scholarly journals Landscape structure and the genetic effects of a population collapse

2014 ◽  
Vol 281 (1796) ◽  
pp. 20141798 ◽  
Author(s):  
Serena A. Caplins ◽  
Kimberly J. Gilbert ◽  
Claudia Ciotir ◽  
Jens Roland ◽  
Stephen F. Matter ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Landscape Structure ◽  
Isolation By Distance ◽  
Spatial Genetic Structure ◽  
Genetic Differentiation Of Populations ◽  
Patch Connectivity ◽  
Landscape Genetic ◽  
Independent Effects ◽  
Patterns And Processes

Both landscape structure and population size fluctuations influence population genetics. While independent effects of these factors on genetic patterns and processes are well studied, a key challenge is to understand their interaction, as populations are simultaneously exposed to habitat fragmentation and climatic changes that increase variability in population size. In a population network of an alpine butterfly, abundance declined 60–100% in 2003 because of low over-winter survival. Across the network, mean microsatellite genetic diversity did not change. However, patch connectivity and local severity of the collapse interacted to determine allelic richness change within populations, indicating that patch connectivity can mediate genetic response to a demographic collapse. The collapse strongly affected spatial genetic structure, leading to a breakdown of isolation-by-distance and loss of landscape genetic pattern. Our study reveals important interactions between landscape structure and temporal demographic variability on the genetic diversity and genetic differentiation of populations. Projected future changes to both landscape and climate may lead to loss of genetic variability from the studied populations, and selection acting on adaptive variation will likely occur within the context of an increasing influence of genetic drift.

scholarly journals Low genetic diversity in the endangered Taxus yunnanensis following a population bottleneck, a low effective population size and increased inbreeding

2016 ◽  
Vol 65 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Y. C. Miao ◽  
Z. J. Zhang ◽  
J. R. Su
Keyword(s):  
Genetic Diversity ◽  
Habitat Fragmentation ◽  
Population Size ◽  
Effective Population Size ◽  
Spatial Genetic Structure ◽  
Population Bottleneck ◽  
Effective Population ◽  
Taxus Yunnanensis ◽  
Low Genetic Diversity ◽  
Two Populations

Abstract Taxus yunnanensis, which is an endangered tree that is considered valuable because it contains the effective natural anticancer metabolite taxol and heteropolysaccharides, has long suffered from severe habitat fragmentation. In this study, the levels of genetic diversity in two populations of 136 individuals were analyzed based on eleven polymorphic microsatellite loci. Our results suggested that these two populations were characterized by low genetic diversity (NE = 2.303/2.557; HO = 0.168/0.142; HE = 0.453/0.517), a population bottleneck, a low effective population size (Ne = 7/9), a high level of inbreeding (FIS = 0.596/0.702), and a weak, but significant spatial genetic structure (Sp = 0.001, b = −0.001*). Habitat fragmentation, seed shadow overlap and limited seed and pollen dispersal and potential selfing may have contributed to the observed gene tic structure. The results of the present study will enable development of practical conservation measures to effectively conserve the valuable genetic resources of this endangered plant.

scholarly journals Temporal patterns of spatial genetic structure and effective population size in European plaice (Pleuronectes platessa) along the west coast of Scotland and in the Irish Sea

2009 ◽  
Vol 67 (4) ◽  
pp. 607-616 ◽  
Author(s):  
Phillip C. Watts ◽  
Suzanne M. Kay ◽  
Drew Wolfenden ◽  
Clive J. Fox ◽  
Audrey J. Geffen ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Population Size ◽  
Effective Population Size ◽  
West Coast ◽  
Isolation By Distance ◽  
Spatial Genetic Structure ◽  
Irish Sea ◽  
Effective Population ◽  
The West ◽  
Pleuronectes Platessa

