Phylogenetic characterisation of Taenia tapeworms in spotted hyenas and reconsideration of the “Out of Africa” hypothesis of Taenia in humans

The African origin of hominins suggests that Taenia spp. in African carnivores are evolutionarily related to the human-infecting tapeworms Taenia solium, Taenia saginata and Taenia asiatica. Nevertheless, the hypothesis has not been verified through molecular phylogenetics of Taenia. This study aimed to perform phylogenetic comparisons between Taenia spp. from African hyenas and the congeneric human parasites. During 2010–2013, 233 adult specimens of Taenia spp. were collected from 11 spotted hyenas in Ethiopia. A screening based on short DNA sequences of the cytochrome c oxidase subunit 1 gene classified the samples into four mitochondrial lineages designated as I–IV. DNA profiles of nuclear genes for DNA polymerase delta (pold) and phosphoenolpyruvate carboxykinase (pepck) showed that lineages II and III can be assigned as two independent species. Common haplotypes of pold and pepck were frequently found in lineages I and IV, suggesting that they constitute a single species. Morphological observations suggested that lineage II is Taenia crocutae, but the other lineages were morphologically inconsistent with known species, suggesting the involvement of two new species. A phylogenetic tree of Taenia spp. was reconstructed by the maximum likelihood method using all protein-coding genes of their mitochondrial genomes. The tree clearly demonstrated that T. crocutae is sister to T. saginata and T. asiatica, whereas T. solium was confirmed to be sister to the brown bear tapeworm, Taenia arctos. The tree also suggested that T. solium and T. arctos are related to two species of Taenia in hyenas, corresponding to lineages I + IV and III. These results may partially support the African origin of human-infecting Taenia spp., but there remains a possibility that host switching of Taenia to hominins was not confined to Africa. Additional taxa from African carnivores are needed for further testing of the “Out of Africa” hypothesis of Taenia in humans.     

Genetic structure of Phlebotomus (Larroussius) ariasi populations, the vector of Leishmania infantum in the western Mediterranean: Epidemiological implications

In recent years there has been growing interest in analyzing the geographical variations between populations of different Phlebotomus spp. by comparing the sequences of various genes. However, little is known about the genetic structure of Phlebotomus ariasi. In this study, we were able to sequence a fragment of the mitochondrial Cyt b gene in 133 sandflies morphologically identified as P. ariasi and proceeding from a wide geographical range covering 35 locations in 11 different regions from five countries. The intra-specific diversity of P. ariasi is high, with 45 haplotypes differing from each other by one to 26 bases and they are distributed in two mitochondrial lineages, one limited geographically to Algeria and the other widely dispersed across Mediterranean countries. The Algerian lineage is characterized by having 13 fixed polymorphisms and is made up of one sole haplotype. The European/Moroccan P. ariasi lineage is characterized by being made up of a great diversity of haplotypes (44) which display some geographical structuring. This could be one of the multiple factors involved in the epidemiological heterogeneity of the foci of leishmaniasis. Phlebotomus chadlii is the sister group of European/Moroccan P. ariasi. The separation of the Algerian haplotype, H45, from the rest of the specimens, European/Moroccan P. ariasi and P. chadlii, is well supported by the bootstrap analysis.     

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。     

Molecular phylogenetics and population structure of Sousa chinensis in Chinese waters inferred from mitochondrial control region sequences

Phylogenetic analyses of the genus Sousa were carried out across their geographic range and focused especially on the genetic variation patterns and population structure of Sousa chinensis in Chinese waters. The analyses were based on 287-bp of the mitochondrial control region from 122 Indo-Pacific humpback dolphins (Sousa chinensis) and two Atlantic humpback dolphins (Sousa teuszii). All specimens from China grouped together in a well-supported clade with high bootstrap (BS) and Bayesian posterior probability values (BPP), strongly suggesting that only one species of Sousa exists in China. Six haplotypes were identified in 65 individuals from Xiamen and Pearl River Estuary in China. The extremely low level of detected mtDNA genetic diversity strongly suggests a high priority in conservation of Sousa. The highly significant genetic differentiation between the two populations in Xiamen and Pearl River Estuary supports the designation of these two populations as separate management units (MUs) when designing management programs for this species.     

