Population genetic structure of the sidespot barb,Barbus neefi,from the north-eastern escarpment,South Africa

Allozyme analysis was used to determine patterns of genetic variation within and between populations of Barbus neefi. The products of 29 loci were analysed, with 17 loci being monomorphic in all populations. The genetic variability estimates compared well with values reported in the literature. The percentage of polymorphic loci (0.95 criterion) ranged from 0–20.69% and average expected heterozygosity from 0.004–0.069. Headstream populations generally revealed lower genetic variability than populations in low lying areas, which emphasizes the importance of conserving headstream populations. Fixed allele mobility differences were observed at the MPI-1 protein coding locus between the Selons River population and the other populations. The measures of genetic differentiation as assessed by F-statistics, the effective number of migrants per generation and Nei's unbiased genetic distance consistently separated the Selons River population from the rest. Nevertheless, these estimates all fell within the range considered for conspecific populations. There was also a clear genetic division between populations from north and south of the Olifants River. The three populations from the Dorps, Spekboom and Blyde Rivers (Limpopo River system) and the population from the Crocodile River (Incomati River system) showed negligible genetic differentiation. Human-assisted transfer of populations may be responsible for this close similarity.     

Analysis of genetic diversity in Glyptosternum maculatum (Sisoridae, Siluriformes) populations with AFLP markers

We determined the genetic diversity of geographic populations from three spawning grounds (Nyang River, Lhasa River, Shetongmon Reach of Yarlung Zangbo River) of Glyptosternum maculatum with amplified fragment length polymorphism (AFLP) markers. Five primer combinations detected 332 products, 51 of them (15.4%) were polymorphic in at least one population. The Shetongmon population was found to be the richest in genetic diversity as was indicated by the percentage of polymorphic loci and heterozygosity, followed by the Nyang population and the Lhasa population. The pair-wise genetic distance between populations were all very close, ranging from 0.0015 to 0.0042 with an average of 0.0024. The genetic distance was not proportional to the geographic distance. The analysis of molecular variance demonstrated that all variation occurred within populations. The average estimated fixation index (F _st) of three populations across all polymorphic loci was −0.0184, indicating the absence of genetic differences among the three sampled populations. The differentiation among populations was not significant, and population structure was weak. Our observations will help identify the genetic relationship among populations as the first approach to understand the genetic diversity of Glyptosternum maculatum.     

Genetic analysis of four wild chum salmon<Emphasis Type="Italic">Oncorhynchus keta</Emphasis> populations in China based on microsatellite markers

Synopsis To assess the genetic variation and population structure of wild chum salmon in China, we analyzed microsatellite loci for populations in the Amur, Wusuli, Suifen Current and the Tumen rivers. We evaluated expected heterozygosity with two estimators of genetic differentiation (F_ST and G_ST) and Nei’s standard genetic distance. The average expected heterozygosity across the 10 loci was 0.65 in the Wusuli River and the Suifen Current River, 0.64 in the Amur River and 0.66 in the Tumen River, The results of this study show that the recent declines in chum salmon have not led to low levels of genetic variability in China. The proportion of inter-population subdivision among chum salmon was between 5.7 and 6.8%. According to the estimator used, the NJ tree based on Nei’s standard genetic distance indicated that there were two different branches (the Sea of Okhotsk branch and the Sea of Japan branch), the Amur River and the Wusuli River populations were closer, while the Suifen Current River and the Tumen River clustered together. The genetic test for population bottlenecks provided no evidence for a significant genetic signature of population decline, which is consistent with the record of the four populations we have in the last few years.     

Conservation genetics of endangeredBrasenia schreberi based on RAPD and AFLP markers

Brasenia schreberi J.F. Gmelin is a declared endangered species found in the lakes and ponds of South Korea. For planning its conservation strategy, we examined the genetic diversity within and among six populations, using randomly amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP). Polymorphisms were more frequently detected per loci with AFLP (69.3%) than RAPD (36.8%). High genetic diversity was recognized within populations: polymorphic loci (PPL) values ranged from 36.3% in the CJM population to 74.5% in the GGT population, with a mean value of 47.8% based on AFLP markers. Great genetic differentiation (θ^B) was detected among the six populations (0.670 on RAPD and 0.196 on AFLP), and we calculated a low rate of gene flow (N_em), i.e., 0.116 on RAPD and 0.977 on AFLP. Furthermore, a Mantel test revealed that no correlation existed between genetic distances and geographical distances among the six local populations, based on RAPD or AFLP markers. These results are attributed to a number of factors, including an insufficient length of time for genetic diversity to be reduced following a natural decline in population size and isolation, adaptation of the genetic system to small population conditions, and a restricted gene flow rate. Based on both its genetic diversity and population structure, we suggest that a strategy for conserving and restoringB. schreberi must focus on maintaining historical processes, such as high levels of outbreeding, while monitoring increased gene flow among populations. This is because a reduction in genetic diversity as a result of genetic drift is undesirable.     