Abstract Watts, P. C., Kay, S. M., Wolfenden, D., Fox, C. J., Geffen, A. J., Kemp, S. J., and Nash, R. D. M. 2010. Temporal patterns of spatial genetic structure and effective population size in European plaice (Pleuronectes platessa) along the west coast of Scotland and in the Irish Sea. – ICES Journal of Marine Science, 67: 607–616. The European plaice (Pleuronectes platessa) is a relatively mobile flatfish species, and previous studies have reported broad-scale genetic homogeneity among samples distributed throughout much of its northern European range, with no evidence for isolation-by-distance (IBD) population structure. Using microsatellite loci, the pattern of spatial genetic structure and effective population size is characterized for >800 plaice collected from locations off the west coast of Great Britain over a 3-year period (2001–2003). The plaice populations are characterized by weak spatial genetic structure, consistent with tagging data, and relatively low effective population sizes. In contrast to previous work, a pattern of isolation by distance is present among pairs of plaice from within each sampling period. However, IBD spatial structure was not observed for comparisons of plaice from different sampling years or using the entire dataset, indicating a patchy temporal genetic structure. Therefore, pooling the data from several years can mask subtle patterns of population structure and potentially confound estimation of other important demographic parameters, such as effective population size.

Genetic diversity and gene flow patterns in two riverine plant species with contrasting life-history traits and distributions across a large inland floodplain

2020 ◽  
Vol 68 (5) ◽  
pp. 384
Author(s):  
William Higgisson ◽  
Dianne Gleeson ◽  
Linda Broadhurst ◽  
Fiona Dyer
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Genetic Structure ◽  
Water Resource ◽  
Isolation By Distance ◽  
Spatial Genetic Structure ◽  
Geographic Distance ◽  
Resource Development ◽  
Water Resource Development ◽  
Floodplain River

Gene flow is a key evolutionary driver of spatial genetic structure, reflecting demographic processes and dispersal mechanisms. Understanding how genetic structure is maintained across a landscape can assist in setting conservation objectives. In Australia, floodplains naturally experience highly variable flooding regimes that structure the vegetation communities. Flooding plays an important role, connecting communities on floodplains and enabling dispersal via hydrochory. Water resource development has changed the lateral-connectivity of floodplain-river systems. One possible consequence of these changes is reduced physical and subsequent genetic connections. This study aimed to identify and compare the population structure and dispersal patterns of tangled lignum (Duma florulenta) and river cooba (Acacia stenophylla) across a large inland floodplain using a landscape genetics approach. Both species are widespread throughout flood prone areas of arid and semiarid Australia. Tangled lignum occurs on floodplains while river cooba occurs along rivers. Leaves were collected from 144 tangled lignum plants across 10 sites and 84 river cooba plants across 6 sites, on the floodplain of the lower and mid Lachlan River, and the Murrumbidgee River, NSW. DNA was extracted and genotyped using DArTseq platforms (double digest RADseq). Genetic diversity was compared with floodplain-river connection frequency, and genetic distance (FST) was compared with river distance, geographic distance and floodplain-river connection frequency between sites. Genetic similarity increased with increasing floodplain-river connection frequency in tangled lignum but not in river cooba. In tangled lignum, sites that experience more frequent flooding had greater genetic diversity and were more genetically homogenous. There was also an isolation by distance effect where increasing geographic distance correlated with increasing genetic differentiation in tangled lignum, but not in river cooba. The distribution of river cooba along rivers facilitates regular dispersal of seeds via hydrochory regardless of river level, while the dispersal of seeds of tangled lignum between patches is dependent on flooding events. The genetic impact of water resource development may be greater for species which occur on floodplains compared with species along river channels.

