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CHAPTER THREE Parasitism in the Endemic Galápagos Dove (Zenaida galapagoensis) and Its Relation to Host Genetic Diversity and Immune Response Diego Santiago-Alarcon, Robert E. Ricklefs, and Patricia G. Parker Abstract. Studies on model organisms have shown that individuals with lower genetic diversity are more susceptible to pathogens and suffer greater fitness costs than less inbred individuals. We investigated how genetic diversity, immune response, and parasitism by one hemosporidian parasite (Haemoproteus multipigmentatus) and two chewing lice (Columbicola macrourae and Physconelloides galapagensis) are related to the body condition of endemic Galápagos Doves (Zenaida galapagoensis) in six island populations. We hypothesized that (1) host genetic diversity would be negatively related to parasite abundance , (2) genetic diversity would be positively related to body condition of birds, (3) immune response would be positively related to blood parasite intensity but not to louse abundance, (4) alternatively, higher blood parasite intensity generates increased immunosuppression, leading to a lower white blood cell count and indirectly to a lower body condition, and (5) the abundances of the three parasite species would be positively correlated. Genetic diversity measured at eight microsatellite loci was an exogenous variable in the path analysis and explained 58% of the variation in body condition. Our results suggest that genetic diversity directly enhances body condition and indirectly depresses parasite abundance ; this pattern was the same for the three parasite species, although it was not significant for C. macrourae. The best model suggested that blood parasites increase the activation of the immune system (measured as white blood cell counts), which may indicate an attempt of the host to control infection. Key Words: avian diseases, Columbiformes, Galápagos , genetic diversity, Haemoproteus, immune function, Phthiraptera, Zenaida galapagoensis. Parasitísmo en la Paloma Endémica de Galápagos (Zenaida galapagoensis) y su Realción con la Diversidad Genética y la Respuesta Inmune del Huésped Resumen. Estudios efectuados en organismos de laboratorio han mostrado que los individuos que tienen una menor diversidad genética son más susceptibles a diferentes tipos de patógenos , y al mismo tiempo sufren un mayor costo de salud en comparación a los individuos que presentan mayor diversidad genética. Investigamos como la diversidad genética, la respuesta inmune, y el parasitísmo por un parásito de sangre (Haemoproteus multipigmentatus) y dos especies de piójos (Columbicola macrourae y Physconelloides galapagensis) se relacionan con la condición del cuerpo de las palomas endémicas Santiago-Alarcon,D.,R.E.Ricklefs,andP.G.Parker.2012.ParasitismintheendemicGalápagosDove(Zenaidagalapagoensis) and its relation to host genetic diversity and immune response. Pp. 31–42 in E. Paul (editor). Emerging avian disease. Studies in Avian Biology (vol. 42), University of California Press, Berkeley, CA. 31 STUDIES IN AVIAN BIOLOGY NO. 42 Paul 32 exógena en el análisis de vías y explicó el 58% de la variación en la condición del cuerpo. Los resultados del análisis de vías sugieren que la diversidad genética mejora la condición del cuerpo e indirectamente disminuye la intensidad o abundancia de los parásitos; este patrón fue el mismo para las tres especies de parásitos, aunque no fue significativo para C. macrourae. El mejor modelo de análisis de vías sugiere que los parásitos de sangre activan el sistema inmune al incrementar los niveles en los conteos de células blancas, lo cuál puede indicar una reacción del huésped para intentar controlar la infección. Palabras Clave: Columbiformes, diversidad genética, enfermedades aviar, función inmune, Galápagos, Haemoproteus, Phthiraptera, Zenaida galapagoensis. responses of the host. Whiteman et al. (2006) studied island populations of the endemic Galápagos Hawk (Buteo galapagoensis) and found that the more inbred populations had lower and more variable natural antibody levels. Furthermore, natural antibody levels explained the abundance of the louse Colpocephalum turbinatum, which directly interacts with the host immune system when feeding on blood; hawks with higher natural antibody titers had lower abundances of the parasite (Whiteman et al. 2006). Interactions between antibodies and infection were not observed for the louse Degeeriella regalis, which feeds only on feathers, dead skin, and keratin and thus does not interact with the host immune system (Whiteman et al. 2006). Parasites affect the condition of hosts, especially when infection intensities are high (Brown et al. 1995, Merino et al. 2000, Marzal et al. 2005). Feather mass is reduced when lice intensities are high; this can impose an energetic cost that directly impacts...

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