Nested analysis of genetic diversity in northwestern North American char, Dolly Varden (Salvelinus malma) and bull trout (Salvelinus confluentus)

2001 ◽  
Vol 58 (2) ◽  
pp. 406-420 ◽  
Author(s):  
Eric B Taylor ◽  
Zoë A Redenbach ◽  
Allan B Costello ◽  
Susan J Pollard ◽  
Charlie J Pacas
Keyword(s):  
Genetic Diversity ◽  
Secondary Contact ◽  
Population Subdivision ◽  
Bull Trout ◽  
Evolutionary Potential ◽  
Biological Organization ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Salvelinus Confluentus ◽  
Dolly Varden Salvelinus Malma

Partitioning within-species genetic diversity is fundamental to conservation of the bioheritage, current viability, and evolutionary potential of individual taxa. We conducted a hierarchical analysis of genetic diversity in Dolly Varden (Salvelinus malma) and bull trout (Salvelinus confluentus) involving analysis of hybrid zones between Dolly Varden and bull trout, analysis of phylogenetic structure within species across their native ranges using mitochondrial DNA, and a microsatellite DNA survey of population subdivision of bull trout within single watersheds. Our analyses documented hybridization and some introgression between Dolly Varden and bull trout across a geographically widespread zone of secondary contact between the two species. Both species were subdivided into two major mtDNA lineages, and one lineage in Dolly Varden may have arisen through introgression with bull trout. Bull trout have low levels of microsatellite diversity within populations, but there was substantial interpopulation variation in allele frequencies. Allele frequency distributions suggested that recent, severe bottlenecks occur frequently in bull trout populations. Our results illustrate partitioning of genetic variation at distinct levels of biological organization (species, phylogeographic lineages, local populations), and we address how such nested variation is fundamental to conservation of biodiversity.

Resource partitioning as a factor limiting gene flow in hybridizing populations of Dolly Varden char (Salvelinus malma) and bull trout (Salvelinus confluentus)

2001 ◽  
Vol 58 (10) ◽  
pp. 2037-2047 ◽  
Author(s):  
John Hagen ◽  
Eric B Taylor
Keyword(s):  
Life History ◽  
Gene Flow ◽  
Secondary Contact ◽  
Life History Stage ◽  
Bull Trout ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Salvelinus Confluentus ◽  
Dolly Varden Char ◽  
Northwestern North America

Dolly Varden char (Salvelinus malma) and bull trout (Salvelinus confluentus) hybridize in areas of secondary contact in northwestern North America but maintain their genetic integrity in spite of gene flow. We examined juvenile stream ecology and adult reproductive ecology of these species in sympatry to test for specializations to alternative niches that may act as a basis for natural selection against hybrids. Juvenile Dolly Varden occupied deeper, faster water and foraged more during daytime in the drift, whereas bull trout used shallower, slower water and made more nighttime foraging attempts towards the substrate. The species showed extensive diet overlap (Schoener's index = 0.7–0.9), and we found evidence for density compensation between species among sites. Our results suggest no obvious basis for selection against hybrids at the juvenile stream-rearing life-history stage. Bull trout, however, are adfluvial, whereas Dolly Varden are permanent stream residents. Bull trout are also much larger at maturity (50–80 cm vs. 12–15 cm) and build redds in faster, deeper water using larger substrate sizes. Consequently, hybrid genotypes may be selected against in these alternative life-history niches or during reproduction owing to their intermediate size at maturity and size-dependent spawning habitat use and mate choice.

