Macrogeographic genetic variability in the Gastropod Mollusk <Emphasis Type="Italic">Littorina sitkana</Emphasis> from the Northwest Pacific

Variation at four highly polymorphic allozyme loci (inorganic pyrophosphatase, peptidase, and two esterase loci) was examined in 25 settlements of the marine snail Littorina sitkana (Mollusca, Gastropoda). The sampling localities covered a wide part of the species range: from the Peter the Great Bay (the Sea of Japan) at the southwest to the Mednyi Island (Commander Islands) at the northeast. Like other littorines lacking the pelagic stage, L. sitkana was characterized by significant genetic differentiation (G _ST for the pooled sample was 0.310). Cluster analysis and nonmetric multidimensional scaling conducted on a matrix of pairwise genetic distances between all of the settlements studied revealed four genetically different groups: southern Primorye, northern Prymorye, Sakhalin, and Kuril-Commanders. The population-genetic structure of the L. sitkana settlements is similar to that described by the isolation-by-distance and stepping-stone models: the geographic and the genetic distances between the most settlements examined are distinctly correlated.Translated from Genetika, Vol. 41, No. 3, 2005, pp. 374–384.Original Russian Text Copyright © 2005 by Zaslavskaya, Pudovkin.     

Allozyme comparison of four littorinid species morphologically similar to Littorina sitkana

Eight species of the genus Littorina were hitherto recognised in the north-western region of the Pacific Ocean: L. sitkana, L. brevicula, L. mandshurica, L. squalida, L. aleutica, L. naticoides, L. kasatka and L. subrotundata. Using allozyme electrophoresis it has been demonstrated that, in the Kurile Islands, three of these species (L. sitkana, L. subrotundata and L. kasatka) co-occur, together with a fourth, still undescribed species (L. sp.). These four species were compared at 16 loci coding for 13 enzymes. All species were easily distinguished by diagnostic enzyme markers. The mean genetic distances and ranges between species pairs are: L. sitkana and L. sp. D = 0.622 (0.561–0.741), L. sitkana and L. subrotundata D=0.981 (0.821–1.110), L. subrotundata and L. sp. D=0.975 (0.955–0.995). The genetic distance between L. kasatka and each of the other three species was greater than 1 (range 1.123–2.087). These data suggest that L. sitkana, L. subrotundata and L. sp could be members of a species complex; according to current classifications these three belong to the subgenus Neritrema. However, the genetic distance between L. kasatka and L. sitkana is much greater than between L. sitkana and other Neritrema species, and thus supports the classification of L. kasatka in the subgenus Littorina.     

Estimation of inbreeding,kinship and genetic distances from surnames--coastal population of middle Dalmatia,Croatia

This work was dedicated to the investigation of the population structure of the middle Dalmatia settlements: Jesenice, Mimice, Zivogos?e and Zaostrog by surname distribution study and applying the isonymous method. The surnames of males and females in marital pairs were analyzed as well as of their first and second-generation ancestors on the sample of a total of 3,024 examinees. The analyses of surnames pointed to the rates of inbreeding, kinship and genetic distances of the populations. Although the values of the inbreeding coefficient are high in all the four settlements, the inbreeding coefficient is exceptionally high in Mimice. A total kinship coefficient for the four settlements speaks also in favor of the high rate of kinship in the examined settlements, i.e. of the high rate of the reproductive isolation of the whole region during the analyzed period. The reasons for such high coefficients are natural features of the examined region (the mountains of Mosor, Biokovo and Rili?), poor traffic connection of this region in the past, the patrilineal mode of inheritance and the demographic specifics of the population. The matrix of genetic distances between examined settlement pairs reveals that Mimice, a settlement with the highest share of isonymous marriages, shows the greatest distances in comparison to the other settlements. On the other hand, Jesenice, Zivogos?e and Zaostrog are characterized by small genetic distances, which is the fact that speaks in favor of their genetic homogenization and "openness" toward interpopulational migrations, i.e. the gene flow.     

