Variation in the prevalence and abundance of mites parasitizing Abrothrix olivacea (Rodentia) in the native forest and Pinus radiata plantations in central Chile

This study aimed to assess the association between habitat type, season, and host density, sex, mass, and body condition with the parasitism (i.e., prevalence and abundance) of two taxa of parasitic mites: Ornithonyssus sp. and Androlaelaps sp. (Mesostigmata) parasitising Abrothrix olivacea (Cricetidae). This study considered habitat types, including both the native forest of westerncentral Chile (NF) and the surrounding pine plantation, which were sub-grouped as adult pine with an abundant understory (AP), young pine with an abundant understory (YPWU), and young pine plantation with a scarce or null understory (YPNU). Rodents were sampled during seasonal trapping sessions in the Los Queules National Reserve (Chile) and in the surrounding pine plantations. The association of these factors with the presence and abundance of mites was assessed with logistic and negative binomial regressions, respectively. Among 484 captured rodents, the prevalence of Ornithonyssus sp. (n=2445 mites) was 70.87%, and that of Androlaelaps sp. (n=182) was 16.1%. Parasitism by Ornithonyssus sp. was higher in plantations than in NF, and it featured seasonal and host sex-associated variation. The parasitism of Androlaelaps sp. in plantations was not significantly different from that in the NF, and only seasonal variation was significant. When comparing YPWU and YPNU, the parasitism of Ornithonyssus sp. was higher in YPWU, and that of Androlaelaps sp. was higher in YPNU. The effect of habitat depended on mite species, as the effect was stronger in Ornithonyssus. Host density was not significantly associated after correcting for habitat and season; this consideration was not frequently found in previous studies. There is a different effect of habitat type for each mite species, and the results also suggest an effect of the understory on the parasitism of each mite species.