Genetic analyses of the federally endangered Echinacea laevigata using amplified fragment length polymorphisms (AFLP)—Inferences in population genetic structure and mating system

Echinacea laevigata (Boynton and Beadle) Blake is a federally endangered flowering plant species restricted to four states in the southeastern United States. To determine the population structure and outcrossing rate across the range of the species, we conducted AFLP analysis using four primer combinations for 22 populations. The genetic diversity of this species was high based on the level of polymorphic loci (200 of 210 loci; 95.24%) and Nei’s gene diversity (ranging from 0.1398 to 0.2606; overall 0.2611). There was significant population genetic differentiation (G_ST = 0.294; Ө^II = 0.218 from the Bayesian f = 0 model). Results from the AMOVA analysis suggest that a majority of the genetic variance is attributed to variation within populations (70.26%), which is also evident from the PCoA. However, 82% of individuals were assigned back to the original population based on the results of the assignment test. An isolation by distance analysis indicated that genetic differentiation among populations was a function of geographic distance, although long-distance gene dispersal between some populations was suggested from an analysis of relatedness between populations using the neighbor-joining method. An estimate of the outcrossing rate based on genotypes of progenies from six of the 22 populations using the multilocus method from the program MLTR ranged from 0.780 to 0.912, suggesting that the species is predominantly outcrossing. These results are encouraging for conservation, signifying that populations may persist due to continued genetic exchange sustained by the outcrossing mating system of the species.     

Assessing genetic diversity of wild populations of Prenantȁ9s schizothoracin, Schizothorax prenanti, using AFLP markers

Prenantȁ9s schizothoracin, Schizothorax prenanti, an endemic fish to China, has undergone a dramatic decline in numbers due to human impacts. We studied its genetic diversity in three tributaries of the Yangtze River: the Qingyi River, which has many hydropower dams, and the Dadu River and Muli River where many hydropower dams are being proposed. Using amplified fragment length polymorphism (AFLP), 621 loci were amplified with seven AFLP primer combinations in 45 individuals. The loci were highly polymorphic and heterozygous (87% polymorphism, 30% heterozygosity). The genetic distances within populations were large. The analysis of molecular variance demonstrated that most variation occurred within populations. The estimated fixation index (Φ_st) value averaged over all polymorphic loci across the three rivers was 0.0837, indicating a moderate genetic differentiation. The differentiations between populations were significant, and population structure was strong. The results suggested that China had wild populations of Prenantȁ9s schizothoracin with considerable genetic diversity in the Muli, Dadu and Qingyi rivers. The proposals to dam these rivers should take into account the importance of conserving their genetic quality.     

Microsatellite Variation in Two Populations of Free-Ranging Yellow Baboons (Papio hamadryas cynocephalus)

We investigated genetic variation at six microsatellite (simple sequence repeat) loci in yellow baboons (Papio hamadryas cynocephalus) at two localities: the Tana River Primate Reserve in eastern Kenya and Mikumi National Park, central Tanzania. The six loci (D1S158, D2S144, D4S243, D5S1466, D16S508, and D17S804) were all originally cloned from and characterized in the human genome. These microsatellites are polymorphic in both baboon populations, with the average heterozygosity across loci equal to 0.731 in the Tana River sample and 0.787 in the Mikumi sample. The genetic differentiation between the two populations is substantial. Kolmogornov–Smirnov tests indicate that five of the six loci are significantly different in allele frequencies in the two populations. The mean F _ST across loci is 0.069, and Shriver's measure of genetic distance, which was developed for microsatellite loci (Shriver et al., 1995), is 0.255. This genetic distance is larger than corresponding distances among human populations residing in different continents. We conclude that (a) the arrays of alleles present at these six microsatellite loci in two geographically separated populations of yellow baboons are quite similar, but (b) the two populations exhibit significant differences in allele frequencies. This study illustrates the potential value of human microsatellite loci for analyses of population genetic structure in baboons and suggests that this approach will be useful in studies of other Old World monkeys.     

