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Limited Gene Flow (limited + gene_flow)
Selected AbstractsDistribution patterns of the Q and B biotypes of Bemisia tabaci in the Mediterranean Basin based on microsatellite variationENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2007B. Simón Abstract At least five of the biotypes described in the Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) complex are known to be present in the Mediterranean Basin area. Only two of them, however, are economically relevant, that is, biotypes B and Q. Biological and genetic differences between the two biotypes have been well studied, but less is known about their patterns of genetic variation and population structure. To address these issues, a study was undertaken based on variation at six microsatellite loci among a subset of nine B. tabaci populations (five belonging to the Q and four to the B biotype). The data obtained show that (i) these loci showed considerable polymorphism in the Q and B biotypes populations although the presence of null alleles can obscure the picture; (ii) the Iberian-Q, Canarian-Q, and Egyptian-B populations exhibit heterozygosity excess as a result of bottleneck events; (iii) the low genetic differentiation between the Israeli, Iberian Peninsula, and Italian populations suggest that these populations share a common gene pool; (iv) the genetic distances between the Canarian-Q population and the geographically close population from Morocco indicates spatial isolation and a limited gene flow; and finally (v) the microsatellite data for the B populations indicate that the whiteflies from Egypt and Israel have a close phylogenetic relationship, but the source of these biotype B invasions into the Mediterranean area remains unknown. [source] SINE insertion polymorphism on the X chromosome differentiates Anopheles gambiae molecular formsINSECT MOLECULAR BIOLOGY, Issue 4 2005M. J. Barnes Abstract Polymorphic SINE insertions can be useful markers for assessing population structure and differentiation. Maque is a family of SINE elements which, based on bioinformatic analysis, was suggested to have been active recently in Anopheles gambiae, the major vector of malaria. Here, we report the development of polymorphic Maque insertions as population genetic markers in A. gambiae, and the use of these markers to better characterize divergence on the X chromosome between A. gambiae M and S molecular forms in populations from Burkina Faso and Mali. Our data are consistent with the recent activity of Maque. Phylogenetic analysis suggests that at least two recently active lineages may have a role in mediating genome evolution. We found differences in element insertion frequency and sequence between the M and S populations analysed. Significant differentiation was observed between these two groups across a 6 Mb region at the proximal (centromeric) end of the X chromosome. Locus-specific FST values ranged from 0.14 to 1.00 in this region, yet were not significantly different from zero in more distal locations on the X chromosome; the trend was consistent in populations from both geographical locales suggesting that differentiation is not due to local adaptation. Strong differentiation between M and S at the proximal end of the X chromosome, but not outside this region, suggests the action of selection counteracting limited gene flow between these taxa and supports their characterization as incipient species. [source] Ecological specialization correlates with genotypic differentiation in sympatric host-populations of the pea aphidJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2006A. FRANTZ Abstract The pea aphid, Acyrthosiphon pisum, encompasses distinct host races specialized on various Fabaceae species, but the extent of genetic divergence associated with ecological specialization varies greatly depending on plant and geographic origins of aphid populations. Here, we studied the genetic structure of French sympatric pea aphid populations collected on perennial (pea and faba bean) and annual (alfalfa and red clover) hosts using 14 microsatellite loci. Classical and Bayesian population genetics analyses consistently identified genetic clusters mostly related to plant origin: the pea/faba bean cluster was highly divergent from the red clover and the alfalfa ones, indicating they represent different stages along the continuum of genetic differentiation. Some genotypes were assigned to a cluster differing from the one expected from their plant origin while others exhibited intermediate genetic characteristics. These results suggest incomplete barriers to gene flow. However, this limited gene flow seems insufficient to prevent ecological specialization and genetic differentiation in sympatry. [source] Population Genetic Structure of the Medicinal Plant Vitex rotundifolia in China: Implications for its Use and ConservationJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2008Yuan Hu Abstract Vitex rotundifolia L. is an important plant species used in traditional Chinese medicine. For its efficient use and conservation, genetic diversity and clonal variation of V. rotundifolia populations in China were investigated using inter-simple sequence repeat markers. Fourteen natural populations