Award Abstract # 1404521
DISSERTATION RESEARCH: The impact of ecological traits on the immunogenetic evolution of bats

NSF Org: DEB
Division Of Environmental Biology
Recipient: THE LELAND STANFORD JUNIOR UNIVERSITY
Initial Amendment Date: May 17, 2014
Latest Amendment Date: May 17, 2014
Award Number: 1404521
Award Instrument: Standard Grant
Program Manager: Samuel Scheiner
DEB
 Division Of Environmental Biology
BIO
 Directorate for Biological Sciences
Start Date: June 1, 2014
End Date: September 30, 2017 (Estimated)
Total Intended Award Amount: $20,822.00
Total Awarded Amount to Date: $20,822.00
Funds Obligated to Date: FY 2014 = $20,822.00
History of Investigator:
  • Elizabeth Hadly (Principal Investigator)
    hadly@stanford.edu
  • Hannah Frank (Co-Principal Investigator)
Recipient Sponsored Research Office: Stanford University
450 JANE STANFORD WAY
STANFORD
CA  US  94305-2004
(650)723-2300
Sponsor Congressional District: 16
Primary Place of Performance: Stanford University
371 Serra Mall
Stanford
CA  US  94305-5020
Primary Place of Performance
Congressional District:
16
Unique Entity Identifier (UEI): HJD6G4D6TJY5
Parent UEI:
NSF Program(s): EVOLUTIONARY ECOLOGY
Primary Program Source: 01001415DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 9169, 9179, EGCH, SMET
Program Element Code(s): 737700
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.074

ABSTRACT

How an organism interacts with its environment influences its exposure to disease; in response, organisms have evolved a variety of immune responses. However, there have been few inquiries into the effect of ecology on the evolution of immune genes outside of primates. In this study we will examine the effect of ecological traits on the evolution of immune genes in bats. Bats are an ideal system because, as the second largest mammalian order, they exhibit a wide variety of diets, roost habits, group sizes and mating systems and host numerous viruses, bacteria and eukaryotic parasites. This work will help identify which ecological traits put groups at the greatest disease risk and shed light on how bats survive infection by pathogens that are lethal to humans. The findings of this research will assist conservationists in preserving species of concern and the ecosystem services they provide. The results will also be directly useful to the public health community and reveal potential targets for disease intervention research.

The researchers will test whether the immune genes of bats that frequently contact other bats or come into contact with other animals are evolving under greater pressure than those with lower disease risk (less contact). They will sequence multiple immune genes from multiple species, with a focus on the ecologically diverse Neotropical bat family Phyllostomidae. Using targeted sequence capture and next generation sequencing techniques, they will obtain information from multiple immune genes, representing both the innate and adaptive immune system and responses to viruses and extracellular pathogens. The genetic information collected will be combined with ecological data while accounting for evolutionary history to discover how bats have evolved their immunity in response to the pathogens of their environment. The examination of multiple immune genes will allow a more comprehensive characterization of immune evolution than single gene studies, reducing the risk of missing positive selection that does not act on certain genes and demonstrating general patterns in ecologically relevant immunogenetic evolution. The particular residues under selection revealed by this study will become important targets for functional studies into the exact nature of the coevolutionary arms race between bats and their pathogens.

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

This project sought to understand the impact of ecological traits on immunogenetic evolution by examining multiple immune genes in different lineages of bats. Bats are the second largest order of mammals, are ecologically diverse and are important for ecosystem function. They are also the reservoirs of a number of emerging diseases and many species are of conservation concern. The researchers analyzed nine bat genomes and amplified 200 genes for proteins known to interact with pathogens in 70 species of bats, spanning most of the globe and most of the evolutionary diversity of bats. Using molecular evolution techniques and ecological statistics, the researchers found that bats whose range overlaps the ranges of more other bat species are under greater pressure to adapt to viruses than bats in less bat species rich areas. This indicates that, evolutionarily, viral sharing appears to have been important for bats and their molecular evolution. Additionally, bats are under strong pressure to adapt to specific viral groups such as coronaviruses. Based on evidence from Toll-like receptors (TLRs), a group of receptors found across vertebrates that recognize highly conserved patterns on pathogens, bats were under strong pressure early in their evolution to recognize single-stranded RNA, especially lineages in areas with many bat species. If bats evolved early to resist pathogens, this may help explain the unique relationship between bats and many single-stranded RNA viruses (e.g. SARS, Ebola, Marburg fever, Hendra, Nipah) that cause lethal disease in humans but not bats.

Despite clear evidence that a species’ ecology shapes its disease risk, studies on the effect of ecology on the macroevolution of multiple immune genes are lacking in taxa outside of primates. Investigating how differences in ecology mediate immunogenetic evolution is important for understanding patterns of disease risk and the nature of coevolutionary relationships. This study has yielded information about the ecological and biogeographical traits that put groups at the greatest disease risk, with potential to shed light on how bats remain asymptomatic in the face of pathogens that kill humans. The particular residues under selection revealed by this study can be explored as targets for functional studies into the exact nature of the coevolutionary arms race between bats and their pathogens.

Significant research effort has been devoted to understanding the host and viral attributes that predict spillover. This study offers evolutionary insight about the ecological and biogeographical factors that put bat lineages under the greatest pathogen pressure. These findings may be useful to both the conservation and public health communities as they help identify the bat lineages most at risk for infection and the traits that affect this risk. Results of this work have been disseminated via public outreach events, a dissertation defense seminar and at scientific meetings and will be further publicized upon publication. This research has facilitated the training and professional development of three female graduate students and two postdoctoral fellows in addition to the Co-PI. 


Last Modified: 12/29/2017
Modified by: Hannah Frank

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