Effects of low-density urbanization on genetic structure in the Song Sparrow

Abstract Background Asarum sieboldii Miq., a species of forest understory vegetation, is an herbaceous perennial belonging to the family Aristolochiaceae. The metapopulation of A. sieboldii is distributed sparsely and has a short seed dispersal distance by ants as their seed distributor. It is known that many flowers of A. sieboldii depend on self-fertilization. Because these characteristics can affect negatively in genetic structure, investigating habitat structure and assessment of genetic structure is needed. A total of 27 individuals in a valley were sampled for measuring genetic diversity, genetic distance, and genetic differentiation by RAPD-PCR. Results The habitat areas of A. sieboldii metapopulation were relatively small (3.78~33.60 m2) and population density was very low (five to seven individuals in 20×20 m quadrat). The habitat of A. sieboldii was a very shady (relative light intensity = 0.9%) and mature forest with a high evenness value (J = 0.81~0.99) and a low dominance value (D = 0.19~0.28). The total genetic diversity of A. sieboldii was quite high (h = 0.338, I = 0.506). A total of 33 band loci were observed in five selected primers, and 31 band loci (94%) were polymorphic. However, genetic differentiation along the valley was highly progressed (Gst = 0.548, Nm = 0.412). The average genetic distance between subpopulations was 0.387. The results of AMOVA showed 52.77% of variance occurs among populations, which is evidence of population structuring. Conclusions It is expected that a small-scale founder effect had occurred, an individual spread far from the original subpopulation formed a new subpopulation. However, geographical distance between individuals would have been far and genetic flow occurred only within each subpopulation because of the low density of population. This made significant genetic distance between the original and new population by distance. Although genetic diversity of A. sieboldii metapopulation is not as low as concerned, the subpopulation of A. sieboldii can disappear by stochastic events due to small subpopulation size and low density of population. To prevent genetic isolation and to enhance the stable population size, conservative efforts such as increasing the size of each subpopulation or the connection between subpopulations are needed.

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Long-distance seed and pollen dispersal inferred from spatial genetic structure in the very low-density rainforest tree, Baillonella toxisperma Pierre, in Central Africa

Molecular Ecology ◽

10.1111/j.1365-294x.2010.04864.x ◽

2010 ◽

Vol 19 (22) ◽

pp. 4949-4962 ◽

Cited By ~ 24

Author(s):

D. NDIADE-BOUROBOU ◽

O. J. HARDY ◽

B. FAVREAU ◽

H. MOUSSAVOU ◽

E. NZENGUE ◽

...

Keyword(s):

Genetic Structure ◽

Spatial Genetic Structure ◽

Pollen Dispersal ◽

Central Africa ◽

Low Density ◽

Long Distance

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Evolution transforms pushed waves into pulled waves

10.1101/266007 ◽

2018 ◽

Cited By ~ 1

Author(s):

Philip Erm ◽

Ben L. Phillips

Keyword(s):

Invasive Species ◽

Genetic Structure ◽

Allee Effect ◽

Evolutionary Dynamics ◽

Low Density ◽

Allee Effects ◽

Invasion Speed ◽

Invasion Dynamics ◽

Invasion Front ◽

Invasion Fronts

AbstractUnderstanding the dynamics of biological invasions is crucial for managing numerous phenomena, from invasive species to tumours. While Allee effects (where individuals in low-density populations suffer lowered fitness) are known to influence both the ecological and evolutionary dynamics of invasions, the possibility that an invader’s susceptibility to the Allee effect might itself evolve on an invasion front has received almost no attention. Since invasion fronts are regions of perpetually low population density, selection should favour vanguard invaders that are resistant to Allee effects. Evolution in response to this pressure could cause invasions to transition from pushed waves, propelled by dispersal from behind the invasion front, to pulled waves, driven by the invasion vanguard. To examine this possibility, we construct an individual-based model in which a trait that governs resistance to the Allee effect is allowed to evolve during an invasion. We find that vanguard invaders rapidly evolve resistance to the Allee effect, causing invasions to accelerate. This also results in invasions transforming from pushed waves into pulled waves, an outcome with consequences for predictions of invasion speed, the population’s genetic structure, and other important behaviours. These findings underscore the importance of accounting or evolution in invasion forecasts, and suggest that evolution has the capacity to fundamentally alter invasion dynamics.