Genetic Diversity Within and Among Populations of Shorea Robusta Roxb. Ex Gaertn. In Bangladesh and Its Implications for Conservation

2021 ◽  
Vol 50 (2) ◽  
pp. 405-412
Author(s):  
Pragga Saha Sharmi ◽  
Md Abul Kashem ◽  
Rifat Samad ◽  
Mohammad Zabed Hossain
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Isolation By Distance ◽  
Genetic Erosion ◽  
Mantel Test ◽  
Small Population ◽  
Deciduous Forests ◽  
Shorea Robusta ◽  
Low Genetic Diversity ◽  
Geographical Regions

Fragmentation and reduction of natural population size render threats to the conservation of forest resources through depletion of genetic diversity. Hence, information on genetic structure of Sal (Shorea robusta Roxb. ex Gaertn.) populations is relevant for proper management and conservation of the tropical deciduous forests. The present study focused on assessing the genetic diversity of the populations of Sal which was the dominant tree species of the deciduous forests of Bangladesh. Plant leaf samples were collected from the three populations of Sal distributed in the three geographical regions including Madhupur tract in the districts Tangail and Gazipur and that of the districts of Cumilla and Dinajpur. DNA band profiles were generated using eight ISSR primers for a total of 13 samples taken from the three populations. Statistical analysis was done using PopGen 32 and GenAlEx 6.5 softwares. Principal coordinate analysis done on the DNA band profiles revealed that Sal populations of Madhupur tract and Cumilla positioned nearby while Dinajpur showed maximum genetic distance with that of Cumilla. Mantel test showed significant (p=0.05) correlation between genetic and geographic distances indicating “Isolation by Distance”. Data of the present study indicated higher genetic polymorphism (68.87%) in the Sal population of Madhupur tract compared to other two populations. Small population size of Sal of Dinajpur forest might be related with its low genetic diversity. Data of the present study suggest immediate attention for the conservation of Sal forests in Bangladesh before further genetic erosion occurs. Bangladesh J. Bot. 50(2): 405-412, 2021 (June)

scholarly journals Genetic diversity and spatial genetic structure within a population of an aromatic shrub, Lippia origanoides (Verbenaceae), in the Chicamocha Canyon, northeastern Colombia

2008 ◽  
Vol 90 (6) ◽  
pp. 455-465 ◽  
Author(s):  
ADRIANA SUÁREZ G. ◽  
GENIS CASTILLO ◽  
MARIA I. CHACÓN S.
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
Diversity Index ◽  
Isolation By Distance ◽  
Spatial Genetic Structure ◽  
Classical Model ◽  
Issr Markers ◽  
Breeding Systems ◽  
Group Method ◽  
Pair Group

SummaryThe geographical scale of genetic structure in a continuous population is highly dependent on its breeding system and dispersion capabilities, and this knowledge is important for the study of population dynamics as well as for conservation purposes. In the present study, spatial autocorrelation statistics and intersimple sequence repeat (ISSR) markers were used to describe the genetic structure of a natural population of a prominent aromatic plant, Lippia origanoides, native to the Chicamocha Canyon in northeastern Colombia. For this purpose, individuals were sampled from two localities within the Chicamocha Canyon, where the species is abundant and continuously distributed. Cluster (principal coordinate analysis (PCO) and unweighted pair group method using arithmetic averages (UPGMA)), analysis of molecular variance (AMOVA) and Bayesian analyses revealed a low level of genetic differentiation among the two localities, suggesting that they belong to a single population. Genetic diversity levels in this population, described as the percentage of polymorphic loci (P=86·21%) and quantified using Shannon's diversity index (I=0·453) and the average panmictic heterozygosity (HB=0·484), were shown to be comparable to or higher than that in other plant species with allogamous breeding systems and to other related Verbenaceae species. Fine-scale autocorrelation analyses showed a pattern consistent with the classical model of isolation by distance with moderate but significant levels of local spatial structure. Our results suggest that sampling individuals at distances greater than ~1·2 km may result in the collection of different genotypes, which could help preserve the levels of genetic diversity in a propagation programme. The causes of this spatial pattern are currently unknown and could be influenced by many contemporary factors such as restricted seed dispersal and/or short-distance pollen movement, among others.

scholarly journals Surrounding landscape structures, rather than habitat age, drive genetic variation of typical calcareous grassland plant species

