population. This finding contrasts with other studies reporting an increase in hemoparasite infection with elevation in the eastern genetic lineage of P. algirus (Álvarez-Ruiz et al 2018), but it is consistent with other studies reporting a decrease in hemoparasite infection with elevation in birds (Zamora-Vilchis et al…”

“…In contrast, regarding ectoparasites, we found that prevalence of ticks was higher in the upland population, being anecdotic the presence of ticks in the lowland population, as it has been previously described in the same species and region (Llanos-Garrido et al 2017). However, other studies have reported a decrease in tick abundance with elevation in the eastern genetic lineage of P. algirus (Álvarez-Ruiz et al 2018). Therefore, our findings suggest that patterns of elevational variation of parasitism may be more complex and be also explained by other habitat factors that show elevational variation, rather than just by the altitude per se.…”

Age structure of a lizard along an elevational gradient reveals nonlinear lifespan patterns with altitude

“…1994 ; Camacho and Avilés 2019 ). Meanwhile, parasites showed a complex pattern: the prevalence of ectoparasites (mites) decreased linearly with ascending elevation, whereas hemoparasites increased linearly ( Álvarez-Ruiz et al. 2018 ).…”

Ecology and evolution along environmental gradients

“… Alvarez-Ruiz et al. (2018) characterized an elevational gradient for patterns of ecto- and endoparasitization in the lizard Psammodromus algirus and reported contrasting patterns of decreasing ecto- but increasing endoparasitism with altitude.…”