Cytochrome C Oxidase Subunit I Haplotypes Research Articles

Population genetic parameters of the emerging corallivorous snail Drupella cornus in the northern Gulf of Eilat and Tanzanian coastlines based on mitochondrial COI gene sequences

The genetic diversity and population genetic structures of Drupella cornus populations from six localities in the northern Gulf of Eilat (GOE) and five localities in Tanzania (269 individuals) were investigated using mitochondrial cytochrome c oxidase subunit I (COI) gene sequences. Overall, 107 haplotypes, 47 in GOE and 61 in Tanzania, revealed similar haplotype diversity for the D. cornus populations within each location (0.9 ± 0.00025 and 0.903 ± 0.00078 respectively), with only a single haplotype shared between the two regions. Network analysis for the 107 COI haplotypes displayed two major clades separated by nine mutations, and Bayesian analyses of population structures revealed two clusters highly correlated with the collecting region. Analysis of molecular variance showed that 73% of the molecular variance for all Drupella populations is based on differences among regions. Within regions, most of the molecular variance is based on within population differences, north vs south in Tanzania (89%) and Israel vs Jordan in GOE (98%). Fu’s Fs and Tajima’s D values for all populations were negative, suggesting that the Drupella populations in both regions underwent population expansion or purifying selection. Based on the differences in genetic structuring within populations, the study strongly recommends application of conservation approaches that suit the description of the population in each region.

Cytochrome c oxidase subunit I haplotype diversity of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae)

The rat lungworm Angiostrongylus cantonensis is a food-borne zoonotic parasite of public health importance worldwide. It is the primary etiologic agent of eosinophilic meningitis and eosinophilic meningoencephalitis in humans in many countries. It is highly endemic in Thailand especially in the northeast region. In this study, A. cantonensis adult worms recovered from the lungs of wild rats in different geographical regions/provinces in Thailand were used to determine their haplotype by means of the mitochondrial partial cytochrome c oxidase subunit I (COI) gene sequence. The results revealed three additional COI haplotypes of A. cantonensis. The geographical isolates of A. cantonensis from Thailand and other countries formed a monophyletic clade distinct from the closely related A. malaysiensis. In the present study, distinct haplotypes were identified in seven regions of Thailand – AC10 in Phitsanulok (northern region), AC11 in Nakhon Phanom (northeastern region), AC15 in Trat (eastern region), AC16 in Chantaburi (eastern region), AC4 in Samut Prakan (central region), AC14 in Kanchanaburi (western region), and AC13 in Ranong (southern region). Phylogenetic analysis revealed that these haplotypes formed distinct lineages. In general, the COI sequences did not differentiate the worldwide geographical isolates of A. cantonensis. This study has further confirmed the presence of COI haplotype diversity in various geographical isolates of A. cantonensis. The COI gene sequence will be a suitable marker for studying population structure, phylogeography and genetic diversity of the rat lungworm.

Cytochrome c oxidase subunit I haplotype reveals high genetic diversity of Angiostrongylus malaysiensis (Nematoda: Angiostrongylidae).

The rat lungworm Angiostrongylus malaysiensis is a metastrongyloid nematode parasite. It has been reported in Malaysia, Thailand, Laos, Myanmar, Indonesia and Japan. In this study, A. malaysiensis adult worms recovered from the lungs of wild rats in different geographical regions/provinces in Thailand were used to determine their haplotype by means of the mitochondrial partial cytochrome c oxidase subunit I (COI) gene sequence. The results revealed high COI haplotype diversity of A. malaysiensis from Thailand. The geographical isolates of A. malaysiensis from Thailand and other countries formed a monophyletic clade distinct from the closely related A. cantonensis. In the present study, five new haplotypes were identified in addition to the four haplotypes reported in the literature. Phylogenetic analysis revealed that four of these five new haplotypes - one from Mae Hong Song (northern region), two from Tak (western region) and one from Phang Nga (southern region) - formed a distinct clade with those from Phatthalung (southern region) and Malaysia. The haplotype from Malaysia was identical to that of Phatthalung (haplotype AM1). In general, the COI sequences did not differentiate unambiguously the various geographical isolates of A. malaysiensis. This study has confirmed the presence of high COI genetic diversity in various geographical isolates of A. malaysiensis. The COI gene sequence will be suitable for studying genetic diversity, population structure and phylogeography.

