RST Values Research Articles

Recurrent selection effects on the genetic structure of maize landrace assessed by SSR markers

Recurrent selection method was applied in one maize landrace (Zea mays L.) population, Macaco, for one cycle of selection. In the present study the changes in genetic structure were investigated at 18 microsatellite loci. A total of 81 alleles were observed in cycle 0 (C0) population which 79 were maintained in cycle 1 (C1) population. Thus, a reduction of 2.5% in the allele frequency was observed after one cycle of selection in C1 population. The heterozygozity reduction was also observed after one cycle of selection. In nearly 44% and 55% of the loci evaluated in C0 and C1 populations, respectivelly, the changes in allelic frequencies in populations were not due exclusively by genetic drift effects. Although few changes have been observed in allelic frequencies, the grain yield increase was observed after one cycle of recurrent selection. The genetic differentiation estimated by GST and RST values, for microsatellite data between C0 and C1 populations indicate that genetic variability degree was maintained in C1 population. This result suggest that C1 population can be used in a new recurrent selection cycles.

Fabrication of yttrium oxide refractory with high strength and thermal shock stability for smelting TiAl alloy

Yttrium oxide materials have a low theoretical flexural strength, making it challenging to simultaneously achieve high strength and thermal shock stability. This limitation hinders their practical utility as refractory materials for the smelting of TiAl alloys. In this work, we have developed high strength and thermal shock resistant yttrium oxide ceramics by the control of pore size distribution. For initial short pore lengths, e.g. pore sizes are concentrated within the range of 0∼5 μm, high strength can be achieved, but thermal shock resistance is poor (low thermal shock parameter, R'''') due to the easy growth of a main crack until sample fracture. For initial long pore (crack) lengths (100–200 μm), the crack propagation mechanism follows a quasi-static pattern, in which crack propagation can lead to excellent thermal shock stability. Nevertheless, the diminished strength resulting from these elongated cracks can directly result in structural damage. If the pore size distribution is primarily controlled within the range of 10∼20 μm, it is possible to attain relatively high strength along with exceptional thermal shock performance (indicated by elevated R'''' and Rst values). Therefore, we have obtained a flexural strength of yttrium oxide of 80 MPa, while the flexural strength retention rate after cooling from 1100 °C in ambient conditions for 15 min, repeated for 5 cycles, reached as high as 95 %. Furthermore, we have successfully fabricated a large-sized ceramic crucible made of yttrium oxide was fabricated for smelting Ti–46Al(wt.%) alloy ingots. Even after 3 cycles, the crucible remains undamaged. The interfacial reaction between yttrium oxide and the Ti–46Al(wt.%) alloy is minimal, which suggests that the yttrium oxide refractory shows great potential as a suitable choice for smelting TiAl based alloys.

Genetic Polymorphism of 38 Y-chromosome Short Tandem Repeats in Beijing Han Population from China

Abstract Objective: To investigate 38 Y-chromosome short tandem repeat (Y-STR) genetic polymorphisms in Beijing Han and analyze the genetic distance with neighboring or linguistically similar populations. Materials and Methods: In the study, we selected 531 unrelated male individuals of Beijing Han, and the results were statistically analyzed by testing with GSTAR™ 41Y reagents. Results: The allele peak heights were balanced among the Y loci, the amplified fragment ranged from 100 to 500 bps. A total of 531 haplotypes were detected in 531 samples. Eight null genotypes were observed on locus DYS448. One and three double alleles were observed on single-copy locus DYS576 and DYS19, respectively. DYS385 a/b, DYF387S1 a/b, and DYS527 a/b were more common in double copies, but 3, 13, and 11 triple alleles were detected, respectively. The gene diversity values of Y-STRs except DYS391, DYS438, and DYS645 were >0.5. Twenty-seven Y-STRs of Beijing Han population were selected for genetic distance comparison with 17 populations including Changchun Han, with Rst values ranging from 0.0002 to 0.1703. Conclusion: The 38 Y-STRs in this study have strong male lineage identification ability and have great potential for individual identification, kinship identification, Y-STR database construction, and genetic relationship research.

Haplotype and Genetic Analysis of 41 Y-STR Loci in the Wuwei Han Population from Gansu Province, China.

