Geology topics

C.O. Ostberg

Publications and source records attributed to C.O. Ostberg.

8 recordsLinked to original sources

USGS2011

Hybridization and cytonuclear associations among native westslope cutthroat trout, introduced rainbow trout, and their hybrids within the Stehekin River drainage, North Cascades National Park

Historic introductions of nonnative rainbow trout Oncorhynchus mykiss into the native habitats of cutthroat trout O. clarkii have impacted cutthroat trout populations through introgressive hybridization, creating challenges and concerns for cutthroat trout conservation. We examined the effects of rainbow trout introductions on the native westslope cutthroat trout O. c. lewisii within the Stehekin River drainage, North Cascades National Park, Washington, by analyzing 1,763 salmonid DNA samples from 18 locations with nine diagnostic nuclear DNA markers and one diagnostic mitochondrial DNA (mtDNA) marker. Pure westslope cutthroat trout populations only occurred above upstream migration barriers in the Stehekin River and Park Creek. Two categories of rainbow trout admixture were observed: (1) less than 10% within the Stehekin River drainage above the Bridge Creek confluence and the middle and upper Bridge Creek drainage and (2) greater than 30% within the Stehekin River below the Bridge Creek confluence and in lower Bridge Creek. Hybrid indices and multilocus genotypes revealed an absence of rainbow trout and reduced hybrid diversity within the Stehekin River above the Bridge Creek confluence relative to hybrid diversity in the Stehekin River below the confluence and within lower Bridge Creek. Cytonuclear disequilibrium statistics revealed assortative mating between westslope cutthroat and rainbow trout but not among hybrids within the same locations. This suggests that a randomly mating hybrid swarm does not currently exist. However, continual migration of parental genotypes into the study location could also create significant cytonuclear disequilibria. The Stehekin River represents a novel and unique example of a dynamic hybridization zone where the invasion of rainbow trout alleles into the Stehekin River westslope cutthroat trout population above the Bridge Creek confluence appears to be impeded, suggesting that divergent ecological or evolutionary mechanisms promote the population structure within the Stehekin River drainage, depending upon location.

Washington↗

USGS2011

Evolutionary relationships among sympatric life history forms of Dolly Varden inhabiting the landlocked Kronotsky Lake, Kamchatka, and a neighboring anadromous population

We investigated the evolutionary relationships among five sympatric morphs of Dolly Varden Salvelinus malma (white, Schmidti, longhead, river, and dwarf) inhabiting landlocked Kronotsky Lake on the Kamchatka Peninsula, Russia, and an anadromous population below the barrier waterfall on the outflowing Kronotsky River. Morphological analyses indicated phenotypic differentiation corresponding to preferred habitat, the longhead (a limnetic piscivorous morph) having a fusiform body, long jaw, and short fins and the Schmidti (a benthic morph) having a robust body, small jaw, and long fins. Analysis of molecular variance among the Kronotsky Lake morphs indicated that contemporary gene flow is restricted both among morphs within locations and among locations within morphs. Gene flow from Kronotsky Lake into the anadromous population also appears to be restricted. Our findings indicate that there are two divergent evolutionary lineages, one consisting of the white, Schmidti, river, and dwarf morphs and the other of the longhead morph and the anadromous population, which suggests that Kronotsky Lake was subject to separate waves of immigration. The Kronotsky Lake Dolly Varden morphs may represent an example of ecological speciation in progress, and we present a working hypothesis for the diversification of morphs within Kronotsky Lake.

Transactions of the American Fisheries Society↗

USGS2011

Growth, morphology, and developmental instability of rainbow trout, Yellowstone cutthroat trout, and four hybrid generations

Hybridization of cutthroat trout Oncorhynchus clarkii with nonindigenous rainbow trout O. mykiss contributes to the decline of cutthroat trout subspecies throughout their native range. Introgression by rainbow trout can swamp the gene pools of cutthroat trout populations, especially if there is little selection against hybrids. We used rainbow trout, Yellowstone cutthroat trout O. clarkii bouvieri, and rainbow trout × Yellowstone cutthroat trout F1 hybrids as parents to construct seven different line crosses: F 1 hybrids (both reciprocal crosses), F 2 hybrids, first-generation backcrosses (both rainbow trout and Yellowstone cutthroat trout), and both parental taxa. We compared growth, morphology, and developmental instability among these seven crosses reared at two different temperatures. Growth was related to the proportion of rainbow trout genome present within the crosses. Meristic traits were influenced by maternal, additive, dominant, overdominant, and (probably) epistatic genetic effects. Developmental stability, however, was not disturbed in F 1 hybrids, F 2 hybrids, or backcrosses. Backcrosses were morphologically similar to their recurrent parent. The lack of developmental instability in hybrids suggests that there are few genetic incompatibilities preventing introgression. Our findings suggest that hybrids are not equal: that is, growth, development, character traits, and morphology differ depending on the genomic contribution from each parental species as well as the hybrid generation.

