MITOCHONDRIAL DNA SEQUENCE VARIATION AMONG NATURAL POPULATIONS OF THE TRINIDAD GUPPY,POECILIA RETICULATA

Guppies were sampled from eight populations representing four river drainage basins in northern Trinidad, and from one population on the nearby island of Tobago. For each individual, a 465 base pair (bp) segment of the control region of the mitochondrial genome was sequenced. The resulting DNA sequences were subjected to sequence divergence calculations and the populations were linked by maximum parsimony analysis to determine their phylogenetic relationships. Mitochondrial DNA (mtDNA) sequence variation was found both within and between river drainages, correlated with the geographic features of northern Trinidad. The variation observed exists primarily between drainages, particularly between the Oropuche drainage and all other Trinidad drainages examined. Estimates of time of divergence between guppy populations of different drainages, based on mtDNA sequence variation, ranged from 100,000 to 200,000 for the most recently separated populations and from 600,000 to 1.2 million years between the Oropuche populations and all others examined. Examination of fish from northeastern South America will be required to determine whether these populations differentiated in their present locations or were the result of separate invasions of Trinidad from different Venezuelan sources. However, genetic isolation of these populations appears to predate the current physical separation of the island of Trinidad from the Venezuelan mainland.     

DIFFERENTIATION OF MITOCHONDRIAL DNA POLYMORPHISMS IN POPULATIONS OF FIVE JAPANESE ABIES SPECIES

Mitochondrial DNA polymorphism of 40 populations of five Abies species was investigated using PCR-amplified coxI and coxIII gene probes. Using four combinations of probe and restriction enzyme, we detected three major haplotypes and 15 total haplotypes. We also found varied levels of gene diversity for the different species: 0.741, 0.604, 0.039, 0.000, and 0.292 for A. firma, A. homolepis, A. veitchii, A. mariesii, and A. sachalinensis, respectively. The marginal and southern populations of A. firma and A. homolepis have unique haplotypes, especially the Kyushu, Shikoku, and Kii Peninsula populations, which inhabit areas coinciding with probable refugia of the last glacial period and possess high levels of mtDNA genetic diversity. The haplotypes in some populations suggested mtDNA capture also occurred between species through introgression/hybridization. The strong mtDNA population differentiation in Abies is most likely due to the maternal inheritance of mitochondria and restricted seed dispersal. A phenetic tree based on the genetic similarity of the mtDNA suggests that some species are polyphyletic. Based on mtDNA variation, the five Abies species could be divided roughly into three groups: (1) A. firma and A. homolepis, (2) A. veitchii and A. sachalinensis, and (3) A. mariesii. However, we found that all these Abies species, except A. mariesii, are genetically very closely related according to an analysis of their cpDNA sequences. This showed that the chloroplast rbcL gene differed by only one base substitutions among the four species. We believe that the mtDNA variation and cpDNA similarity clearly reflect relationships among, and the dissemination processes affecting these Abies species since the last glacial period.     

CHROMOSOMAL VERSUS MITOCHONDRIAL DNA EVOLUTION: TRACKING THE EVOLUTIONARY HISTORY OF THE SOUTHWESTERN EUROPEAN POPULATIONS OF THE SOREX ARANEUS GROUP (MAMMALIA,INSECTIVORA)

The shrews of the Sorex araneus group have undergone a spectacular chromosome evolution. The karyotype of Sorex granarius is generally considered ancestral to those of Sorex coronatus and S. araneus. However, a sequence of 777 base pairs of the cytochrome b gene of the mitochondrial DNA (mtDNA) produces a quite different picture: S. granarius is closely related to the populations of S. araneus from the Pyrenees and from the northwestern Alps, whereas S. coronatus and S. araneus from Italy and the southern Alps represent two well-separated lineages. It is suggested that mtDNA and chromosomal evolution are in this case largely independant processes. Whereas mtDNA haplotypes are closely linked to the geographical history of the populations, chromosomal mutations were probably transmitted from one population to another. Available data suggest that the impressive chromosome polymorphism of this group is quite a recent phenomenon.     

从12S rRNA基因序列研究中国蛙科24种的进化关系

测定了中国蛙科动物24种和蟾蜍科的中华大蟾蜍线粒体12S rRNA基因长约400bp片段的序列。采用邻接法,对其数据的系统发生分析表明24种可分成3个支系：第一个支系包括棘腹蛙、合江棘蛙、棘胸蛙、大头蛙、虎纹蛙、倭蛙、泽陆蛙共７种,其中３种棘蛙组成一个单系;第二个支系由３种湍蛙,即戴云湍蛙、华南湍蛙和武夷湍蛙组成,应属于湍蛙亚科;第三支系包含余下的１４种蛙,其中５种林蛙和４种臭蛙分别组成一个单系;２种侧褶蛙先聚合后,再与弹琴水蛙聚合,２种粗上先聚合在一起,再与由林蛙组成的单系群聚合。第三支系首先与第二支系相聚,然后它们与第一支系形成姐妹群,即由蛙亚科的７个物种组成的第一支系,不与蛙亚科另１４个物种组成的第三支系直接聚合,表明第一支系的物种可能不属于蛙亚科。此外,分子证据提示把陆蛙属、大头蛙属、虎纹蛙属、棘棘属、臭蛙属、粗皮蛙属和侧褶蛙属从原来的蛙属分出有其合理性。、     

林氏果蝇种群间mtDNA的比较研究

运用１０种限制性内切酶分析了林氏果蝇来自不同地区的２２个单雌系的线粒体ＤＮＡ限制性片段长度多态性。采自台湾省的ＴＡＷ３１４６．１与大多数采自广东的品系相同,而广东省品中则存在一定度的分化,ＤＨＳ３０７、３１５和ＮＫＳ９２３４仅在ＨｉｎｄⅢ的酶切位点上与其余单雌系不同;ＴＡＷ３１４６．１与来自缅甸中部的ＭＭＹ３０７,ＭＤＭＹ３２６之间的遗传距离为０．００２７４;ＭＭＹ３０７与ＭＭＹ３２６之间无差异。     

我国大陆部分地区黑腹果蝇群体线粒体DNA多态性研究

用１０种限制性内切酶对我国大陆５个地方（武汉,长沙,桂林,南宁和北海）６个黑腹果蝇（Ｄｒｏｓｏｐｈｉｌａｍｅｌａｎｏｇａｓｔｅｒ）群体的线粒体ＤＮＡ进行了限制片段长度多态性分析,在５６个单雌系中,发同了２５种不同的限制类型,应用Ｎｅｉ等（１９７９）的数学模型和ＵＰＧ法,构建了限制类型间和群体间的系统进化树,结果发现：所研究的群体分为３个类群,对应于南,中和北３个亚热带地区,除长沙玉合醋厂外,所有采     

MOLECULAR PHYLOGENETICS AND EVOLUTION OF SEXUAL DICHROMATISM AMONG POPULATIONS OF THE YARROW'S SPINY LIZARD (SCELOPORUS JARROVII)

Understanding evolution of geographic variation in sexually dimorphic traits is critical for understanding the role that sexual selection may play in speciation. We performed a phylogenetic analysis of geographic variation in sexual dichromatism in the Yarrow's spiny lizard (Sceloporus jarrovii), a taxon that exhibits remarkable diversity in male coloration among populations (e.g., black, red, green, yellow, blue, brown). An mtDNA phylogeny based on approximately 880 bp from the 12S ribosomal RNA gene and 890 bp from the ND4 gene was reconstructed for 30 populations of S. jarrovii and eight other species of the torquatus species group using maximum-likelihood and parsimony methods. The phylogeny suggests that S. jarrovii consists of at least five evolutionary species, none of which are sister taxa. Although intraspecific diversity in male coloration is less than indicated by previous taxonomy, two species formerly referred to as S. jarrovii exhibit impressive geographic variation in sexual dichromatism. In one of these species, the phylogeny shows the independent evolution of a distinctive blue color morph in different parts of the species range. This pattern suggests that sexual selection may lead to striking phenotypic divergence among conspecific populations and striking convergence. Results also demonstrate the importance of a phylogenetic perspective in studies of evolutionary processes within nominal species and the problematic nature of “polytypic” species recognized under the biological species concept.     

MITOCHONDRIAL DNA SEQUENCE-BASED PHYLOGENY AND THE EVOLUTION OF VIVIPARITY IN THE SCELOPORUS SCALARIS GROUP (REPTILIA,SQUAMATA)

The lizard genus Sceloporus contains both oviparous and viviparous species. The scalaris complex is the only monophyletic group within the genus that includes both reproductive modes, thus it is particularly well suited for studies of the evolution of viviparity. Approximately 874 nucleotides of mtDNA sequence data, collected from 38 specimens, comprising 25 populations of all five recognized species within the group, were used in a phylogenetic analysis of the origin of viviparity. Viviparity appears to have evolved twice in this group: once in S. goldmani, included in a clade formed by a northern group consisting of S. scalaris, S. chaneyi, and S. goldmani, and one more time in S. bicanthalis, included in the southern group formed by S. bicanthalis and S. aeneus. An oviparous population of S. bicanthalis nested within that viviparous clade, indicates that reversal from viviparity to oviparity may be possible. Degree of sequence divergence among several S. bicanthalis individuals pertaining to a population in which both parity modes occur, was no larger between oviparous and viviparous lizards than among viviparous lizards. This suggests that this population is a single species, and it may represent a transition from oviparity to viviparity or vice-versa.     

中国大陆若干群体的黑果蝇的线粒体DNA多态性研究

本文研究了果蝇Ｄ．ｖｉｒｉｌｉｓ种群Ｄ．ｖｉｒｉｌｉｓ线粒体ＤＮＡ（ｍｉｔｏｃｈｏｎｄｒｉａｌＤＮＡ,ｍｔＤＮＡ）的多态性。用９种限制性内切酶ＸｂａⅠ,ＥｃｏＲⅠ,ＰｓｔⅠ,ＨｉｎｄⅢ,ＢｇｌⅡ,ＳａｃⅠ,ＳｃａⅠ,ＥｃｏＲＶ和ＰｕｖⅡ,对青岛、南京、上海、宁波与泉州５个Ｄ．ｖｉｒｉｌｉｓ群体的ｍｔＤＮＡ进行了限制性片段长度多态性（ｒｅｓｔｒｉｃｔｉｏｎｆｒａｇｍｅｎｔｓｌｅｎｇｔｈｐｏｌｙｍｏｒｐｈｉｓｍ,ＲＦＬＰ）的研究。在５群体中,发现５种不同的酶切图谱,它们彼此之间的遗传差异π为０．４６％－１．７６％,群体内遗传差异πｉｊ为０．００％－０．３３％,群体间的差异ｄｘｙ,为０．００％－０．８２％。分布于中国大陆的Ｄ．ｖｉｒｉｌｉｓ的群体间遗传差异在总遗传差异中所占比例γｓｔ值为２４．６２％。我们发现,Ｄ．ｖｉｒｉｌｉｓ的栖息环境对ｍｔＤＮＡ的遗传变异有十分明显的影响,而不同地理纬度的群体之间其遗传距离并无倾群（ｃｌｉｎｅ）表现。     

MITOCHONDRIAL GENE GENEALOGY AND GENE FLOW AMONG ISLAND AND MAINLAND POPULATIONS OF A SEDENTARY SONGBIRD,THE GREY-CROWNED BABBLER (POMATOSTOMUS TEMPORALIS)

Distinguishing between ongoing gene flow and purely historical association of populations can be difficult without data on times of population separation and effective population sizes. To help discriminate between these two scenarios, I examined mitochondrial DNA sequence diversity in three geographically close populations of the grey-crowned babbler (Pomatostomus temporalis) separated by water barriers of known age in the Northern Territory, Australia, using the polymerase chain reaction (PCR), direct sequencing, and genealogical methods of inference. PCR primers were designed to obtain sequences from region I, a highly variable segment of the control region. Sequence diversity in all populations was consistent with neutrality. In the population on Melville Island, a Pleistocene land-bridge island, sequence variability is as high as on the mainland and consists of two mitochondrial lineages differing by 2%. Phylogenetic analyses of the sequence variation observed among 44 individuals suggest that the number of times lineages in one population trace back to ancestors of a different population (between-population coalescent events) was too high to be compatible with a model of population divergence solely by drift since rising of the water barriers, implying instead recent or ongoing gene flow across water barriers. Similar estimates of F_st, the fraction of genetic diversity apportioned among populations, were obtained when calculated using the divergence times of alleles and when estimated from Nm values derived from trees and ranging from 0.29-0.55. Both the phylogenies and patterns of allelic divergence suggest that the population on Melville Island exchanges migrants with both continental populations, although statistical tests indicated that some alternative phylogenies implying restricted gene flow among the populations could not be discounted.     

GENETIC SUBDIVISIONS AMONG SMALL CANIDS: MITOCHONDRIAL DNA DIFFERENTIATION OF SWIFT,KIT, AND ARCTIC FOXES

Gene flow can effectively suppress genetic divergence among widely separated populations in highly mobile species. However, the same may not be true of species that typically disperse over shorter distances. Using mtDNA restriction-site and sequence analyses, we evaluate the extent of divergence among populations of two small relatively sedentary North American canids, the kit and swift foxes (genus Vulpes). We determine the significance of genetic differentiation among populations separated by distance and those separated by discrete topographic barriers. Our results show the among-population component of genetic variation in kit and swift foxes is large and similar to that of small rodents with limited dispersal ability. In addition, we found two distinct groupings of genotypes, separated by the Rocky Mountains, corresponding to the traditional division between kit and swift fox populations. Previous workers have characterized these morphologically similar populations either as separate species or subspecies. Our mtDNA data also suggest that kit and swift fox populations hybridize over a limited geographic area. However, the sequence divergence between kit and swift foxes is similar to that between these taxa and the arctic fox (Alopex lagopus), a morphologically distinct species commonly placed in a separate genus. This result presents a dilemma for species concepts, and we conclude that kit and swift foxes should be recognized as separate species.     

MITOCHONDRIAL DNA ANALYSES AND THE ORIGIN AND RELATIVE AGE OF PARTHENOGENETIC CNEMIDOPHORUS: PHYLOGENETIC CONSTRAINTS ON HYBRID ORIGINS

Within the genus Cnemidophorus, parthenogenesis has arisen by hybridization several times. This provides the opportunity to investigate general features of hybridization events that result in the formation of parthenogenetic lineages. The relationships of mtDNA from all bisexual species of Cnemidophorus known to be parents of parthenogens were investigated to evaluate phylogenetic constraints on the hybrid-origin of parthenogenesis. No phylogenetic clustering of the parental species, either maternal or paternal, was apparent. However, the combination of bisexual species that have resulted in parthenogenetic lineages are generally distantly related or genetically divergent. This contrasts with the expectation if parthenogenesis in hybrids is due to the action of a single rare allele, but is consistent with the hypothesis that some minimal level of divergence is necessary to stimulate parthenogenetic reproduction in hybrids.     

隼形目鹰科四种鸟类线粒体DNA研究

本实验采用ＡｐａＩ,ｆＢａｍＨＩ,ＢｇｉＩＩ,ＥｃｏＲＩ,ＥｃｏＲＶ,ＨｉｎｄⅢＨｐａＩ,ＫｐｎＩ,ＰｓｔＩ,ＰｒｕＩＩ,ＳａｌＩ,ＳｃａＩ,ＸｂａＩ和ＸｈｏＩ１４种限制性内切酶,对鹰科４种鸟类即雀鹰（Ａｃｃｉｐｉｔｅｒｎｉｓｕｓ）,松雀鹰（Ａ．ｖｉｒｇａｔｕｓ）苍鹰（Ａ．ｇｅｎｔｉｌｉｓ）和灰险鹰（Ｂｕｆｔａｔｕｒｉｎｄｉｃｕｓ）ｍｔＤＮＡ限制性片段长度多态分析。结果表明,４种鸟类中雀鹰和松１主     

基于线粒体D-loop区和Cyt b基因分析广西禾花鲤三个群体遗传结构

研究基于线粒体D-loop区和Cyt b基因部分序列, 分析了广西全州、融水、环江三地禾花鲤(Cyprinus carpio)的遗传结构。在3个群体中共鉴定到19种D-loop与Cyt b序列的组合单倍型, 总的单倍型多样性(H_d)和核苷酸多样性(π)分别为0.916±0.010和0.008±0.004, 禾花鲤线粒体DNA具有单倍型多样性高和核苷酸多样性低的特点。环江群体单倍型多样性最低, 但是核苷酸多样性却最高, 反映了环江群体存在最明显的谱系混杂。分子方差分析(AMOVA)显示遗传变异主要来源于群体内部(71.54%), 禾花鲤三个群体间有显著的遗传分化(F_st=0.285; P<0.01)。系统发育分析表明, 多数样本的线粒体单倍型属于华南鲤(C. carpio rubrefusus)类型, 同时三地禾花鲤中均检测到一定频率的西鲤(C. carpio carpio)或远东鲤(C. carpio haematopterus)类型的线粒体单倍型, 提示禾花鲤可能受到鲤养殖品种的杂交渐渗。研究初步揭示了广西禾花鲤的种质资源现状, 为禾花鲤这一地方特色“稻鱼共作”品种的选育和苗种管理提供了必要的依据。     

THE ORIGIN OF WEST EUROPEAN SUBSPECIES OF HONEYBEES (APIS MELLIFERA): NEW INSIGHTS FROM MICROSATELLITE AND MITOCHONDRIAL DATA

Apis mellifera is composed of three evolutionary branches including mainly African (branch A), western and northern European (branch M), and southeastern European (branch C) populations. The existence of morphological clines extending from the equator to the Polar Circle through Morocco and Spain raised the hypothesis that the branch M originated in Africa. Mitochondrial DNA analysis revealed that branches A and M were characterized by highly diverged lineages implying very remote links between both branches. It also revealed that mtDNA haplotypes from lineages A coexisted with haplotypes M in the Iberian Peninsula and formed a south-north frequency cline, suggesting that this area could be a secondary contact zone between the two branches. By analyzing 11 populations sampled along a France-Spain/Portugal-Morocco-Guinea transect at 8 microsatellite loci and the DraI RFLP of the COI-COII mtDNA marker, we show that Iberian populations do not present any trace of “africanization” and are very similar to French populations when considering microsatellite markers. Therefore, the Iberian Peninsula is not a transition area. The higher haplotype A variability observed in Spanish and Portuguese samples compared to that found in Africa is explained by a higher mutation rate and multiple and recent introductions. Selection appears to be the best explanation to the morphological and allozymic clines and to the diffusion and maintenance of African haplotypes in Spain and Portugal.     

长江中游水系鲢和草鱼群体mtDNA遗传变异的研究

采用PCR技术进行了长江中游鲢和草鱼四个地理群体的线粒体DNA（mtDNA)限制性片段长度多态性（RFLP）的研究。四个地理群体包括长江中游的湖北嘉鱼和江西瑞昌两个地理群体,长江中游的两大支流江汉和湘江群体。PCR技术扩增出mtDNA ND5-ND6基因,选用10种限制性内切酶对PCR产物进行酶切。从鲢中共检出18种单倍型,在草鱼中没有发现多态现象,只有一种单倍型存在。进一步地证实了长江鲢的遗传多样性比草鱼的要丰富得多,与这两种鱼类在长江现有生物量成反比的反常现象。     

THE HISTORICAL PATTERN OF GENE FLOW AMONG MIGRATORY AND NONMIGRATORY POPULATIONS OF PRAIRIE WARBLERS (AVES: PARULINAE)

Within a group of interbreeding organisms, the balance of gene flow among populations and microevolutionary forces acting within populations is expected to result in clinal transitions in the phenotypes possessed by members of differentiated populations. Discontinuous variation between geographically adjacent populations suggests the presence of a significant barrier to gene flow. Here I present genetic evidence for restricted gene flow between migratory and nonmigratory populations of prairie warblers. The nonmigratory form of this species is restricted to coastal mangroves in Florida and is morphologically distinguishable from the typical, migratory form that occurs across the remainder of the eastern United States. Pairs of migratory populations exhibited little population subdivision (Φ_ST ? 0.09), whereas pairs of migratory and nonmigratory populations are much more differentiated (Φ_ST = 0.27–0.42). A phylogenetic analysis of mitochondrial DNA haplotypes did not offer evidence of long-term isolation of migratory and nonmigratory populations. Together with the population genetic analysis, the phylogenetic relationship of haplotypes suggests that isolation between these forms must have arisen relatively recently in their history. Evidence for significant population structure is unexpected, given the geographic proximity of migratory and nonmigratory populations, the capacity for long-distance movements (e.g., migration) by prairie warblers, and several previous studies of population structure in North American birds. However, the findings are consistent with the geographic distribution of morphological and behavioral variation and demonstrate that significant boundaries between populations of vagile organisms may be relatively cryptic.     

MOLECULAR AND REPRODUCTIVE CHARACTERIZATION OF SIBLING SPECIES IN THE EUROPEAN EARWIG (FORFICULA AURICULARIA)

The European earwig (Forficula auricularia) was formerly thought to present a mosaic of populations differing in their reproductive biology. We show that it is comprised of two as yet unrecognized sibling species. The molecular divergence between the two species, for a 627-bp amplified fragment overlapping the COI and COII mitochondrial loci, is six times larger than intraspecific variation. A species with two clutches a year lives predominantly in lowland and oceanic European habitats. A species with one clutch a year—except in the Mediterranean area where it has two clutches—lives predominantly in highland and continental European habitats. They both invaded North America during the 20th century, respectively, from the west and the east coasts, with no apparent mixing of their populations. The two species can occur in sympatry in Europe and are reproductively isolated by nearly complete failure to produce F₁ hybrids.     

MULTIPLE ORIGINS OF GENDER-ASSOCIATED MITOCHONDRIAL DNA LINEAGES IN BIVALVES (MOLLUSCA: BIVALVIA)

Previous studies have shown that marine mussels (genus Mytilus) and a freshwater mussel (Pyganodon grandis) contain two distinct gender-associated mitotypes, which is a characteristic feature of the phenomenon of doubly uniparental inheritance (DUI) of mitochondrial DNA (mtDNA). Here we present evidence for the presence of distinct male (M) and female (F) mitotypes in three other bivalve species, the mytilid Geukensia demissa, and the unionid species P. fragilis and Fusconaia flava. Nucleotide sequences of a segment of the COI gene from the M and F mitotypes from each of the three mytilid species (M. edulis, M. trossulus, G. demissa) and three unionid species (P. grandis, P. fragilis, F. flava) were used for phylogenetic analysis. The analysis suggests three independent origins of M and F mitotypes for the six species examined; one for the three unionid species, one for the two Mytilus species, and one for Geukensia. The first of these F/M divergence events, while of uncertain age, predates the divergence of the two unionid genera and is likely older than either of the two F/M divergence events in the mytilid taxa. The most parsimonious explanation of multiple F/M divergence events is that they represent independent origins of DUI. Another possibility is that, in a given taxon, an F or M mitotype assumes the role of the opposite mitotype (by virtue of a mechanism that remains to be clarified) and subsequently was fixed within its new gender. The fixation of a mtDNA lineage derived from a mitotype of switched function would reset the divergence of the gender-associated lineages to zero, thereby mimicking a de novo split of F and M lineages from a preexisting mtDNA genome that was not gender specific. Further broad-scale taxonomic studies of the occurrence of distinct M and F mitotypes may allow for the evaluation of the latter hypothesis.     

PATERNAL LEAKAGE OF MITOCHONDRIAL DNA IN A FUCUS (PHAEOPHYCEAE) HYBRID ZONE1

Eukaryotic mitochondria are mostly uniparentally (maternally) inherited, although mtDNA heteroplasmy has been reported in all major lineages. Heteroplasmy, the presence of more than one mitochondrial genome in an individual, can arise from recombination, point mutations, or by occasional transmission of the paternal mtDNA (=paternal leakage). Here, we report the first evidence of mtDNA paternal leakage in brown algae. In Denmark, where Fucus serratus L. and Fucus evanescens C. Agardh have hybridized for years, we found eight introgressed individuals that possessed the very distinct haplotypes of each parental species. The finding of heteroplasmy in individuals resulting from several generations of backcrosses suggests that paternal leakage occurred in earlier generations and has persisted through several meiotic bottlenecks.