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Genetic changes in an irradiated population of wild meadow voles (Microtus pennsylvanicus)

Canadian Journal of Zoology ◽

10.1139/z86-103 ◽

1986 ◽

Vol 64 (3) ◽

pp. 698-703 ◽

Cited By ~ 3

Author(s):

Howard A. Ross

Keyword(s):

Genetic Structure ◽

Population Growth ◽

Gamma Radiation ◽

Radiation Treatment ◽

Late Summer ◽

Microtus Pennsylvanicus ◽

Low Density ◽

Meadow Voles ◽

Genetic Characteristics ◽

And Control

Changes observed in the genetic structure of a wild population of meadow voles (Microtus pennsylvanicus) exposed to chronic gamma radiation are compared with those observed in a nearby unirradiated population. An average exposure of 14.6 ± 0.8 mGy/d of gamma radiation was administered from a 137Cs field irradiator to an otherwise unmanipulated population over 47 weeks. The demographic and genetic characteristics of the populations were estimated by livetrapping and by electrophoresis of the polymorphic plasma proteins encoded by transferrin and leucine aminopeptidase, respectively. Both the irradiated and control populations showed highly synchronous demographic changes: an autumn decline, very low density throughout the winter, a late spring increase, and late summer peak. Allele frequencies and F-statistics fluctuated dramatically throughout the low-density phase. Coincident with the acceleration of population growth, the genetic variables began to converge in the two populations. At the termination of the experiment, when population growth was slowing, the irradiated and control populations were genetically very similar. Sexual activity, longevity, and recruitment were each homogeneous among genotypes in both populations. The radiation treatment had no apparent effect on the genetic structure of the vole population. Gene flow at the beginning of an increase phase is suggested as a possible cause for convergence of the genetic attributes of the irradiated and unirradiated populations.

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Application of Improved Voltage Compensation in the SEM to Imaging of Organic Materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072666 ◽

1973 ◽

Vol 31 ◽

pp. 444-445

Author(s):

P.J. Killingworth ◽

M. Warren

Keyword(s):

Electron Beam ◽

Organic Materials ◽

Operating Parameters ◽

Low Density ◽

Beam Diameter ◽

Incident Electron Beam ◽

Specimen Material ◽

Voltage Compensation ◽

Selection Of ◽

Scanning Electron

Ultimate resolution in the scanning electron microscope is determined not only by the diameter of the incident electron beam, but by interaction of that beam with the specimen material. Generally, while minimum beam diameter diminishes with increasing voltage, due to the reduced effect of aberration component and magnetic interference, the excited volume within the sample increases with electron energy. Thus, for any given material and imaging signal, there is an optimum volt age to achieve best resolution.In the case of organic materials, which are in general of low density and electric ally non-conducting; and may in addition be susceptible to radiation and heat damage, the selection of correct operating parameters is extremely critical and is achiev ed by interative adjustment.

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Quantitative defect studies in semiconductor TEM samples prepared by low angle ion milling

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138932 ◽

1995 ◽

Vol 53 ◽

pp. 512-513

Author(s):

L. Mulestagno ◽

J.C. Holzer ◽

P. Fraundorf

Keyword(s):

Sample Preparation ◽

Milling Time ◽

High Density ◽

Low Density ◽

Ion Milling ◽

High Quality ◽

Variable Angle ◽

Major Disadvantage ◽

Induced Defects

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).

