Thesis
Spatial variation in selection and multivariate estimates of local adaptation in a salamander-virus system
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/104001
Abstract
It is expected that pathogens should be locally adapted to their hosts because of higher evolutionary and reproductive rates and shorter generation times. We chose four Ambystoma tigrinum virus (ATV) strains and their sympatric salamander hosts (Ambystoma tigrinum) to test for the presence of local adaptation in a fully crossed infection experiment. Infectivity has been the sole measure of local adaptation in most studies though it does not measure pathogen fitness in its complexity. Our study incorporated four measures of pathogen fitness including infectivity, within host growth, virulence, and transmission. We combined two analysis methods to identify local adaptation: "local vs. foreign" and "home vs. away" as both discern local adaptation in unique ways. As host- pathogen interactions vary across space, different patterns of selection can lead to trait divergence and local adaptation. We chose viral strains from different selection regimes based on putative pathogenesis genes to assess the affect the strength of selection had on local adaptation. We predicted that strains under weak selection would be locally adapted or ahead of their sympatric hosts, while those under strong selection would be locally maladapted or "lagging" behind their sympatric hosts. Infectivity alone was a misleading determinant of pathogen local adaptation. Nearly all ATV strains appeared locally adapted based on infectivity while other measures of pathogen fitness suggested local maladaptation. When coupled, the two analysis methods gave a clearer picture of the interaction than when used independently. Using these combined analysis methods, we found that the strength of selection appears to affect local adaptation in the predicted manner. The viral strain under weak selection and that under intermediate selection appeared to be locally adapted to their sympatric hosts. The strain under strong selection appeared to be locally maladapted to its sympatric host, which is indicative of the pathogen experiencing a lag as the host is temporarily ahead. Our data capture a specific moment in time of the interaction between ATV strains and their sympatric hosts, so the observed range of states of local adaptation may be an expected outcome.
Metrics
2 File views/ downloads
7 Record Views
Details
- Title
- Spatial variation in selection and multivariate estimates of local adaptation in a salamander-virus system
- Creators
- Karen M. Chojnacki
- Contributors
- Andrew T. Storfer (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Sciences, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525295101842
- Language
- English
- Resource Type
- Thesis