Genetic diversity of common carp from two largest Chinese lakes and the Yangtze River revealed by microsatellite markers

Six polymorphic microsatellites (eight loci) were used to study the genetic diversity and population structure of common carp from Dongting Lake (DTC), Poyang Lake (PYC), and the Yangtze River (YZC) in China. The gene diversity was high among populations with values close to 1. The number of alleles per locus ranged from 2 to 11, and the average number of alleles among 3 populations ranged from 6.5 to 7.9. The mean observed (H _O) and expected (H _E) heterozygosity ranged from 0.4888 to 0.5162 and from 0.7679 to 0.7708, respectively. Significant deviations from Hardy–Weinberg Equilibrium expectation were found at majority of the loci and in all three populations in which heterozygote deficits were apparent. The analysis of molecular variance (AMOVA) indicated that the percent of variance among populations and within populations were 3.03 and 96.97, respectively. The Fst values between populations indicated that there were significant genetic differentiations for the common carp populations from the Yangtze River and two largest Chinese freshwater lakes. The factors that may result in genetic divergence and significant reduction of the observed heterozygosity were discussed.     

Assessment of genetic diversity and population structure of Chinese wild almond, Amygdalus nana, using EST- and genomic SSRs

Amygdalus nana L., commonly known as wild almond, is an endangered wild relative of cultivated almond, which has great potential in almond crop breeding. In this study, we used microsatellite (SSR) loci derived from both expressed sequence tag (EST) and anonymous genomic sequence to explore the genetic diversity and population structure of A. nana in Xinjiang of China. Seven natural populations were collected across the whole distribution of A. nana in China, including populations from both inside (four populations) and outside (three populations) the established protected areas. A total of 22 and 19 alleles were detected from the seven pairs of EST and genomic SSR loci, respectively. Generally, the genomic SSRs showed lower levels of variation than EST-SSRs, which may partially due to the higher cross-species transferability in EST-SSRs than in genomic SSRs. The population-level genetic diversity (A = 1.84, P = 50.00%, H_o = 0.3491, H_E = 0.2271) was lower than cultivated almond and several wild fruit species with similar breeding system. Most of the genetic variation (82.16%) was partitioned within populations. In particular, the population collected from Tacheng County (outside the protected areas) had the highest levels of genetic diversity and had significantly different genetic constitution from other populations.     

Genetic diversity and hierarchical population structure of a rare autotetraploid plant,Aster kantoensis (Asteraceae)

We sampled 17 populations of a rare autotetraploid Aster kantoensis (Asteraceae) from three river systems located in central Japan, and studied them for allelic variation at 22 enzyme loci. There was no significant correlation between the actual population size and three genetic diversity parameters, suggesting that the effective population size was very small even for the large populations, i.e., even large populations may still have a high probability of being of recent origin and remain influenced by the founder effect. Compared to other autotetraploid species, the total genetic variation of A. kantoensis is small. The number of alleles and gene diversity of a population were not significantly different among the river systems, although the percentage of polymorphic loci was different. Genetic differentiation among river systems was larger than between populations within the river systems, thereby indicating that gene flow between river systems is small, especially between the Kinu River system and Tama or Sagami River systems.     

Genetic variation in westslope cutthroat trout <Emphasis Type="Italic">Oncorhynchus clarkii lewisi</Emphasis>: implications for conservation

Twenty-five populations of westslope cutthroat trout from throughout their native range were genotyped at 20 microsatellite loci to describe the genetic structure of westslope cutthroat trout. The most genetic diversity (heterozygosity, allelic richness, and private alleles) existed in populations from the Snake River drainage, while populations from the Missouri River drainage had the least. Neighbor-joining trees grouped populations according to major river drainages. A great amount of genetic differentiation was present among and within all drainages. Based on Nei’s D _S , populations in the Snake River were the most differentiated, while populations in the Missouri River were the least. This pattern of differentiation is consistent with a history of sequential founding events through which westslope cutthroat trout may have experienced a genetic bottleneck as they colonized each river basin from the Snake to the Clark Fork to the Missouri river. These data should serve as a starting point for a discussion on management units and possible distinct population segments. Given the current threats to the persistence of westslope cutthroat trout, and the substantial genetic differentiation between populations, these topics warrant attention.     

