Genetic Differentiation between Geographically Distant Populations of DROSOPHILA MELANOGASTER

We have studied allozyme variation at 26 gene loci in nine populations of Drosophila melanogaster originating on five different continents. The distant populations show significant genetic differentiation. However, only half of the loci studied have contributed to this differentiation; the other half show identical patterns in all populations. The genetic differentiation in North American, European and African populations is correlated with the major climatic differences between north and south. These differences arise mainly from seven loci that show gene-frequency patterns suggestive of latitudinal clines in allele frequencies. The clinal variation is such that subtropical populations are more heterozygous than temperate populations. These results are discussed in relation to the selectionist and neutralist hypotheses of genetic variation in natural populations.     

Relationship Between Morphology and Parasitism in Two Populations of Meloidogyne incognita

The reliability of morphological characters and host differential plants for distinguishing between two populations of Meloidogyne incognita was studied. Population A (originally from North Carolina) had incognita-type perineal patterns. A single egg mass subpopulation of population A had a mixture of incognita and acrita perineal patterns with 33% of the patterns atypical for either species. Population B (from Georgia) had predominantly acrita-type patterns with only about 5% atypical patterns. The head shapes of males from both populations were mainly M. incognita. On the basis of stylet length, both populations conformed to M. incognita acrita. Both populations were identified as M. incognita race 1 by reaction on the North Carolina differential hosts. Reactions on azalea and pepper gave no clear identification of the populations. We concluded that there is no relation between perineal pattern, male head shape, and parasitism of host differentials with the two populations studied.     

Inter- and intrapopulational variations in the peroxidase isozyme ofAsarum nipponicum F. Maekawa

Both the inter- and intrapopulational variations in five natural populations ofAsarum nipponicum F. Maekawa were demonstrated for peroxidase isozymes using gel electrofocusing. The patterns of isozymic variation suggested that a very short distance (100 m) effectively isolates populations. The reason why some bands were not detected in a particular population is discussed in terms of genetic drift.     

Variation in flavonoid patterns in relation to chromosome changes in Gibasis schiedeana

The distribution of $\text{C-}\text{glycoflavones}$ has been examined in the leaves of plants from five diploid and 12 tetraploid populations of Gibasis schiedeana. Five different chromatographic patterns were found; one occurs only in a single population of diploid plants, two were found in seven populations of tetraploids and the other two in the remaining plants from both diploid and tetraploid populations. Flavonoids were also investigated in three different types of artificially produced triploids. The effects of the changes in ploidy, which are accompanied by Robertsonian fusion and variation in the number of B chromosomes as contributory factors in the observed differences in flavonoid patterns are discussed.     

Molecular genetic polymorphism of androgen receptor gene (AR) in African populations of Hadza and Datoga

The molecular genetic analysis of the polymorphic variants of the CAG repeat-containing locus of the androgen receptor (AR) gene was performed in the populations of Hadza and Datoga. Allele frequency distribution patterns were established. Alleles containing 20–25 repeats were the most abundant in both populations. The populations studied were compared with Asians (Han), white Americans, and Africans (Ariaal). Statistically significant difference between populations of Hadza and Datoga in the distribution of the AR allelic variants was demonstrated.     

Comparison of Populations of Pratylenchus brachyurus Based on Isozyme Phenotypes

Enzymes from females of five Pratylenchus brachyurus populations and one P. scribneri population were analyzed by isoelectric focusing electrophoresis. Of the 18 enzyme systems investigated, only malate dehydrogenase (MDH), phosphoglucomutase (PGM), and phosphoglucose isomerase (PGI) were detected from all five P. brachyurus populations and P. scribneri. Faint bands were detected for isocitrate dehydrogenase and phosphogluconate dehydrogenase from one P. brachyurus population. Three distinct phenotypic groups were found in the MDH and PGM systems for P. brachyurus populations, but only a single electromorph was detected for PGI. Multiple electromorphs for MDH, PGM, and PGI were detected for P. scribneri; there was no similarity among these patterns with those from P. brachyurus. No phenotypic differences in PGI were observed between females and mixed juveniles of one population of P. brachyurus.     

