Unique haplotypes in ant‐attended aphids and widespread haplotypes in non‐attended aphids

Aphid species within the genus Tuberculatus Mordvilko (Hemiptera: Aphididae) exhibit a variety of interactions with ants, ranging from close associations to non‐attendance. A previous study indicated that despite wing possession, ant‐attended Tuberculatus species exhibited low dispersal rates compared with non‐attended species. This study examined if presence or absence of mutualistic interactions and habitat continuity of host plants affected intraspecific genetic diversity and genetic differentiation in mitochondrial DNA cytochrome oxidase I (COI) sequences. Sympatric ant‐attended Tuberculatus quercicola (Matsumura) (Hemiptera: Aphididae) and non‐attended Tuberculatus paiki Hille Ris Lambers (Hemiptera: Aphididae) were collected from the daimyo oak Quercus dentata Thunberg (Fagales: Fagaceae) in Japan and examined for haplotype variability. Seventeen haplotypes were identified in 568 T. quercicola individuals representing 23 populations and seven haplotypes in 425 T. paiki representing 19 populations. Haplotype diversity, which indicates the mean number of differences between all pairs of haplotypes in the sample, and nucleotide diversity were higher in T. quercicola than T. paiki. Analysis of molecular variance (AMOVA) showed higher genetic differentiation among populations within groups of T. quercicola (39.8%) than T. paiki (22.6%). The effects of attendant ant species on genetic differentiation in T. quercicola were not distinguishable from geographic factors. Despite low dispersal rates, host plant habitat continuity might facilitate widespread dispersal of a T. quercicola haplotype in Hokkaido. These results suggested that following T. quercicola colonization, gene flow among populations was limited, resulting in genetic drift within populations. However, frequent T. paiki dispersal is clearly evident by low genetic differentiation among populations within groups, resulting in lower haplotype diversity.     

Genetic structure of a native cyprinid in a reservoir‐altered stream network

1. Reservoirs modify riverine ecosystems worldwide, and often with deleterious impacts on native biota. The immediate effects of reservoirs on native fish species below dams and in impounded reaches have received considerable attention, but it is unclear how reservoirs may affect fish species at larger spatial and temporal scales. Documented declines of stream fish populations in direct tributaries of reservoirs suggest reservoir pools may reduce gene flow among historically connected populations. 2. Because of increased predator densities in reservoirs and the extent of habitat alteration in impounded reaches, I predicted reservoir habitats would reduce gene flow among small‐bodied fish populations separated by reservoir habitat. I used microsatellite markers to assess the spatial genetic structure of populations of the red shiner (Cyprinella lutrensis), in a reservoir‐fragmented stream network (Lake Texoma, U.S.A.). I also tested the prediction that populations in two direct tributaries that have experienced population declines would have low genetic diversity. Individuals were collected from six sites upstream of the reservoir, three sites in the reservoir and three sites in direct tributaries of the reservoir during 2008 and 2009. 3. Results indicate that most populations were isolated by distance with little divergence among populations. In one direct tributary population, however, there was substantial genetic divergence, and genetic diversity was significantly lower than in other populations. Gene flow also seemed to be lower in reservoir habitats than in intact stream habitats, suggesting reservoir habitats may be reducing gene flow among the reservoir‐separated populations. These results indicate that reservoirs may reduce gene flow among reservoir‐fragmented stream fish populations, altering the evolutionary trajectories of fragmented populations.     

Phylogeography of Camellia taliensis (Theaceae) inferred from chloroplast and nuclear DNA: insights into evolutionary history and conservation