were included to estimate genetic diversity, and a large population with 135 individuals was used to analyze clonal variation and fine-scale spatial genetic structure. The overall genetic diversity (GD) of V. rotundifolia populations in China was moderate (GD = 0.190), with about 40% within-population variation. Across all populations surveyed, the average within-population diversity was moderate (P = 22.6%; GD = 0.086). A relatively high genetic differentiation (Gst = 0.587) among populations was detected based on the analysis of molecular variance data. Such characteristics of V. rotundifolia are likely attributed to its sexual/asexual reproduction and limited gene flow. The genotypic diversity (D = 0.992) was greater than the average values of a clonal plant, indicating its significant reproduction through seedlings. Spatial autocorrelation analysis showed a clear within-population structure with gene clusters of approximately 20 m. Genetic diversity patterns of V. rotundifolia in China provide a useful guide for its efficient use and conservation by selecting particular populations displaying greater variation that may contain required medicinal compounds, and by sampling individuals in a population at >20 m spatial intervals to avoid collecting individuals with identical or similar genotypes. [source] ISSR Analysis of the Genetic Diversity of the Endangered Species Sinopodophyllum hexandrum (Royle) Ying from Western Sichuan Province, ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 10 2006Meng Xiao Abstract Sinopodophyllum hexandrum (Royle) Ying is an important medicinal and endangered species. Inter-simple sequence repeats (ISSR) analysis was conducted on seven natural populations from western Sichuan Province to investigate the genetic diversity of S. hexandrum. Leaf samples of 140 individuals were collected. Of the 139 discernible fragments generated by 12 selected primers (among 100 primers), 54 appeared to be polymorphic. The percentage of polymorphic bands (PPB) was 38.85% at the species level, and PPB within a population ranged from 7.91% to 23.74%. Low levels of genetic variation (He= 0.092, Ho= 0.142) and high levels of genetic differentiation among the populations (Gst= 62.25%) was detected on the basis of results from POPGENE and analysis of molecular variance (AMOVA), respectively. Furthermore, the limited gene flow (Nm= 0.361) may result from biological characteristics, such as self-pollination and short distance seed dispersal. Based on the genetic and ecological information available for S. hexandrum, we propose some appropriate strategies for the conservation of the endangered medicinal species in this region, namely rescuing and conserving the core populations for in situ conservation and sampling and preserving more populations with fewer individuals from each population for ex situ conservation. (Managing editor: Li-Hui Zhao) [source] Nuclear and chloroplast microsatellites reveal extreme population differentiation and limited gene flow in the Aegean endemic Brassica cretica (Brassicaceae)MOLECULAR ECOLOGY, Issue 23 2007KRISTINA EDH Abstract Nuclear and chloroplast microsatellite markers were used to study population structure and gene flow among seven Cretan populations of the Aegean endemic plant species Brassica cretica (Brassicaceae). Both nuclear and chloroplast markers revealed exceptionally high levels of population differentiation (overall FST = 0.628 and 1.000, respectively) and relatively little within-population diversity (overall HS = 0.211 and 0.000, respectively). Maximum-likelihood estimates of directional migration rates were low among all pairs of populations (average Nm = 0.286). There was no evidence that differences in flower colour between populations had any influence on historical levels of gene flow. In addition, a haplotype network showed that all five chloroplast haplotypes found in the sample were closely related. Together, these results suggest that current patterns of diversification in B. cretica are mainly a result of genetic drift during the last half million years. The main conclusions from the present study are consistent with the prevailing hypothesis that plant diversification in the Aegean region is driven by random rather than adaptive differentiation among isolated populations. [source] Phylogeography of the mountain chickadee (Poecile gambeli): diversification, introgression, and expansion in response to Quaternary climate changeMOLECULAR ECOLOGY, Issue 5 2007GARTH M. SPELLMAN Abstract Since the late 1990s, molecular techniques have fuelled debate about the role of Pleistocene glacial cycles in structuring contemporary avian diversity in North America. The debate is still heated; however, there is widespread agreement that the Pleistocene glacial cycles forced the repeated contraction, fragmentation, and expansion of the North American biota. These demographic processes should leave genetic ,footprints' in modern descendants, suggesting that detailed population genetic studies of contemporary species provide the key to elucidating the impact of the late Quaternary (late Pleistocene,Holocene). We present an analysis of mitochondrial DNA (mtDNA) variation in the mountain chickadee (Poecile gambeli) in an attempt to examine the genetic evidence of the impact of the late Quaternary glacial cycles. Phylogenetic analyses reveal two strongly supported clades of P. gambeli: an Eastern Clade (Rocky Mountains and Great Basin) and a Western Clade (Sierra Nevada and Cascades). Post-glacial introgression is apparent between these two clades in the Mono Lake region of Central California. Within the Eastern Clade there is evidence of isolation-by-distance in the Rocky Mountain populations, and of limited gene flow into and around the Great Basin. Coalescent analysis of genetic variation in the Western Clade indicates that northern (Sierra Nevada/Cascades) and southern (Transverse/Peninsular Ranges) populations have been isolated and evolving independently for nearly 60 000 years. [source] Genetic structure of the widespread and common Mediterranean bryophyte Pleurochaete squarrosa (Brid.) Lindb. (Pottiaceae) , evidence from nuclear and plastidic DNA sequence variation and allozymesMOLECULAR ECOLOGY, Issue 4 2007MICHAEL GRUNDMANN Abstract The Mediterranean Basin as one the world's most biologically diverse regions provides an interesting area for the study of plant evolution and spatial structure in plant populations. The dioecious moss Pleurochaete squarrosa is a widespread and common bryophyte in the Mediterranean Basin. Thirty populations were sampled for a study on molecular diversity and genetic structure, covering most major islands and mainland populations from Europe and Africa. A significant decline in nuclear and chloroplast sequence and allozyme variation within populations from west to east was observed. While DNA sequence data showed patterns of isolation by distance, allozyme markers did not. Instead, their considerable interpopulation genetic differentiation appeared to be unrelated to geographic distance. Similar high values for coefficients of gene diversity (GST) in all data sets provided evidence of geographic isolation and limited gene flow among populations (i) within islands, (ii) within mainland areas, and (iii) between islands and mainland. Notably, populations in continental Spain are strongly genetically isolated from all other investigated areas. Surprisingly, there was no difference in gene diversity and GST between islands and mainland areas. Thus, we conclude that large Mediterranean islands may function as ,mainland' for bryophytes. This hypothesis and its implication for conservation biology of cryptogamic plants warrant further investigation. While sexually reproducing populations were found all over the Mediterranean Basin, high levels of multilocus linkage disequilibrium provide evidence of mainly vegetative propagation even in populations where sexual reproduction was observed. [source] Chloroplast diversity in Vouacapoua americana (Caesalpiniaceae), a neotropical forest treeMOLECULAR ECOLOGY, Issue 9 2000C. Dutech Abstract The chloroplast genome has been widely used to describe genetic diversity in plant species. Its maternal inheritance in numerous angiosperm species and low mutation rate are suitable characters when inferring historical events such as possible recolonization routes. Here we have studied chloroplast DNA variation using PCR,RFLP (polymerase chain reaction,restriction fragment length polymorphism) with seven pairs of primers and four restriction enzymes in 14 populations of Vouacapoua americana (Caesalpiniaceae) a neotropical tree sampled throughout French Guiana. Population diversity (Hs), total gene diversity (Ht) and differentiation among populations (GST) were estimated using Nei's method as 0.09, 0.87 and 0.89, respectively. This is consistent with the limited gene flow associated with synzoochory in this species. The genetic structure observed in the north of French Guiana suggests that historical events such as contractions and recent recolonizations have had a large impact on the distribution of genetic diversity in this species. [source] Microsatellite DNA markers for the study of horseshoe crab (Limulus polyphemus) population structureMOLECULAR ECOLOGY RESOURCES, Issue 3 2004TIM L. KING Abstract Twenty-two microsatellite DNA loci were identified and characterized for horseshoe crabs (Limulus polyphemus) collected from two Atlantic coast and one Gulf of Mexico site. These markers revealed a high degree of genetic diversity (8,35 alleles per locus), heterozygosity (25.0% to 100.0%), and allelic heterogeneity (69.8% of comparisons). Considerable regional differentiation was observed as genetic distances (chord) ranged between 0.25 and 0.45, and all FST values (0.014,0.092) were significant. These preliminary findings are consistent with patterns of regional differentiation observed using allozyme variation and contradictory to findings of limited gene flow reported for sequence variation at the mitochondrial DNA COI region. [source] Conservation genetics of the endangered depressed river mussel, Pseudanodonta complanata, using amplified fragment length polymorphism (AFLP) markersAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2010Richard Skidmore Abstract 1.Genetic analysis is increasingly recognized as a key tool for understanding demography, and is particularly useful for describing patterns of gene flow between putative populations. Most effort has been directed towards vertebrate systems, where any one study often benefits from marker development in related species. The greater diversity of invertebrate taxa presents a challenge, but amplified fragment length polymorphism (AFLP) markers offer a solution, yielding high levels of polymorphism and no prior knowledge of a species' genome. 2.AFLP markers have been used to analyse an unusual metapopulation of an invertebrate, the endangered freshwater mussel, Pseudanodonta complanata, sampled from river systems across the UK. This was done to assess the extent to which individual river systems were genetically isolated from one another. 3.The results show patterns of weak genetic differentiation across the UK, with one hydrologically isolated population in the south west showing clear genetic differentiation from the rest of the country. However, the UK population as a whole exhibits significant isolation by distance, particularly when one population subject to fish stocking is removed, this population probably being seeded with mussel glochidia larvae which use fish as vectors. Genetic estimates of inbreeding reveal a complicated pattern in which inbreeding peaks at intermediate densities. High-density populations may be genetically diverse due to their size, while the lowest density populations may represent transient groups of emigrants from other, larger populations. 4.The findings show that limited gene flow does exist between some but not all river systems. The isolation of the south-west population indicates that dispersal is variable and should not be assumed to be present. Waterways that remain hydrologically isolated may require special attention in conservation programmes as they can harbour genetically distinct populations. The balance between river management activities and conservation priorities therefore needs careful consideration. Copyright © 2010 John Wiley & Sons, Ltd. [source] Limited male dispersal in a social spider with extreme inbreedingBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009YAEL LUBIN Cooperatively breeding animals commonly avoid incestuous mating through pre-mating dispersal. However, a few group-living organisms, including the social spiders, have low pre-mating dispersal, intra-colony mating, and inbreeding. This results in limited gene flow among colonies and sub-structured populations. The social spiders also exhibit female-biased sex ratios because survival benefits to large colonies favour high group productivity, which selects against 1 : 1 sex ratios. Although propagule dispersal of mated females may occasionally bring about limited gene flow, little is known about the role of male dispersal. We assessed the extent of male movement between colonies in natural populations both experimentally and by studying colony sex ratios over the mating season. We show that males frequently move to neighbouring colonies, whereas only 4% of incipient nests were visited by dispersing males. Neighbouring colonies are genetically similar and movement within colony clusters does not contribute to gene flow. Post-mating sex ratio bias was high early in the mating season due to protandry, and also in colonies at the end of the season, suggesting that males remain in the colony when mated females have dispersed. Thus, male dispersal is unlikely to facilitate gene flow between different matrilineages. This is consistent with models of non-Fisherian group-level selection for the maintenance of female biased sex ratios, which predict the elimination of male dispersal. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society 2009, 97, 227,234. [source] Amplified fragment length polymorphism fingerprints support limited gene flow among social spider populationsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009DEBORAH SMITH We used DNA fingerprints to determine whether the population structure and colony composition of the cooperative social spider Stegodyphus dumicola are compatible with requirements of interdemic (,group') selection: differential proliferation of demes or groups and limited gene flow among groups. To investigate gene flow among groups, spiders were collected from nests at 21 collection sites in Namibia. Analysis of molecular variance showed a small but highly significant differentiation among geographic regions (,PT = 0.23, P = 0.001). Thirty-three nests at four collection sites (6,10 spiders per nest, 292 individual spiders) were investigated in more detail to evaluate variation within and among colonies and among collection sites. In these 33 nests, an average of 15% of loci (fingerprint bands) were polymorphic among nestmates; 16% of observed variance was partitioned among collection sites, 48% among nests within a collection site, and 36% among individuals within nests. Spatial autocorrelation analyses of spiders at three collection sites showed that the maximum extent of detectable spatial autocorrelation among individuals was approximately 30 m, indicating dispersal over greater distances is not typical. These results indicate limited gene flow among nests, as well as spatial structuring at the level of regions, local populations, and nests, compatible with interdemic selection. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 235,246. [source] | ||||||||||||||||||||||