Genetic variation and population genetic structure of Rhizophora apiculata (Rhizophoraceae) in the greater Sunda Islands,Indonesia using microsatellite markers

Genetic variations within and among Rhizophora apiculata populations in the Greater Sunda Islands of Indonesia were studied using microsatellite markers. The study found 38 alleles on five loci in 15 populations. The observed (H _o) and expected (H _e) heterozygosity values are 0.338 and 0.378, respectively. Inbreeding effect from self-pollination might explain its heterozygote deficiency. Population genetic differentiation (F _ST = 0.381) was similar to other mangrove species. The genetic diversity of R. apiculata populations along the coastline inside the archipelago (e.g., Buleleng, Donggala, Mamuju, and Takalar) was higher than those of population along the coastline outside the archipelago, especially northern Sumatra populations (i.e., Langkat, Tapanuli Tengah, Dumai, and Padang). The isolation by distances and sea currents directions as well as their connectivity might affect the gene flow and genetic exchange. The more isolated with fewer connections by sea currents, the smaller gene flow and genetic exchange observed between populations. The higher genetic exchange, on the contrary, occurred when population location was closer to the meeting point of the sea currents. The study also showed that the patterns of sea current movement seemed to have influence genetic clustering of populations which fell into three main groups (Sunda Shelf Mangroves) and one isolated population (New Guinea Mangroves).     

Sea surface temperature,rather than land mass or geographic distance,may drive genetic differentiation in a species complex of highly dispersive seabirds

Seabirds, particularly Procellariiformes, are highly mobile organisms with a great capacity for long dispersal, though simultaneously showing high philopatry, two conflicting life‐history traits that may lead to contrasted patterns of genetic population structure. Landmasses were suggested to explain differentiation patterns observed in seabirds, but philopatry, isolation by distance, segregation between breeding and nonbreeding zones, and oceanographic conditions (sea surface temperatures) may also contribute to differentiation patterns. To our knowledge, no study has simultaneously contrasted the multiple factors contributing to the diversification of seabird species, especially in the gray zone of speciation. We conducted a multilocus phylogeographic study on a widespread seabird species complex, the little shearwater complex, showing highly homogeneous morphology, which led to considerable taxonomic debate. We sequenced three mitochondrial and six nuclear markers on all extant populations from the Atlantic (lherminieri) and Indian Oceans (bailloni), that is, five nominal lineages from 13 populations, along with one population from the eastern Pacific Ocean (representing the dichrous lineage). We found sharp differentiation among populations separated by the African continent with both mitochondrial and nuclear markers, while only mitochondrial markers allowed characterizing the five nominal lineages. No differentiation could be detected within these five lineages, questioning the strong level of philopatry showed by these shearwaters. Finally, we propose that Atlantic populations likely originated from the Indian Ocean. Within the Atlantic, a stepping‐stone process accounts for the current distribution. Based on our divergence time estimates, we suggest that the observed pattern of differentiation mostly resulted from historical and current variation in sea surface temperatures.     

Diversity of Wolbachia in Natural Populations of Spider Mites (genus Tetranychus): Evidence for Complex Infection History and Disequilibrium Distribution

Wolbachia are endosymbiotic bacteria that commonly infect arthropods and cause reproductive disorders in host. Within several Tetranychus species, Wolbachia have been detected and shown to affect their reproduction. However, little is known about their transmission and distribution patterns in natural populations of Tetranychus species. Here, we used multilocus sequence typing to confirm Wolbachia infection status and examined the relationship between Wolbachia infection status and host phylogeny, mitochondrial diversity, and geographical range in five Tetranychus species (Tetranychus truncatus, Tetranychus urticae, Tetranychus pueraricola, Tetranychus phaselus, and Tetranychus kanzawai) from 21 populations in China. The prevalence of Wolbachia within the five Tetranychus species ranged from 31.4 to 100 %, and the strains were remarkably diverse. Together, these observations indicate that Wolbachia was introduced to these populations on multiple separate occasions. As in other arthropods, the same Tetranychus species can accommodate very different strains, and identical Wolbachia occasionally infect different species. These observations suggest that Wolbachia are transmitted both vertically and horizontally. Horizontally, transmission is probably mediated by the host plants. The distribution patterns of Wolbachia were quite different among populations of the same species, suggesting that the dynamics of Wolbachia in nature may be affected by ecological and other factors.     

