Patterns of genetic diversity in the sumac gall aphid, Melaphis rhois

Genome ◽  
1991 ◽  
Vol 34 (5) ◽  
pp. 757-762 ◽  
Author(s):  
Paul D. N. Hebert ◽  
Terrie L. Finston ◽  
Robert Foottit
Keyword(s):  
Genetic Diversity ◽  
Life Cycle ◽  
Gene Flow ◽  
Gene Frequency ◽  
Dispersal Ability ◽  
Pest Species ◽  
Prior Work ◽  
Local Populations ◽  
Important Interaction ◽  
Plant Characteristics

In contrast to prior work on aphids, which has focused on pest species, the present study involved the analysis of genetic diversity in Melaphis rhois, a species that employs sumac and moss as alternate hosts. The life cycle involves a spring migration to sumac, with each sexual female producing a single offspring, which elicits a gall and subsequently proliferates clonally within it. Allozyme surveys at 52 sites in Ontario and Quebec established the absence of migration among galls and indicated that this species shares the low level of genetic diversity found in pest aphids. Genotypic frequencies in local populations of M. rhois showed frequent heterozygote deficits, suggesting the prevalence of inbreeding. Gene frequency divergence among populations was exceptionally pronounced, providing further evidence that gene flow was restricted. The unusual genetic attributes of this species suggest the important interaction among host-plant characteristics and the dispersal ability of aphids and their genetic systems.Key words: aphid, Melaphis, parthenogenesis, allozyme, cyclic parthenogen.

GENIC HETEROZYGOSITY AND PROTEIN POLYMORPHISM AMONG LOCAL POPULATIONS OF OENOTHERA BIENNIS

Genetics ◽  
1975 ◽  
Vol 79 (3) ◽  
pp. 477-491
Author(s):  
Donald A Levin
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
Gene Frequency ◽  
Genetic Variance ◽  
Polymorphic Locus ◽  
Cook County ◽  
Oenothera Biennis ◽  
Polymorphic Loci ◽  
Local Populations ◽  
The Mean

ABSTRACT Twenty enzyme loci were studied in 44 Illinois populations of Oenothera biennis; four were polymorphic. Most of the variation was distributed between populations. Fifty-nine percent of the populations had one genotype, 27% two genotypes and the remaining 16% from three to five genotypes; the average was 1.50. The proportion of genetic diversity present in single populations is.38 of that present in the state. Members of single populations were uniformly heterozygous for 1 to 4 loci. The mean heterozygosity per population ranged from 0 to 20%. For Illinois populations collectively, heterozygosity averaged 4.5%. There was much gene frequency heterogeneity between populations. The true standardized genetic variance among populations for alleles at polymorphic loci varied from.40 to.78. Populations from Cook County were much more similar inter se than those downstate, had fewer genotypes and polymorphic loci, and had less heterozygosity than downstate populations. The mean normalized genetic identity among Cook County populations was.987 versus.947 for downstate populations. The mean number of genotypes per population in Cook County was 1.06 versus 2.40 in downstate populations. There was only one polymorphic locus in Cook County, VLP. The genetic structure of Oe. biennis suggests that single populations are colonized by one, or at best a few individuals. Cook County populations are judged to be less variable than downstate populations because the mean age of the populations probably is less than that of those downstate.

scholarly journals Effects of Colonization Processes on Genetic Diversity: Differences Between Annual Plants and Tree Species

Genetics ◽  
2000 ◽  
Vol 154 (3) ◽  
pp. 1309-1321 ◽  
Author(s):  
Frédéric Austerlitz ◽  
Stéphanie Mariette ◽  
Nathalie Machon ◽  
Pierre-Henri Gouyon ◽  
Bernard Godelle
Keyword(s):  
Genetic Diversity ◽  
Life Cycle ◽  
Gene Flow ◽  
Tree Species ◽  
Population Diversity ◽  
Pollen Flow ◽  
Nuclear Genes ◽  
Annual Plants ◽  
High Level ◽  
The Impact

Abstract Tree species are striking for their high within-population diversity and low among-population differentiation for nuclear genes. In contrast, annual plants show much more differentiation for nuclear genes but much less diversity than trees. The usual explanation for this difference is that pollen flow, and therefore gene flow, is much higher for trees. This explanation is problematic because it relies on equilibrium hypotheses. Because trees have very recently recolonized temperate areas, they have experienced many foundation events, which usually reduce within-population diversity and increase differentiation. Only extremely high levels of gene flow could counterbalance these successive founder effects. We develop a model to study the impact of life cycle of forest trees, in particular of the length of their juvenile phase, on genetic diversity and differentiation during the glacial period and the following colonization period. We show that both a reasonably high level of pollen flow and the life-cycle characteristics of trees are needed to explain the observed structure of genetic diversity. We also show that gene flow and life cycle both have an impact on maternally inherited cytoplasmic genes, which are characterized both in trees and annual species by much less diversity and much more differentiation than nuclear genes.