Genetic diversity of infective larvae of Gnathostoma spinigerum (Nematoda: Gnathostomatidae) in freshwater swamp eels from Thailand

Human gnathostomiasis is a food-borne zoonosis caused by a tissue nematode of the genus Gnathostoma. The disease is highly endemic in Asia, including Thailand. The freshwater swamp eel (Monopterus albus), the second intermediate host of the gnathostome nematode, has an important role in transmitting the infection in Thailand. Surveys on the infective larvae of Gnathostoma spinigerum based on morphological features in freshwater swamp eels have been performed continuously and reported in Thailand. However, there is still limited molecular data on intra-species variations of the parasite. In this study, a total of 19 third-stage larvae of morphologically identified G. spinigerum were collected from 437 liver samples of freshwater swamp eels purchased from a large wholesale market in Bangkok, Thailand. Molecular characterization based on mitochondrial cytochrome c oxidase subunit I (COI) sequences was performed to elucidate their genetic variations and phylogenetic relationship. Among the 19 infective larvae recovered from these eels, 16 were sequenced successfully. Phylogenetic analyses inferred from the partial COI gene showed the presence of three distinct COI haplotypes. Our findings confirm the presence of G. spinigerum as the main species in Thailand.

Cosmopolitan or Cryptic Species? A Case Study of Capitella teleta (Annelida: Capitellidae).

Capitella teleta Blake et al., 2009 is an opportunistic capitellid originally described from Massachusetts (USA), but also reported from the Mediterranean, NW Atlantic, and North Pacific, including Japan. This putatively wide distribution had not been tested with DNA sequence data; intraspecific variation in morphological characters diagnostic for the species had not been assessed with specimens from non-type localities, and the species status of the Japanese population(s) was uncertain. We examined the morphology and mitochondrial COI (cytochrome c oxidase subunit I) gene sequences of Capitella specimens from two localities (Ainan and Gamo) in Japan. Specimens from Ainan and Gamo differed from C. teleta from Massachusetts in methyl-green staining pattern, shape of the genital spines, and shape of the capillary chaetae; we concluded that these characters vary intraspecifically. Species delimitation analyses of COI sequences suggested that worms from Ainan and Massachusetts represent C. teleta; these populations share a COI haplotype. The specimens from Gamo may represent a distinct species and comprise a sister group to C. teleta s. str.; we refer to the Gamo population as Capitella aff. teleta. The average Kimura 2-parameter (K2P) distance between C. teleta s. str. and C. aff. teleta was 3.7%. The COI data indicate that C. teleta actually occurs in both the NW Atlantic and NW Pacific. Given the short planktonic larval duration of C. teleta, this broad distribution may have resulted from anthropogenic dispersal.

Low genetic diversity and lack of genetic structure in the giant jellyfish Nemopilema nomurai in Chinese coastal waters

ABSTRACTThe giant jellyfish Nemopilema nomurai is a scyphozoan species well-known in East Asian Marginal Seas for its damage to fisheries. The genetic diversity and population structure of N. nomurai, collected from five geographic regions in Chinese coastal seas, were examined based on mitochondrial cytochrome c oxidase subunit I (COI) gene and nuclear internal transcribed spacer one (ITS1) sequences. A total of 26 and five unique haplotypes were recovered from the COI and ITS1 genes, respectively. The overall genetic diversity of N. nomurai calculated by the COI and ITS1 sequences was low (haplotype diversity 0.727% and 0.108%, nucleotide diversity 0.212% and 0.039%). The median-joining network analysis revealed a star-like haplotype network. The hierarchical Analysis of Molecular Variance (AMOVA) of COI haplotypes showed that N. nomurai populations form a single population, with a low FST (0.0149, p = 0.1036). The dispersal ability, together with the biological characteristics, could be important factors for the lack of a geographically structured pattern in N. nomurai in Chinese coastal waters.

