Genetic variation in allozymes of western larch

1986 ◽  
Vol 16 (5) ◽  
pp. 1013-1018 ◽  
Author(s):  
Lauren Fins ◽  
Lisa W. Seeb
Keyword(s):  
Genetic Variation ◽  
Genetic Drift ◽  
Fire History ◽  
Glacial History ◽  
Geographic Proximity ◽  
Electrophoretic Variation ◽  
Inland Empire ◽  
Genetic History ◽  
Expected Heterozygosity ◽  
History Of

Seed samples from 19 stands of Larixoccidentalis Nutt. were analyzed for electrophoretic variation at 23 loci. Because sample sizes consisted of only 9 or 10 trees per stand (18–20 alleles per locus per stand), samples were grouped by geographic proximity into four larger samples. For all measures of variation, this species scored lower than most, but within the range observed for other western conifers. Most of the variation was found within rather than between the population groups. The single southern sample appeared to be genetically distinct from the others. Although some variation was observed between individual stand samples in expected heterozygosity, the consistently low values for all samples suggest that genetic drift has played a major role in the genetic history of the species in the Inland Empire, both through its glacial history in postulated refugia and through fire history in recent times.

The breed structure and genetic analysis of the pedigree cattle breeds in Australia. III. The Hereford

1963 ◽  
Vol 14 (1) ◽  
pp. 93 ◽  
Author(s):  
GP Davey ◽  
JSF Barker
Keyword(s):  
Genetic Variation ◽  
Genetic Analysis ◽  
Sampling Methods ◽  
Rapid Expansion ◽  
Genetic Contribution ◽  
Genetic History ◽  
Effective Generation ◽  
History Of ◽  
The One

(i) The structure and genetic history of the pedigree Hereford breed in Australia are analysed by pedigree sampling methods. (ii) The pattern of the breed structure is generally similar to that found in other breeds, but it is extremely dynamic owing to the present rapid expansion of the breed. Changes are taking place in the herd composition of the major breeders' groups and there are many new herds yet to find their level in the structure. (iii) Considerable emphasis has been placed on the use of imported animals in the development of the breed. Of all herds registering in Volume 24 of the herd book, 31.6% used imported sires, and the percentage of genes in the breed in 1949 derived from animals imported since 1880 was 97.7, and from animals imported since 1930, 53.9%. (iv) The most important herd in 1949 made a genetic contribution to the breed of 33.1%, while the contributions of the four next most important herds were 17.4, 10.1, 7.4, and 6.1%. In the four-generation pedigrees from which these figures were derived, the contribution of imported animals was 56.1%. (v) The animal with the highest relationship to the breed was Free Town Director (Imp.), with direct relationships of 5.6 and 9.2% to the 1941 and 1949 samples respectively. Of the 16 sires and one dam whose direct relationships are 3.0% or more in any of the three sample years, 12 sires were imported. (vi) The total inbreeding in 1949 (base year 1880) was 2.6%. This comprised 0.2% current inbreeding, 1.6% long-term inbreeding, and 0.8% strain inbreeding. There was no evidence of subdivision of the breed into separate strains. (vii) The effective generation length has decreased since 1930 to about 5.5 years in the 1949–50 sample. Nearly 50% of the animals in this sample were sired by bulls 4 years old or younger, while about 33% were from dams 4 years old or younger. (viii) Bulls from major breeders' herds are used widely throughout the breed, while about 90% of sires and 45% of dams were bred in herds other than the one in which they were used. Therefore, it is unlikely that there is much genetic variation between herds.

Range-wide patterns of allozyme variation in Douglas-fir (Pseudotsugamenziesii)

1989 ◽  
Vol 19 (2) ◽  
pp. 149-161 ◽  
Author(s):  
Peng Li ◽  
W. T. Adams
Keyword(s):  
Genetic Variation ◽  
Sierra Nevada ◽  
Allozyme Variation ◽  
Douglas Fir ◽  
Transition Zones ◽  
Seed Sources ◽  
Expected Heterozygosity ◽  
Major Exception ◽  
History Of ◽  
Geographical Locations

Seeds from 104 geographical locations throughout the range of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were analyzed at 20 enzyme loci to determine patterns of genetic variation and to make phylogenetic inferences. On average, the populations were polymorphic at 37% of the loci (range 5.0–65.0). Mean expected heterozygosity was 0.137 (range 0.021–0.239). Of the total genie diversity (HT = 0.182) observed, 24% was due to differentiation among populations. One Mexican population was genetically distinct from the rest of the species, which suggests the possibility of additional Pseudotsuga species in Mexico. The rest of the populations clustered into two groups corresponding to the recognized coastal and interior varieties. In addition, the interior variety separated into northern and southern subgroups near 44° latitude. Transition zones between the varieties were found to be narrower and more abrupt than has been suggested previously. Populations within the coastal variety and the northern interior subgroup averaged higher expected heterozygosity than the southern interior subgroup, but in the southern interior subgroup, populations were much more highly differentiated. Allozyme variation followed a latitudinal cline in the interior variety, but only weak geographical patterning was observed in the coastal variety. In general, genetic diversity decreased towards the periphery of the species range. Range-wide patterns of allozyme variation were similar to those in terpene studies, with the major exception that the Sierra Nevada seed sources in this study were closely aligned with the coastal variety rather than with the interior variety. Range-wide patterns of genetic variation in Douglas-fir largely reflect the evolutionary history of the species as revealed by paleobotanical studies.