Cranial morphometrics and mitochondrial DNA sequences distinguish cryptic species of the longface emperor (Lethrinus olivaceus), an emblematic fish of Indo-West Pacific coral reefs

Range-wide morphometric variability (cranial measurements) and genetic variability (nucleotide sequences of the cytochrome b gene) were investigated in the longface emperor, Lethrinus olivaceus (Lethrinidae), an emblematic large predatory fish of Indo-West Pacific coral reefs. Two cranial morphotypes were observed, one present from the Indian Ocean to the Coral Triangle and the other one, from the Coral Triangle to the western Central Pacific. The two morphotypes are concordant with reciprocally monophyletic mitochondrial lineages separated by 9.5% net nucleotide distance. These results suggest an old evolutionary history for L. olivaceus, which consists of two distinct species (Lethrinus sp. A in the Indian Ocean and Coral Triangle, Lethrinus sp. B in the western Pacific Ocean), whose distribution ranges meet or overlap in the eastern part of the Coral Triangle, in Taiwan and in West Papua. Lethrinus sp. A comprises two distinct mitochondrial lineages separated by 1.7% net nucleotide distance, one exclusive to the populations from the Indian Ocean, the other exclusive to Coral Triangle populations. The latter observation might be explained by vicariance, whereby the two lineages have been isolated from one another on either side of the Sunda Shelf because of low sea level in the Pleistocene. To clarify the nomenclature of this species complex, we recommend sequencing a fragment of the cytochrome b gene of the holotypes of L. olivaceus and of its first junior synonyms L. rostratus and L. waigiensis.     

Genetic diversity and inter-specific relations of western Mediterranean relic Abies taxa as compared to the Iberian A. alba

Several Abies species are currently present in the Mediterranean region and most of them are endemic taxa and tertiary relicts. Using six nuclear microsatellites, we studied the genetic structure and inter-specific relationships among West Mediterranean firs, A. pinsapo (Spain), A. maroccana and A. tazaotana (Morocco). Based on the hypothesis that A. pinsapo could historically exchange genes with A. alba growing in the Pyrenees via secondary contact, we investigated the level of genetic admixture between these species using a Bayesian approach. The studied populations showed moderate genetic diversity (mean H_E = 0.598) and a high level of genetic differentiation (F_ST = 0.225) that was especially pronounced between A. alba and the African firs. All populations experienced a strong bottleneck effect that was likely induced by climatic changes occurring in the West Mediterranean during the last glacial cycle and the Holocene. According to Bayesian clustering, both African taxa grouped together in a single cluster, the two A. pinsapo populations formed a second cluster, and two additional clusters were detected within A. alba. Our results indicate that A. tazaotana is genetically very close to A. maroccana, and hence these two taxa should probably not be considered as separate species. We found no genetic admixture between A. pinsapo and A. alba and only minor between A. pinsapo and the African fir populations suggesting an isolation effect of the Gibraltar Strait. Current limited distributions of firs in the Mediterranean region together with changing climate may lead to further deterioration of the genetic diversity levels. Hence, future efforts should focus on monitoring the demography and genetic threats to existing populations.     

Dual African Origins of Global Aedes aegypti s.l. Populations Revealed by Mitochondrial DNA

Background

Aedes aegypti is the primary global vector to humans of yellow fever and dengue flaviviruses. Over the past 50 years, many population genetic studies have documented large genetic differences among global populations of this species. These studies initially used morphological polymorphisms, followed later by allozymes, and most recently various molecular genetic markers including microsatellites and mitochondrial markers. In particular, since 2000, fourteen publications and four unpublished datasets have used sequence data from the NADH dehydrogenase subunit 4 mitochondrial gene to compare Ae. aegypti collections and collectively 95 unique mtDNA haplotypes have been found. Phylogenetic analyses in these many studies consistently resolved two clades but no comprehensive study of mtDNA haplotypes have been made in Africa, the continent in which the species originated.