Population Genetic structure ofPotentilla fragariodes var.major (Rosaceae) in Korea

The genetic diversity and population structure of eighteenPotentilla fragariodes var.major (Rosaceae) populations in Korea were determined using genetic variations at 22 allozyme loci. The percent of polymorphic loci within the enzymes was 66.7%. Genetic diversity at the species level and at the population level was high (Hes = 0.203; Hep = 0.185, respectively), whereas the extent of the population divergence was relatively low (G_ST = 0.069). F_IS, a measure of the deviation from random mating within the 18 populations, was 0.075. An indirect estimate of the number of migrants per generation (Nm = 3.36) indicated that gene flow was high among Korean populations of the species. In addition, analysis of fixation indices revealed a slight heterozygote deficiency in some populations and at some loci. Wide geographic ranges, perennial herbaceous nature and the persistence of multiple generations are associated with the high level of genetic variation. AlthoughP. fragariodes var.major usually propagated by asexually-produced ramets, we could not rule out the possibility that sexual reproduction occurred at a low rate because each ramet may produce terminal flowers. Mean genetic identity between populations was 0.983. It is highly probable that directional movement toward genetic uniformity in a relatively homogeneous habitat operates among Korean populations ofP. fragariodes var.major.     

BIOCHEMICAL GENETICS OF MOSQUITOFISH. IV. CHANGES OF ALLELE FREQUENCIES THROUGH TIME AND SPACE

Gene frequency data from samples of Gambusia affinis populations at 76 localities across the Savannah River drainage were used to investigate temporal and spatial patterns in population genetic structure. Localities in the Par Pond system on the Savannah River Plant were sampled in 1971, 1977, and 1979. Allelic frequencies in these populations were generally stable through time, although significant temporal changes were observed among samples from Pond C, an impoundment receiving thermal effluent. Significant spatial heterogeneity in allele frequencies was observed on both microgeographic and regional scales. Populations within the Par Pond system were spatially subdivided at four of the five loci surveyed (mean F_ST = 0.051). Subdivision was even more pronounced when samples from across the Savannah River drainage were compared (mean F_ST = 0.196). A hierarchial analysis of gene diversity (G_ST) demonstrated that most of the genic diversity across the drainage exists as within-subdivision diversity. Even when populations from such contrasting habitats as rivers, creeks, ponds, and reservoirs are compared, an average of only 13% of the total gene diversity was attributed to between-group diversity. Greatest between-group gene diversity was observed when reservoirs were compared with one another. This general pattern of low between-habitat diversity suggests that differential selection pressures are not playing a major role in producing the observed levels of subdivision. In the Par Pond system, neither single locus nor multilocus genetic distances were significantly associated with geographic distance or with its reciprocal. For samples from over the Savannah River drainage, significant correlations between genetic and geographic distance were observed only for the Gpi-2 and Pgm-2 loci. Thus, there was a general lack of concordance between genetic and geographic distances. Spatial autocorrelation demonstrated patterns consistent with Wright's isolation by distance model. Significant positive correlations in allelic frequencies among neighboring populations were observed for five of six alleles; allelic frequencies in more distantly separated populations were typically not correlated.     

Conservation genetics of bull trout: Geographic distribution of variation at microsatellite loci

We describe the genetic population structure of65 bull trout (Salvelinus confluentus)populations from the northwestern United Statesusing four microsatellite loci. Thedistribution of genetic variation as measuredby microsatellites is consistent with previousallozyme and mitochondrial DNA analysis. Thereis relatively little genetic variation withinpopulations (H ^S = 0.000 – 0.404,average H ^S = 0.186, but substantialdivergence between populations (F ^ST = 0.659). In addition, those populations that had low genetic variation forallozymes also tended to have low geneticvariation at microsatellite loci. Microsatellite analysis supports the existenceof at least three major geneticallydifferentiated groups of bull trout: (1)``Coastal' bull trout populations, (2) ``SnakeRiver' populations, which also include the JohnDay, Umatilla, and Walla Walla Rivers and, (3)populations from the upper Columbia River,primarily from the Clark Fork basin. Withinthe major assemblages, populations are furthersubdivided, primarily at the river basin level. Most of the genetic similarities we havedetected probably reflect patterns of historicisolation and gene flow. However, in somecases, genetic drift and low levels ofvariation appear to have influenced therelationships inferred from these data. Finally, we suggest using a hierarchicalapproach to direct management actions inspecies such as bull trout for which most ofthe genetic variation exists among populationsand local populations in close proximitytypically are genetically distinct.     