Unique COI haplotypes in Hediste diversicolor populations in lagoons adjoining the Ionian Sea

The present study examines the genetic diversity (using cytochrome c oxidase subunit I (COI) haplotypes) of polychaete Hediste diversicolor populations in the Amvrakikos Gulf (western Greece) in order to test Cognetti's hypothesis on the formation of distinct isolated populations of species living in stressed transitional water habitats. To this purpose, the intraspecific diversity of H. diversicolor and the similarities among its populations in the brackish water habitats of the Eastern Mediterranean were investigated. Samples were collected from the lagoonal complex of Am - vrakikos Gulf in 2010 and 2011. Analysis showed that populations in the Amvrakikos Gulf share unique haplotypes which are distinct from the haplotypes hitherto reported, suggesting that these populations are highly isolated. This evidence partially supports Cognetti's hypothesis. The results indicate that the genetic differentiation in the studied populations was probably caused by the com- plete isolation of the gulf and periodic hypoxic conditions during its formation history. The occur- rence of unique haplotypes in the gulf underlines the importance of considering genetic diversity in the design of long-term biodiversity management and conservation plans.

Genetic diversity and population genetics of the warble flies Hypoderma bovis and H. sinense in Qinghai Province, China.

BackgroundHypoderma bovis and H. sinense (Diptera: Oestridae) mainly parasitise cattle and yaks. The two parasites are pathogenic and cause economic losses that result from reduced amounts of livestock products, including milk, meat, and skin. Genetic diversity and population genetic structure of H. bovis and H. sinense have not been evaluated, but could be used to inform appropriate strategies to control these parasites.MethodsWe cloned and sequenced part of the mitochondrial cytochrome c oxidase subunit I (COI) gene from 60 H. bovis isolates and 52 H. sinense isolates from five locations in Qinghai Province, China, to identify polymorphisms, and infer their phylogenetic relationships, historical population expansions, and divergence time.ResultsWe identified 17 COI haplotypes from the H. bovis samples, and 23 COI haplotypes from the H. sinense samples. The haplotype and nucleotide diversities were 0.738 and 0.00202 for H. bovis, and 0.867 and 0.00300 for H. sinense, respectively, which indicates rich genetic diversity in H. bovis and H. sinense populations. Bayesian phylogenetic analysis revealed that the two species are monophyletic, and geographical structuring of haplotypes was significantly different in H. sinense (P < 0.05), but not H. bovis. Neutrality tests and mismatch distribution statistical analysis revealed that populations of the two species have undergone demographic expansions. The divergence three Hypoderma spp. (H. bovis, H. lineatum, and H. sinense) was estimated to have occurred approximately 4.5 million years ago (Mya), which indicates that the rapid uplift of the Qinghai-Tibetan Plateau during the late Miocene-Pliocene was associated with divergence of Hypoderma species.ConclusionsResults of the present study revealed that both H. bovis and H. sinense displayed high genetic diversity and widespread population genetic differentiation within and among populations; these data, along with the molecular phylogeny, demographic history, and divergence time estimation, provide new insight into evolutionary history of these species. These findings will help elucidate speciation in Hypoderma and provide theoretical basis for epidemiological surveillance and control of these species on the Qinghai-Tibetan Plateau.