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Intralysosomal Accumulation of Colloidal Gold-Low Density Lipoprotein Conjugates in Chloroquine-Treated Fibroblasts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010011951x ◽

1985 ◽

Vol 43 ◽

pp. 546-547 ◽

Cited By ~ 1

Author(s):

Dean A. Handley ◽

Cynthia M. Arbeeny ◽

Larry D. Witte

Keyword(s):

Colloidal Gold ◽

Cultured Cells ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Coated Vesicle ◽

Low Density ◽

Cholesterol Esters ◽

Cultured Fibroblasts ◽

Surface Receptors ◽

Ldl Particles

Low density lipoproteins (LDL) are the major cholesterol carrying particles in the blood. Using cultured cells, it has been shown that LDL particles interact with specific surface receptors and are internalized via a coated pit-coated vesicle pathway for lysosomal catabolism. This (Pathway has been visualized using LDL labeled to ferritin or colloidal gold. It is now recognized that certain lysomotropic agents, such as chloroquine, inhibit lysosomal enzymes that degrade protein and cholesterol esters. By interrupting cholesterol ester hydrolysis, chloroquine treatment results in lysosomal accumulation of cholesterol esters from internalized LDL. Using LDL conjugated to colloidal gold, we have examined the ultrastructural effects of chloroquine on lipoprotein uptake by normal cultured fibroblasts.

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ALCHEMI of B2-Ordered Fe50Al45Me5 alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165203 ◽

1996 ◽

Vol 54 ◽

pp. 548-549

Author(s):

Ian M. Anderson

Keyword(s):

Room Temperature ◽

Iron Aluminide ◽

Low Density ◽

Intermetallic Alloys ◽

Practical Applications ◽

Alloying Additions ◽

Site Distribution ◽

Good Corrosion Resistance ◽

Room Temperature Ductility ◽

The Matrix

B2-ordered iron aluminide intermetallic alloys exhibit a combination of attractive properties such as low density and good corrosion resistance. However, the practical applications of these alloys are limited by their poor fracture toughness and low room temperature ductility. One current strategy for overcoming these undesirable properties is to attempt to modify the basic chemistry of the materials with alloying additions. These changes in the chemistry of the material cannot be fully understood without a knowledge of the site-distribution of the alloying elements. In this paper, the site-distributions of a series of 3d-transition metal alloying additions in B2-ordered iron aluminides are studied with ALCHEMI.A series of seven alloys of stoichiometry Fe50AL45Me5, with Me = {Ti, V, Cr, Mn, Co, Ni, Cu}, were prepared with identical heating cycles. Microalloying additions of 0.2% B and 0.1% Zr were also incorporated to strengthen the grain boundaries, but these alloying additions have little influence on the matrix chemistry and are incidental to this study.

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Characterization of machined polystyrene foam

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015383x ◽

1989 ◽

Vol 47 ◽

pp. 372-373

Author(s):

C. W. Price ◽

E. F. Lindsey ◽

R. M. Franks ◽

M. A. Lane

Keyword(s):

Surface Finish ◽

Cell Walls ◽

Surface Structures ◽

Efficient Technique ◽

Low Density ◽

Polystyrene Foam ◽

Planar Surfaces ◽

Machining Characteristics

Diamond-point turning is an efficient technique for machining low-density polystyrene foam, and the surface finish can be substantially improved by grinding. However, both diamond-point turning and grinding tend to tear and fracture cell walls and leave asperities formed by agglomerations of fragmented cell walls. Vibratoming is proving to be an excellent technique to form planar surfaces in polystyrene, and the machining characteristics of vibratoming and diamond-point turning are compared.Our work has demonstrated that proper evaluation of surface structures in low density polystyrene foam requires stereoscopic examinations; tilts of + and − 3 1/2 degrees were used for the stereo pairs. Coating does not seriously distort low-density polystyrene foam. Therefore, the specimens were gold-palladium coated and examined in a Hitachi S-800 FESEM at 5 kV.

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