Geology topics

M. A. Cronin

Publications and source records attributed to M. A. Cronin.

4 recordsLinked to original sources

USGS1997

Genetic differentiation of sockeye salmon subpopulations from a geologically young Alaskan lake system

The Tustumena Lake drainage in southcentral Alaska is glacially turbid and geologically young (<2,000 years old). Previous field studies identified at least three subpopulations of sockeye salmon Oncorhynchus nerka at Tustumena Lake, based on the distribution and timing of spawners. The subpopulations included early‐run salmon that spawned in six clearwater tributaries of the lake (mid August), lake shoreline spawners (late August), and late‐run fish that spawned in the lakeˈs outlet, the Kasilof River (late September). Our objective was to determine the degree of genetic differentiation among these subpopulations based on restriction enzyme analyses of the cytochrome b gene of mitochondrial DNA and analyses of four polymorphic allozyme loci. Mitochondrial DNA haplotype frequencies for outlet‐spawning sockeye salmon differed significantly from those of all other subpopulations. The most common (36%) haplotype in the outlet subpopulation did not occur elsewhere, thus suggesting little or no gene flow between outlet spawners and other spatially close subpopulations at Tustumena Lake. Allele frequencies at two allozyme loci also indicated a degree of differentiation of the outlet subpopulation from the shoreline and tributary subpopulations. Allele frequencies for three tributary subpopulations were temporally stable over approximately 20 years (based on a comparison to previously published results) despite initiation of a hatchery program in two of the tributaries during the intervening period. Collectively, our results are consistent with the hypothesis that significant genetic differentiation has occurred within the Tustumena Lake drainage since deglaciation approximately 2,000 years ago.

Alaska↗

USGS1993

Sex identification of polar bears from blood and tissue samples

Polar bears ( Ursus maritimus ) can be adversely affected by hunting and other human perturbations because of low population densities and low reproduction rates. The sustainable take of adult females may be as low as 1.5% of the population. Females and accompanying young are most vulnerable to hunting, and hunters have not consistently reported the sex composition of the harvest, therefore a method to confirm the sexes of polar bears harvested in Alaska is needed. Evidence of the sex of harvested animals is often not available, but blood or other tissue samples often are. We extracted DNA from tissue and blood samples, and amplified segments of zinc finger (ZFX and ZFY) genes from both X and Y chromosomes with the polymerase chain reaction. Digestion of amplified portions of the X chromosome with the restriction enzyme Hae III resulted in subdivision of the original amplified segment into four smaller fragments. Digestion with Hae III did not subdivide the original segment amplified from the Y chromosome. The differing fragment sizes produced patterns in gel electrophoresis that distinguished samples from male and female bears 100% of the time. This technique is applicable to the investigation of many wildlife management and research questions.

Alaska↗

USGS1992

Intraspecific mitochondrial DNA variation in North American cervids

Intraspecific variation in mitochondrial DNA of North American cervids was assessed with restriction enzymes to determine relationships among populations and subspecies. No variation was detected in moose ( Alces alces ) and little in elk ( Cervus elaphus ). Caribou ( Rangifer tarandus ), white-tailed deer ( Odocoileus virginianus ), and mule deer ( Odocoileus hemionus ) possessed considerable variation. Characteristic genotypes exist in caribou and white-tailed deer from different geographic areas although subspecies are not discernable as distinct mtDNA assemblages. Except for O. hemionus , intraspecific mtDNA sequence divergences are small (<2%). Subspecies of mule deer have divergent mtDNA (7%) and are the only subspecies of cervids with distinct genotypes.

Journal of Mammalogy↗

USGS1991

Spatial heterogeneity of mitochondrial DNA and allozymes among populations of white-tailed deer and mule deer

A white-tailed deer ( Odocoileus virginianus ) population in northeastern Minnesota and a mule deer ( O. hemionus ) population in the Bridger Mountains Montana, have previously been shown to be spatially subdivided into contiguous subpopulations. We assessed the degree of genetic differentiation among subpopulations and tested the hypothesis that differentiation will be greater for mitochondrial DNA (mtDNA) than for nuclear-encoded allozymes. Differentiation of the white-tailed deer subpopulations was significant for two allozyme loci but not for mtDNA, and the overall degree of differentiation was low. Gene flow, recent founding of the subpopulations, and polygamous breeding structure may all have contributed to this pattern. Greater differentiation was evident among disjunct populations than between the contiguous subpopulations of white-tailed deer. The contiguous mule deer subpopulations were significantly differentiated for mtDNA and one allozyme locus. Differentiation was greater for mtDNA than for allozymes. These results are consistent with demographic data that indicate mule deer males disperse more than do females. Disjunct mule deer populations may be similar or dramatically different in mtDNA haplotype frequencies that do not necessarily vary with geographic distance. Current and historical gene flow and breeding structure will influence population genetic patterns.

Journal of Heredity↗