Transactions of the American Fisheries Society↗

USGS2004

Spatial partitioning and asymmetric hybridization among sympatric coastal steelhead trout (Oncorhynchus mykiss irideus), coastal cutthroat trout (O. clarki clarki) and interspecific hybrids

Hybridization between sympatric species provides unique opportunities to examine the contrast between mechanisms that promote hybridization and maintain species integrity. We surveyed hybridization between sympatric coastal steelhead (Oncorhynchus mykiss irideus) and coastal cutthroat trout (O. clarki clarki) from two streams in Washington State, Olsen Creek (256 individuals sampled) and Jansen Creek (431 individuals sampled), over a 3-year period. We applied 11 O. mykiss-specific nuclear markers, 11 O. c. clarki-specific nuclear markers and a mitochondrial DNA marker to assess spatial partitioning among species and hybrids and determine the directionality of hybridization. F1 and post-F1 hybrids, respectively, composed an average of 1.2% and 33.6% of the population sampled in Jansen Creek, and 5.9% and 30.4% of the population sampled in Olsen Creek. A modest level of habitat partitioning among species and hybrids was detected. Mitochondrial DNA analysis indicated that all F 1 hybrids (15 from Olsen Creek and five from Jansen Creek) arose from matings between steelhead females and cutthroat males implicating a sneak spawning behaviour by cutthroat males. First-generation cutthroat backcrosses contained O. c. clarki mtDNA more often than expected suggesting natural selection against F1 hybrids. More hybrids were backcrossed toward cutthroat than steelhead and our results indicate recurrent hybridization within these creeks. Age analysis demonstrated that hybrids were between 1 and 4 years old. These results suggest that within sympatric salmonid hybrid zones, exogenous processes (environmentally dependent factors) help to maintain the distinction between parental types through reduced fitness of hybrids within parental environments while divergent natural selection promotes parental types through distinct adaptive advantages of parental phenotypes.

Washington↗

USGS2003

Bi-parentally inherited species-specific markers identify hybridization between rainbow trout and cutthroat trout subspecies

Eight polymerase chain reaction primer sets amplifying bi-parentally inherited species-specific markers were developed that differentiate between rainbow trout (Oncorhynchus mykiss) and various cutthroat trout (O. clarki) subspecies. The primers were tested within known F1 and first generation hybrid backcrosses and were shown to amplify codominantly within hybrids. Heterozygous individuals also amplified a slower migrating band that was a heteroduplex, caused by the annealing of polymerase chain reaction products from both species. These primer sets have numerous advantages for native cutthroat trout conservation including statistical genetic analyses of known crosses and simple hybrid identification.

Molecular Ecology Notes↗

USGS2002

Novel molecular markers differentiate Oncorhynchus mykiss (rainbow trout and steelhead) and the O. clarki (cutthroat trout) subspecies

A suite of 26 PCR-based markers was developed that differentiates rainbow ( Oncorhynchus mykiss ) and coastal cutthroat trout ( O. clarki clarki ). The markers also differentiated rainbow from other cutthroat trout subspecies ( O. clarki ), and several of the markers differentiated between cutthroat trout subspecies. This system has numerous positive attributes, including: nonlethal sampling, high species-specificity and products that are easily identified and scored using agarose gel electrophoresis. The methodology described for developing the markers can be applied to virtually any system in which numerous markers are desired for identifying or differentiating species or subspecies.

Molecular Ecology Notes↗

USGS2001

Genetic characterization of hybridization and introgression between anadromous rainbow trout (oncorhynchus mykiss irideus) and coastal cutthroat trout (o. clarki clarki)

Interspecific hybridization represents a dynamic evolutionary phenomenon and major conservation problem in salmonid fishes. In this study we used amplified fragment length polymorphisms (AFLP) and mitochondrial DNA (mtDNA) markers to describe the extent and characterize the pattern of hybridization and introgression between coastal rainbow trout (Oncorhynchus mykiss irideus) and coastal cutthroat trout (O. clarki clarki). Hybrid individuals were initially identified using principle coordinate analysis of 133 polymorphic AFLP markers. Subsequent analysis using 23 diagnostic AFLP markers revealed the presence of F1, rainbow trout backcross, cutthroat trout backcross and later-generation hybrids. mtDNA analysis demonstrated equal numbers of F1 hybrids with rainbow and cutthroat trout mtDNA indicating reciprocal mating of the parental types. In contrast, rainbow and cutthroat trout backcross hybrids always exhibited the mtDNA from the recurrent parent, indicating a male hybrid mating with a pure female. This study illustrates the usefulness of the AFLP technique for generating large numbers of species diagnostic markers. The pattern of hybridization raises many questions concerning the existence and action of reproductive isolating mechanisms between these two species. Our findings are consistent with the hypothesis that introgression between anadromous populations of coastal rainbow and coastal cutthroat trout is limited by an environment-dependent reduction in hybrid fitness.

Pacific Northwest↗

USGS1999

Geographic distribution of chromosome and microsatellite DNA polymorphisms in Oncorhynchus mykiss native to western Washington

Chromosome studies of native populations of Oncorhynchus mykiss (steelhead and rainbow trout) in western Washington and southern British Columbia revealed the presence of two evolutionarily distinct chromosome lineages. Populations between, and including, the Elwha River, Washington, and Chilliwack River, British Columbia, contained 2n = 60 chromosomes. Populations on the central Washington coast contained 2n = 58 chromosomes. The north Washington coast and western Strait of Juan de Fuca contained individuals with 58, 59, or 60 chromosomes, suggesting this is a transition zone between 58 and 60 chromosome groups. The differences in chromosomal structure between 2n = 58 and 2n = 60 groups are presumably a Robertsonian rearrangement and an inversion. Allelic variation at three microsatellite loci (One ??6, One ??11 and Omy 77) also was examined, and no significant variation was detected among the 58 and 60 chromosome races. A hypothesis is presented concerning the origin of the 60 chromosome lineage.

British Columbia, Washington↗