Temperature-related activity of Gomphiocephalus hodgsoni (Collembola) mitochondrial DNA (COI) haplotypes in Taylor Valley, Antarctica

Gomphiocephalus hodgsoni (Collembola) is the most common and widely distributed arthropod in the Dry Valleys of southern Victoria Land, and is genetically diverse with over 70 mitochondrial cytochrome c oxidase subunit I (COI) haplotypes. There is also considerable physiological variation among G. hodgsoni individuals in their cold tolerance and metabolic activity. Here, we assessed genetic haplotypes of G. hodgsoni relative to the environmental conditions during which individuals were active. We sequenced the COI region of 151 individuals collected in pitfall traps from three sites within Taylor Valley and found 19 unique haplotypes that separated into two distinct lineages (1.6 % divergence), with one lineage comprising 80 % of the sequenced population. During two-hourly sampling, air temperature was the strongest predictor of activity between the two lineages (R 2 = 0.56), and when combined with subsurface soil temperature, relative humidity and photosynthetically active radiation, explanatory power increased to R 2 = 0.71. With steadily increasing air temperatures predicted for much of Antarctica, it is likely that some haplotypes will have a selective advantage and potentially result in decreased genetic variability within populations. We suggest that temporal monitoring of the relative proportions of COI haplotypes or other appropriate genetic markers may provide a subtle measure of biological responses to environmental changes within Antarctic terrestrial ecosystems.

Exploring the Impact of Habitat Size on Phylogeographic Patterning in the Overberg Velvet Worm Peripatopsis overbergiensis (Onychophora: Peripatopsidae).

Evolutionary relationships in the velvet worm species, Peripatopsis overbergiensis, were examined in 3 forest areas in the Overberg region of South Africa to explore the impact of historical habitat fragmentation on the population genetic structure of the species. We collected 84 P. overbergiensis specimens from Grootvadersbosch, Koppie Alleen, and Marloth Nature Reserves and sequenced all these specimens for the cytochrome c oxidase subunit I (COI) locus, whereas a subset of 13 specimens were also sequenced for the 18S rRNA locus. Phylogenetic analyses of the 20 unique COI haplotypes revealed 4 genetically distinct clades, a result that is corroborated by the haplotype network. A hierarchical analysis of genetic variation was performed on the COI haplotype data within the 2 large forested areas, Grootvadersbosch and Marloth Nature Reserves, and across all 3 of the sample localities. These results revealed low haplotypic and nucleotide diversity within the largest Grootvadersbosch Nature Reserve forest and high haplotypic and nucleotide diversity within the fragmented Marloth Nature Reserve forest, whereas Koppie Alleen had the lowest haplotypic and nucleotide diversity. Across all 3 main localities statistically significant F ST values were found, together with the absence of shared haplotypes indicating the absence of maternal gene flow. Divergence time estimations based on the 20 COI haplotypes calculated in BEAST suggest a Pleistocene/Holocene divergence between the 4 clades as a result of habitat fragmentation and the aridification of the region. Our results indicate that conservation efforts should also prioritize linked, smaller fragmented habitats together with continuous habitats to maximize the genetic diversity of saproxylic fauna.

Phylogeography of Batrachospermum gelatinosum (Batrachospermales, Rhodophyta) shows postglacial expansion in Europe

:The freshwater red alga Batrachospermum gelatinosum inhabits streams of Europe and North America and has been collected frequently on both continents. A study of this species in North America showed evidence of a glacial refugium in the southeastern United States with little genetic variation throughout its more northern range in eastern North America. The present study was initiated to investigate its phylogeography throughout Europe and to compare these results with those obtained for North America. Specimens were collected from Belgium, Estonia, Finland, France, Great Britain, Italy, Latvia, Lithuania, Poland and Spain. Both the mitochondrial cytochrome c oxidase subunit I (COI) barcode region and the nuclear rDNA internal transcribed spacer (ITS 1 and 2) regions were analysed. Of the 70 individuals analysed, 12 COI haplotypes were uncovered. In addition, ITS variation of 67 individuals was surveyed and showed 21 haplotypes. The haplotype network of COI data showed a large number of the individuals distributed among three common haplotypes. The other nine haplotypes differed from the common ones by only one to two base pairs and were represented by only one to six individuals. The ITS network had a star appearance with a common haplotype (17 individuals) and many closely related haplotypes with few individuals per haplotype. Compared to North America, there were more COI haplotypes present in Europe (12 vs 5), and the relationship among haplotypes was more complex. The geographic distribution of haplotypes did not appear to follow a glaciation pattern; rather, the common haplotypes were widespread, suggesting a recent expansion.