ALLOZYME SIMILARITY OF ATLANTIC AND PACIFIC SPECIES OF LITTORINA (GASTROPODA: LITTORINIDAE)

Four Littorina species from the Pacific (L. sitkana, L. brevicula,L. mandshurica, L. squalida) and four from the Atlantic (L.mariae, L. obtusata, L. saxatilis and L. littorea) were comparedelectrophoretically using 17 loci. Analysis of genetic identities showed that there were threegroups. The first group comprises L. sitkana, L. mariae, L.obtusata and L. saxatilis The second group consists of L. breviculaand L. mandshurica and the third one includes L. squalida andL. littorea. Our results support Reid's hypothesis of the originof Atlantic littorines from two Pacific ancestors. (Received 18 December 1991; accepted 30 March 1992)     

Mitochondrial and nuclear DNA analysis revealed a cryptic species and genetic introgression in Littorina sitkana (Mollusca, Gastropoda)

We investigated mitochondrial and nuclear DNA genotypes in nominal Littorina sitkana samples from 2 localities in Eastern Hokkaido, northern Japan. Our results indicated the existence of cryptic species. In the analysis of partial mitochondrial Cytchrome b gene sequences, haplotypes of L. sitkana samples were monophyletic in a phylogenetic tree with orthologous sequences from other Littorina species, but were apparently separated in 2 clades. One included typical L. sitkana (CBa clade) samples, which formed a clade with an allopatric species, L. horikawai. The other, CBb, was independent from CBa and L. horikawai. Haplotypes of the mitochondrial 16S rRNA gene also separated into 2 clades. We additionally examined intron sequence of the heat shock cognate 70 (HSC70) nuclear gene and identified 17 haplotypes. These were also separated into 2 clades, HSCa and HSCb. Among the examined Hokkaido samples, 60% of individuals were heterozygotes. However, each heterozygote consisted of haplotypes from the same clade, HSCa or HSCb, and no admixture of HSCa and HSCb haplotypes was observed. These results indicate reproductive isolation between the 2 clades. Among the genotyped Hokkaido samples, 93% of individuals had CBa?+?HSCa or CBb?+?HSCb genotypes, and 7% had CBb?+?HSCa genotypes. The discrepancy between the mtDNA and nuclear DNA haplotypes in a few individuals may have been caused by genetic introgression due to past hybridization.     

Spatial and temporal population genetic structure of four northeastern Pacific littorinid gastropods: the effect of mode of larval development on variation at one mitochondrial and two nuclear DNA markers

We investigated the effect of development mode on the spatial and temporal population genetic structure of four littorinid gastropod species. Snails were collected from the same three sites on the west coast of Vancouver Island, Canada in 1997 and again in 2007. DNA sequences were obtained for one mitochondrial gene, cytochrome b ( Cyt b ), and for up to two nuclear genes, heat shock cognate 70 ( HSC70 ) and aminopeptidase N intron ( APN54 ). We found that the mean level of genetic diversity and long-term effective population sizes ( N _e) were significantly greater for two species, Littorina scutulata and L. plena , that had a planktotrophic larval stage than for two species, Littorina sitkana and L. subrotundata , that laid benthic egg masses which hatched directly into crawl-away juveniles. Predictably, two poorly dispersing species, L. sitkana and L. subrotundata , showed significant spatial genetic structure at an 11- to 65-km geographical scale that was not observed in the two planktotrophic species. Conversely, the two planktotrophic species had more temporal genetic structure over a 10-year interval than did the two direct-developing species and showed highly significant temporal structure for spatially pooled samples. The greater temporal genetic variation of the two planktotrophic species may have been caused by their high fecundity, high larval dispersal, and low but spatially correlated early survivorship. The sweepstakes-like reproductive success of the planktotrophic species could allow a few related females to populate hundreds of kilometres of coastline and may explain their substantially larger temporal genetic variance but lower spatial genetic variance relative to the direct-developing species.     

Microsatellite diversity among the primitive tribes of India

The present study was undertaken to determine the extent of diversity at 12 microsatellite short tandem repeat (STR) loci in seven primitive tribal populations of India with diverse linguistic and geographic backgrounds. DNA samples of 160 unrelated individuals were analyzed for 12 STR loci by multiplex polymerase chain reaction (PCR). Gene diversity analysis suggested that the average heterozygosity was uniformly high ( >0.7) in these groups and varied from 0.705 to 0.794. The Hardy-Weinberg equilibrium analysis revealed that these populations were in genetic equilibrium at almost all the loci. The overall G(ST) value was high (G(ST) = 0.051; range between 0.026 and 0.098 among the loci), reflecting the degree of differentiation/heterogeneity of seven populations studied for these loci. The cluster analysis and multidimensional scaling of genetic distances reveal two broad clusters of populations, besides Moolu Kurumba maintaining their distinct genetic identity vis-à-vis other populations. The genetic affinity for the three tribes of the Indo-European family could be explained based on geography and Language but not for the four Dravidian tribes as reflected by the NJT and MDS plots. For the overall data, the insignificant MANTEL correlations between genetic, linguistic and geographic distances suggest that the genetic variation among these tribes is not patterned along geographic and/or linguistic lines.     