ABSTRACT: BACKGROUND: As one of the most important but seriously endangered wild relatives of the cultivated tea, Camellia taliensis harbors valuable gene resources for tea tree improvement in the future. The knowledge of genetic variation and population structure may provide insights into evolutionary history and germplasm conservation of the species. RESULTS: Here, we sampled 21 natural populations from the species' range in China and performed the phylogeography of C. taliensis by using the nuclear PAL gene fragment and chloroplast rpl32-trnL intergenic spacer. Levels of haplotype diversity and nucleotide diversity detected at rpl32-trnL (h = 0.841; pi = 0.00314) were almost as high as at PAL (h = 0.836; pi = 0.00417). Significant chloroplast DNA population subdivision was detected (GST = 0.988; NST = 0.989), suggesting fairly high genetic differentiation and low levels of recurrent gene flow through seeds among populations. Nested clade phylogeographic analysis of chlorotypes suggests that population genetic structure in C. taliensis has been affected by habitat fragmentation in the past. However, the detection of a moderate nrDNA population subdivision (GST = 0.222; NST = 0.301) provided the evidence of efficient pollen-mediated gene flow among populations and significant phylogeographical structure (NST > GST; P < 0.01). The analysis of PAL haplotypes indicates that phylogeographical pattern of nrDNA haplotypes might be caused by restricted gene flow with isolation by distance, which was also supported by Mantel's test of nrDNA haplotypes (r = 0.234, P < 0.001). We found that chlorotype C1 was fixed in seven populations of Lancang River Region, implying that the Lancang River might have provided a corridor for the long-distance dispersal of the species. CONCLUSIONS: We found that C. taliensis showed fairly high genetic differentiation resulting from restricted gene flow and habitat fragmentation. This phylogeographical study gives us deep insights into population structure of the species and conservation strategies for germplasm sampling and developing in situ conservation of natural populations.     

Bumblebee commercialization will cause worldwide migration of parasitic mites

We investigated natural populations of three Japanese native bumblebee species to determine the status of infestation by a tracheal mite, Locustacarus buchneri, which we had earlier detected in introduced commercial colonies of the European bumblebee, Bombus terrestris. We also investigated mite infestation in commercial colonies of a Japanese native species, B. ignitus, which are mass-produced in the Netherlands and reimported into Japan. We detected the mite in both natural and commercial colonies of the Japanese species. Comparison of 555 bp sequences of the mitochondrial DNA (mtDNA) cytochrome oxidase 1 (CO1) gene from the mite showed that there were seven haplotypes, on the basis of combinations of substitutions at eight sites in the gene. The haplotypes of the mites in the Japanese native bumblebees and the haplotypes of the mites in B. terrestris did not overlap; however, mtDNA of mites detected in the commercial colonies of B. ignitus possessed the same sequence as a European haplotype. These results indicate that transportation of bumblebee colonies will cause overseas migration of parasitic mites of different origins.     

Mitochondrial evidence for distinct phylogeographic units in the endangered Malagasy poison frog Mantella bernhardi

Mantella bernhardi is an endemic species of Malagasy poison frog threatened by loss and fragmentation of its natural habitat and collection for the pet trade. It is classified as threatened according to the International Union for Conservation of Nature and Natural Resources (IUCN) categories and included in Appendix II of the Convention on the International Trade of Endangered Species (CITES). A recent survey has increased the known distributional range of the species from one to eight populations across southeastern Madagascar, but little is known about its biology and genetic diversity. Here we estimate inter- and intrapopulation mitochondrial genetic variation of four populations. Populations from the northern and southern parts of the distributional range showed a high degree of divergence (maximum of 11.35% in cytochrome b) and were recovered as reciprocally monophyletic groups. Nine haplotypes were detected in the northern and 12 in the southern populations. The population from Ranomafana National Park showed the lowest number of haplotypes and nucleotide diversity, and shared its most common haplotype with the second northern population from Tolongoina. All the other detected haplotypes were unique to each of the four populations. This suggests the existence of important barriers to gene flow, pre-dating human colonization of Madagascar at about 2000 years ago, in distinct contrast to other Mantella species that show a high degree of haplotype sharing throughout their range. The continued habitat fragmentation within the distribution range of M. bernhardi prevents any connection between its populations. Our data indicate the existence of at least two different management units for conservation in this species, corresponding to the North and South of its distribution range, and highlight the existence of strong regional endemism in southeastern Madagascar.     

Genetic diversity of captive forest musk deer (Moschus berezovskii) inferred from the mitochondrial DNA control region

Forest musk deer ( Moschus berezovskii ) were once distributed widely in China. However, wild populations have declined dramatically because of poaching and habitat loss. Captive breeding populations have been established for several decades, but the genetic backgrounds of most captive populations were unclear and the population sizes increased very slowly. To provide useful information for conservation and management of this species, we investigated the genetic diversity and population structure of forest musk deer by analysing a 582-bp fragment of the mitochondrial DNA (mtDNA) control region (CR) in three captive breeding populations in Sichuan Province, China. Ninety-four variable sites and 27 haplotypes were observed in 109 individuals, and the nucleotide and haplotype diversities were relatively high compared with those of other endangered mammals. Of the three investigated populations, the Maerkang population had the highest nucleotide diversity ( π  = 0.0568), haplotype diversity ( h  =   0.836) and average intra-population genetic distance (0.062). The analysis of molecular variance demonstrated that most variation occurred within samples and that there was significant differentiation of the three populations. Estimates of gene flow indicated that there were few genetic exchanges among the three populations. Building pedigree records and increasing gene flow between populations will be helpful for conserving these populations and this species.     

Bank voles in linear habitats show restricted gene flow as revealed by mitochondrial DNA (mtDNA)

Genetic structure of bank vole populations in linear river bank habitat in southeast Norway was determined from analyses of DNA sequences for the mitochondrial D-loop. Animals were sampled at sites separated by 1 km, along two forested river banks separated by ≈ 100 m of open water. Twenty-six distinct haplotypes were found among 120 voles. The voles showed significant deviation from panmixis on both sides of the river. Animals from the same site or from sites 1 km apart were more likely to share haplotypes than animals 2 km apart or more. Common haplotypes were widespread on both river banks, and had a wider distribution than relatively rare haplotypes. Some rare haplotypes were found on both banks, but most were restricted to a single bank. The results suggest that short-term gene flow may be restricted for female bank voles in linear habitats. Female territorial behaviour may vary with habitat geometry. In the linear habitat described here, females defend only two territorial borders and may effectively limit female dispersal. Results were compared to a previous study of bank voles from this region in a two-dimensional habitat. Gene flow in the linear habitat was much more restricted than gene flow in the two-dimensional habitat. Probable mechanisms underlying this difference are discussed.     

Phylogenetic Relationships Among Fragmented Asian Black Bear (Ursus Thibetanus) Populations in Western Japan

The number of Asian black bears (Ursus thibetanus) in Japan has been reduced and their habitats fragmented and isolated because of human activities. Our previous study examining microsatellite DNA loci revealed significant genetic differentiation among four local populations in the western part of Honshu. Here, an approximate 700-bp nucleotide sequence of mitochondrial DNA (mtDNA) control region was analysed in 119 bears to infer the evolutionary history of these populations. Thirteen variable sites and variation in the number of Ts at a T-repeat site were observed among the analysed sequences, which defined 20 mtDNA haplotypes with the average sequence divergence of 0.0051 (SD = 0.00001). The observed haplotype frequencies differed significantly among the four populations. Phylogeographic analysis of the haplotypes suggested that black bears in this region have gone through two different colonisation histories, since the observed haplotypes belonged to two major monophyletic lineages and the lineages were distributed with an apparent border. The spatial genetic structure revealed by using mtDNA was different from that observed using microsatellite DNA markers, probably due to female philopatry and male-biased dispersal. Since nuclear genetic diversity will be lost in the three western populations because of the small population size and genetic isolation, their habitats need to be preserved, and these four populations should be linked to each other by corridors to promote gene flow from the easternmost population with higher nuclear genetic diversity.     

Intraspecific differentiation of Allium wallichii (Amaryllidaceae) inferred from chloroplast DNA and internal transcribed spacer fragments

In the present study, we used two chloroplast DNA (cpDNA) fragments (trnL-F and rps16) and the nuclear ribosomal internal transcribed spacer (ITS) sequence data to examine intraspecific differentiation and phylogeographical history of Allium wallichii. Based on wide scale sampling (28 populations and 174 individuals) across the entire distribution range of this species, 33 cpDNA haplotypes and 25 ITS ribotypes were detected in our investigation. These cpDNA haplotypes were divided into three major lineages, which was further supported by the ITS phylogenetic results. High haplotype/ribotype diversity and population differentiation, together with most of the haplotypes/ribotypes being exclusive to single populations, implied restricted gene flow among populations and significant geographical isolation. Nearly all populations with high haplotype/ribotype diversity were found in the Hengduan Mountain Region (HMR), whereas the populations of the Himalayas and Nanling Mountains showed a lower level, suggesting the HMR might serve as a potential divergence center for A. wallichii. The main lineages of A. wallichii diverged from each other between Mid–Late Pliocene and Early Quaternary based on two sets of molecular markers, indicating that the Quaternary climatic fluctuation could not have contributed greatly to the divergence of the main lineages of A. wallichii. Instead, the intricate topography and heterogeneous habitats resulting from the drastic uplift of the Qinghai–Tibet Plateau from the Late Pliocene could be responsible for the intraspecific differentiation of A. wallichii. The present study further highlights the importance of geographic isolation and habitat heterogeneity in shaping and maintaining high species diversity within the HMR.     

基于叶绿体基因序列rbcL-accD研究莛子藨的分子遗传多样性和谱系地理结构

莛子藨是莛子藨属的一种多年生草本植物,主要分布在青藏高原东北部及邻近高山地区和日本,为东亚特有种。本文基于叶绿体DNA基因间隔区rbcL-accD序列,对莛子藨物种水平的序列特征、分子遗传多样性和谱系地理结构进行研究。分析结果发现该区域莛子藨种群的遗传变异主要来自于居群间（72.28%）,优势单倍型（H2）广泛分布,特有单倍型分散在多个居群。居群间遗传分化系数N_STST,没有检测到显著谱系地理结构,而且居群间基因流较低（N_m=0.096）,青藏高原及其邻近地区特殊地形和生态环境造成的地理隔离或者生境异质化可能是现有单倍型分布格局形成的原因。种群动态历史分析显示莛子藨经历过不显著的种群选择或者扩张事件,综合分析推测莛子藨居群应该是在间冰期或者冰期后从不同避难所扩散形成现在的分布格局,具体避难所还需进一步深入研究才能确认。     

Molecular insights into the genetic and haplotype diversity among four populations of Catla catla from Madhya Pradesh revealed through mtDNA cyto b gene sequences

In the present investigation, the genetic structure of four populations of Catla catla, sequences of mitochondrial gene, cytochrome b (cyto b) from four populations were sequenced and analyzed. The sequences of mitochondrial regions revealed high haplotype diversity and low nucleotide diversity. The lowest 249 polymorphic sites and 0.00 parsimony informative sites were detected in populations of Fish Federation Pond (CCFFB) whereas highest 330 polymorphic sites and 56 parsimony informative sites were detected in populations of Narmada River (CCNRH) in the cyto b gene sequences in Catla catla populations. The twelve different haplotypes were detected among the four populations studied, lowest population specific haplotype as 2.00 was observed in Fish Federation Pond (CCFFB) and highest was in Population of Narmada River and Tighra reservoir. Sequencing of cyto b gene revealed 12 number of haplotypes (h) with haplotype (gene) diversity (Hd) 0.8736 and nucleotide diversity (π) 0.6474. These data clearly indicated that, feral/wild population showing highest values of polymorphisms, parsimony, haplotype diversity showing good, healthy habitat is lotic water (Narmada River) and lentic water body (Tighra reservoir). The results also concluded that the partial cyto b is polymorphic and can be a potential marker to determine ecological habitat based genetic differentiation among the populations.     

Variation in mitochondrial COII gene sequences among two species of Japanese knotweed-boring moths, Ostrinia latipennis and O. ovalipennis (Lepidoptera: Crambidae)

The Ostrinia latipennis group contains two species, O. latipennis (Warren) and O. ovalipennis Ohno. These two species commonly utilize perennial knotweeds (Fallopia spp.) as their host plants, which are serious invasive weeds in Europe and North America. Ostrinia latipennis is widely distributed across north-east Asia including Japan whereas O. ovalipennis is restricted to north Japan (Hokkaido Is.) and highland areas of central Japan (Nagano Prefecture in Honshu Is.). To estimate the phylogenetic relatedness and geographical differentiation of the two species, mitochondrial COII gene sequences were determined for specimens covering their distribution ranges in Japan. The uncorrected sequence divergence between O. latipennis and O. ovalipennis was 0.6-0.7%, supporting a close relationship. According to the standard molecular clock proposed for arthropod mtDNA, the two species are speculated to have diverged about 0.3 Myr ago. A single COII gene haplotype was found in O. latipennis irrespective of collection locality. In contrast, two haplotypes were found in O. ovalipennis, and their frequencies were significantly different between the Hokkaido and Honshu populations. The patterns of geographical variation in the COII gene within the two species were in agreement with previously reported patterns of geographical differentiation in morphology of the two species in Japan. The present results support the hypothesis that gene flow among local populations of O. ovalipennis has been limited by geographical isolation.     