Bulk and Rhizosphere Soil Bacterial Communities Studied by Denaturing Gradient Gel Electrophoresis: Plant-Dependent Enrichment and Seasonal Shifts Revealed

The bacterial rhizosphere communities of three host plants of the pathogenic fungus Verticillium dahliae, field-grown strawberry (Fragaria ananassa Duch.), oilseed rape (Brassica napus L.), and potato (Solanum tuberosum L.), were analyzed. We aimed to determine the degree to which the rhizosphere effect is plant dependent and whether this effect would be increased by growing the same crops in two consecutive years. Rhizosphere or soil samples were taken five times over the vegetation periods. To allow a cultivation-independent analysis, total community DNA was extracted from the microbial pellet recovered from root or soil samples. 16S rDNA fragments amplified by PCR from soil or rhizosphere bacterium DNA were analyzed by denaturing gradient gel electrophoresis (DGGE). The DGGE fingerprints showed plant-dependent shifts in the relative abundance of bacterial populations in the rhizosphere which became more pronounced in the second year. DGGE patterns of oilseed rape and potato rhizosphere communities were more similar to each other than to the strawberry patterns. In both years seasonal shifts in the abundance and composition of the bacterial rhizosphere populations were observed. Independent of the plant species, the patterns of the first sampling times for both years were characterized by the absence of some of the bands which became dominant at the following sampling times. Bacillus megaterium and Arthrobacter sp. were found as predominant populations in bulk soils. Sequencing of dominant bands excised from the rhizosphere patterns revealed that 6 out of 10 bands resembled gram-positive bacteria. Nocardia populations were identified as strawberry-specific bands.     

Phylogeography and Sex-Biased Dispersal across Riverine Manatee Populations (Trichechus inunguis and Trichechus manatus) in South America

Phylogeographic patterns and sex-biased dispersal were studied in riverine populations of West Indian (Trichechus manatus) and Amazonian manatees (T. inunguis) in South America, using 410bp D-loop (Control Region, Mitochondrial DNA) sequences and 15 nuclear microsatellite loci. This multi-locus approach was key to disentangle complex patterns of gene flow among populations. D-loop analyses revealed population structuring among all Colombian rivers for T. manatus, while microsatellite data suggested no structure. Two main populations of T. inunguis separating the Colombian and Peruvian Amazon were supported by analysis of the D-loop and microsatellite data. Overall, we provide molecular evidence for differences in dispersal patterns between sexes, demonstrating male-biased gene flow dispersal in riverine manatees. These results are in contrast with previously reported levels of population structure shown by microsatellite data in marine manatee populations, revealing low habitat restrictions to gene flow in riverine habitats, and more significant dispersal limitations for males in marine environments.     

Brief communication: Allelic and haplotypic structure at the DRD2 locus among five North Indian caste populations

The dopamine D2 receptor (DRD2) gene, with its known human‐specific derived alleles that can facilitate haplotype reconstruction, presents an important locus for anthropological studies. The three sites (TaqIA, TaqIB, and TaqID) of the DRD2 gene are widely studied in various world populations. However, no work has been previously published on DRD2 gene polymorphisms among North Indian populations. Thus, the present study attempts to understand the genetic structure of North Indian upper caste populations using the allele and haplotype frequencies and distribution patterns of the three TaqI sites of the DRD2 gene. Two hundred forty‐six blood samples were collected from five upper caste populations of Himachal Pradesh (Brahmin, Rajput and Jat) and Delhi (Aggarwal and Sindhi), and analysis was performed using standard protocols. All three sites were found to be polymorphic in all five of the studied populations. Uniform allele frequency distribution patterns, low heterozygosity values, the sharing of five common haplotypes, and the absence of two of the eight possible haplotypes observed in this study suggest a genetic proximity among the selected populations. The results also indicate a major genetic contribution from Eurasia to North Indian upper castes, apart from the common genetic unity of Indian populations. The study also demonstrates a greater genetic inflow among North Indian caste populations than is observed among South Indian caste and tribal populations. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

