Presentation Detail

Ecological Genetics and/or Genomics

Jones, Matthew R [1], Cheviron, Zachary [2], Carling, Matthew [3].

Spatial variation in parasite-mediated selection on the major histocompatibility complex of a passerine.

Host-parasite interactions are often highly context-dependent. For example, parasite virulence or abundance and host immunogenetic resistance to pathogens can vary substantially by environment. The major histocompatibility complex (MHC) is an essential component of the vertebrate adaptive immune system, involved in pathogen recognition and immune response initiation. High allelic variability in MHC loci is believed to arise through one or several parasite-mediated selection mechanisms: heterozygote advantage, negative frequency-dependent selection, or fluctuating selection. In the latter case, the environment governs spatial or temporal variability in parasite diversity, virulence, or abundance, which creates a dynamic selection landscape on hosts. Investigating host-parasite systems across heterogeneous landscapes may provide insight into how parasite-mediated selection on host immune system genes is altered by environment. Avian malaria blood parasites occupy a wide range of environments and can infect birds at high rates. Rufous-collared Sparrows (Zonotrichia capensis) are broadly distributed, common Neotropical residents, which inhabit a wide variety of habitats. I investigated: 1) spatial patterns in avian malaria infection prevalence, including the environmental factors dictating prevalence, and 2) modes of parasite-mediated selection on Z. capensis MHC loci across environmental gradients. A PCR screening of avian malaria infection revealed mid-altitude peaks in infection prevalence for a single malaria lineage. Infection prevalence was strongly associated with temperature and precipitation variables related to seasonality. I employed next-generation 454 sequencing to investigate variation at Z. capensis MHC and found evidence for fluctuating spatial selection driving MHC variability. Specific MHC alleles and functional supertypes were strongly associated with infection resistance or susceptibility to infection. The effects of these alleles and supertypes varied substantially across altitudinal and latitudinal gradients. My research highlights the importance of considering host-parasite systems in the context of their external environment and suggests adaptation to parasites occurs at a local population level.

1 - University of Wyoming, Zoology and Physiology, 1000 E. University Ave., Laramie, Wyoming, 82071, USA
2 - University of Illinois, Animal Biology, 505 South Goodwin Ave., Urbana, IL, 61801, USA
3 - University of Wyoming, Zoology and Physiology, 1000 E. University Ave., Laramie, WY, 82071, United States

Keywords:
Adaptation
avian malaria
major histocompatibility complex
Natural selection
parasites.

Presentation Type: Regular Oral Presentation
Session: 26
Location: Cotton C/Snowbird Center
Date: Saturday, June 22nd, 2013
Time: 1:30 PM
Number: 26001
Abstract ID:374
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation