Microsatellite analysis reveals substantial levels of genetic variation but low levels of genetic divergence among isolated populations of Kaka (Nestor meridionalis)

2006 ◽  
Vol 106 (4) ◽  
pp. 329-338 ◽  
Author(s):  
James P. Sainsbury ◽  
Terry C. Greene ◽  
Ron J. Moorhouse ◽  
Charles H. Daugherty ◽  
Geoffrey K. Chambers
Keyword(s):  
Genetic Variation ◽  
Genetic Divergence ◽  
Microsatellite Analysis ◽  
Isolated Populations ◽  
Low Levels

Genetic variation in central and disjunct populations of Lilium parryi

1994 ◽  
Vol 72 (1) ◽  
pp. 79-85 ◽  
Author(s):  
Yan B. Linhart ◽  
Andrea C. Premoli
Keyword(s):  
Population Structure ◽  
Genetic Variation ◽  
Genetic Variability ◽  
The Other ◽  
Significant Genetic Differentiation ◽  
Isolated Populations ◽  
Disjunct Populations ◽  
Large Populations ◽  
Low Levels ◽  
Hawkmoth Pollination

We compared levels of genetic variability in small, isolated populations of Lilium parryi in Arizona with those found in large populations in California. Arizona populations were presumably derived from California populations; they were significantly less variable and showed evidence of much higher levels of inbreeding. One California locality whose population structure is similar to those found in Arizona also had relatively low levels of genetic variability. However, the other California populations were highly variable and showed lower levels of inbreeding than Arizona populations. There was significant genetic differentiation among all populations. In Arizona, there was no relationship between current population size and genetic variability. Arizona populations may be vulnerable to extinction, given the magnitude of environmental modifications in their habitats, their small sizes, and their low levels of variability. Key words: genetic structure, rare species, hawkmoth pollination, Lilium, disjunct populations.

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.

Low levels of genetic variation inPhenakospermum guyannense (Strelitziaceae), a widespread bat-pollinated Amazonian herb

1996 ◽  
Vol 199 (1-2) ◽  
pp. 1-15 ◽  
Author(s):  
Cheryl S. Roesel ◽  
W. John Kress ◽  
Brunella Martire Bowditch
Keyword(s):  
Genetic Variation ◽  
Low Levels

Comparative Study of Genetic Variation at 15 STR Loci in Three Isolated Populations of the Bosnian Mountain Area

Human Biology ◽  
2004 ◽  
Vol 76 (1) ◽  
pp. 15-31 ◽  
Author(s):  
D Marjanovic ◽  
L Kapur ◽  
K Drobnic ◽  
Bruce Budowle ◽  
N Pojskic ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Comparative Study ◽  
Isolated Populations ◽  
Mountain Area ◽  
Str Loci

High Levels of Genetic Variability in an Isolated Colony of Rock-wallabies (Petrogale assimilis): Evidence from Three Classes of Molecular Markers

1997 ◽  
Vol 45 (2) ◽  
pp. 199 ◽  
Author(s):  
Peter B. S. Spencer ◽  
Mark Adams ◽  
Helene Marsh ◽  
David J. Miller ◽  
Mark D. B. Eldridge
Keyword(s):  
Genetic Variation ◽  
Molecular Markers ◽  
Genetic Variability ◽  
Mating Systems ◽  
Selective Pressure ◽  
Multiple Mating ◽  
Dna Fingerprints ◽  
Average Heterozygosity ◽  
Low Levels ◽  
High Level

Estimates of genetic variation for a small (Ne = 39) colony of allied rock-wallabies (Petrogale assimilis) were calculated with three different categories of molecular marker. Average heterozygosity was estimated at 3·8% for allozymes, 47·3% for multilocus ‘DNA fingerprints’ and 85·5% for microsatellite markers. Overall these values indicate that this small isolated colony of rock-wallabies maintains a high level of genetic variation despite its relative isolation and the apparently low levels of migration between colonies. It is likely that mechanisms exist (such as kin avoidance, multiple mating systems, high and variable selective pressure in extreme and fluctuating environmental conditions) that promote the maintenance of high levels of genetic variation in isolated colonies of P. assimilis. These mechanisms are discussed in the context of the results obtained from the molecular markers.