P-M phenotypes and their correlation with longitude in natural populations of Drosophila melanogaster from Turkey

We analyzed the P-M gonadal dysgenesis characteristics and the molecular patterns of P and KP elements of 35 populations from distinct locations of Turkey and Cyprus to find out P element dynamics in natural populations of Drosophila melanogaster. The results of Gonadal dysgenesis (GD) tests showed a predominat M?? phenotype for this region. Besides Q populations were also found in less numbers. It was also noticed that there is a strong tendency for the presence of a Q type ??buffer zone?? in the Western part of Turkey. The variation in GD percentage (as a index for P element activity and susceptibility) observed among the populations did not show any clear relationship with some geoclimatic variables, but a significant correlation was found between longitude, and P element susceptibility. The P and KP element were also characterized by polymerase chain reaction amplification. The molecular analyses showed that all the populations examined have the entire of 1.15 kb KP element. The molecular patterns of KP elements have been found similar between the populations studied.     

Local scale population genetic structure of Entomophthora muscae epidemics

Isolates of the entomopathogenic fungus Entomophthora muscae were obtained from houseflies sampled at five stables on Zealand during an epidemic in fall 2005. DNA fingerprints were generated from single conidia from 40 E. muscae isolates using the PCR-based method of Inter-Simple Sequence Repeats (ISSR). This resulted in fingerprint patterns consisting of about 50 fragments, of which, 14 were polymorphic. From the polymorphic loci we estimated the reproductive mode, genetic differentiation and gene diversity of E. muscae populations using the statistics of index of association, Weir & Cockerhams theta and Nei's analysis of gene diversity in subdivided populations. Our results revealed no significant differences in allele frequencies among the five populations. The index of association test rejected the null hypothesis of random mating, but the test for paired locus compatibility showed weak or no linkage between loci indicating recombination or homoplasy in the dataset. From this study we cannot exclude the possibility that the population genetic structure underlying E. muscae epidemics could be panmictic consisting of several lineages with a high level of reciprocal migration.     

Low genetic differentiation among widely separated populations of the pearl oyster Pinctada fucata as revealed by AFLP

Genetic variation within and among five populations of the pearl oyster Pinctada fucata, from China (Daya Bay, Sanya Bay and Beibu Bay), Japan (Mie Prefecture) and Australia (Port Stephens) was studied using AFLP. Three primer pairs generated 184 loci among which 91.8-97.3% is polymorphic. An overall genetic diversity of 0.38 among populations and an average of 0.37 within populations (ranging from 0.35 in Japanese population to 0.39 in Beibu Bay population) were observed. Genetic differentiation among the five populations is low but significant as indicated by pairwise G_ST (0.0079-0.0404). AMOVA further shows that differentiation is significant among the five populations but is not significant at a broader geographical scale, among the three groups of Chinese, Japanese and Australian populations or among the two groups of Australian and north Pacific populations. The low level of genetic differentiation indicated that P. fucata populations in the west Pacific are genetically linked. Among the five populations, the Australian one is more differentiated from the others, based on both pairwise AMOVA and G_ST analyses, and is genetically isolated by distance as indicated by Mantel test. However, genetic differences among the three Chinese populations are not correlated with the geographic distances, suggesting that Hainan Island and Leizhou Peninsula may act as barriers blocking gene flow.     

Chemotypes of Artemisia herba-alba in Israel based on their sesquiterpene lactone and essential oil constitution

Analysis of sesquiterpene lactones and essential oils of various Artemisia herba-alba populations growing in Israel revealed the existence of five different chemotypes. These vary in their chemical profile from populations of the Sinai Desert, Egypt, Morocco and Spain. On the basis of the substitution patterns of the sesquiterpene lactones isolated from the Israeli populations which bear a hydroxyl or acetoxy function at C-9 it is suggested that these constitute a chemotaxonomic subspecies in the A. herba-alba complex.     

