Date of Graduation
Davis College of Agriculture, Natural Resources and Design
Wildlife and Fisheries Resources
Amy B Welsh
Lake sturgeon are large, freshwater fish and the only species of sturgeon native to the Great Lakes. Their historic range extends from the Hudson Bay, down through the Great Lakes and into the Mississippi River basin. In the early 1900's, sturgeon became a valuable fishery and were soon overfished for both meat and caviar. This, in combination with damming, pollution, and habitat degradation, caused a drastic decline in their population. Some populations were extirpated, while others have been reduced to 1% of their historic population size (Auer, 1996). The St. Clair-Detroit River System (SCDRS) hosts one of the largest lake sturgeon populations in the Great Lakes, despite habitat degradation. This system has no dams and provides an excellent study site to understand both population structure and the movements of an unimpeded population. The lake sturgeon in the SCDRS appear to have fine-scale genetic structure. Lake sturgeon were grouped according to sampling location (upper St. Clair, lower St. Clair, and Detroit Rivers). Bayesian analysis, implemented by the program STRUCTURE, revealed that there are two clusters (K =2) within the SCDRS. The FST values calculated for the sampling locations showed that the upper St. Clair River is genetically differentiated from the lower St. Clair River (F ST = 0.0135, p=0.02). Additionally, results from the discriminant analysis of principal components showed moderate clustering of the sampling locations. Lake sturgeon in the SCDRS exhibit partial migration with some individuals migrating from lakes to rivers and others inhabiting the rivers year-round. An integrative approach employing morphometrics, genetic and epigenetic techniques was used to characterize the migratory phenotypes. Based on telemetry data, fish were grouped according to migratory phenotype and then analyzed for differences in morphometrics, genetics, and epigenetics. The principal components analysis, performed on 18 morphological features, did not support the hypothesis that there are morphological differences between lake sturgeon (n=63; 38 residents, 27 migrants). To identify a genetic component to the variation in migratory phenotypes, a subset of those samples (n=41; 19 residents, 22 migrants) were analyzed at 11 microsatellite loci. Bayesian analysis revealed that there is one population, indicating gene flow between the migratory phenotypes. The FST value calculated to determine genetic differentiation between migratory phenotypes was 0.0148 (p=0.11), which is interpreted as no genetic differentiation between the two groups. DNA extractions from blood samples were analyzed using the methylation sensitive amplified fragment length polymorphism (MS-AFLP) protocol to test for epigenetic differences. The AMOVA performed on all restriction sites (81) showed that the migratory phenotypes are differentially methylated (p≤0.05). The AMOVA performed on individual restriction sites showed that 13 were differentially methylated. Using BayeScan, restriction sites were tested for deviation from a neutral model of selection, and none of these sites were determined to be under selection. While there is no evidence for a genetic component to the migratory phenotypes of lake sturgeon in the SCDRS, DNA methylation may play a role in the observed plasticity of movement patterns.
Whitaker, Justine, "Migratory Genomics of Lake Sturgeon" (2016). Graduate Theses, Dissertations, and Problem Reports. 6941.