Inbreeding and Inbreeding Depression

2020 ◽  
Author(s):  
Donald M. Waller ◽  
Lukas F. Keller
Keyword(s):  
Genetic Variation ◽  
Inbreeding Depression ◽  
Charles Darwin ◽  
Extinction Risk ◽  
Random Mating ◽  
Genetic Material ◽  
Great Length ◽  
Genetic Rescue ◽  
Isolated Populations ◽  
Genetic Transmission

Inbreeding (also referred to as “consanguinity”) occurs when mates are related to each other due to incest, assortative mating, small population size, or population sub-structuring. Inbreeding results in an excess of homozygotes and hence a deficiency of heterozygotes. This, in turn, exposes recessive genetic variation otherwise hidden by heterozygosity with dominant alleles relative to random mating. Interest in inbreeding arose from its use in animal and plant breeding programs to expose such variation and to fix variants in genetically homogenous lines. Starting with Gregor Mendel’s experiments with peas, geneticists have widely exploited inbreeding as a research tool, leading R. C. Lewontin to conclude that “Every discovery in classical and population genetics has depended on some sort of inbreeding experiment” (see Lewontin’s 1965 article “The Theory of Inbreeding.” Science 150:1800–1801). Charles Darwin wrote an entire book on the effects of inbreeding as measured in fifty-two taxa of plants. He and others noted that most plants and animals go to great length to avoid inbreeding, suggesting that inbreeding has high costs that often outweigh the benefits of inbreeding. Benefits of inbreeding include increased genetic transmission while the costs of inbreeding manifest as inbreeding depression when deleterious, mostly recessive alleles otherwise hidden as heterozygotes emerge in homozygote form upon inbreeding. Inbreeding also reduces fitness when heterozygotes are more fit than both homozygotes, but such overdominance is rare. Recurrent mutation continuously generates deleterious recessive alleles that create a genetic “load” of deleterious mutations mostly hidden within heterozygotes in outcrossing populations. Upon inbreeding, the load is expressed when deleterious alleles segregate as homozygotes, causing often substantial inbreeding depression. Although inbreeding alone does not change allele frequencies, it does redistribute genetic variation, reducing it within families or populations while increasing it among families or populations. Inbreeding also increases selection by exposing deleterious recessive mutations, a process called purging that can deplete genetic variation. For all these reasons, inbreeding is a central concept in evolutionary biology. Inbreeding is also central to conservation biology as small and isolated populations become prone to inbreeding and thus suffer inbreeding depression. Inbreeding can reduce population viability and increase extinction risk by reducing individual survival and/or reproduction. Such effects can often be reversed, however, by introducing new genetic material that re-establishes heterozygosity (“genetic rescue”). The current availability of DNA sequence and expression data is now allowing more detailed analyses of the causes and evolutionary consequences of inbreeding.

scholarly journals Spatial Structure and Genetic Variation of a Mangrove Species (Avicennia marina (Forssk.) Vierh) in the Farasan Archipelago

Forests ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1287
Author(s):  
Rahmah N. Al-Qthanin ◽  
Samah A. Alharbi
Keyword(s):  
Genetic Variation ◽  
Genetic Differentiation ◽  
Species Conservation ◽  
Natural Populations ◽  
Avicennia Marina ◽  
Conservation Strategies ◽  
Isolated Populations ◽  
Mangrove Species ◽  
Population Genetic Differentiation ◽  
Sea Currents

Avicennia marina (Forssk.) Vierh is distributed in patches along the Farasan archipelago coast and is the most common mangrove species in the Red Sea. However, to date, no studies have been directed towards understanding its genetic variation in the Farasan archipelago. In this investigation, genetic variations within and among natural populations of Avicennia marina in the Farasan archipelago were studied using 15 microsatellite markers. The study found 142 alleles on 15 loci in nine populations. The observed (Ho) and expected (He) heterozygosity values were 0.351 and 0.391, respectively, which are much lower than those of earlier studies on A. marina in the Arabian Gulf. An inbreeding effect from self-pollination might explain its heterozygote deficiency. Population genetic differentiation (FST = 0.301) was similar to other mangrove species. Our findings suggest that the sea current direction and coastal geomorphology might affect genetic dispersal of A. marina. The more isolated populations with fewer connections by sea currents exhibited lower genetic variation and differentiation between populations. The genetic clustering of populations fell into three main groups—Group 1 (populations of Farasan Alkabir Island), Group 2 (populations of Sajid Island), and Group 3 (mix of one population of Farasan Alkabir Island and a population of Zifaf Island). More genetic variation and less genetic differentiation occurred when the population was not isolated and had a direct connection with sea currents. Both of these factors contributed to limited propagule dispersal and produced significant structures among the population. It is expected that the results of this research will be useful in determining policy and species-conservation strategies and in the rehabilitation of A. marina mangrove stands on the Farasan islands in an effort to save this significant natural resource.

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