Population genetic structure of Bellamya aeruginosa (Mollusca: Gastropoda: Viviparidae) in China: weak divergence across large geographic distances

Bellamya aeruginosa is a widely distributed Chinese freshwater snail that is heavily harvested, and its natural habitats are under severe threat due to fragmentation and loss. We were interested whether the large geographic distances between populations and habitat fragmentation have led to population differentiation and reduced genetic diversity in the species. To estimate the genetic diversity and population structure of B. aeruginosa, 277 individuals from 12 populations throughout its distribution range across China were sampled: two populations were sampled from the Yellow River system, eight populations from the Yangtze River system, and two populations from isolated plateau lakes. We used seven microsatellite loci and mitochondrial cytochrome oxidase I sequences to estimate population genetic parameters and test for demographic fluctuations. Our results showed that (1) the genetic diversity of B. aeruginosa was high for both markers in most of the studied populations and effective population sizes appear to be large, (2) only very low and mostly nonsignificant levels of genetic differentiation existed among the 12 populations, gene flow was generally high, and (3) relatively weak geographic structure was detected despite large geographic distances between populations. Further, no isolation by linear or stream distance was found among populations within the Yangtze River system and no signs of population bottlenecks were detected. Gene flow occurred even between far distant populations, possibly as a result of passive dispersal during flooding events, zoochoric dispersal, and/or anthropogenic translocations explaining the lack of stronger differentiation across large geographic distances. The high genetic diversity of B. aeruginosa and the weak population differentiation are likely the results of strong gene flow facilitated by passive dispersal and large population sizes suggesting that the species currently is not of conservation concern.     

Microsatellite polymorphism and genetic differentiation in three Norwegian populations of Elymus alaskanus (Poaceae)

 Variation at seven microsatellite loci was investigated in three local E. alaskanus populations from Norway and microsatellite variation was compared with allozyme variation. The percentage of polymorphic loci was 81%, the mean number of alleles per polymorphic locus was 5.7 and expected heterozygosity was 0.37. An F-statistic analysis revealed an overall 48% deficit of heterozygotes over Hardy-Weinberg expectations. Gene diversity is mainly explained by the within population component. The averaged between population differentiation coefficient, F _st , over 7 loci is only 0.13, which accounts for only 13% of the whole diversity and was contrary to allozyme analysis. The mean genetic distance between populations was 0.12. However, a χ² -test showed that allele frequencies were different (p < 0.05) among the populations at 5 of the 7 loci. In comparison with the genetic variation detected by allozymes, microsatellite loci showed higher levels of genetic variation. Microsatellite analysis revealed that population H10576 possesses the lowest genetic variation among the tested three populations, which concur with allozyme analysis. The dendrogram generated by microsatellites agreed very well with allozymic data. Our results suggest that natural selection may be an important factor in shaping the genetic diversity in these three local E. alaskanus populations. Possible explanations for deficit heterozygosity and incongruence between microsatellites and allozymes are discussed. Received November 6, 2001; accepted April 24, 2002 Published online: November 14, 2002 Addresses of the authors: Genlou Sun (e-mail: Genlou.sun@STMARYS.CA), Biology Department, Saint Mary's University, Halifax. Nova Scotia, B3H 3C3, Canada. B. Salomon, R. von Bothmer, Department of Crop Science, The Swedish University of Agricultural Sciences, P.O. Box 44, SE-230 53, Alnarp, Sweden.     

Development of microsatellite markers for southern catfish (Silurus meriaionalis) and cross‐species amplification in northern sheatfish (Silurus soldatovi)

Forty microsatellite markers were developed from a (CA)_n enrichment library created from the DNA of southern catfish (Silurus meriaionalis). Also, the population structure of northern sheatfish (Silurus soldatovi) was examined by 24 microsatellite loci. They are polymorphic in at least one of the two geographically distant populations sampled from the Heilongjiang River and the Songhuajiang River in North China, respectively. Unbiased expected heterozygosity levels varied from 0.435 to 0.946 and number of alleles per locus varied from three to 20. Results indicated that these microsatellite loci were highly polymorphic and could be used as genetic markers.     