Genetic structure after forest fragmentation: a landscape ecology perspective on Acer saccharum

1992 ◽  
Vol 70 (8) ◽  
pp. 1659-1668 ◽  
Author(s):  
Stephanie A. Foré ◽  
R. James Hickey ◽  
John L. Vankat ◽  
Sheldon I. Guttman ◽  
Robert L. Schaefer
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Forest Fragmentation ◽  
Acer Saccharum ◽  
Sugar Maple ◽  
Fragmented Landscape ◽  
Starch Gel Electrophoresis ◽  
Long Distance ◽  
Local Populations ◽  
Genetic Diversity And Structure

Fragmentation of large expanses of forests into small stands has isolated local populations of organisms. Sugar maple (Acer saccharum) was used to determine if the degree of forest fragment isolation affects genetic diversity and structure of local populations. Genetic data were collected from canopy (prefragmentation) and juvenile (postfragmentation) individuals in 15 woodlots. Genotypes were inferred from phenotypic enzyme patterns of seven enzymes representing eight loci extracted from cambium and resolved with starch gel electrophoresis. Analyses of allelic data indicated that genetic diversity was not significantly different between juvenile or canopy subdivisions, or between woodlots with low and high degrees of isolation. Genetic differentiation among woodlots was significantly greater for the canopy than for the juvenile subdivision. Estimates of gene flow indicate that postfragmentation gene flow rates are higher than prefragmentation rates. Apparently, sugar maple's high potential for long-distance gene flow is enhanced by altered wind flux across a fragmented landscape. The results also show that forest fragmentation does not always result in greater isolation of local populations. Key words: sugar maple, gene flow, conservation, isolation, allozymes.

Host traits explain the genetic structure of parasites: a meta-analysis

Parasitology ◽  
2013 ◽  
Vol 140 (10) ◽  
pp. 1316-1322 ◽  
Author(s):  
ISABEL BLASCO-COSTA ◽  
ROBERT POULIN
Keyword(s):  
Life Cycle ◽  
Gene Flow ◽  
Genetic Structure ◽  
Spatial Scales ◽  
Meta Analysis ◽  
Dispersal Ability ◽  
Trematode Species ◽  
Genetic Structuring ◽  
Geographic Scale ◽  
Strong Correlate

SUMMARYGene flow maintains the genetic integrity of species over large spatial scales, and dispersal maintains gene flow among separate populations. However, body size is a strong correlate of dispersal ability, with small-bodied organisms being poor dispersers. For parasites, small size may be compensated by using their hosts for indirect dispersal. In trematodes, some species use only aquatic hosts to complete their life cycle, whereas others use birds or mammals as final hosts, allowing dispersal among separate aquatic habitats. We performed the first test of the universality of the type of life cycle as a driver of parasite dispersal, using a meta-analysis of 16 studies of population genetic structure in 16 trematode species. After accounting for the geographic scale of a study, the number of populations sampled, and the genetic marker used, we found the type of life cycle to be the best predictor of genetic structure (Fst): trematode species bound to complete their life cycle within water showed significantly more pronounced genetic structuring than those leaving water through a bird or mammal host. This finding highlights the dependence of parasites on host traits for their dispersal, suggesting that genetic differentiation of parasites reflects the mobility of their hosts.

scholarly journals Genetic structure at national and regional scale in a long-distance dispersing pest organism, the bird cherry–oat aphid Rhopalosiphum padi

2019 ◽  
Author(s):  
Ramiro Morales-Hojas ◽  
Asier Gonzalez-Uriarte ◽  
Fernando Alvira Iraizoz ◽  
Todd Jenkins ◽  
Lynda Alderson ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Great Britain ◽  
Genetic Structure ◽  
Environmental Change ◽  
Isolation By Distance ◽  
Rhopalosiphum Padi ◽  
Regional Scale ◽  
Pest Species ◽  
Long Distance

