A ten-year change in blood parasite infection in a sympatric wall-lizard community (genus Podarcis) from the Atlantic coast of Portugal.

Abstract

Understanding how host-parasite relationships respond to environmental factors across long periods of time is vital to understanding the dynamics of parasitic infections. We studied blood parasite infections in two sympatric species of Podarcis lizards in Northern Portugal between 2011 and 2013 and in 2021, analysing parasite data together with host traits and microclimatic conditions to understand how this relationship was maintained through time. Relationships between host traits and parasite infection remained consistent across years, suggesting changes to infection parameters are more dependent on environmental factors than host adaptation. Warmer and drier conditions were significantly related with higher parasite infection prevalence and drier conditions with intensity, although the magnitude of the latter was dependant on host sex. The climatic trend observed during sampled years was of cooling conditions, congruent with the decrease in parasite infection parameters observed, although the lack of intermediate time points means it is unclear if this is a trend or just an isolated drop in prevalence. We also provide insights into a framework for using data obtained through different methodologies in linear model analyses, by homogenising the varying certainty of observations from different methods.