Population Structure and Stock Identification of Eulachon (Thaleichthys pacificus), an Anadromous Smelt, in the Pacific Northwest

The genetic structure of eulachon (Thaleichthys pacificus) populations was examined in an analysis of variation of 14 microsatellite loci representing approximately 1900 fish from 9 sites between the Columbia River and Cook Inlet, Alaska. Significant genetic differentiation occurred among the putative populations. The mean F_ST for all loci was 0.0046, and there was a significant correlation between population genetic differentiation (F_ST) and geographic distance. Simulated mixed-stock samples comprising populations from different regions suggested that variation at microsatellite loci provided reasonably accurate estimates of stock composition for potential fishery samples. Marine sampling indicated that immature eulachons from different rivers, during the 2 to 3 years of prespawning life in offshore marine waters, do not mix thoroughly. For eulachons captured incidentally in offshore trawl fisheries, there was a clear geographic cline in relative abundance of eulachons from different geographic areas. The sample from northern British Columbia was dominated by northern and central coastal populations of British Columbia, the sample from central British Columbia was composed of eulachons from all regions, and the sample from southern British Columbia was dominated by Columbia River and Fraser River populations. These results have implications for the management of trawl fisheries and conservation of spawning populations in some rivers where abundance is at historically low levels.     

The genetic diversity of wild Oreochromis mossambicus populations from the Mozambique southern watersheds as evaluated by microsatellites

Tilapia is native to Africa, and one of the most cultivated fish in the world. The goal of this research was to evaluate the genetic diversity of tilapia Oreochromis mossambicus from the Limpopo, Incomati, Umbeluzi and Sabié rivers in Mozambique. Microsatellite markers were used to assess the genetic structure and to compare the genetic variability of wild populations of O. mossambicus. DNA samples from 200 specimens were analyzed. All five loci (UNH104, UNH129, UNH142, UNH222 and UNH231) used in this study were polymorphic, with observed heterozygosity ranging from 0.940 to 1.000 and the allelic richness average (Ar) ranging from 8.937 to 15.751. All of the stocks exhibited a remarkably significant excess of heterozygosity relative to the Hardy‐Weinberg Equilibrium. Evidence of a genetic bottleneck was found in the four populations evaluated herein. The genetic structure of the population was investigated using the analogues F_ST and D_EST. The most genetic variability occurred within populations. Differentiation among populations ranged from low to moderate levels. No significant correlation was found between geographic and genetic distances. Implications of these findings for management and conservation of O. mossambicus stocks are discussed.     

A reintroduced lake sturgeon population comes of age: A genetic evaluation of stocking success in the St. Louis River

Lake sturgeon (Acipenser fulvescens) have experienced significant declines throughout the Great Lakes, leading to stocking efforts at some locations to reestablish extirpated populations. Given the late sexual maturity of the species, assessment of stocking program success is often delayed. Lake sturgeon were extirpated from the St. Louis River in western Lake Superior. Stocking began in 1983 and continued until 1994, using the Wolf River (Lake Winnebago) in the Lake Michigan basin as the source. Stocking resumed from 1998 to 2000, using the Sturgeon River in Lake Superior as the source. Our objectives were to (a) determine the movement patterns of stocked Wolf River sturgeon, (b) determine whether stocked individuals are migrating into natural spawning populations during the spawning season, (c) identify the origins of individuals captured in the St. Louis River, and (d) assess the genetic diversity of the reintroduced St. Louis River population. All collected samples were analyzed using 12 microsatellite loci, followed by genetic assignment testing to achieve the first three objectives. Genetic diversity was compared to natural spawning populations in Lake Superior. The highest proportion of stocked Wolf River lake sturgeon was detected in western Lake Superior, close to the stocking site. However, individuals were detected throughout Lake Superior. Wolf River individuals were detected in most of the spawning populations in Lake Superior, with the greatest number in the Sturgeon River and the Goulais River. The majority of individuals captured in the St. Louis River were of stocked origin (88.1%), with 73.5% from the Wolf River and 14.6% from the Sturgeon River. These observed proportions differed from the expected proportions based on the number of sturgeon released from each source (χ² = 55.37, p < 0.00001), with a higher representation of Sturgeon River individuals. Evidence of natural recolonization in the St. Louis River was detected from Lake Huron and Goulais River individuals. Genetic diversity of the St. Louis River population was comparable to levels observed in the remnant natural populations in Lake Superior. However, the effective population size of the St. Louis River was small (N_e = 38.1) and average relatedness among individuals was relatively high (r = 0.151). Monitoring of movement of stocked Wolf River sturgeon throughout Lake Superior should continue, with careful attention to the potential for outbreeding depression in remnant populations. Genetic diversity of the St. Louis River population should also continue to be monitored to see if it improves with increased natural reproduction.