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375 results for “island population”
Data from: Islands and streams: clusters and gene flow in wild barley populations from the Levant
The domestication of plants frequently results in a high level of genetic differentiation between domesticated plants and their wild progenitors. This process is counteracted by gene flow between wild and domesticated plants because they are usually able to inter-mate and to exchange genes. We investigated the extent of gene flow between wild barley Hordeum spontaneum and cultivated barley Hordeum vulgare, and its effect on population structure in wild barley by analyzing a collection of 896 wild barley accessions (Barley1K) from Israel and all available Israeli H. vulgare accessions from the Israeli gene bank. We compared the performance of simple sequence repeats (SSR) and single nucleotide polymorphisms (SNP) marker data genotyped over a core collection in estimating population parameters. Estimates of gene flow rates with SSR markers indicated a high level of introgression from cultivated barley into wild barley. After removing accessions from the wild barley sample that were recently admixed with cultivated barley, the inference of population structure improved significantly. Both SSR and SNP markers showed that the genetic population structure of wild barley in Israel corresponds to the three major ecogeographic regions: the coast, the Mediterranean north, and the deserts in the Jordan valley and the South. Gene flow rates were estimated to be higher from north to south than in the opposite direction. As has been observed in other crop species, there is a significant exchange of alleles between the wild species and domesticated varieties that needs to be accounted for in the population genetic analysis of domestication.
Data from: Measuring population differentiation using GST or D? A simulation study with microsatellite DNA markers under a finite island model and nonequilibrium conditions
Genetic differentiation of populations is a key question in population genetic investigations. Wright's FST (and its relatives such as GST) has been a standard measure of differentiation. However, the deficiencies of these indexes and their significance have been increasing realized in recent years, leading to some new measures being proposed, such as Jost's (2008) D. This has also stimulated some considerable debate which, in certain sense, makes empirical biologists even more confused, for example, on statistics which should be used for estimating population differentiation. Here we report a simulation study with neutral microsatellite DNA loci under a finite island model to compare the performance of GST and D, under non-equilibrium conditions, in particular. Our results suggest that there exist fundamental differences between the two statistics and neither GST nor D operate satisfactorily in all situations for quantifying differentiation. D is very sensitive to mutation models but GST noticeably less so ...
Data from: Population size and time since island isolation determine genetic diversity loss in insular frog populations
Understanding the factors that contribute to loss of genetic diversity in fragmented populations is crucial for conservation measurements. Land-bridge archipelagoes offer ideal model systems for identifying the long-term effects of these factors on genetic variations in wild populations. In this study, we used 9 microsatellite markers to quantify genetic diversity and differentiation of 810 pond frogs (Pelophylax nigromaculataus) from 24 islands of the Zhoushan Archipelago and 3 sites on nearby mainland China and estimated the effects of the island area, population size, time since island isolation, distance to the mainland and distance to the nearest larger island on reduced genetic diversity of insular populations. The mainland populations displayed higher genetic diversity than insular populations. Genetic differentiations and no obvious gene flow were detected among the frog populations on the islands. Hierarchical partitioning analysis showed that only time since island isolation (square root transformed) and population size (log transformed) significantly contributed to insular genetic diversity. These results suggest that decreased genetic diversity and genetic differentiations among insular populations may have been caused by random genetic drift following isolation by rising sea levels during the Holocene. The results provide strong evidence for a relationship between retained genetic diversity and population size and time since island isolation for pond frogs on the islands, consistent with the prediction of the neutral theory for finite populations. Our study highlights the importance of the size and estimated isolation time of populations in understanding the mechanisms of genetic diversity loss and differentiation in fragmented wild populations.
Data from: Population genomic analysis uncovers African and European admixture in Drosophila melanogaster populations from the southeastern United States and Caribbean Islands
Drosophila melanogaster is postulated to have colonized North America in the past several 100 years in two waves. Flies from Europe colonized the east coast United States while flies from Africa inhabited the Caribbean, which if true, make the south-east US and Caribbean Islands a secondary contact zone for African and European D. melanogaster. This scenario has been proposed based on phenotypes and limited genetic data. In our study, we have sequenced individual whole genomes of flies from populations in the south-east US and Caribbean Islands and examined these populations in conjunction with population sequences from the west coast US, Africa, and Europe. We find that west coast US populations are closely related to the European population, likely reflecting a rapid westward expansion upon first settlements into North America. We also find genomic evidence of African and European admixture in south-east US and Caribbean populations, with a clinal pattern of decreasing proportions of African ancestry with higher latitude. Our genomic analysis of D. melanogaster populations from the south-east US and Caribbean Islands provides more evidence for the Caribbean Islands as the source of previously reported novel African alleles found in other east coast US populations. We also find the border between the south-east US and the Caribbean island to be the admixture hot zone where distinctly African-like Caribbean flies become genomically more similar to European-like south-east US flies. Our findings have important implications for previous studies examining the generation of east coast US clines via selection.
