Date of Award
Master of Science
When a species is introduced outside their native range, the genetic diversity of the introduced population is generally decreased due to the founder effect, and the fitness of individuals in the introduced population may decrease due to inbreeding depression. Invasive species are a paradox to this paradigm because while the initial population size of an invasive species may be small in their non-native range, the individuals are able to survive, eat, and reproduce so successfully, that they have deleterious effects on native species. One mechanism that invasive species use to overcome a lack of genetic diversity and adapt to their new environment is CpG methylation, a heritable and environmentally influenced epigenetic modification that regulates the expression of certain genes to alter phenotypes without altering an organism’s DNA sequence.Bighead and silver carps, two species of bigheaded carp native to eastern Asia, are believed to have been introduced to the United States in the 1970s. Since that time, populations of both bighead and silver carp have surged, particularly in the Mississippi River drainage, where they compete with native planktivores for food, injure boaters, and threaten the multi-million dollar fisheries industry in the Great Lakes. In this study, methylation-sensitive amplified fragment length polymorphisms (MS-AFLPs) were used to analyze the genetic and epigenetic diversity of bighead and silver carp from the Gan, Pearl, and Yangtze rivers in their native China and from the Illinois River in the United States. While the heterozygosity of silver carp in Illinois was not found to be significantly lower than that of silver carp in China, the silver carp in Illinois did show a significantly higher level of methylation compared to Chinese silver carp. There is evidence that CpG methylation may play a significant role in allowing silver carp to adapt and thrive in an introduced environment.
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