Electrophoretic examination of the population structure of brown trout, Salmo trutta L., from the Lough Neagh catchment, Northern Ireland

Samples of brown trout, Salmo trutia L., from 34 locations throughout the Lough Neagh system in north-east Ireland were electrophoretically examined for genetic variation at 28 enzyme loci. Patterns of allelic variation at 12 polymorphic loci indicated the existence of genetic differentiation within as well as among several river systems, suggesting the existence of multiple brown trout populations. Significant gene frequency differences were detected over distances as little as 3 km, demonstrating the propensity of this species for microgeographic genetic differentiation. This was confirmed by a hierarchical analysis of genetic variance, some 35% of among-sample variance being distributed within tributaries. Within Lough Neagh itself significant genetic differentiation was detected between two morphotypes (dollaghan and salmon-trout) and for one of these (dollaghan) among samples from different years and from different areas of the lough. This suggests the existence of genetically differentiated subpopulations of originating from separate river catchments.     

山东省长岛县南部四岛藜（Chenopodium album L.）天然种群遗传多样性的ISSR分析

采用ISSR分子标记对分布于山东省长岛县南部的北长山、南长山、大黑山和小黑山4个岛屿上的藜天然种群共81个个体进行了遗传多样性及遗传结构的研究。13个引物共检测到157个可重复的位点。遗传多样性研究结果表明：种内的多态位点比率为66.24％,具有较高的遗传多样性（Shannon（I）指数在物种水平上为0.332 0）;种群间有一定的遗传分化,根据G_st值,种群间的遗传多样性占总群体的9.27％。遗传距离分析表明,XHS种群和NCS种群的遗传一致度最高,与地理距离无相关性。     

Population genetic differentiation in taxa of Lotus (Fabaceae: Loteae) endemic to the Gran Canarian pine forest

A survey of allozyme variation at 17 loci in 14 populations representing four taxonomically problematic Gran Canarian pine forest endemic taxa of Lotus (L. genistoides, L. holosericeus, L. spartioides and some taxonomically uncertain populations collected under the designation Lotus sp.) was conducted to examine their diversification and systematic relationships. All groups exhibited high values of genetic variation, although inbreeding was common within populations. Considerable among-population genetic homogeneity was detected, as inferred from low values of Gst within each of the groups. The high population sizes of these taxa and a lack of evidence for isolation by distance or genetic bottlenecks indicate that diversity has accumulated over a long period of environmental stability. The association of high genetic distances with low linear distances, and the substantial increase in the values of Gst when the taxa considered were merged in different combinations hint at an incipient (yet probably taxonomically insufficient) reproductive isolation. The genetic similarity between L. genistoides, L. holosericeus and L. spartioides, together with the different behaviour of the populations collected under the designation Lotus sp., may have important implications for the restructuring of the taxonomy of this group when the ongoing morphological studies are completed.     

A striking example of the founder effect in the mollusc Littorina saxatilis

Two South African populations of Littorina saxatilis were examined by starch-gel electrophoresis at 16 enzyme loci and compared with 13 populations of North Atlantic saxatilis from both American and European coasts, and with six British populations of the closely related species Littorina arcana. The South African animals showed a severely reduced heterozygosity (– 0.052) compared with Atlantic populations of saxatilis ( = 0.181), and the mean genetic distance between the two areas was high ( = 0.203) compared with distances within the North Atlantic saxatilis populations (D = 0.034). In fact, the saxatilis from South Africa were genetically more distant from the North Atlantic samples of L. saxatilis than were the arcana from British shores. The reduced genetic heterozygosity and genetic divergence of the South African populations is attributed to founder effects following a postulated recent introduction by man.     

Do polymorphic loci require large sample sizes to estimate genetic distances?

The coefficient of variation of estimates of three genetic distances (standard genetic distance of Nei, chord distance, FST) was examined with computer simulation to determine if large samples (per population) are necessary to precisely estimate genetic distances at loci with high levels of polymorphism. These simulations showed that loci with high mutation rates produce estimates of genetic distance with lower coefficients of variation than loci with lower mutation rates--without requiring larger sample sizes from each population. In addition, the rate at which increasing sample sizes decreases the coefficient of variation of estimates of genetic distances was shown to be approximately determined by the value of FST between the populations being sampled. When FST was greater than 0.05, sampling fewer than 20 individuals (per population) should be sufficient. When FST was less than 0.01, sampling 100 individuals (per population) or more will be useful.     