Population Genetics ofCaenorhabditis elegans: The Paradox of Low Polymorphism in a Widespread Species

Genetics ◽  
2003 ◽  
Vol 163 (1) ◽  
pp. 147-157 ◽  
Author(s):  
Arjun Sivasundar ◽  
Jody Hey
Keyword(s):  
Genetic Variation ◽  
Microsatellite Loci ◽  
Population Expansion ◽  
Widespread Species ◽  
C Elegans ◽  
Model Research ◽  
The World ◽  
Natural Isolates ◽  
History Of ◽  
Low Levels

AbstractCaenorhabditis elegans has become one of the most widely used model research organisms, yet we have little information on evolutionary processes and recent evolutionary history of this widespread species. We examined patterns of variation at 20 microsatellite loci in a sample of 23 natural isolates of C. elegans from various parts of the world. One-half of the loci were monomorphic among all strains, and overall genetic variation at microsatellite loci was low, relative to most other species. Some population structure was detected, but there was no association between the genetic and geographic distances among different natural isolates. Thus, despite the nearly worldwide occurrence of C. elegans, little evidence was found for local adaptation in strains derived from different parts of the world. The low levels of genetic variation within and among populations suggest that recent colonization and population expansion might have occurred. However, the patterns of variation are not consistent with population expansion. A possible explanation for the observed patterns is the action of background selection to reduce polymorphism, coupled with ongoing gene flow among populations worldwide.

Morphometrics of the aerial roots of Kingia australis (Liliales)

1981 ◽  
Vol 29 (1) ◽  
pp. 81 ◽  
Author(s):  
B Lamont
Keyword(s):  
Fire History ◽  
Dead Zone ◽  
Dry Weight ◽  
Root Primordia ◽  
Stem Apex ◽  
Primary Roots ◽  
Aerial Roots ◽  
History Of ◽  
Lateral Branches ◽  
Potential Height

Kingia australis, common in the heaths and forests of south-western Australia, is distinguished from all other grass trees in Australia by the presence of a mantle of concealed aerial roots. A ring of up to 50 root primordia is initiated in winter from the stem apex. In plants more than 1 m high, initiation and commencement of elongation of the primary roots are no longer annual but dependent on the fire history of the plant. These roots descend between the stem and persistent leaf bases at about 2 cm per growing month, sending many lateral branches among the leaf bases. Aerial roots gradually replace the space occupied by the leaf bases until they may account for 45% of the dry weight of the aerial caudex. The caudex of one 6-m-high specimen bore up to 27 roots per cm2 transection of the root mantle, with about 3000 primary roots entering the soil. All underground primary roots (except the initial contractile roots) have an aerial origin and are concentrated vertically under the canopy. After 300-400 years the stem starts to die back from the base, and the aerial roots attached to that portion disintegrate. By propping up the stem and bridging the dead zone of the stem, the living aerial roots greatly extend the potential height and longevity of the plant. In addition, the hairy laterals are ideally located to absorb water and nutrients directly from the leaf bases. Protective and aerating functions are also indicated.

Holocene stand-scale vegetation dynamics and fire history of an old-growth spruce forest in southern Finland

2015 ◽  
Vol 24 (6) ◽  
pp. 731-741 ◽  
Author(s):  
Jennifer L. Clear ◽  
Heikki Seppä ◽  
Niina Kuosmanen ◽  
Richard H. W. Bradshaw
Keyword(s):  
Vegetation Dynamics ◽  
Fire History ◽  
Spruce Forest ◽  
Old Growth ◽  
History Of

scholarly journals Investigating the glacial history of the northern sector of the Cordilleran Ice Sheet with cosmogenic 10Be concentrations in quartz

2010 ◽  
Vol 29 (25-26) ◽  
pp. 3630-3643 ◽  
Author(s):  
Arjen P. Stroeven ◽  
Derek Fabel ◽  
Alexandru T. Codilean ◽  
Johan Kleman ◽  
John J. Clague ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Glacial History ◽  
History Of ◽  
Cordilleran Ice Sheet ◽  
Cosmogenic 10Be ◽  
Northern Sector
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