Seasonal dynamics of the phenotypic structure of a population of the paper wasp Polistes dominulus (Christ) (Hymenoptera, Vespidae)

Seasonal changes in the coloration of the clypeus, mesonotum, and abdomen were studied in populations of the paper wasp, Polistes dominulus (Christ) in southern Ukraine. The color patterns in the populations were found to be different before and after hibernation. The frequencies of color morphs observed in the autumns of different years are similar, while the frequencies observed in spring vary from year to year. A tendency for pleometrosis is manifested by females of different color morphs in different years. The nest usurpers have darker patterns of the clypeus. A polyfunctional role of the coloration and pattern is supposed.     

Genetic Diversity and Population Structure of Indian Golden Silkmoth (Antheraea assama)

Background

The Indian golden saturniid silkmoth (Antheraea assama), popularly known as muga silkmoth, is a semi-domesticated silk producing insect confined to a narrow habitat range of the northeastern region of India. Owing to the prevailing socio-political problems, the muga silkworm habitats in the northeastern region have not been accessible hampering the phylogeography studies of this rare silkmoth. Recently, we have been successful in our attempt to collect muga cocoon samples, although to a limited extent, from their natural habitats. Out of 87 microsatellite markers developed previously for A. assama, 13 informative markers were employed to genotype 97 individuals from six populations and analyzed their population structure and genetic variation.

Methodology/Principal Findings

We observed highly significant genetic diversity in one of the populations (WWS-1, a population derived from West Garo Hills region of Meghalaya state). Further analysis with and without WWS-1 population revealed that dramatic genetic differentiation (global F_ST = 0.301) was due to high genetic diversity contributed by WWS-1 population. Analysis of the remaining five populations (excluding WWS-1) showed a marked reduction in the number of alleles at all the employed loci. Structure analysis showed the presence of only two clusters: one formed by WWS-1 population and the other included the remaining five populations, inferring that there is no significant genetic diversity within and between these five populations, and suggesting that these five populations are probably derived from a single population. Patterns of recent population bottlenecks were not evident in any of the six populations studied.

Conclusions/Significance

A. assama inhabiting the WWS-1 region revealed very high genetic diversity, and was genetically divergent from the five populations studied. The efforts should be continued to identify and study such populations from this region as well as other muga silkworm habitats. The information generated will be very useful in conservation of dwindling muga culture in Northeast India.     

Genetic variability in mitochondrial DNA of the screwworm,Cochliomyia hominivorax (Diptera: Calliphoridae), from Brazil

Restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA) was used to examine genetic variation and population structure of screwworm flies in four populations from São Paulo State, Brazil. The total DNA of 405 individuals was digested with 15 restriction endonucleases and probed with five clonedHindIII fragments representing the entire mitochondrial genome ofCochliomyia hominivorax. The survey revealed that four enzymes (HaeIII,HindIII,MspI, andPvuII) were suitable to detect mtDNA variation among all populations. Based on the fragment patterns obtained for these four enzymes, a total of 15 haplotypes in combination was detected. Heteroplasmic individuals for thePvuII pattern were obtained in one of the populations. The estimated average for nucleotide sequence divergence (δ) was 0.92%. The cladogram of the geographical distribution among the observed haplotypes suggests that the sampled screwworms probably belong to a single evolutionary lineage with populations interconnected by reduced gene flow.     

Population Fluctuations of Three Nematode Genera in Putting Greens in Northern Illinois

Field experiments were conducted in 1989 and 1990 to examine the population fluctuation patterns of Tylenchorhynchus nudus, Criconemella curvata, and Helicotylenchus cornurus in mixed bentgrass and annual bluegrass putting greens on two golf courses near Chicago, Illinois, to determine if fluctuation patterns could be extrapolated to unsampled greens. Fenamiphos-treated and untreated plots were established on seven putting greens on two golf courses. Greens were sampled intensively five times during the growing season, and statistical comparisons of population levels per gram of root were made among dates for each green. Population levels per gram of root changed significantly on all greens in both years for each of the three nematode populations. Within a putting green in either year, population fluctuation patterns in fenamiphos-treated and untreated plots were similar. Population fluctuation patterns were different between years, however. Within a year, population fluctuation patterns among greens showed similarities indicating that carefully monitoring a few locations may allow extrapolation of population fluctuation data to other locations within that year.