2020 ◽  
Vol 35 (12) ◽  
pp. 2881-2893
Author(s):  
Theresa Anna Lehmair ◽  
Ellen Pagel ◽  
Peter Poschlod ◽  
Christoph Reisch
Keyword(s):  
Genetic Diversity ◽  
Land Use ◽  
Genetic Variation ◽  
Population Size ◽  
Habitat Quality ◽  
Landscape Structure ◽  
Calcareous Grassland ◽  
Calcareous Grasslands ◽  
Surrounding Landscape ◽  
Swabian Alb

Abstract Context Land use change reduced calcareous grasslands throughout Europe during the last decades. Subsequent fragmentation and habitat deterioration led, moreover, to a massive biodiversity decline. To counteract this alarming development, a clear understanding of genetic variation patterns, as fundamental level of biodiversity, becomes inevitable. Objectives The aim of our study was to identify the drivers of genetic variation in common calcareous grassland plant species. More specifically, we tested whether genetic diversity or differentiation of Asperula cynanchica, Campanula rotundifolia, and Linum catharticum depend on habitat age, landscape structure, habitat quality, and/or population size. Methods We investigated 912 individuals, 304 per study species, from 19 calcareous grasslands across the Swabian Alb in Baden-Württemberg (Germany) using AFLP analyses. Results We observed no significant influence of habitat age on genetic diversity and differentiation. Habitat quality also had no impact on genetic diversity and population size only showed weak effects. However, genetic diversity strongly depended on landscape structure represented by distance to the nearest settlement, total area of surrounding calcareous grasslands, and their connectivity. Conclusions Migratory sheep herding is considered as main land use in calcareous grasslands on the Swabian Alb and thus, landscape structures in the study region may describe movement patterns of grazing livestock. In this study, genetic variation in calcareous grassland populations was strongly affected by surrounding landscape structures and subsequent grazing patterns. Therefore, we assume that moderate grazing intensities over the long term may increase levels of genetic diversity, whereas periods of overgrazing or abandonment could lower genetic diversity.

scholarly journals Genetic differentiation is determined by geographic distance in Clarkia pulchella

2018 ◽  
Author(s):  
Megan Bontrager ◽  
Amy L. Angert
Keyword(s):  
Genetic Diversity ◽  
Genetic Differentiation ◽  
Geographic Distance ◽  
Geographic Range ◽  
Range Limits ◽  
North West ◽  
Range Edge ◽  
Genetic Differentiation Of Populations ◽  
Landscape Genetic ◽  
Clarkia Pulchella

AbstractBoth environmental differences and geographic distances may contribute to the genetic differentiation of populations on the landscape. Understanding the relative importance of these drivers is of particular interest in the context of geographic range limits, as both swamping gene flow and lack of genetic diversity are hypothesized causes of range limits. We investigated the landscape genetic structure of 32 populations of the annual wildflower Clarkia pulchella from across the species’ geographic range in the interior Pacific North-west. We tested whether climatic differences between populations influenced the magnitude of their genetic differentiation. We also investigated patterns of population structure and geographic gradients in genetic diversity. Contrary to our expectations, we found an increase in genetic diversity near the species’ northern range edge. We found no notable contribution of climatic differences to genetic differentiation, indicating that any processes that might operate to differentiate populations based on temperature or precipitation are not affecting the putatively neutral loci in these analyses. Rather, these results support seed and pollen movement at limited distances relative to the species’ range and that this movement and the subsequent incorporation of immigrants into the local gene pool are not influenced by temperature or precipitation similarities among populations. We found that populations in the northern and southern parts of the range tended to belong to distinct genetic groups and that central and eastern populations were admixed between these two groups. This pattern could be the result of a past or current geographic barrier associated with the Columbia Plateau, or it could be the result of spread from separate sets of refugia after the last glacial maximum.

scholarly journals Levels and patterns of genetic diversity differ between two closely related endemicArabidopsisspecies