Methods and Findings

ND4 haplotypes were sequenced in 426 Ae. aegypti s.l. from Senegal, West Africa and Kenya, East Africa. In Senegal 15 and in Kenya 7 new haplotypes were discovered. When added to the 95 published haplotypes and including 6 African Aedes species as outgroups, phylogenetic analyses showed that all but one Senegal haplotype occurred in a basal clade while most East African haplotypes occurred in a second clade arising from the basal clade. Globally distributed haplotypes occurred in both clades demonstrating that populations outside Africa consist of mixtures of mosquitoes from both clades.

Conclusions

Populations of Ae. aegypti outside Africa consist of mosquitoes arising from one of two ancestral clades. One clade is basal and primarily associated with West Africa while the second arises from the first and contains primarily mosquitoes from East Africa     

Pan-African Genetic Structure in the African Buffalo (Syncerus caffer): Investigating Intraspecific Divergence

The African buffalo (Syncerus caffer) exhibits extreme morphological variability, which has led to controversies about the validity and taxonomic status of the various recognized subspecies. The present study aims to clarify these by inferring the pan-African spatial distribution of genetic diversity, using a comprehensive set of mitochondrial D-loop sequences from across the entire range of the species. All analyses converged on the existence of two distinct lineages, corresponding to a group encompassing West and Central African populations and a group encompassing East and Southern African populations. The former is currently assigned to two to three subspecies (S. c. nanus, S. c. brachyceros, S. c. aequinoctialis) and the latter to a separate subspecies (S. c. caffer). Forty-two per cent of the total amount of genetic diversity is explained by the between-lineage component, with one to seventeen female migrants per generation inferred as consistent with the isolation-with-migration model. The two lineages diverged between 145 000 to 449 000 years ago, with strong indications for a population expansion in both lineages, as revealed by coalescent-based analyses, summary statistics and a star-like topology of the haplotype network for the S. c. caffer lineage. A Bayesian analysis identified the most probable historical migration routes, with the Cape buffalo undertaking successive colonization events from Eastern toward Southern Africa. Furthermore, our analyses indicate that, in the West-Central African lineage, the forest ecophenotype may be a derived form of the savanna ecophenotype and not vice versa, as has previously been proposed. The African buffalo most likely expanded and diverged in the late to middle Pleistocene from an ancestral population located around the current-day Central African Republic, adapting morphologically to colonize new habitats, hence developing the variety of ecophenotypes observed today.     

Genetic distinctiveness of the damselfly <Emphasis Type="Italic">Coenagrion puella</Emphasis> in North Africa: an overlooked and endangered taxon

North African odonates are facing conservation challenges, not only by increased degradation and loss of habitat, but also by having poorly understood taxonomy. Coenagrion puella is a widely distributed damselfly but there is debate about the taxonomic status of North African populations, where the species is very rare. We evaluate the genetic distinctiveness of North African C. puella using mitochondrial and nuclear genetic markers. We found a clear genetic differentiation between North African and European populations (3.4 % mtDNA) and a lack of shared haplotypes between individuals from the two continents. These results suggest that the damselfly C. puella comprises two genetically distinct phylogenetic lineages: one in Europe and one in North Africa, and re-invigorate the debate on the validity of the North African endemic C. puella kocheri. We propose that these two lineages of C. puella should be managed as distinct molecular operational taxonomic units. More generally, this study reinforces the important role of North Africa as centre of speciation and differentiation for odonates, and highlights the relevance of incorporating genetic data to understand the evolutionary history and taxonomy for effective biodiversity conservation.     