AbstractGenetic diversity is determinant for pest species’ success and vector competence. Understanding the ecological and evolutionary processes that determine the genetic diversity is fundamental to help identify the spatial scale at which pest populations are best managed. In the present study, we present the first comprehensive analysis of the genetic diversity and evolution of Rhopalosiphum padi, a major pest of cereals and a main vector of the barley yellow dwarf virus (BYDV), in Great Britain. We have used a genotype by sequencing approach to study whether i) there is any underlying population genetic structure in this long distant disperser pest at a national and regional scale; ii) the populations evolve as a response to environmental change and selective pressures, and; iii) the populations comprise anholocyclic lineages. Individual R. padi were collected using the Rothamsted Insect Survey’s suction-trap network at several sites across England between 2004 and 2016 as part of the RIS long-term nationwide surveillance. Results identified two genetic clusters in Great Britain that mostly paralleled a North – South division, although gene flow is ongoing between the two subpopulations. These different groups do not correspond to sexual and asexual types, sexual reproduction being predominant in Great Britain, and could correspond to ecotypes. Results also show that there is migration with gene flow across Great Britain, although there is a reduction between the northern and southern sites with the Southwestern population being the most genetically differentiated. There is no evidence for isolation-by-distance and other factors like primary host distribution could influence the migration patterns. Finally, results also show no evidence for the evolution of the R. padi population, and it is demographically stable despite the ongoing environmental change. These results are discussed in view of their relevance to pest management and the transmission of BYDV.

Genetic rescue by augmenting gene flow

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Inbreeding Coefficient ◽  
Outbreeding Depression ◽  
Genetic Rescue ◽  
Evolutionary Potential ◽  
Beneficial Effects ◽  
The Difference ◽  
Inbred Populations ◽  
Harmful Effects

Inbreeding is reduced and genetic diversity enhanced when a small isolated inbred population is crossed to another unrelated population. Crossing can have beneficial or harmful effects on fitness, but beneficial effects predominate, and the risks of harmful ones (outbreeding depression) can be predicted and avoided. For crosses with a low risk of outbreeding depression, there are large and consistent benefits on fitness that persist across generations in outbreeding species. Benefits are greater in species that naturally outbreed than those that inbreed, and increase with the difference in inbreeding coefficient between crossed and inbred populations in mothers and zygotes. However, benefits are similar across invertebrates, vertebrates and plants. There are also important benefits for evolutionary potential of crossing between populations.

scholarly journals Mitogenomics of the endangered Mediterranean monk seal (Monachus monachus) reveals dramatic loss of diversity and supports historical gene-flow between Atlantic and eastern Mediterranean populations

2020 ◽  
Author(s):  
Alba Rey-Iglesia ◽  
Philippe Gaubert ◽  
Gonçalo Espregueira Themudo ◽  
Rosa Pires ◽  
Constanza De La Fuente ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
North Atlantic ◽  
Marine Mammals ◽  
Eastern Mediterranean ◽  
The Black Sea ◽  
Mediterranean Populations ◽  
Geographic Ranges ◽  
Western Sahara ◽  
The Mediterranean

Abstract The Mediterranean monk seal Monachus monachus is one of the most threatened marine mammals, with only 600–700 individuals restricted to three populations off the coast of Western Sahara and Madeira (North Atlantic) and between Greece and Turkey (eastern Mediterranean). Its original range was from the Black Sea (eastern Mediterranean) to Gambia (western African coast), but was drastically reduced by commercial hunting and human persecution since the early stages of marine exploitation. We here analyse 42 mitogenomes of Mediterranean monk seals, from across their present and historical geographic ranges to assess the species population dynamics over time. Our data show a decrease in genetic diversity in the last 200 years. Extant individuals presented an almost four-fold reduction in genetic diversity when compared to historical specimens. We also detect, for the first time, a clear segregation between the two North Atlantic populations, Madeira and Cabo Blanco, regardless of their geographical proximity. Moreover, we show the presence of historical gene-flow between the two water basins, the Atlantic Ocean and the Mediterranean Sea, and the presence of at least one extinct maternal lineage in the Mediterranean. Our work demonstrates the advantages of using full mitogenomes in phylogeographic and conservation genomic studies of threatened species.

Genetic diversity, population structure and gene flow pattern among populations of Lasiurus sindicus Henr. - an endemic, C4 grass of Indian Thar desert

Plant Gene ◽  
2020 ◽  
Vol 21 ◽  
pp. 100206 ◽  
Author(s):  
Bhuwnesh Goswami ◽  
Rekha Rankawat ◽  
Wahlang Daniel Regie ◽  
Bhana Ram Gadi ◽  
Satyawada Rama Rao
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Gene Flow ◽  
Flow Pattern ◽  
Thar Desert ◽  
C4 Grass
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