Data from: High genetic diversity in the offshore island populations of the tephritid fruit fly Bactrocera dorsalis
Background: Geographic isolation is an important factor that limit species dispersal and thereby affects genetic diversity. Because islands are often small and surrounded by a natural water barrier to dispersal, they generally form discrete isolated habitats. Therefore, islands may play a key role in the distribution of the genetic diversity of insects, including flies. Results: To characterize the genetic structure of island populations of Bactrocera dorsalis, we analyzed a dataset containing both microsatellite and mtDNA loci of B. dorsalis samples collected from six offshore islands in Southern China. The microsatellite data revealed a high level of genetic diversity among these six island populations based on observed heterozygosity (Ho), expected heterozygosity (HE), Nei's standard genetic distance (D), genetic identity (I) and the percentage of polymorphic loci (PIC). These island populations had low F ST values (F ST = 0.04161), and only 4.16 % of the total genetic variation in the species was found on these islands, as determined by an analysis of molecular variance. Based on the mtDNA COI data, high nucleotide diversity (0.9655) and haplotype diversity (0.00680) were observed in all six island populations. F-statistics showed that the six island populations exhibited low or medium levels of genetic differentiation among some island populations. To investigate the population differentiation between the sampled locations, a factorial correspondence analysis and both the unweighted pair-group method with arithmetic mean and Bayesian clustering methods were used to analyze the microsatellite data. The results showed that Hebao Island, Weizhou Island and Dong'ao Island were grouped together in one clade. Another clade consisted of Shangchuan Island and Naozhou Island, and a final, separate clade contained only the Wailingding Island population. Phylogenetic analysis of the mtDNA COI sequences revealed that the populations on each of these six islands were closely related to different populations on mainland China. Conclusions: Our study suggests that these island populations have high genetic diversity, experience frequent gene flow and exhibit low or medium levels of genetic differentiation among some island populations. Therefore, the geographic isolation of the six islands does not appear to be a major dispersal barrier to B. dorsalis. Such knowledge is helpful for a better understanding of evolutionary processes of the species of island populations.
Data from: An isolated white-tailed deer (Odocoileus virginianus) population on St. John, US Virgin Islands shows low inbreeding and comparable heterozygosity to other larger populations
<p><span>This is the first study to document the genetic diversity of the white-tailed deer population on St. John, US Virgin Islands. The island population was founded by a small number of animals, has very limited hunting or predation, and recently experienced a reduction in size following an extended drought in 2015. DNA samples were collected from hair from 23 anesthetized adult deer (13 males, 10 females) ranging in age from 1-8 years (3.36<u>+</u> 1.9 yr) and also from fecal DNA samples, for a total of 42 individuals analyzed for genetic diversity. The St. John deer data set averaged 4.19 alleles per marker and demonstrates the second lowest number of alleles (A) when compared to other populations of <i>Odocoileus virginianus</i> (4.19). Heterozygosity was similar to the other studies (0.54) with little evidence of inbreeding. To explain the level of heterogygosity and lack of inbreeding within the St. John population, three hypotheses are proposed, including the effect of intrinsic biological traits within the population, a recent infusion of highly heterogeneous loci from North American populations, and a consistent level of immigration from a nearby island. Additional work is needed to further understand the genetic history of the St. John and regional deer populations. </span></p>
Figure 4 in Effects of islanding on the genetics of Niviventer confucianus (Mamalia: Rodentia: Muridae) populations in the Thousand Island Lake region
Figure 4. Relationship between polymorphic information content (PIC) and island area.
Figure 3 in Effects of islanding on the genetics of Niviventer confucianus (Mamalia: Rodentia: Muridae) populations in the Thousand Island Lake region
Figure 3. Relationship between values of FST and geographic distance, n = 78.