Patterns of morphological variation among populations of the widespread annual killifish Nothobranchius orthonotus are independent of genetic divergence and biogeography

Populations of annual killifish of the genus Nothobranchius occur in patchily distributed temporary pools in the East African savannah. Their fragmented distribution and low dispersal ability result in highly structured genetic clustering of their populations. In this study, we examined body shape variation in a widely distributed species, Nothobranchius orthonotus with known phylogeographic structure. We tested whether genetic divergence of major mitochondrial lineages forming two candidate species is congruent with phenotypic diversification, using linear and geometric morphometry analyses of body shape in 23 wild populations. We also conducted a common‐garden experiment with two wild‐derived populations to control for the effect of local environmental conditions on body shape. We identified different allometric trajectories for different mitochondrial lineages and candidate species in both sexes. However, in a principal components analysis of population‐level body shape, the separation among mitochondrial lineages was incomplete. Higher similarity of mitochondrial lineages belonging to different candidate species than that of same candidate species prevented distinction of the two candidate species on the basis of body shape. Analysis at the individual level demonstrated that N. orthonotus express high intrapopulation variability, with major overlap among individuals from all populations. In conclusion, we suggest that N. orthonotus be considered as a single species with an extensive geographic range, strong population genetic structure and high morphological variability.     

The Past and Present of an Estuarine-Resident Fish,the “Four-Eyed Fish” Anableps anableps (Cyprinodontiformes,Anablepidae), Revealed by mtDNA Sequences

Historical events, such as changes in sea level during the Pleistocene glacial cycles, had a strong impact on coastal habitats, limiting connectivity and promoting the genetic divergence of various species. In this study, we evaluated the influence of climate oscillations and the possibility of estuary function as a barrier to gene flow among populations of the four-eyed fish, Anableps anableps. This species is fully estuarine-resident, has internal fertilization, is viviparous and does not migrate across long distances. These features make the four-eyed fish an excellent model for the study of evolutionary processes related to genetic differentiation of species and populations in estuaries. The evolutionary history of A. anableps was inferred from phylogeographic and population analyses using sequences of the mitochondrial DNA Control Region of 13 populations distributed in the Amazon and Northeast Coast of Brazil from Calcoene (Amapa) to Parnaiba (Piaui). The 83 retrieved haplotypes show a pattern of four distinct mitochondrial lineages, with up to 3.4% nucleotide divergence among them. The evolutionary reconstruction suggests that these lineages diverged recently in the late Pleistocene/early Holocene after the Atlantic Ocean reaching current levels. Analysis of variability, neutrality and the genetic expansion pattern revealed that the lineages have distinct characteristics, which were shaped by the different geomorphological features of coastal regions combined with sea level oscillations over a very long period of time. Only few neighboring populations show a discreet gene flow. This study may also be helpful for designing new experiments to better understand the geomorphological evolutionary history of the estuaries of the Amazon and the Northeast Coast of Brazil using estuarine-resident species as a model.     

African DNA lineages in mitochondrial gene pool of Europeans

Mitochondrial DNA (mtDNA) nucleotide sequences of African origin have been found at low frequency (1%, in average) in different European populations. In the present study, data on mtDNA variability in populations of Eurasia and Africa are analyzed and search of African-specific lineages present in Europeans is conducted. The results of analysis indicate that, despite a high diversity of African mtDNA haplotypes found in Europeans, monophyletic clusters of African mtDNA lineages, arisen in Europe and characterized by long-term diversity, are nearly absent in Europe. Only two respective clusters (belonging to haplogroups L1b and L3b), which evolutionary age does not exceed 6.5 thousands years, were revealed. Comparative analysis of distribution of frequencies of autosomal microsatellite alleles found in Russian individuals, carrying the African-specific mitochondrial haplotypes, in populations of Europe and Africa has indicated that autosomal genotypes of those Russian individuals are characterized by the presence of alleles characteristic mostly for Europeans.     