Genetic variation and population differentiation in the lichen-forming ascomycete Xanthoria parietina on the island Storfosna, central Norway

Genetic diversity and fine-scale population structure in the lichen-forming ascomycete Xanthoria parietina was investigated using sequence variation in part of the intergenic spacer (IGS) and the complete internal transcribed spacer (ITS) regions of the nuclear ribosomal DNA. Sampling included 213 and 225 individuals, respectively, from seven populations in two different habitats, bark and rock, on the island Storfosna off the central west coast of Norway. Both markers revealed significant variation and a total of 10 IGS and 16 ITS haplotypes were found. There were no signs of significant positive spatial autocorrelation at any spatial size class down to 10% of transect length, nor did we find significant deviations from neutrality or signs of historical population expansion. Analysis of molecular variance (amova) indicated that most of the genetic variance observed was within populations, but when populations were grouped according to habitat, more than a quarter of the variance was explained among groups. Pairwise comparisons of populations (F(ST), exact tests of population differentiation) revealed significant differentiation between populations in different habitats (on bark or rock), but not between populations in the same habitat. Haplotype networks show that internal and presumably old haplotypes are shared between habitats, whereas terminal haplotypes tend to be unique to a habitat, mostly bark. We interpret the observed pattern to mean that there is no evidence of restricted gene flow between populations in the same habitat at the present spatial scale (interpopulation distances one or a few kilometres). On the other hand, differentiation between habitats is considerable, which we attribute to restricted gene flow between habitats (habitat isolation). Evidence suggests that the observed differentiation did not evolve locally. Estimates of divergence time between populations in the respective habitats indicate that an ancestral population started to diverge at least 34,000 years ago but probably much further back in time.     

Genetic variation and Wolbachia infection status of the lycaenid butterfly Zizina emelina (Lepidoptera,Lycaenidae) from Korean populations

The lycaenid butterfly Zizina emelina emelina (de l’Orza) (previously Zizina otis emelina; Lepidoptera, Lycaenidae) has populations distributed across Japan and Korea. Zizina emelina is listed on Japan’s Red List as an endangered species, owing to the loss of its principal plant food and habitat. Researchers previously investigated the genetic diversity and structure in Japanese populations by using mitochondrial and nuclear DNA analyses alongside their Wolbachia infection status to consider the conservation strategy. In this study, we investigated the genetic variation and Wolbachia infection status of Korean populations and compared our findings with these traits in the Japanese populations. Four novel mitochondrial haplotypes were found in the Korean populations, whereas nuclear DNA analysis revealed one new haplotype and another that matched the one reported previously in Japan. The two known strains of Wolbachia in the Japanese populations were also found in the Korean ones. Mitochondrial DNA analysis demonstrated that no gene flow had occurred between the Japanese and Korean populations. The fact that they share the same nuclear haplotype and Wolbachia strains, however, indicates a low level of population differentiation between the two.     

Phylogeographic structure and late Quaternary population history of the Japanese oak Quercus mongolica var. crispula and related species revealed by chloroplast DNA variation

