Biological invasions by exotic species impose substantial ecological, economic and social costs worldwide, being a major threat to biodiversity conservation. Because not all individuals introduced in the new environments become successful invaders, the identification of factors underlying variation in invasion success would be essential for evaluating invasion risk. Here, we test several host–parasite hypotheses accounting for invasion success of house sparrows Passer domesticus in Peru. According to the Enemy Release Hypothesis, invasive house sparrows from Peru showed lower prevalence and genetic diversity of haemosporidian parasites than sparrows from their natural range (Spain), indicating that the release from their natural parasites may have favoured the spread of sparrows in the new area of occurrence. We also showed that Peruvian sparrows had larger uropygial glands and higher anti‐bacterial activity in its secretion than sparrows from Spain, suggesting selection in defensive mechanisms driven by pathogens when colonizing new environments. Finally, we showed that uninfected sparrows had larger uropygial glands and higher anti‐bacterial activity than malaria‐infected house sparrows, implying that uropygial gland secretions may act as a defensive mechanism against haemosporidian infections. Alternatively, a condition‐dependent trade‐off exists between synthesis of uropygial secretion and immune response. These outcomes provide essential information for identifying potential invaders and designing interventions.
Chlamydiaceae bacteria infect many vertebrate hosts, and previous reports based on polymerase chain reaction (PCR) assays and serologic assays that are prone to cross-reaction among chlamydial organisms have been used to describe the prevalence of either DNA fragments or antibodies to Chlamydia spp. in wild raptorial populations. This study reports the PCR-based prevalence of Chlamydiaceae DNA that does not 100% match any avian or mammalian Chlamydiaceae in wild populations of hawks in California Buteo species. In this study, multimucosal swab samples ( n = 291) for quantitative PCR (qPCR) and plasma ( n = 78) for serology were collected from wild hawks. All available plasma samples were negative for antibodies using a C. psittaci-specific elementary body agglutination test (EBA; n = 78). For IgY antibodies all 51 available samples were negative using the indirect immunofluorescent assay. The overall prevalence of Chlamydiaceae DNA detection in wild Buteo species sampled was 1.37% (4/291) via qPCR-based analysis. Two fledgling Swainson's hawks ( Buteo swainsoni) and two juvenile red-tailed hawks ( Buteo jamaicensis) were positive by qPCR-based assay for an atypical chlamydial sequence that did not 100% match any known C. psittaci genotype. Positive swab samples from these four birds were sequenced based on the ompA gene and compared by high-resolution melt analysis with all known avian and mammalian Chlamydiaceae. The amplicon sequence did not 100% match any known avian chlamydial sequence; however, it was most similar (98.6%) to C. psittaci M56, a genotype that is typically found in muskrats and hares. Culture and full genome sequence analysis of Chlamydia spp. isolated from diseased hawks will be necessary to classify this organism and to better understand its epizootiology and potential health impact on wild Buteo populations in California.
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