Microsatellite data from: Multiple colonizations and genetic differentiation from the mainland populations in insular populations of the perennial herb Solidago virgaurea complex (Asteraceae) on recently formed nearshore oceanic islands
<p><b>Aim: </b>Although the evolution of island endemic plants has long been investigated, the majority of such studies have focused on species with remarkable levels of morphological variation and on islands substantially far from the mainland. Except for a few examples such as the Canary Islands, endemic plants on nearshore oceanic islands have received less attention. In this study, we examined the <i>Solidago virgaurea </i>complex on the Japanese mainland Honshu and the adjacent Izu Islands to investigate the population genetic structure and dynamics in plants endemic to nearshore and recently formed oceanic islands.</p> <p><b>Location: </b>Japanese mainland Honshu and the adjacent Izu Islands</p> <p><b>Taxon: </b><i>Solidago virgaurea</i> (Asteraceae)</p> <p><b>Methods: </b>Sixteen and nine populations of <i>S. virgaurea</i> complex were sampled from the mainland and islands, respectively; phylogeographic and population genetics analyses were performed using plastid DNA and nuclear microsatellite DNA variations.</p> <p><b>Results: </b>Phylogenetically close plastid DNA haplotypes were shared between the mainland and islands, although the populations of <i>S. virgaurea</i> from different islands tended to exhibit phylogenetically distinct haplotypes. Admixture analyses based on nuclear DNA variations revealed distinct genetic structures between the mainland and island populations. Gene flow among islands is restricted but may partially offset genetic drift on each island.</p> <p><b>Main conclusions: </b>The genetic structure observed in this study may not have originated from a single dispersal event and successive expansion but rather from at least three colonization events and subsequent gene flow among island populations. Based on the nuclear DNA variations, the Izu Island populations of <i>S. virgaurea</i> are genetically distinct from the mainland ones. Repeated colonization events may have provided sufficient genetic diversity, which would generally be susceptible to founder effects and exert a driving force for evolutionary adaptation, to these oceanic island populations.</p>
Pollinator surveys of two populations located in the North and South of Mallorca (Balearic Islands, Spain) in 2021 from May to July focused on Eryngium maritimum pollinators
<p>The aim of this study is to analyse the role played by E. maritimum in the dune pollination network of the Balearic Islands, where there is an intense anthropogenic impact in its habitat. For this purpose, two populations located in the North and South of Mallorca were chosen, in which diurnal transects were carried out to observe and capture pollinators on 15 plant species during the anthesis period of E. maritimum. The flowering period of 10 plant species flowering at the same period than E. maritimum was analysed to identify periods of competition</p> <p>First sampling area was located in Son Serra de Marina (SS, 39.7309N, 3.2382E), in the North of the island. We carried out three 50m linear transects along the seashore. Transects were randomly located at a minimum of 100 m from each other in order to enhance the chances of a fair sampling of most of the flora. In both areas, vegetation, and so transects, followed a clear sequence from the seashore inland. Areas were sampled for 10 weeks, from the beginning of E. maritimum flowering in the first week of June until the second week of July, plus two weeks extra (one after and one before) in order two observe pollinator diversity variation. Surveys took place between 08:00–18:00h under favourable weather conditions. A pollinator survey involved an observer slowly walking (40 min) along a transect and recording only those insects that contacted the plant's reproductive structures while actively searching for pollen and/or nectar. </p> <p>The dataset indicates each observation in a single row. Population, hour, transect, pollinator and plant taxonomical information, if the pollinator was captured, photographed or if it visited multiple species is indicated. </p>
Figure 5 from: Watts C, Thornburrow D, Stringer I, Cave V (2017) Population expansion by Cook Strait giant wētā, Deinacrida rugosa (Orthoptera: Anostostomatidae), following translocation to Matiu/Somes Island, New Zealand, and subsequent changes in abundance. Journal of Orthoptera Research 26: 171-180. https://doi.org/10.3897/jor.26.21712
Figure 5 - Distribution of geckos and skinks as detected using tracking tunnels on Matiu/Somes Island. Data are combined presence-absence of footprints on cards from tracking tunnels baited with peanut butter during three nights in 2008 and four nights in both 2013 and 2015. 2008 data from Watts et al. (2009, 2011).
Figure 4 from: Watts C, Thornburrow D, Stringer I, Cave V (2017) Population expansion by Cook Strait giant wētā, Deinacrida rugosa (Orthoptera: Anostostomatidae), following translocation to Matiu/Somes Island, New Zealand, and subsequent changes in abundance. Journal of Orthoptera Research 26: 171-180. https://doi.org/10.3897/jor.26.21712
Figure 4 - Distribution of adult Deinacrida rugosa presence as evidenced by combining detection with tracking tunnels baited with peanut butter and finding them by searching at night. Searches extended 15 m from each tracking tunnel. Results are presence-absence derived from three searches over three nights in 2008, and four searches over four nights in both 2013 and 2015. Areas searched (tracking tunnel transects) are indicated as white lines. 2008 data from Watts et al. (2009, 2011).