Generally, oaks dominate the broadleaf deciduous forests in Japan. The genetic variation in 6 cpDNA regions (trnT-trnL, trnL-trnF, atpB-rbcL, and trnH-psbA speacers, trnL intron, and matK gene) with regard to the Japanese oak (Quercus mongolica var. crispula) and 3 related species in the section Prinus (Q. serrata, Q. dentata and Q. aliena) was investigated in 598 trees belonging to 44 populations distributed throughout the Japanese archipelago. Additional samples were collected from Korea, China, and Russia (Sakhalin). Thirteen haplotypes (I to XIII) were identified on the bases of 15 nucleotide substitutions and 3 indels. Haplotypes I and II were discovered in northeastern Japan, whereas haplotypes III to IX were distributed in southwestern Japan. The boundary distinguishing these 2 groups was located in central Japan coincident with the Itoigawa-Shzuoka tectonic line. Haplotype I was also found in Sakhalin, whereas haplotypes VI, VII, VIII, X, XI, XII, and XIII were found in Korea and China. Four oak species in the same location shared identical haplotypes, suggesting cpDNA introgression by occasional hybridization. Both the values of total haplotype diversity (HT) and haplotype diversity within populations (HS) in Q. mongolica var. crispula were higher in the southwestern populations than in the northeastern populations. A haplotype network indicated that haplotype VI is the ancestral haplotype. The presence of identical haplotypes in Korea, China, and Japan suggested that the haplotypes diversified on the Eurasian continent before the last glacial period. The difference in genetic structure between the northeastern and southwestern regions indicates a difference in the history of migration and recolonization in Japan during the last glacial period.     

Haplotype diversity of mt<Emphasis Type="Italic">COI</Emphasis> in the fall webworm <Emphasis Type="Italic">Hyphantria cunea</Emphasis> (Lepidoptera: Arctiidae) in introduced regions in China,Iran, Japan,Korea, and its homeland,the United States

Hyphantria cunea (Drury) has colonized many countries outside its native range of North America and has become a model species for studies of the colonization and subsequent adaptation of agricultural pests. Molecular genetic analyses can clarify the origin and subsequent adaptations to non-native habitats. Using the mitochondrial COI gene, we examined the genetic relationships between invasive populations (China, Iran, Japan, and Korea) and native populations (i.e., the United States). The Jilin (China) and Guilan (Iran) populations showed nine previously unknown haplotypes that differed from those found in the south–central United States, suggesting multiple colonization events and different regions of invasion. A dominant mtDNA haplotype in populations in the United States was shared by all of the populations investigated, suggesting that H. cunea with that haplotype have successfully colonized China, Iran, Japan, and Korea.     

Linked vs unlinked markers: multilocus microsatellite haplotype-sharing as a tool to estimate gene flow and introgression

We have explored the use of multilocus microsatellite haplotypes to study introgression from cultivated (Malus domestica) into wild apple (Malus sylvestris), and to study gene flow among remnant populations of M. sylvestris. A haplotype consisted of alleles at microsatellite loci along one chromosome. As destruction of haplotypes through recombination occurs much faster than loss of alleles due to genetic drift, the lifespan of a multilocus haplotype is much shorter than that of the underlying alleles. When different populations share the same haplotype, this may indicate recent gene flow between populations. Similarly, haplotypes shared between two species would be a strong signal for introgression. As the expected lifespan of a haplotype depends on the strength of the linkage, the length [in centiMorgans (cM)] of the haplotype shared contains information on the number of generations passed. This application of shared haplotypes is distinct from using haplotype-sharing to detect association between markers and a certain trait. We inferred haplotypes for four to eight microsatellite loci on Linkage Group 10 of apple from genotype data using the program phase, and then identified those haplotypes shared between populations and species. Compared with a Bayesian analysis of unlinked microsatellite loci using the program structure, haplotype-sharing detected a partially different set of putative hybrids. Cultivated haplotypes present in M. sylvestris were short (< 1.5 cM), indicating that introgression had taken place many generations ago, except for two Belgian plants that contained a haplotype of 47.1 cM, indicating recent introgression. In the estimation of gene flow, F(ST) based on unlinked loci indicated small (0.032-0.058) but statistically significant differentiation between some populations only. However, various M. sylvestris haplotypes were shared in nearly all pairwise comparisons of populations, and their length indicated recent gene flow. Hence, all Dutch populations should be considered as one conservation unit. The added value of using sharing of multilocus microsatellite haplotypes as a source of population genetic information is discussed.     