Y-Chromosomal short tandem repeat polymorphism (Y-STR) analysis plays an indispensable role in the identification of male individuals, population genetics, and biogeographic research. While profiles of many populations based on Y-STR markers in human genomes are ample, haplotype data for the Wuwei Han are still scarce. In this study, 2180 unrelated Wuwei Han male individuals residing in Gansu Province, China were collected and genotyped using the novel Microreader™ 40Y Plus ID system. Phylogenetic relationship reconstructions, multidimensional scaling (MDS), and heatmap analysis were performed based on the genetic distance (Rst) values between our studied population and other populations of the Ymax module in the Y-STR Haplotype Reference Database (YHRD). A total of 2129 unique haplotypes were obtained, and the haplotype diversity (HD) and discrimination capacity (DC) for the Wuwei Han were 0.9999 and 0.9931, respectively. Our results demonstrate that the Wuwei Han population had intimate genetic relationships with East Asians, especially the geographically close Han populations. Overall, this Y-Chromosomal assay gives valuable information about paternal lineages in male individual tracking and genealogical database construction.

Assessment of Genetic Polymorphisms in the Rewa Population of Central India Using Y-Chromosomal STR Markers.

The aim of the study was to analyze unrelated samples from the Rewa male population of Central India by targeting Y-short tandem repeats (STR) and then compare the results to previously published Y-STR haplotype data.Materials and MethodsA total of 181 unrelated male subjects from the Rewa population were genotyped for seventeen Y-STRs (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385a/b, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635, and Y-GATA-H4) by using an AmpFlSTR® Yfiler™ multiplex kit (Thermo Fisher Scientific, USA). The allele frequencies and forensic parameters were evaluated.ResultsA total of 111 distinct Y-STR alleles with corresponding frequencies ranging from 0.006 to 0.829 were identified. The gene diversity values ranged from 0.3092 at DYS437 to 0.8188 at DYS385b. The studied population showed a high level of haplotype diversity (0.9985) and discrimination capacity (0.927). A haplotype analysis was also conducted. Among the 181 unrelated male samples, 165 haplotypes and 153 unique haplotypes were found. Additionally, Rst (genetic distance) values were calculated using the analysis of molecular variance (AMOVA) for the studied population and for other 18 populations described in the literature. The Rst provides a convenient parameter for estimating the level of genetic differentiation from the microsatellite data. Based on these Rst values and using the multidimensional scaling plot, a neighbor-joining tree was constructed.ConclusionThe high values of haplotype diversity and discrimination capacity indicate a great potential for distinguishing between male individuals in the studied population. The present population data are expected to find their use in forensic caseworks and population genetics.

Surnames in south-eastern France: structure of the rural population during the 19th century through isonymy.

An analysis of the distribution of surnames through time and space allows us to understand the structure of human groups, their exchanges or even their possible isolation. The French population has already been studied through surnames and it has been shown that the Sud-Provence-Alpes-Côte d'Azur region differed from the rest of France in both the 20th and 21st centuries (Mourrieras et al., ; Scapoli et al., ). The objective of this study was to understand the population evolution and particularities of the Sud-Provence-Alpes-Côte d'Azur region through an analysis of the distribution of surnames over an earlier period: the 19th century. For this work, 806,069 birth records from 521 communes between 1810 and 1890 were recorded and a total of 23,340 surnames were collected. The estimation of various isonymic parameters has allowed a description of this corpus never exploited before. In order to appreciate the population evolution, the data set was divided into three periods of 25 years. The canton was the geographical unit of this study, and similarities and differences between each of them were evaluated using Lasker distances, which allow the construction of dendrograms. A positive and significant correlation (p<0.0001) was found between Lasker distances and geographical distances using the Mantel test. The lowest inbreeding estimates were found in the Durance Valley. Migration, estimated from the v-index of Karlin and McGregor (), showed higher values in the south-western quarter of the region. The decrease in Rst values across the three periods is consistent with a homogenization of the patronymic between the cantons. This three-period approach showed a population evolution influenced by linguistic, cultural, historical and migratory phenomena since the Middle Ages, disrupted by the socioeconomic changes of the 19th century.

Genetic polymorphisms and haplotypic structure analysis of the Guizhou Gelao ethnic group based on 35 Y-STR loci.

In this research, 35 Y-chromosomal short tandem repeat (Y-STR) loci were analyzed in 286 unrelated healthy Gelao male individuals from Guizhou Province, China. Allelic and haplotype frequencies, haplotype diversity (HD), haplotype match probability (HMP), and discrimination capacity (DC) values were computed. Pairwise Rst values were assessed by AMOVA analysis and visualized through multidimensional scaling and neighbor-joining tree construction. A total of 609 alleles were detected at the 35 Y-STR loci, and the allelic frequencies ranged from 0.0035 to 0.8322. The HD, HMP, and DC were 0.9999, 0.0036, and 0.9825, respectively. A total of 281 haplotypes were found at 35 loci in the 286 Gelao individuals, 98.25% of which were unique. Related forensic parameters revealed that this panel of 35 loci had a high level of genetic polymorphisms in the Gelao group. However, the use of multi-copy and rapidly mutating Y-STR loci could significantly increase the discrimination power of a common Y-STR panel. Analyses of population differentiation with the same set of common Y-STR loci demonstrated that the Gelao group has a closer genetic relationship with the Guizhou Han and Guizhou Miao groups than other groups.

Uncovering population structure in the Humboldt penguin (Spheniscus humboldti) along the Pacific coast at South America.

The upwelling hypothesis has been proposed to explain reduced or lack of population structure in seabird species specialized in food resources available at cold-water upwellings. However, population genetic structure may be challenging to detect in species with large population sizes, since variation in allele frequencies are more robust under genetic drift. High gene flow among populations, that can be constant or pulses of migration in a short period, may also decrease power of algorithms to detect genetic structure. Penguin species usually have large population sizes, high migratory ability but philopatric behavior, and recent investigations debate the existence of subtle population structure for some species not detected before. Previous study on Humboldt penguins found lack of population genetic structure for colonies of Punta San Juan and from South Chile. Here, we used mtDNA and nuclear markers (10 microsatellites and RAG1 intron) to evaluate population structure for 11 main breeding colonies of Humboldt penguins, covering the whole spatial distribution of this species. Although mtDNA failed to detect population structure, microsatellite loci and nuclear intron detected population structure along its latitudinal distribution. Microsatellite showed significant Rst values between most of pairwise locations (44 of 56 locations, Rst = 0.003 to 0.081) and 86% of individuals were assigned to their sampled colony, suggesting philopatry. STRUCTURE detected three main genetic clusters according to geographical locations: i) Peru; ii) North of Chile; and iii) Central-South of Chile. The Humboldt penguin shows signal population expansion after the Last Glacial Maximum (LGM), suggesting that the genetic structure of the species is a result of population dynamics and foraging colder water upwelling that favor gene flow and phylopatric rate. Our findings thus highlight that variable markers and wide sampling along the species distribution are crucial to better understand genetic population structure in animals with high dispersal ability.

Genetic diversity and haplotype structure of 27 Y-STR loci in a Yanbian Korean population from Jilin Province, Northeast China.

In this study, 27 Y-STRs were analyzed in 347 male individuals from the Yanbian Korean population. Haplotype diversity (HD) and discrimination capacity (DC) values were calculated. Pairwise Rst values were evaluated in AMOVA analysis and visualized through multidimensional scaling (MDS). Yflier Plus system indicated higher Discrimination Power (DP), HD and DC which is 0.9969, 0.9998 and 0.9769. There is no significant genetic distance between Yanbian Koreans and South Koreans, however, there is a great distance from Chinese Han population. The present results may provide useful information for paternal lineages in forensic cases and increase our understanding of the genetic relationships between Yanbian Korean and other groups.

Petrographic and Raman spectroscopic characterization of coal from Himalayan fold-thrust belts of Sikkim, India

The present study focuses on the investigation of the optical anisotropy, optical sign, textural heterogeneity and deformational features of the maceral grains along with the Raman spectral characteristics of the seven coal samples collected from the Himalayan fold-thrust belts of Sikkim State, India. The coal samples were extremely fragile and pulverized due to the intense tectonic deformation. The maceral composition revealed the dominance of semifusinite over collotelinite grains. The calculated maximum vitrinite reflectance (5.94–8.66%) and mean random reflectance (4.11–5.36%) suggest anthracite A rank of the coal samples following ISO 11760:2005. The proximity of the intermediate reflectance axis value (RINT) to maximum reflectance axis value (RMAX) as well as the range of Reflectance Indicating Surface (RIS) style (Rst) values (−9.98 to −19.37) indicates the biaxial negative optical texture of the vitrinite grains. The augmented bireflectance values due to enhancement of the RMAX associated with strong decline in RMIN may suggest the commencement of pregraphitization. In addition, the strong linear correlation (r = 0.94) of the RIS-anisotropy (Ram) parameter with the bireflectance values may imply the role of tectonic stress on the optical transformations of the samples. The range of the peak temperature (334.94–369.01 °C) calculated from mean random vitrinite reflectance may suggest the effect of thermo-stress coupling on the metamorphism of these coal samples. Microlithotype study combined with deformational aspects of macerals shows the presence of “deformed”, “sheared” and “smashed” grains within each sample, which may, additionally, document the tectonic stress influence on the coal particles. Moreover, relatively, larger area of ‘defect band 1 (D1)’ than that of ‘graphitic band (G)’ along with the broad G band in the first order Raman spectra may indicate the considerable presence of structural dislocations and aromatic compounds with disordered bond angle within the microstructure induced by the tectonic deformation. The lowest intensity of the ‘defect band 4 (D4)’ may suggest the preferential removal of aliphatic compounds from the samples in response to the tectonic stress degradation. In addition, the relative area ratio calculated from the D1 and the G bands (AD1/(AD1 + AG)) may indicate that the studied anthracite samples would have attained the metamorphic temperature ranging from 325.12–387.89 °C.

Development of the Kazakhstan Y-chromosome haplotype reference database: analysis of 27 Y-STR in Kazakh population.

To improve available databases of forensic interest, all Y-STR haplotypes from Kazakh population were presented in this study. The reference database accumulated almost 3650 samples from academic and citizen science. Additionally, 27 Y-STR from Yfiler Plus System were first analyzed in 300 males from Kazakh (Qazaq) populations residing in Kazakhstan. The data is available in the YHDR under accession numbers YA004316 and YA004322. A total of 270 unique haplotypes were observed. Discrimination capacity was 90%. Obtained Y-STR haplotypes exhibited a high intra-population diversity. Analysis of pairwise genetic distances showed lowest RST values from Uighur and Mongolian populations.

Inner and inter population structure construction of Chinese Jiangsu Han population based on Y23 STR system.

In this study, we analyzed the genetic polymorphisms of 23 Y-STR loci from PowerPlex® Y23 system in 916 unrelated healthy male individuals from Chinese Jiangsu Han, and observed 912 different haplotypes including 908 unique haplotypes and 4 duplicate haplotypes. The haplotype diversity reached 0.99999 and the discrimination capacity and match probability were 0.9956 and 0.0011, respectively. The gene diversity values ranged from 0.3942 at DYS438 to 0.9607 at DYS385a/b. Population differentiation within 10 Jiangsu Han subpopulations were evaluated by RST values and visualized in Neighbor-Joining trees and Multi-Dimensional Scaling plots as well as population relationships between the Jiangsu Han population and other 18 Eastern Asian populations. Such results indicated that the 23 Y-STR loci were highly polymorphic in Jiangsu Han population and played crucial roles in forensic application as well as population genetics. For the first time, we reported the genetic diversity of male lineages in Jiangsu Han population at a high-resolution level of 23 Y-STR set and consequently contributed to familial searching, offender tracking, and anthropology analysis of Jiangsu Han population.

Evidence of Low Chloroplast Genetic Diversity in Two Carpinus Species in the Northern Balkans

Genetic diversity and differentiation in two Carpinus species (C. betulus and C. orientalis) occurring in Romania was investigated by using three chloroplast Simple Sequence Repeat markers (cpSSRs). A total of 96 and 32 individuals were sampled in eighteen C. betulus and six C. orientalis populations, respectively. A total of four chloroplast haplotypes were observed. Two haplotypes were specific for C. betulus and two for C. orientalis. Most of C. betulus populations were fixed for the predominant haplotype (H1), which was observed in 82% of the individuals. All C. orientalis populations were fixed for one haplotype or the other. Populations with haplotype (H3) are spread in southern Romania and the haplotype (H4) was observed at the northern limit of C. orientalis natural distribution range. Genetic differentiation among populations was moderate in C. betulus (GST = 0.422), compared to the high value observed in C. orientalis (GST = 1.000), which can be explained by the occurrence of a distinct haplotype in the peripheral population. RST values for both species suggest low levels of recurrent gene flow through seeds among populations. Our data on geographic distribution of chloroplast DNA haplotypes may be useful for the identification and conservation of distinct genetic resources of the two Carpinus species.

Haplotype diversity of 17 Y-chromosome STR loci in Han population from different areas of Sichuan Province, Southwest China.

The distribution of 17 Y-chromosome short tandem repeat (STR) loci, included in the AmpFlSTR®Yfiler™ amplification kit, were analyzed in six different samplings (N=878) from Sichuan, China. Haplotype diversity and discrimination capacity (DC) values were calculated. Pairwise Rst values were evaluated in AMOVA analysis and visualized through multidimensional scaling (MDS). A total of 547 unique haplotypes were detected. The observed haplotype diversity and discrimination capacity were 0.9995 and 0.7745, respectively. The homogeneity of Sichuan Han population was detected when microareas were analyzed. This population exhibited no significant genetic difference to both of the minorities in reference databases, Mongolian and Manchu, which had been through mass ethnic amalgamation with Sichuan Han population in history.

Repeated randomized selection of genotypes for reliable estimates of population differentiation in data containing siblings

In population genetic studies, a proper sampling design is crucial for reliable population differentiation estimates. For genetic studies on amphibians, fish or insects, larvae are often sampled instead of adults due to their higher accessibility and abundance. However, population genetic parameters derived from larval (sibling) sampling can be biased if adults are represented unevenly in the larval population. The removal of full-siblings from data may improve the quality of the results but entails in a low number of individuals per site, especially in small populations. Using simulated data of ten microsatellite loci for ten populations, we estimated pairwise FST and RST values as well as FIS and RIS values for the F0 generation (parental) and the F1 generation (descendant). We applied a repeated randomized selection of genotypes (RRSG) to investigate the impact of removing full-siblings from the data. We also investigated the impact of reduced sample size on the results generated by RRSG as well as the advantages of RRSG over a single estimate of genetic parameters after removal of full-siblings. The RRSG approach produced pairwise FST values that deviated on average only by 0.0050 (N = 45) from their respective estimates for F0. Estimates for HE deviated less the 5% over all data sets. We henceforth suggest applying the described method to interpretations of genetic differentiations in studies with (i) small effective population sizes and (ii) data containing siblings where (iii) offspring can be assigned to at least one parent due to reproduction practice.

Strong Genetic Differentiation of Submerged Plant Populations across Mountain Ranges: Evidence from Potamogeton pectinatus in Iran.

Biogeographic barriers for freshwater biota can be effective at various spatial scales. At the largest spatial scale, freshwater organisms can become genetically isolated by their high mountain ranges, vast deserts, and inability to cross oceans. Isolation by distance of aquatic plants is expected to be stronger across than alongside mountain ridges whereas the heterogeneity of habitats among populations and temporary droughts may influence connectivity and hamper dispersal. Suitable aquatic plant habitats became reduced, even for the widespread submerged Potamogeton pectinatus L. (also named Stuckenia pectinata) giving structure to various aquatic habitats. We compared the level of genetic diversity in a heterogeneous series of aquatic habitats across Iran and tested their differentiation over distances and across mountain ranges (Alborz and Zagros) and desert zones (Kavir), with values obtained from temperate region populations. The diversity of aquatic ecosystems across and along large geographic barriers provided a unique ecological situation within Iran. P. pectinatus were considered from thirty-six sites across Iran at direct flight distances ranging from 20 to 1,200 km. Nine microsatellite loci revealed a very high number of alleles over all sites. A PCoA, NJT clustering and STRUCTURE analysis revealed a separate grouping of individuals of southeastern Iranian sites and was confirmed by their different nuclear ITS and cpDNA haplotypes thereby indicating an evolutionary significant unit (ESU). At the level of populations, a positive correlation between allelic differentiation Dest with geographic distance was found. Individual-based STRUCTURE analysis over 36 sites showed 7 genetic clusters. FST and RST values for ten populations reached 0.343 and 0.521, respectively thereby indicating that allele length differences are more important and contain evolutionary information. Overall, higher levels of diversity and a stronger differentiation was revealed among Iranian P. pectinatus than previously observed for temperate European regions, due to regional differences across mountain ranges over long distances.

Genetic differentiation of the Korean striped field mouse, Apodemus agrarius (Muridae, Rodentia), based on microsatellite polymorphism

Abstract The striped field mouse (Apodemus agrarius) is one of the most common mammals in Korea, however, limited research has focused on the population structure and biogeography of this mouse throughout Korea. In addition, the taxonomic status of the species remains unresolved. The objectives of our study were to address the inadequacies in understanding the population structure, biogeography, and taxonomic status of A. agrarius. We collected 160 samples from 13 localities throughout the South Korean Peninsula, two nearby islands and two remote islands. We used five microsatellite loci and estimated genetic diversity measures and populations divergence estimates (i.e. F ST and R ST) to address the objectives. Except for populations on the two remote islands, Jeju and Heuksan, the populations on the peninsula and nearby islands indicated low F ST and R ST values. The population structure based on microsatellite loci supported only one subspecies opposing three subspecies reported previously on the Korean Peninsula and nearby islands. However, populations on Jeju Island and Heuksan Island showed subspecific differences from each other and the populations on the Korean Peninsula and nearby islands. The information reported on the population genetics of the striped field mouse in Korea will allow resolving the taxonomy and biogeography of this species.

Y-STR markers from Ladakh in the Himalayas.

A total of 223 samples from the general population of Ladakh in Northwestern India were amplified at 17 Y-STR loci using the AmpFlSTR® Yfiler™ system. The DNA profiles generated were employed to generate allelic frequencies, gene diversity, haplotype diversity and discrimination capacity values as well as number of different haplotypes, fraction of unique haplotypes and Rst pair wise genetic distances. Multidimensional Scaling (MDS) and Correspondence Analysis (CA) were performed with the Rst values and allelic frequencies, respectively. The 17-loci discrimination capacity of Ladakh was found to be 0.8093. Eleven out of the 16 loci have diversity values greater than 0.6, and 13 loci possess values greater than 0.5. Ladakh exhibits no significant genetic difference to seven of the 15 reference forensic databases after Bonferroni correction, three of which are located in South Central Asian and four are from the Himalayan region. Rst genetic distance values before and after Bonferroni corrections illustrate the capacity of the Yfiler system to discriminate among Himalayan populations. The intermediate position of the Ladakh population in the MDS and CA plots likely reflects genetic flow and admixture with neighboring populations. In addition, the longitudinal partition of populations in the MDS and CA plots likely reflect human dispersals such as the silk road migrations.

Loss of genetic diversity in farmed populations of Colossoma macropomum estimated by microsatellites.

The genetic variability of four Colossoma macropomum broodstocks, three from fish farms in different regions and one from the natural environment in Brazil, was analyzed using microsatellite markers. The wild progeny (n=30) were caught in the Solimões-Amazonas River, at the varzea lakes; this location is used to mature the fish from larvae to juveniles. The three fish farms were selected according to the age of their lineages and broodstock availability: DNOCS (n=21) is located in the Ceará State, representing the oldest lineage of cultivated tambaqui in Brazil; Balbina (n=30) is located in the Amazonas State, representing the youngest stocks of tambaqui farmed in Brazil (approximately 15years); and UFRPE (n=30) is located in the Pernambuco State and is considered to be a mixed stock formed from the DNOCS and Balbina lineages. The analysis of 13 microsatellite loci indicated the occurrence of a variability reduction in the farmed populations; the UFRPE stock was the population with the highest diversity level. Low values of molecular coancestry were found in these populations. Additionally, significant differences in the RST values among the populations were detected, as was the occurrence of genetic structure. The genetic loss found in these populations may have been influenced by the founder effect. Because no breeding programs were during the entire production period and no pedigree records were kept for these broodstocks, we suggest that a wild population might be used as an important genetic resource to increase the genetic diversity of renewal stock lineages.

One step ahead: a parasitoid disperses farther and forms a wider geographic population than its fig wasp host.

The structure of populations across landscapes influences the dynamics of their interactions with other species. Understanding the geographic structure of populations can thus shed light on the potential for interacting species to co-evolve. Host-parasitoid interactions are widespread in nature and also represent a significant force in the evolution of plant-insect interactions. However, there have been few comparisons of population structure between an insect host and its parasitoid. We used microsatellite markers to analyse the population genetic structure of Pleistodontes imperialis sp. 1, a fig-pollinating wasp of Port Jackson fig (Ficus rubiginosa), and its main parasitoid, Sycoscapter sp. A, in eastern Australia. Besides exploring this host-parasitoid system, our study also constitutes, to our knowledge, the first study of population structure in a nonpollinating fig wasp species. We collected matched samples of pollinators and parasitoids at several sites in two regions separated by up to 2000km. We found that pollinators occupying the two regions represent distinct populations, but, in contrast, parasitoids formed a single population across the wide geographic range sampled. We observed genetic isolation by distance for each species, but found consistently lower FST and RST values between sites for parasitoids compared with pollinators. Previous studies have indicated that pollinators of monoecious figs can disperse over very long distances, and we provide the first genetic evidence that their parasitoids may disperse as far, if not farther. The contrasting geographic population structures of host and parasitoid highlight the potential for geographic mosaics in this important symbiotic system.