Figure 1 from: Watts C, Thornburrow D, Stringer I, Cave V (2017) Population expansion by Cook Strait giant wētā, Deinacrida rugosa (Orthoptera: Anostostomatidae), following translocation to Matiu/Somes Island, New Zealand, and subsequent changes in abundance. Journal of Orthoptera Research 26: 171-180. https://doi.org/10.3897/jor.26.21712
Figure 1 - Arrangement of tracking tunnel transects (shown in white) along the footpaths on Matiu-Somes Island. Each circle indicates the location of a tracking tunnel. The dark hatched area indicates where Deinacrida rugosa were released in 1996. The light hatched area shows where 186 adult D. rugosa were taken for translocation in 2007 and 2008. Note that no wētā were removed from the North transect.
Figure 3 from: Watts C, Thornburrow D, Stringer I, Cave V (2017) Population expansion by Cook Strait giant wētā, Deinacrida rugosa (Orthoptera: Anostostomatidae), following translocation to Matiu/Somes Island, New Zealand, and subsequent changes in abundance. Journal of Orthoptera Research 26: 171-180. https://doi.org/10.3897/jor.26.21712
Figure 3 - Distribution of tracking tunnels with footprints of adult Deinacrida rugosa in 2008, 2013 and 2015. Cards were set over 3 nights in 2008 (Watts et al. (2009, 2011)) and over 4 nights in 2013 and 2015.
Figure 2 from: Watts C, Thornburrow D, Stringer I, Cave V (2017) Population expansion by Cook Strait giant wētā, Deinacrida rugosa (Orthoptera: Anostostomatidae), following translocation to Matiu/Somes Island, New Zealand, and subsequent changes in abundance. Journal of Orthoptera Research 26: 171-180. https://doi.org/10.3897/jor.26.21712
Figure 2 - Locations where all adult Deinacrida rugosa were found in 2008, 2013, 2015 and 2016. Tracking tunnel transects are indicated as white lines. 2008 data from Watts et al. (2009, 2011).
High genetic diversity but no geographic structure of Aedes albopictus populations in Reunion Island _ Dataset
<p>Microsatellite dataset of <em>Aedes albopictus</em> individuals sampled in Reunion Island. </p>
Figure 2 from: Degtjarenko P, Jüriado I, Mandel T, Tõrra T, Saag A, Scheidegger C, Randlane T (2019) Microsatellite based genetic diversity of the widespread epiphytic lichen Usnea subfloridana (Parmeliaceae, Ascomycota) in Estonia: comparison of populations from the mainland and an island. MycoKeys 58: 27-45. https://doi.org/10.3897/mycokeys.58.36557
Figure 2 Total number of shared haplotypes between populations of Usnea subfloridana in the south-eastern (SE), the western (W) and northern (N) regions of Estonia; the thickness of lines reflects the number of shared haplotypes between populations.
Figure 3 from: Degtjarenko P, Jüriado I, Mandel T, Tõrra T, Saag A, Scheidegger C, Randlane T (2019) Microsatellite based genetic diversity of the widespread epiphytic lichen Usnea subfloridana (Parmeliaceae, Ascomycota) in Estonia: comparison of populations from the mainland and an island. MycoKeys 58: 27-45. https://doi.org/10.3897/mycokeys.58.36557
Figure 3 Usnea subfloridana multilocus genotypes in the principal component analysis (PCA) ordination plot of the first and second axes. Samples are grouped according to the presence of lichen substance: samples containing thamnolic (square) or squamatic acid (circle).
Figure 1 from: Degtjarenko P, Jüriado I, Mandel T, Tõrra T, Saag A, Scheidegger C, Randlane T (2019) Microsatellite based genetic diversity of the widespread epiphytic lichen Usnea subfloridana (Parmeliaceae, Ascomycota) in Estonia: comparison of populations from the mainland and an island. MycoKeys 58: 27-45. https://doi.org/10.3897/mycokeys.58.36557
Figure 1 Distribution map of Usnea subfloridana in Estonia (light grey squares) and study populations (black circles) on Hiiumaa island in the western region (W), in the south-eastern region (SE) and in the northern region of Estonia; the map of Scandinavia was taken from free map resource http://d-maps.com/carte.php?num_car=5977&lang=en.
Figure 6 from: Degtjarenko P, Jüriado I, Mandel T, Tõrra T, Saag A, Scheidegger C, Randlane T (2019) Microsatellite based genetic diversity of the widespread epiphytic lichen Usnea subfloridana (Parmeliaceae, Ascomycota) in Estonia: comparison of populations from the mainland and an island. MycoKeys 58: 27-45. https://doi.org/10.3897/mycokeys.58.36557
Figure 6 Alleles of Usnea subfloridana and explanatory variables mean annual air temperature ('Temp') and geographical longitude of populations ('Long') in the bi-plot of the redundancy analysis (RDA) of the first and second axes. Labels of alleles prefixed by '8' or '9' indicate that these alleles belong to loci Us08 or Us09, respectively; for example, 8201 means that allele 201 is from Us08
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