Genetic diversity and historical biogeography of the Maltese wall lizard,Podarcis filfolensis (Squamata: Lacertidae)

Podarcis filfolensis is an endemic lizard from the Maltese archipelago. There is evidence of human-mediated decline and even extirpation of some insular populations of this species. However, information about the intraspecific genetic diversity and phylogeographic patterns of this species is limited. Here we analyze genetic markers from a multi-locus dataset (mtDNA, 2,533 bp; nuclear c-mos gene, 353 bp; 11 microsatellites) for individuals from extant populations of P. filfolensis. Despite generally low genetic variability, two main mitochondrial groupings were clearly identified. In general, individuals from the main island of Malta were genetically distinct from those from Gozo, Comino, Cominotto and Small Blue Lagoon Rock, and also from Linosa and Lampione individuals. Three genetic clusters were detected based on microsatellite data: one was found at higher frequency on Malta, while the other two included samples from the remaining islands, showing some concordance with the mtDNA pattern. A time-calibrated Bayesian tree for the principal mitochondrial lineages indicated strong statistical support for two P. filfolensis lineages that originated in the Pleistocene (105.4–869 Ka). We show that these lineages largely meet the criteria for recognition as evolutionary significant units despite some recent admixture (possibly due to recent translocations between islands). Human disturbance, low genetic variability, evidence of bottlenecks and extirpation on one island indicate that a thorough review of the current conservation status of P. filfolensis would be timely.     

基于细胞色素b基因的中国岩羊不同地理种群遗传差异分析

为了揭示中国岩羊不同地理种群的遗传差异,探讨岩羊亚种分化的分子机制,采用中国岩羊不同地理种群的细胞色素b(Cyt b)基因的全序列,分析了碱基变异情况、遗传距离以及核苷酸序列差异。用最大似然法和贝叶斯法构建分子系统树并对获得的拓扑结构进行分析。结果发现,西藏亚种与四川亚种Cyt b基因平均序列差异为4.2%(±0.007),处于偶蹄目亚种的序列差异范围内,支持了目前对岩羊西藏亚种的分类地位。四川亚种内部各地理种群之间的遗传距离(0.033±0.0 111)与它们分别到西藏种群的遗传距离(0.042±0.007)差异不显著(t=1.824,P=0.084),说明四川亚种内部各地理种群间已经发生较显著的遗传分化。其中,四川、甘肃和青海种群亲缘关系较近,并与四川亚种内部的其它种群已产生了显著的遗传分化。因此认为四川亚种内部各地理种群的种下分化需要深入研究。     

基于线粒体DNA控制区的斑翅草螽不同地理种群遗传分化研究

采用PCR扩增结合DNA克隆测序技术,分析了斑翅草螽Conocephalus maculates 9个地理种群mtDNA控制区序列的变异及遗传多样性。切除侧翼RNA基因序列后,最终获得的斑翅草螽mtDNA控制区比对后全长为676 bp,平均碱基组成T(37.8%),C(11.7%),A(41.3%)和G(9.1%)。共检测到98个可变位点,占总位点数的14.5%,其中,9处碱基插入/缺失,74处转换(40个T/C,34个A/G),50处颠换(18个A/T,11个T/G,15个A/C,6个C/G)。共定义46个单倍型,其中,4个为种群间共享单倍型(H02、H05、H08和H10),其余42个为各种群独有单倍型,包括6个种群内共享单倍型(H09、H11、H15、H18、H26和H38)。单倍型总数占实验个体总数的69.7%,除四川峨眉山外,其余种群单倍型百分比均﹥50%。通过两两地理种群间的FST值差异显著性检验,将这些群体分为4组,分别为SC+CQ,GX+FLB+HN+YN,XZ和HB。以长瓣草螽C.gladiatus、峨眉草螽C.emeiensis、悦鸣草螽C.melaenus、竹草螽C.bambusanus为外群,构建的斑翅草螽mtDNA控制区单倍型NJ法系统树形成3个自举支持度较高的分支,其中,分支A由28种单倍体组成,包括本研究中除四川峨眉山(SC)和重庆万州(CQ)以外的7个种群;分支B由12种单倍体组成,包含除菲律宾拉乌尼翁(FLB)和江西南昌(JX)以外的7个种群;分支C由6种单倍型组成,全部来自西藏林芝(XZ)的单倍型。聚类结果表明,斑翅草螽不同地理种群间的遗传分化并不明显,即使是两两群体间FST值差异显著的群体,也未能形成完全独立的分支。     