Genetic divergence of Far Eastern dace species belonging to the genus Tribolodon (Pisces,Cyprinidae) and closely related taxa

Based on a biochemical-genetic approach, heterozygosity and divergence of structural genes of 30 enzyme loci were analyzed in six dace species. In addition, intra- and interspecific divergence of gene expression was analyzed based on a sample of 12 to 15 loci. Mean heterozygosities per individual varied as follows: Tribolodon species, Hobs = 0.007 +/- 0.007 and Hexp = 0.007 +/- 0.007; T. ezoe, Hobs = 0.045 +/- 0.016 and Hexp = 0.067 +/- 0.029. Several variants of genetic distances were estimated. Standard Nei's distances (DN) varied from 0.145 to 0.284 in four dace species studied. As related to Tribolodon dace species, the following genetic distances were obtained for two members of other genera: Pseudaspius leptocephalus, DN = 0.269; Leuciscus waleckii, DN = 0.769. Based on the distance matrices, different clustering algorithms were realized. The main feature shared by different dendrograms was a separate position of the cluster joining Far-Eastern dace species, to which P. leptocephalus and L. waleckii are successively added. Among the species studied, the proportion of loci similar by expression (E) varied from 87 to 100%. The greatest difference was found between anadromous and nonanadromous ecotypes of T. hakonensis, E = 67%. The following conclusions can be made: (1) Four studied species of the genus Tribolodon are rather well genetically differentiated. Diagnostic loci are available. (2) A nominal dace species, T. species, should be considered the fourth isolated species of this genus, which is confirmed by its recent zoological acceptance of this species. (3) The origin and divergence of dace species belonging to the genus Tribolodon are relatively late (1 to 3 Myr ago) historical events. (4) Taxonomically, the genus Tribolodon belong to the tribe Pseudaspinini together with P. leptocephalus, which is confirmed by genetic data. (5) Data on heterozygosity and the divergence of structural and regulatory elements of genome, along with the proposed scheme of speciation types, suggest the following speciation modes for the species studied: for four species, adaptive divergence and for two species, genetic transformation.     

大猿叶虫四地理种群遗传多样性的RAPD分析

以大猿叶虫Colaphellus bowringi Baly 4个地理种群的基因组DNA为材料, 进行RAPD分析。从80条引物中筛选出11条稳定性好、多态性高的引物进行扩增, 共得到65个扩增位点, 53个多态位点, Nei氏遗传多样性指数为0.1049~0.2061, Shannon多样性指数为0.1641~0.3167。结果表明所分析的大猿叶虫遗传变异很高, 其中江西龙南种群遗传变异最小, 山东泰安种群遗传变异最高。种群间的遗传距离范围为0.0636~0.3200, 其中江西龙南种群和江西修水种群间的遗传距离最小, 哈尔滨种群与江西龙南种群间的遗传距离最大, 种群遗传距离的大小与其相对地理距离的远近吻合。结果提示种群遗传距离的大小与它们生物学上的相似性有关联。     

Determination of Genetic Diversity of Vitis vinifera cv. Kabarcik Populations from the Coruh Valley Using SSR Markers

Northeastern Turkey is recognized as one of the most important germplasm centers for the grape in the world. In the present study, simple sequence repeat markers were used to investigate the genetic diversity between four Vitis vinifera cv. Kabarcik populations sampled from the Coruh Valley in Turkey, at altitudes of 800-1,150 m. The mean observed number of alleles per locus varied from 2 (loci VVMD7 and VVMD24) to 6 (VVS2) among populations. The population from the highest altitude showed the greatest average number of alleles, 4.5. With regard to the six loci examined in all populations, the mean observed heterozygosity was higher than the expected heterozygosity. Among the loci, VVS2 (probability of identity = 0.137) was found to be the most informative among populations. Genetic distances between populations ranged from 0.072 to 0.216. Genetic differentiation among populations was strongly related to geographic distances in all populations.     

Population genetic structure of the malaria mosquito Anopheles arabiensis across Nigeria suggests range expansion

Ten microsatellite loci, four located within and six outside chromosome inversions, were employed to study the genetic structure of Anopheles arabiensis across the ecological zones of Nigeria (arid savannah in the north gradually turns into humid forest in the south). Regardless of location within or outside inversions, genetic variability at all loci was characterized by a reduction in both the number of alleles per locus and heterozygosity from savannah to forest. Across all loci, all but one allele in the forest also occurred in the savannah, whereas at least 78 alleles in the savannah were missing in the forest. Genetic differentiation increased with geographical distance; consequently, genetic distances between zones exceeded those within zones. The largest genetic distances were between localities at the extremes of the transect (range F(ST) = 0.196-0.258 and R(ST) = 0.183-0.468) and were as large as those between A. arabiensis and Anopheles gambiae s.s. Gene flow across the country was very low, so that Nm between the extremes of the transect was < 1. These data suggest that A. arabiensis has extended its range from the savannah into the forest during which it experienced a reduction in effective population size due to sequential founder effects. Gene flow post range expansion appears too restricted by geographical distance to homogenize the gene pool of A. arabiensis across Nigeria.     