Systematics and Distributions of Dolly Varden (Salvelinus malma) and Bull Trout (Salvelinus confluentus) in North America

1991 ◽  
Vol 48 (11) ◽  
pp. 2191-2211 ◽  
Author(s):  
Gordon R. Haas ◽  
J. D. McPhail
Keyword(s):  
North America ◽  
Principal Component ◽  
Bull Trout ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Salvelinus Confluentus ◽  
Linear Discriminant ◽  
Dolly Varden Char ◽  
Dolly Varden Salvelinus Malma ◽  
Single Character

Dolly Varden char in North America separate into two species: Dolly Varden (Salvelinus malma (Walbaum)) and bull trout (Salvelinus confluentus (Suckley)). Principal component analyses reveal two distinct morphotypes, and a linear discriminant function is derived (based on three field measureable variables) for their consistent classification. No single character can always distinguish both species, although branchiostegal ray number often will. The morphology of the two species remains relatively constant across their large ranges. The two species occur in strict sympatry in several areas with no evidence of interbreeding. The two species also exist parapatrically or syntopically and appear to exhibit broad scale competitive exclusion in these situations. Dolly Varden are distributed largely along the coast and range further north, while bull trout are mostly interior and range further south. Laboratory crosses demonstrate that the morphology of both species remain distinctive when they are reared under similar conditions and that their artificial hybrids are morphologically intermediate. No such natural hybrids were conclusively found, and there is no evidence of introgression.

Genetic analysis of Dolly Varden (Salvelinus malma) across its North American range: evidence for a contact zone in southcentral Alaska

2015 ◽  
Vol 72 (7) ◽  
pp. 1048-1057 ◽  
Author(s):  
Eric B. Taylor ◽  
Shannan L. May-McNally
Keyword(s):  
Contact Zone ◽  
North American ◽  
Salvelinus Alpinus ◽  
Glacial Refugia ◽  
Bull Trout ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Genetic Lineages ◽  
Dolly Varden Salvelinus Malma ◽  
Northern Dolly Varden

Contact zones between divergent lineages of aquatic taxa have been described from the northeastern Pacific Ocean. We surveyed samples of Dolly Varden (Salvelinus malma) from their North American range for variation at 14 microsatellite DNA loci. After accounting for hybridization between Dolly Varden and co-occurring bull trout (Salvelinus confluentus) and Arctic char (Salvelinus alpinus), we found evidence for two genetic lineages of Dolly Varden consistent with the previously recognized subspecies, northern Dolly Varden (S. m. malma) and southern Dolly Varden (S. m. lordii). We documented a contact zone between the two subspecies from the eastern Alaska Peninsula to Cook Inlet, Alaska, where admixture values (i.e., the proportion of the genome estimated to be composed of northern Dolly Varden, QNDV) ranged between QNDV = 0.245 and 0.754 across about 700 ocean kilometres. Populations of Dolly Varden showing low admixture (i.e., less than 5%) were located a minimum of 346 km to the west to 1200 km to the southeast, respectively, from the contact zone. The two lineages of Dolly Varden probably stem from isolation and subsequent divergence in, and dispersal from, distinct northern and southern Pleistocene glacial refugia and substantiate the treatment of S. malma as two subspecies and as at least two designatable units under Canada’s Species at Risk Act.

Fecundity of Resident and Anadromous Dolly Varden (Salvelinus malma) in Southeastern Alaska

1973 ◽  
Vol 30 (4) ◽  
pp. 543-548 ◽  
Author(s):  
R. F. Blackett
Keyword(s):  
Egg Size ◽  
Fish Length ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Ovary Weight ◽  
Dolly Varden Salvelinus Malma ◽  
Egg Number ◽  
Unit Of Length ◽  
The Right ◽  
Linear Regressions

Fecundity of resident Dolly Varden (Salvelinus malma) in an isolated population of southeastern Alaska averaged 66 eggs per female in comparison with 1888 eggs for anadromous Dolly Varden from two nearby streams. A relatively large egg size, averaging 3.6 mm in diameter and overlapping the range for the anadromous char, has been retained by the females in the resident population. Curvilinear regressions between egg number and fish length and linear regressions between egg number and body and ovary weights show that resident females have fewer eggs per unit of length, approximately the same number of eggs per gram of body weight, and more eggs per gram of ovary weight than anadromous females. The resident char attain sexual maturity a year earlier in life and at a smaller size than the migratory char. Development of a larger left ovary containing more eggs than the right was a common occurrence for both resident and anadromous Dolly Varden.

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