Constanza Napolitano¹ | Irene Sacristán² | Francisca Acuña³ | Emilio Aguilar³ | Sebastián García³ | María José López-Jara³ | Javier Cabello⁴ | Ezequiel Hidalgo-Hermoso⁵ | Warren E. Johnson⁶ | Catherine Grueber⁷ | Elie Poulin⁸

1. Departamento de Ciencias Biológicas y Biodiversidad, Universidad de Los Lagos, Osorno, Chile; 2. PhD Program in Conservation Medicine, Universidad Andres Bello, Santiago, Chile; 3. FAVET, Universidad de Chile, Santiago, Chile; 4. Centro de Conservación de la Biodiversidad Chiloé Silvestre, Ancud, Chile; 5. Conservation and Research Department (CIBZ), Parque Zoológico Buin Zoo, Buin, Chile; 6. Smithsonian Institution, Suitland, Maryland, USA; 7. School of Life and Environmental Sciences, Faculty of Science, University of Sydney, Sydney, Australia; 8. Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile.

Ponente: Constanza Napolitano, constanza.napolitano@ulagos.cl

Investigating functional genetic diversity at the major histocompatibility complex (MHC), responsible for vertebrate immune response, is key to understanding the evolutionary and adaptive potential of populations or species in the face of emerging infectious disease threats. Variation at MHC loci is partly maintained by balancing selection driven by pathogenic selective pressures, differentially spread across the landscape. We hypothesize that genetic diversity and signatures of selection differ between populations inhabiting human-dominated landscapes with higher pathogen pressures and those inhabiting more pristine habitats. We characterized for the first time the genetic diversity at MHC class I and II genes in 128 guignas (Leopardus guigna) from their whole distribution range in Chile (32-46 º S) and a few animals from a small strip of land in Argentina, sampled across landscapes with differential human disturbance and using Illumina next-generation sequencing. We found evidence of positive selection acting over MHC class I exon 3 and MHC class II-DRB exon 2. Significantly higher genetic diversity (MHC class I exon 3) was found in guignas from human-disturbed landscapes, associated with the presence of houses and with a higher number of houses, compared to continuous forest landscapes. We found significantly higher genetic diversity (MHC Class I exon 2) in animals both infested and harboring a higher intensity of infection with cardiorespiratory helminths, and in those with higher helminth species richness. We found no statistically significant associations among microparasites infection status (FeLV, FIV, hemoplasmas, Carnivore protoparvovirus-1) and MHC diversity. Our results suggest that pathogen selection forces are dominating over neutral genetic processes (drift) for guigna MHC diversity. Guigna populations inhabiting human-dominated landscapes with high (non-vaccinated) domestic cat and dog densities may have higher exposure to pathogens. The medium to high MHC genetic diversity described here is advantageous for the persistence of guigna populations.