2016 ◽  
Author(s):  
Julie Jacquemin ◽  
Nora Hohmann ◽  
Matteo Buti ◽  
Alberto Selvaggi ◽  
Thomas Müller ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Effective Population Size ◽  
Endemic Species ◽  
Isolation By Distance ◽  
Demographic History ◽  
Adaptive Potential ◽  
Effective Population ◽  
Distribution Ranges ◽  
Small Effective Population Size

AbstractTheory predicts that a small effective population size leads to slower accumulation of mutations, increased levels of genetic drift and reduction in the efficiency of natural selection. Therefore endemic species should harbor low levels of genetic diversity and exhibit a reduced ability of adaptation to environmental changes.Arabidopsis pedemontanaandArabidopsis cebennensis, two endemic species from Italy and France respectively, provide an excellent model to study the adaptive potential of species with small distribution ranges. To evaluate the genome-wide levels and patterns of genetic variation, effective population size and demographic history of both species, we genotyped 53A. pedemontanaand 28A. cebennensisindividuals across the entire species ranges with Genotyping-by-Sequencing. SNPs data confirmed a low genetic diversity forA. pedemontanaalthough its effective population size is relatively high. Only a weak population structure was observed over the small distribution range ofA. pedemontana, resulting from an isolation-by-distance pattern of gene flow. In contrary,A. cebennensisindividuals clustered in three populations according to their geographic distribution. Despite this and a larger distribution, the overall genetic diversity was even lower forA. cebennensisthan forA. pedemontana.A demographic analysis demonstrated that both endemics have undergone a strong population size decline in the past, without recovery. The more drastic decline observed inA. cebennensispartially explains the very small effective population size observed in the present population. In light of these results, we discuss the adaptive potential of these endemic species in the context of rapid climate change.

Genetic impacts of habitat loss on the rare Banded Ironstone Formation endemic Ricinocarpos brevis (Euphorbiaceae)

2019 ◽  
Vol 67 (3) ◽  
pp. 183 ◽  
Author(s):  
Siegfried L. Krauss ◽  
Janet Anthony
Keyword(s):  
Genetic Diversity ◽  
Genetic Differentiation ◽  
Isolation By Distance ◽  
Spatial Genetic Structure ◽  
Geographic Distance ◽  
Mining Operations ◽  
Analysis Of Molecular Variance ◽  
Mantel Tests ◽  
Tests Of Association ◽  
Potential Impact

Ricinocarpos brevis (Euphorbiaceae) is a declared rare species currently known from only three Banded Ironstone Formation (BIF) ranges (Perrinvale, Johnston and Windarling Ranges) in the Yilgarn region of Western Australia. The present study assessed the potential impact of proposed mining on genetic diversity within R. brevis. Approximately 30 plants were sampled from each of 14 sites across the known distribution of R. brevis. Genetic variation and its spatial structure was assessed with 144 polymorphic AFLP markers that were generated by two independent primer pairs: M-CTG/P-AC (81 markers) and M-CTA/P-AC (63 markers). Hierarchical spatial genetic structure was assessed by an analysis of molecular variance (AMOVA), Mantel tests of association between genetic- and geographic-distance and ordination. Specific attention was given to the extent of genetic differentiation of the three populations on the Windarling Range W4 deposit, which was proposed for mining operations. Strong genetic differentiation (ΦPT=0.186–0.298) among the three ranges was found. Genetic differentiation of the Johnston Range populations from Windarling and Perrinvale was greater than expected under isolation by distance predictions, suggesting adaptive genetic differentiation driven by site environmental differences, reflected by differences in plant community, substrate and landscape features. In contrast, genetic differentiation among the three Windarling Range regions (W2, W3, W4) was weaker (ΦPT=0.055–0.096). Mean pairwise ΦPT=0.078 for the 10 Windarling sites, which was unchanged with the removal of the W4 populations. In addition, none of the markers scored were unique to the W4 populations. Thus, for this set of markers, the removal of plants on the Windarling Range W4 deposit had little impact on genetic diversity within R. brevis. Strong concordance in results from the independent datasets generated by the two AFLP primer pairs provides overall support for the conclusions drawn.

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