Genetic structure of the star sea squirt, Botryllus schlosseri, introduced in southern European harbours

The introduction of new genetic variants or species is often caused by maritime transport between harbours. Botryllus schlosseri is a cosmopolitan ascidian species that is found in both harbours and open shore habitats. In order to determine the influence of ship traffic on the genetic structure and phylogeography of B. schlosseri in southern Europe, we analyzed the variability of a fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI). We sampled seven Atlanto-Mediterranean harbour populations and three open-shore populations. In addition, we sequenced some colonies from the US-Atlantic coast and from other Mediterranean localities to perform phylogenetic analyses. Although the number of polymorphic sites recorded (25.8%) was within the range observed in other population studies based on ascidian COI sequences, the haplotypic diversity (16 haplotypes out of 181 sequences) was much lower. Moreover, a lack of intermediate haplotypes was observed. This pattern of high nucleotide diversity and low haplotype diversity was consistent with introduction events of a few divergent haplotypes. We found a strong genetic structure in the study populations. Gene flow was only appreciable between some harbour populations. Harbour- and open-shore populations were well differentiated, although there was no evidence for isolation by distance. A nested clade analysis pointed to long-distance colonization, possibly coupled with subsequent fragmentation, as the underlying process. Our results suggest that B. schlosseri entered the study area via harbour-hopping, possibly through recurrent introduction events. The haplotypes from North America and most of the European ones were grouped in the same phylogenetic clade. This suggests occasional gene flow between both continents, probably through ship transport.     

陕西省林麝mtDNA D-loop区序列结构和种群遗传多样性

林麝(Moschus berezovskii)曾广泛分布于中国,由于盗猎和栖息地缩小,秦岭地区野生种群数量迅速下降,圈养繁殖种群已成立了几十年,但大多数圈养种群的遗传背景不清,种群规模增长非常缓慢。为了给这一物种的保护和管理提供有用的信息,调查了陕西省林麝1个圈养种群3个野生种群线粒体DNA(mt DNA)D-Loop 632 bp片段的遗传多样性和种群结构。在69个个体中其碱基组成为A+T的平均含量63.2%高于G+C含量36.8%,共检测到变异位点171个(约占总位点数的27.05%)。核苷酸多样性(Pi)为0.04424,平均核苷酸差异数(K)为19.908。69个个体分属32个单倍型,单倍型间的平均遗传距离(P)为0.070。32个单倍型构建的NJ系统树聚为3个分支,4个林麝群体中的单倍型是随机分布的。4个群体的平均遗传距离为0.043(标准误SE为0.005),凤县养殖场群体与留坝和陇县群体的亲缘关系较远。单倍型间的平均遗传距离为0.043,可见其遗传分化尚未达到种群分化的水平。结果表明,陕西省林麝群体mt DNA D-loop区序列存在着较丰富的变异和遗传多样性,凤县野生群体和凤县养殖场群体的核苷酸多样性和单倍型多样较高,养殖场种群没有出现近亲繁殖及遗传多样性下降的情况。凤县野生群体和凤县养殖场群体两者遗传分化较小,存在着较高的基因流水平。     

Species relationships and population structure of Littorina saxatilis Olivi and L. tenebrosa Montagu in Ireland using single-strand conformational polymorphisms (SSCPs) of cytochrome b fragments

Littorina saxatilis is a ubiquitous snail of intertidal habitats in the North Atlantic. Shell type in littorinids is extremely polymorphic and defined by habitat. Taxonomy based upon shell type has been revised in the light of anatomic and genetic information, but uncertainties remain. In this study, the population structure of L. saxatilis and L. tenebrosa was studied at 11 sites in Ireland using single-strand conformational polymorphisms of a 375-bp portion of the cytochrome b gene, and the status of L. tenebrosa, the small, fragile-shelled, brackish water type, was considered. The genetic patterns among L. saxatilis and L. tenebrosa populations were examined over varying distances and L. tenebrosa was compared with adjacent L. saxatilis populations at four sites on the west coast of Ireland and one site on the east coast. Haplotype diversity was high with 32 haplotypes present among 995 individuals. Pairwise tests suggest gene flow over small scales among and between habitat types and may reflect the stochastic legacy of postglacial recolonization over larger scales. In AMOVA tests, geography explained nearly twice as much of the variance (30%) as habitat type (18%), indicating that gene flow is more restricted by distance than by habitat type, and supporting the status of L. tenebrosa as an ecotype of L. saxatilis rather than a separate species.