A reappraisal of the systematic affinities of Socotran,Arabian and East African scops owls (Otus,Strigidae) using a combination of molecular,biometric and acoustic data

We investigated phylogenetic relationships among Otus scops owls from Socotra Island, the Arabian Peninsula and East Africa using molecular, vocalization and biometric data. The Socotra Scops Owl Otus senegalensis socotranus, currently treated as a subspecies of the African Scops Owl Otus senegalensis, is more closely related to the Oriental Scops Owl Otus sunia and to the endemic Seychelles Scops Owl Otus insularis. Considerable mitochondrial genetic distance and significant morphological differentiation from its two closest relatives, as well as its distinctive vocalizations compared with O. insularis, strongly support recognition of Socotra Scops Owl as a full species. Unexpectedly, two taxa from the Arabian Peninsula, Pallid Scops Owl Otus brucei and African Scops Owl Otus senegalensis pamelae, represent very distinct lineages; O. brucei is basal to a clade that includes taxa found in the Indo‐Malayan region and on Indian Ocean islands. In contrast, O. s. pamelae occupies a well‐supported basal position within a clade of continental Afro‐Palaearctic taxa. The uncorrected‐p genetic distance between O. s. pamelae and its closest relatives (other populations of senegalensis from mainland Africa) is c. 4%. As O. s. pamelae is also well differentiated phylogenetically, morphologically and vocally from O. s. senegalensis, we recommend its elevation to species status, as Otus pamelae. Among mainland African O. senegalensis subspecies, Ethiopian populations appear to represent the most divergent lineage, whereas other lineages from Somalia, Kenya and South Africa are poorly differentiated. The large genetic distance between the Ethiopian haplotype and other African haplotypes (3.2%) suggests that the Ethiopian Otus may represent a cryptic taxon, and we recommend that more individuals be sampled to assess the taxonomic status of this population.     

Cryptic divergence and strong population structure in the colonial invertebrate Pycnoclavella communis (Ascidiacea) inferred from molecular data

We studied sequence variation in the mitochondrial gene cytochrome c oxidase subunit I (COI) for 135 individuals from eight Mediterranean populations of the colonial ascidian Pycnoclavella communis across most of its presently known range of distribution in the Mediterranean. Three haplotypes from Atlantic locations were also included in the study. Phylogenetic, phylogeographic and population genetic analyses were used to unravel the genetic variability within and between populations. The study revealed 32 haplotypes for COI, 29 of them grouped within two Mediterranean lineages of P. communis (mean nucleotide divergence between lineages was 8.55%). Phylogenetic and network analyses suggest the possible existence of cryptic species corresponding to these two lineages. Population genetic analyses were restricted to the five populations belonging to the main genetic lineage, and for these localities we compared the information gleaned from COI sequence data and from eight microsatellite loci. A high genetic divergence between populations was substantiated using both kinds of markers (COI, global Fst=0.343; microsatellite loci, global Fst=0.362). There were high numbers of private haplotypes (COI) and alleles (microsatellites) in the populations studied. Restricted gene flow and inbreeding occur in the present range of distribution of the species. Microsatellite loci showed a strong incidence of failed amplifications, which we attribute to the marked intraspecies variability that hampered the application of these highly specific markers. Our results show important genetic variability at all levels studied, from within populations to between basins, possibly coupled to speciation processes. This variability is attributable to restricted gene flow among populations due to short-distance dispersal of the larvae.     

Genetic differentiation in the mud crab Scylla serrata (Decapoda: Portunidae) within the Indian Ocean

Scylla serrata (Decapoda: Portunidae) is a swimming crab that is widespread in the Indo-Pacific region and commonly found in estuarine and mangrove waters. An extended planktonic larval phase suggests high dispersal potential and the possibility of extensive gene flow between conspecific populations at least on a geographic mesoscale (tens to hundreds of kilometres).Intraspecific variation of the mitochondrial DNA cytochrome oxidase subunit I (mtDNA COI) gene was investigated in 77 individuals from four representative mangrove swamps of the African tropics (Kenya and Zanzibar) by means of DNA sequencing. We examined 535 base pairs (bp) and identified 24 different haplotypes. Each population sample is characterised by a single most frequent haplotype, shared among all four populations, and a small number of rare ones, typically present in only one or two individuals and representative of a specific population.Analysis of molecular variance (AMOVA), F_ST statistics and χ² contingency analysis of spatial distribution of mtDNA haplotype frequencies revealed in toto a significant genetic differentiation among populations. These results could indicate that gene flow might be reduced, even between geographically close sites, despite the high potential for dispersal; anyway, at the recorded level of divergence and owing to the abundance of rare haplotypes and singletons in our data set, repeated sampling over time is necessary to establish whether the recorded pattern of genetic differentiation is stable and biologically significant.Finally, integration of our data with those reported by Gopurenko et al. [Mar. Biol. 134 (1999) 227] on S. serrata from South Africa, Red Sea and Mauritius Islands allowed to infer S. serrata population structure within a larger area of the Indian Ocean region.     

Genetic structure analysis of mantis shrimp <Emphasis Type="Italic">Oratosquilla oratoria</Emphasis> based on mitochondrial DNA control region sequence

The genetic relationships of mantis shrimp Oratosquilla oratoria between the coastal waters of China and Japan were not well studied. To reveal the genetic differentiation and genetic structure among populations, we collected populations of mantis shrimp O. oratoria from the coastal waters of China and Japan to analyze the mtDNA control region variation. A total of 309 individuals of O. oratoria were collected from 13 localities (11 from China and 2 from Japan) and a segment of mitochondrial DNA control region was sequenced. Three hundred nine haplotypes were defined, yielding a very high haplotype diversity and nucleotide diversity. Two lineages of O. oratoria were revealed and displayed strong differences in the geographical distribution. In the coastal waters of China, the geographic distribution of the two lineages was completely separated by the Yangtze River estuary; however, the lineages showed geographic sympatry in two populations from Japan. Based on the lineage distribution, three groups were defined. There was no significant genetic differentiation among the populations within the three groups, indicating high gene flow within each group. Significant and negative values for Tajima D and Fu’s Fs tests, and mismatch distributions for two lineages indicated population expansion. The present result confirmed that the freshwater outflow from the Yangtze River formed a physical barrier and affected gene exchange. The different distribution patterns of the two lineages in coastal waters of China and Japan indicated that the larvae of O. oratoria were transferred from China to the coastal waters of Japan with a one-way gene flow.     

Genetic analyses of two spawning stocks of the short-finned squid (Illex argentinus) using nuclear and mitochondrial data

Short-finned squid Illex argentinus (Omastrephidae) is an economically important species which supports a long-term and intensive commercial fishery in the South-West Atlantic Ocean. In this study, the genetic variability of allozymes (40 loci) and mitochondrial regions, COI (556 bp) and 16S rDNA (439 bp), were addressed in the two most important species’ spawning stocks, the Summer Spawning Stock (SSS) and the South Patagonic Stock (SPS). Five out of 20 polymorphic allozyme loci were polymorphic at 95% criterion and heterozygosity levels were low. The concatenated analysis of mitochondrial molecular markers revealed high to low values of haplotype and nucleotide diversity, respectively. Nuclear and mitochondrial data revealed no significant genetic differences between these two spawning stocks. Our results and the biological characteristics of I. argentinus deal with a no simple genetic structure of populations described as spatial and temporal chaotic patchiness. SSS and SPS spawning stocks of I. argentinus could not be elevated to the status of genetic stocks.