Genetic structure and relationships of four populations of the stalk boring moth, Eldana saccharina

Twenty-seven protein coding loci were examined by means of horizontal starch gel electrophoresis in samples of larvae from four populations of the stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae) in Natal, South Africa. The populations were collected in two localities approximately 250 km apart. In each locality a sample was obtained from sugarcane and also from the locally most abundant indigenous host plant of this insect (Cyperuspapyrus L. in one locality and C. dives Delile - synonomous with C. immensus CB CI. - in the other). More than one allele was detected at eight of the loci in all four populations and at a further locus in three of the populations; the other 18 loci were monomorphic for the same allele in all populations. Average expected heterozygosity over the 27 loci was approximately 0.12 in all populations. Genetic distances among the populations were small, but were greater between the two populations from the indigenous hosts and the two from sugarcane than within either of these pairs of populations. Possible explanations of these results are discussed.     

大连地区岛屿与大陆藜（Chenopodium album L.）种群遗传多样性的ISSR分析

采用ISSR分子标记对分布于大连市周边的4个藜的天然种群100个个体进行了遗传多样性及遗传结构的研究。13个引物共检测了157个位点,多态位点比率为67.52%,Shannon信息指数在物种水平上为0.332 9。根据G_ST值,藜遗传变异有40.03%发生在种群间。遗传距离分析表明,DT种群与MLN种群遗传一致度最高,遗传距离与地理距离之间没有相关性。     

Factors influencing the distribution of nests of the Argentine ant Linepithema humile Mayr (hymenoptera: formicidae), in a foothills ecosystem of the central zone of Chile

The purpose of this research was to demonstrate the dependant relationship between the Argentine ant Linepithema humile Mayr, plant coverage, and human settlements. A method was designed in order to sample the presence of the Argentine ant and other ant species that may had influenced L. humile distribution, under different types of vegetation and percentages of plant coverage, taking in consideration the distance from human settlements. Eight sample stations were established. Four of these stations were found on a dwelling home and the other four were found on similar areas, but far from human settlements. Three transects were established from the center of each sampling station (Tt1, shrublike vegetation, Tt2, herblike vegetation and Tt3, no vegetation). Transects were compound by 10 m side quadrants. A negative correlation was found between nest number of L. humile and human settlement distance, therefore nests were not found at distances higher than 80 m, in all studied areas. There was a positive and significant correlation between nest number of L. humile and plant coverage percentage, regardless the type of vegetation found. The same trend was found for other ant species studied in the area. Finally, it was proved that the distribution of L. humile nests is not influenced by other ant species.     

Allozyme variability and differentiation in Serbian roe deer populationsCapreolus capreolus

The present study investigates the genetic structure of 12 roe deerCapreolus capreolus Linnaeus, 1758 population samples from Serbia, by screening a total of 334 individuals. We examined whether genetic differentiation exists in local populations in Serbia, and addressed the question whether management policies may affect genetic structure. The populations were analysed by multilocus protein electrophoresis, with 33 protein loci examined. Screening of 20 enzymes and one group of general proteins revealed polymorphism at the following 12 loci: Sdh, Mdh-1, Me-1, Idh-2, 6-Pgd-1,αGpd, Ak, Pgm-1, Pgm-2, Ca, Mpi andGpi. Among samples, the proportion of polymorphic loci varied between 3–15.2% (mean 11.9%), while the average gene diversity was in the range of 1.1–4.2%. The overall genetic differentiation was low (θ = 0.03). The comparison of two regional population groups (northern-southern, separated by the Danube River) showed an absence of genetic differentiation between regions. Gene flow was estimated at 8.96 migrants per generation, and was higher in the lowland than in the highland group. Three loci (Ca, 6-Pgd andGpd-1) showed clinal variation along a geographical gradient. Additional five alleles of four loci (Ak, Pgm-1, Gpi, 6-Pgd) showed significant spatial autocorrelation. Genetic distances were small (D = 0–0.004). Northern and southern populations clustered separately. For at least three populations game management practices provide evidence for outlying genetic parameters. The observed heterogeneity in the inbreeding level was deemed more under the influence of non-random mating strengthened by game management, than by overall selective pressure.