Thesis
HOW DOES GENOMIC VARIATION EVOLVE IN ASEXUAL POPULATIONS AFTER AN INVASION EVENT?
Washington State University
Master of Science (MS), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000005496
Handle:
https://hdl.handle.net/2376/118976
Abstract
Genetic variation is typically associated with the ability to establish a population in a newenvironment. Most invasion events should be relatively unsuccessful because population
bottlenecks reduce genetic variation. This reduction in genetic variation makes new populations
susceptible to parasites, disease, and the loss of beneficial variants. Invasive asexual species pose
an interesting case as their populations are often presumed to be genetically depauperate and
encounter more genetic “challenges”. To establish a new population, they must also overcome
the accumulation of deleterious mutations and clonal interference. Despite this, many asexual
species have become highly invasive. We asked the question; how does genomic variation
evolve in asexual populations after invasion? To answer this question, we investigated genomic
variation within North American populations of the highly invasive asexual snail, Potamopygrus
antipodarum (New Zealand Mud Snail). The New Zealand Mud Snail is a parthenogenetic
freshwater species that originally invaded Idaho’s Snake River in 1987. To determine how their
genomes have changed post invasion, we aligned previously sequenced methylated DNA
immunoprecipitation reads to a reference transcriptome for two old (river) sites and three new
iv
(lake) sites. We then called single nucleotide polymorphisms (SNPs) to quantify genomic
diversity, identify population substructure, and investigate invasion history. To quantify genomic
diversity, we calculated population mutation rate (θ) and nucleotide diversity (π). We used
hierarchical F statistics to investigate how genetic variation was structured. Lastly, we analyzed
allele frequency spectra and calculated Tajima’s D to investigate invasion history. We found that
all populations had a similar amount of nucleotide diversity (.354 -.379) and a similar population
mutation rate (.038-.065). Variation was structured at the site level (FST =.497), and all pairwise
FST comparisons showed genetic differentiation (FST > .15). Recent bottlenecks were inferred
from the allele frequency spectra of all populations. This result was supported by Tajima’s D
values which were all positive (.941 - 1.40). We found North American populations of P.
antipodarum to have high levels of genetic variation and were genetically differentiated. We
believe this research highlights the importance of testing for genetic diversity in invasive
populations before assuming a lack of genetic variation.
Metrics
7 File views/ downloads
30 Record Views
Details
- Title
- HOW DOES GENOMIC VARIATION EVOLVE IN ASEXUAL POPULATIONS AFTER AN INVASION EVENT?
- Creators
- Harrison Anthony
- Contributors
- Mark Dybdahl (Advisor)Jeremiah Busch (Committee Member)Omar Cornejo (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Biological Sciences
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 55
- Identifiers
- 99900592159101842
- Language
- English
- Resource Type
- Thesis