Multiple reversals of chirality in the land snail genus Albinaria (Gastropoda,Clausiliidae)

Reversed chirality has frequently evolved in snails, although the vast majority coils dextrally. However, there are often sinistral species within a dextral genus or almost exclusively sinistral families, such as the Clausiliidae. Some populations of the predominantly sinistral clausiliid genus Albinaria, in the southern Greek mainland, coil dextrally. The origin, evolution and distribution of the dextral Albinaria are puzzling, and as there is no reliable phylogenetic reconstruction for this speciose genus, it remains unclear how many times a shift in chirality has really occurred. In this study, our aim was to elucidate the evolutionary pathways of dextrality in Albinaria. We undertook a molecular phylogenetic analysis of two mtDNA (16S and COI) and one nDNA marker (ITS1) and included dextral and sinistral representatives found in syntopy or not. Both mtDNA and nDNA tree topologies imply that dextrals did not evolve as a monophyletic lineage. Instead, dextral lineages have evolved from sinistral ancestors multiple times independently. The fragmented population structure in Albinaria facilitates genetic drift and contributes to fixation of the opposite chirality and overcoming of the mating disadvantage of left–right reversal. Stochastic phenomena and biogeographical barriers have trapped those reversals in a limited geographical area.     

林氏果蝇线粒体DNA分析

本文对Tamura(1988)提纯mtDNA的方法进行改进,建立了林氏果蝇Drosophila lini 线粒体DNA大量制备的方法;对采自原产地台湾省的单雌晶系TAW3146.1的线粒体DNA用10种限制性内切酶进行了酶切,得出了林氏果蝇mtDNA的分子量大小为16.3kb;用双酶切法制作了林氏果蝇线粒体DNA酶切图谱,并与属于同一复合种组的D.Kikkawai的酶切图谱进行比较。所用的内切酶有XbaI、AvaI、EcoRV、ScaI、SacI、EcoR I、HindIII、PvuⅡ、BamHI、PstⅡ。     

Novel features of metazoan mtDNA revealed from sequence analysis of three mitochondrial DNA segments of the land snail Albinaria turrita (Gastropoda: Clausiliidae)

The mitochondrial DNA (mtDNA) size of the terrestrial gastropod Albinaria turrita was determined by restriction enzyme mapping and found to be approximately 14.5 kb. Its partial gene content and organization were examined by sequencing three cloned segments representing about one-fourth of the mtDNA molecule. Complete sequences of cytochrome c oxidase subunit II (COII), and ATPase subunit 8 (ATPase8), as well as partial sequences of cytochrome c oxidase subunit I (COI), NADH dehydrogenase subunit 6 (ND6), and the large ribosomal RNA (IrRNA) genes were determined. Nine putative tRNA genes were also identified by their ability to conform to typical mitochondrial tRNA secondary structures. An 82-nt sequence resembles a noncoding region of the bivalve Mytilus edulis, even though it might contain a tenth tRNA gene with an unusual 5-nt overlap with another tRNA gene. The genetic code of Albinaria turrita appears to be the same as that of Drosophila and Mytilus edulis. The structures of COI and COII are conservative, but those of ATPase8 and ND6 are diversified. The sequenced portion of thelrRNA gene (1,079 nt) is characterized by conspicuous deletions in the 5 and 3 ends; this gene represents the smallest coelomate IrRNA gene so far known. Sequence comparisons of the identified genes indicate that there is greater difference between Albinaria and Mytilus than between Albinaria and Drosophila. An evolutionary analysis, based on COII sequences, suggests a possible nonmonophyletic origin of molluskan mtDNA. This is supported also by the absence of the ATPase8 gene in the mtDNA of Mytilus and nematodes, while this gene is present in the mtDNA of Albinaria and Cepaea nemoralis and in all other known coelomate metazoan mtDNAs.     

Constitution of Mitochondrial and Chloroplast Genomes in Male Sterile Tobacco Obtained by Protoplast Fusion of Nicotiana tabacum and N. debneyi

Chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) of malesterile tobacco plants obtained by fusion of Nicotiana tabacumprotoplasts and X-irradiated N. debneyi protoplasts were analyzed.Digestion of cpDNA isolated from ten male sterile lines withfour restriction endonucleases (EcoRI, XhoI, SmaI and HindIII)indicated that these lines possessed either one or the otherparental chloroplast genome. Neither mixture of two types ofcpDNA nor unique restriction fragments were detected in anyof the cases examined. The genetic constitution of chloroplastgenomes identified by restriction analysis of cpDNA showed goodagreement with that based on isoelectric focusing of the largesubunit of the Fraction I protein. The mtDNA from five fusion-derivedmale sterile plants showed banding patterns quite differentfrom each other and from the parental plants. Each plant exhibitednew restriction fragments not found in the parental species.These findings indicate that recombinational events in the mitochondrialgenomes take place rather frequently in the mixed cytoplasmsafter protoplast fusion, whereas the mixed chloroplasts becomesegregated to homogeneity. (Received June 19, 1987; Accepted October 5, 1987)     

Polymorphism of the Noncoding Region of the Mitochondrial Genome in Three Kazakh Populations Inhabiting Different Areas of Kazakhstan and in DNA Samples from Ancient Populations of the Kazakhstani Altai

The polymorphism of the major noncoding region of mitochondrial DNA (mtDNA D loop, 528 bp) has been studied in samples from three modern Kazakh populations (from Almaty, the Semipalatinsk Region, and the Altai Mountains) and in DNA samples of ancient human populations of the Kazakhstani Altai. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis for 13 restriction sites, including BamHI, EcoRV, Sau3AI (one site each), KpnI (two sites), HaeIII (three sites), and RsaI (five sites) were used. The frequency distributions of all sites have been determined. The gene diversity (h) and the genetic distances between different Kazakh populations and other populations of the world have been calculated. The RFLP analysis of the mtDNA control region of fossil samples has been performed similarly to the analysis of modern mtDNA samples. Two fossil mtDNA samples from burial mound 11 are monomorphic with respect to all restriction sites analyzed.     

MITOCHONDRIAL PHYLOGEOGRAPHY OF THE LAND SNAIL ALBINARIA IN CRETE: LONG-TERM GEOLOGICAL AND SHORT-TERM VICARIANCE EFFECTS

The land snail genus Albinaria exhibits an extreme degree of morphological differentiation in Greece, especially in the island of Crete. Twenty-six representatives of 17 nominal species and a suspected hybrid were examined by sequence analysis of a PCR-amplified mitochondrial DNA fragment of the large rRNA subunit gene. Maximum parsimony and neighbor-joining phylogenetic analyses demonstrate a complex pattern of speciation and differentiation and suggest that Albinaria species from Crete belong to at least three distinct monophyletic groups, which, however, are not monophyletic with reference to the genus as a whole. There is considerable variation of genetic distance within and among “species” and groups. The revealed phylogenetic relations do not correlate well with current taxonomy, but exhibit biogeographical coherence. Certain small- and large-scale vicariance events can be traced, although dispersal and parapatric speciation may also be present. Our analysis suggests that there was an early and rapid differentiation of Albinaria groups across the whole of the range followed by local speciation events within confined geographical areas.     

MITOCHONDRIAL-DNA RESTRICTION-SITE POLYMORPHISMS IN THE TELEOST FUNDULUS HETEROCLITUS SUPPORT SECONDARY INTERGRADATION

Fundulus heteroclitus is a highly polymorphic fish distributed along the Atlantic coast of North America. Several loci show directional changes in gene frequency with latitude (i.e., clines). Such directional changes have classically been described by two general models: primary and secondary intergradation. Previously, it has not been possible to distinguish between these models for Fundulus heteroclitus on the basis of allelic isozymes or morphological data. However, recent analysis of mitochondrial-DNA (mtDNA) restriction electromorphs helps resolve this issue. Mitochondrial-DNA samples from 48 individuals representing four populations were digested with 17 restriction endonucleases. After electrophoresis, the sizes of the mtDNA fragments were used to analyze the phylogenetic relatedness of fish collected over most of the species range. The analysis clearly identified two major races within the species: a northern and a southern form. The distribution of the mtDNA electromorphs, combined with zoogeographical changes in allelic isozymes and in eggs and adult morphologies (published elsewhere), makes the secondary-intergradation hypothesis most compelling.     

五种常见嗜尸性蝇类的分子鉴定

为了解决法医学人员对于嗜尸性蝇类的鉴定难题,对中山市、广州市及西安市5种常见嗜尸性蝇类共17个样本,对其线粒体COⅠ基因的348 bp大小片段进行了RFLP和DNA序列分析,采用ABI377测序仪测序,DNASTAR软件预测限制性位点,DdeⅠ, DraⅠ和HinfⅠ3种限制性内切酶消化,非变性聚丙烯酰胺凝胶电泳检测酶切结果,MEGA3.0软件包进行序列分析和构建系统发育树。结果表明： 采用mtDNA扩增结合银染技术和DNA序列分析,均可以方便快捷地进行上述三地5种常见嗜尸性蝇类的种类鉴定。本文结果为法医昆虫学中嗜尸性昆虫DNA鉴定数据库的建立提供了数据资料。     

Gene flow patterns of the euphausiid, Meganyctiphanes norvegica, in the NW Atlantic based on mtDNA sequences for cytochrome b and cytochrome oxidase I

Population genetic structure and patterns of gene flow are describedfor the euphausiid, Meganyctiphanes norvegica, in the NW AtlanticOcean based on DNA sequence variation of two regions of mitochondrialDNA (mtDNA). DNA sequences were determined for portions of cytochromeoxidase I (COI; 400 base pairs; 76 individuals) and cytochromeb (CYB; 300 base pairs; 101 individuals) for euphausiids collectedfrom the Gulf of Maine in 1991, the Gulf of St Lawrence in 1993and 1994, the Scotian Shelf in 1994, and Georges Bank in 1994.For comparison, M.norvegica collected from the fjords of westernNorway in 1992 were sequenced for COI (20 individuals) and CYB(18 individuals). COI was less variable than CYB, based on bothhaplotype (h=0.6847 for COI; 0.9077 for CYB) and nucleotidediversities (     

Ancient DNA analyses reveal high mitochondrial DNA sequence diversity and parallel morphological evolution of late pleistocene cave bears

Cave bears (Ursus spelaeus) existed in Europe and western Asiauntil the end of the last glaciation some 10,000 years ago.To investigate the genetic diversity, population history, andrelationship among different cave bear populations, we havedetermined mitochondrial DNA sequences from 12 cave bears thatrange in age from about 26,500 to at least 49,000 years andoriginate from nine caves. The samples include one individualfrom the type specimen population, as well as two small-sizedhigh-Alpine bears. The results show that about 49,000 yearsago, the mtDNA diversity among cave bears was about 1.8-foldlower than the current species-wide diversity of brown bears(Ursus arctos). However, the current brown bear mtDNA gene poolconsists of three clades, and cave bear mtDNA diversity is similarto the diversity observed within each of these clades. The resultsalso show that geographically separated populations of the high-Alpinecave bear form were polyphyletic with respect to their mtDNA.This suggests that small size may have been an ancestral traitin cave bears and that large size evolved at least twice independently.     

Population structure and local differentiation in the delicate loach, Niwaella delicata, as revealed by mitochondrial DNA and morphological analyses

Population structures of the delicate loach, Niwaella delicata, were inferred from morphology and restriction fragment length polymorphism (RFLP) analysis of part of the mitochondrial DNA (mtDNA) of 25 populations, representing the species range in central Honshu Island. The existence of two types of morphological variation corresponding to regional distributions, the "Pacific slope type" and "Sea of Japan slope type," has been known in N. delicata. Our morphological reexamination of the two types revealed some discrepancies in their distribution pattern. Therefore, we reclassified two new color types corresponded to their distribution areas as "gathered spots type (G type)" and "scattered spots type (S type)," respectively. The present classification of G and S types is closely related to the mtDNA divergence pattern. The current analysis also indicated that each G and S type population was further divided into two genetic groups, corresponding to geographic proximity. In spite of marked morphological differentiation, the genetic diversity between G and S type populations (1.153%) was comparable only to that reported for intraspecific levels in most freshwater fishes. Moreover, in the population of which the color patterns of all fish were characterized to the S type, mtDNA haplotypes corresponding to G and S types were sympatrically detected. This result indicates secondary contact between the two type populations and the possibility that they are not reproductively isolated. Received: June 11, 1999 / Revised: September 30, 2000 / Accepted: January 16, 2001     

The marine indo-west pacific break: contrasting the resolving power of mitochondrial and nuclear genes

Simultaneous studies of both nuclear and mitochondrial markerswere undertaken in two widespread Indo-West Pacific (IWP) marineinvertebrates to compare and contrast the ability of these markersto resolve genetic structure. In particular, we were interestedin the resolution of a genetic break between the Indian andPacific Oceans due to historical isolation. Sequence variationfrom the nuclear gene encoding myosin heavy chain (MyHC) andthe mitochondrial gene cytochrome oxidase I (COI) were examinedfor the snapping shrimp Alpheus lottini from wide-ranging populationsthroughout the Indian and Pacific Oceans. A previously identifiedgenetic break between oceans based on COI sequences appearsto have been an artifact caused by the inadvertent inclusionof pseudogene sequences; our new COI data provide evidence onlyof a break between IWP and East Pacific populations. Distributionof a single nucleotide polymorphism in MyHC, on the other hand,shows evidence of a cline between Indian and Pacific Oceans.New allozyme and mtDNA sequence data were also obtained forthe starfish Linckia laevigata. Allozyme data show a clear geneticbreak between Indian Ocean populations and Pacific (includingwestern Australian) populations, whereas the distribution ofmtDNA haplotypes shows a region of overlap in the central IWP.Comparisons of our data for both Alpheus and Linckia with datafrom other population genetic studies in the IWP suggest thatnuclear markers (allozymes, sequence data and morphologicalcharacters) may in some instances reveal historical patternsof genetic population structure whereas mtDNA variation betterreflects present day patterns of gene flow.     

厚壳贻贝养殖群体与野生群体线粒体DNA的遗传分析(英文）

采用线粒体DNA COI基因序列对厚壳贻贝2个养殖群体与2个野生群体的遗传多样性进行了研究。4个群体共获得30个单倍型。结果显示：在养殖群体中单倍型的数量和遗传多样性要比野生群体的低,可能是由于只有少量的有效父母本对养殖群体的遗传变异有贡献所致。养殖群体与当地野生群体之间也未发生显著的遗传分化,可能是因为它们之间存在基因流。在今后厚壳贻贝养殖过程中,本研究可以用在对养殖群体进行遗传监测,从而保证养殖群体的遗传多样性水平。     

Mitochondrial DNA analysis in Tibet: Implications for the origin of the Tibetan population and its adaptation to high altitude

Mitochondrial DNAs (mtDNAs) of 54 Tibetans residing at altitudes ranging from 3,000–4,500 m were amplified by polymerase chain reaction (PCR), examined by high-resolution restriction endonuclease analysis, and compared with those previously described in 10 other Asian and Siberian populations. This comparison revealed that more than 50% of Asian mtDNAs belong to a unique mtDNA lineage which is found only among Mongoloids, suggesting that this lineage most likely originated in Asia at an early stage of the human colonization of that continent. Within the Tibetan mtDNAs, sets of additional linked polymorphic sites defined seven minor lineages of related mtDNA haplotypes (haplogroups). The frequency and distribution of these haplogroups in modern Asian populations are supportive of previous genetic evidence that Tibetans, although located in southern Asia, share common ancestral origins with northern Mongoloid populations. This analysis of Tibetan mtDNAs also suggests that mtDNA mutations are unlikely to play a major role in the adaptation of Tibetans to high altitudes. © 1994 Wiley-Liss, Inc.     

VARIATION IN MITOCHONDRIAL DNA OF AEDES SPECIES (DIPTERA: CULICIDAE)

Relationships among seven species of the Aedes scutellaris subgroup and four of the Aedes albopictus subgroup were determined using restriction fragment analysis of mtDNA. Considerable polymorphism was found among species, with an average proportion of 0.338 restriction fragments being shared among them. Fitch-Margoliash, Wagner parsimony and UPGMA analyses revealed that the phylogeny based on mtDNA was only partially congruent with that based on allozymes and morphology. All three analyses, however, suggested that three species pairs, A. flavopictus-A. pseudalbopictus, A. pseudoscutellaris-A. riversi, and A. albopictus-A. polynesiensis were monophyletic with regard to their mtDNA. The results indicated that although the species in the A. scutellaris and the A. albopictus subgroups do not exhibit significant morphological divergence, their mtDNA has diverged extensively.     

EMBRYONIC ABNORMALITIES IN POPULATIONS OF LITTORINA SAXATILIS (OLIVI) (GASTROPODA: PROSOBRANCHIA) IN THE WHITE SEA

The incidence of abnormally developing embryos in brood pouchesof females was studied in five populations of Littorina saxatilisliving under different salinity conditions. The proportion ofabnormals decreased during embryonic development. Age of femaleand infection with the ciliate Protophrya ovi-cola had no effecton the frequency of abnormals. The proportion of abnormal eggs(PAE) increased at the end of the reproductive season; a similartrend was found for the proportion of abnormal veligers (PAV)although it was not always significant. The proportion of abnormaljuveniles (PAJ) showed no seasonality. The increase of PAE coincidedwith decrease of water temperature in September. Environmentalsalinity was significantly correlated with frequency of abnormalsin L. saxatilis populations: the highest values of PAV and PAJwere observed in estuarine population (salinity range 5–8%),intermediate in populations living under conditions of 10–20%osalinityand lowest in control populations (23–24%). Itis suggested that critical salinity (sensu Khle-bovich, 1974)(approximately 8–10%) may also be a crucial point forstability of embryonic development in the White Sea populationsof L. saxatilis. (Received 28 June 1994; accepted 28 November 1994)     

Population Analysis of Licuala glabra Griff. var. glabra (Palmae) using RAPD Profiling

Random amplified polymorphic DNA (RAPD) profiling revealed geneticdiversity among three populations ofLicuala glabra var. glabra,an understorey palm growing in the dipterocarp forests of Terengganu,Malaysia. The Bukit Bauk population had individuals withoutaerial stems. The Bukit Besi individuals had stem heights to30 cm, while those of the Rasau Kerteh population had stemsup to 4 m in height. Southern blot analysis confirmed that anapparent monomorphic band generated by the primer OPU-17 amongthe three different populations corresponds to the same locus.Six primers were used to generate 87 RAPD bands that formed2-state character raw data for estimating genetic distancesusing the simple matching coefficient of similarity. The phenogramgenerated by UPGMA of the RAPD data grouped the individualsfrom the three populations under three clusters. This was inagreement with the morphological grouping. The infraspecificL. glabra var.selangorensis Becc. was grouped closer to theL. glabra var. glabra individuals than to the outgroupL. scortechiniiBecc. Principal component analysis supported the observationfrom the phenogram. The results show discrete genetic structuringin the populations studied and provide useful information forfuture conservation measures. Copyright 1999 Annals of BotanyCompany Licuala glabra Griff. var. glabra, RAPD, palm, AMOVA, population, genetic diversity, conservation.     

UNUSUAL POPULATION GENETICS OF A PARASITIC NEMATODE: mtDNA VARIATION WITHIN AND AMONG POPULATIONS

Very little is known about the distribution of genetic variance within and among populations of parasitic helminths. In this study we used mitochondrial DNA (mtDNA) restriction fragment analysis to describe the population genetic structure of Ostertagia ostertagi, a nematode parasite of cattle, in the United States. Estimates of within-population mtDNA diversity are 5 to 10 times greater than typical estimates reported for species in other taxa. Although populations are genetically differentiated for a key life–history trait, greater than 98% of the total genetic diversity is partitioned within populations, and the geographic distribution of individual mtDNA haplotypes suggests high gene flow among populations.     

EVIDENCE FOR MULTIPLE ORIGINS AND SYMPATRIC DIVERGENCE OF TROPHIC ECOTYPES OF SMELT (OSMERUS) IN NORTHEASTERN NORTH AMERICA

The rainbow smelt, Osmerus mordax (Mitchill), is an osmerid fish that exhibits extensive life-history diversity throughout watersheds of northeastern North America. There are both ???sea-run (anadromous) and lake-resident (lacustrine) populations and the latter have diversified further into “dwarf-” and “normal-sized” life-history types. Anadromous and lacustrine smelt may inhabit the same watershed and there are several instances where dwarf and normal populations reside within the same lake. We assayed variation among smelt for morphological traits linked to feeding performance in fishes to see if trophic ecology might promote life-history diversity in Osmerus. We also examined mitochondrial DNA (mtDNA) restriction site variation among forms to assess their evolutionary interrelationships. Dwarf smelt had significantly more gill rakers, larger eyes, but shorter upper jaws than normal lake and anadromous smelt. The populations clustered into two trophic “morphotypes”; an anadromous/normal lake group of populations and a group consisting only of dwarf smelt. The mtDNAs of 444 smelt from 16 populations were digested with 12 restriction enzymes revealing 93 composite mtDNA genotypes that clustered (UPGMA) into two major phylogenetic groups differing by 0.78% in sequence. Both genetic groups were present in dwarf and normal smelt as well as in anadromous fish. Further, geographic proximity, rather than trophic morphotype, appeared to be the major determinant of genetic affinities among populations. In two lakes, however, dwarf and normal smelt populations had significantly different mtDNA genotype frequency distributions indicating that the forms are reproductively isolated within both lakes. A clustering analysis of population affinities suggested that the divergence of sympatric dwarf and normal populations had occurred independently in the two lakes. We concluded (1) that trophic ecology is an important factor promoting differentiation in smelt life histories; (2) that smelt ecotypes are polyphyletic and there have been multiple, independent divergences of Osmerus life-history types throughout northeastern North America; and (3) that the biological and mtDNA differences between coexisting dwarf and normal lake smelt argue strongly that their genetic isolation may have developed sympatrically.