Fine‐scale phylogeography reveals cryptic biodiversity in Pederson's cleaner shrimp,Ancylomenes pedersoni(Crustacea: Caridea: Palaemonidae), along the Florida Reef Tract

AbstractPopulations of continuously distributed marine organisms that disperseviapelagic larvae are often assumed to exist in a state of genetic panmixia because of their potential ability for long‐distance dispersal. However, obligate symbionts may have more restricted gene flow due to recruitment limitations, making host specificity an important potential driver of biodiversity. To explore the tension between broad dispersal ability and limited recruitment potential, we used sequences of mtDNA cytochromecoxidase subunit I (COI) to assess the fine‐scale phylogeography of the cleaner shrimp,Ancylomenes pedersoni, an obligate symbiont of sea anemones, along 300 km of the Florida Reef Tract (FRT). The results indicate high genetic diversity withinA. pedersonipopulations along the FRT. Pair‐wise ϕSTvalues indicate significant genetic structuring between northern (Fort Lauderdale and Upper Keys) and southwestern (Lower Keys) populations, with significant isolation by distance. Two divergent COI haplotype lineages were detected through statistical parsimony analysis: one evenly distributed across the entire FRT (Clade 1) and one found primarily in two sample localities in the Lower Keys (Clade 2). Phylogenetic analyses using 16S‐rDNAindicates that this genetic diversity is of paraphyletic origin, and possibly the result of multiple colonization events. These results reveal a complex demographic and evolutionary history forA. pedersonipopulations and provide the first evidence of highly divergent intra‐specific lineages independently colonizing the FRT. Because the FRT is a highly impacted coral reef system, understanding phylogeographic patterns along it has value beyond documentation of the factors that generate genetic diversity in tropical reef systems: these data are critical for creating scientifically based management strategies.

Phylogeography of Neptune whelk (Neptunea arthritica) suggests sex-biased impact of tributyltin pollution and overfishing around northern Japan

The Neptune whelk, Neptunea arthritica, is a sublittoral snail from Pacific waters that is a food resource and supports a commercially important fishery in northern Japan. This species showed a severe decline during the 1970s and 1980s, possibly because of overfishing, imposex caused by tributyltin (TBT) pollution and parasite infection. In the present study, we investigated genetic variation among the populations of N. arthritica from eight localities in northern Japan, including Hokkaido and Aomori, using a mitochondrial DNA (mtDNA) marker, a partial sequence of the cytochrome c oxidase subunit I (COI) gene. We also addressed the evolutionary history of N. arthritica and human impact on the population genetic profiles of this species. The parsimony network showed 14 COI haplotypes separated into two groups (Groups A and B), with an intermediate haplotype connecting both groups. Among eight populations, six were fixed for only one or two haplotypes, and no geographic-genetic correlation was found; they were probably affected by random drift. These results contrasted with those from previous microsatellite analysis, which indicated that geographic structure was the result of restricted gene flow between populations. Our results suggested that N. arthritica diverged into Groups A and B during the Pliocene; however, recent TBT pollution and size-selective fishing pressure have reduced genetic diversity and concealed the natural population structure. The present study also suggested that human impact may cause longstanding and possibly irreversible modification of ecosystems, particularly for species forming discrete and relatively small local populations, such as N. arthritica. Thus, the combined use of mtDNA and microsatellite genetic data provides a powerful tool to investigate the health of biodiversity in molluscs.

Theodoxus fluviatilis’ re-establishment in the River Rhine: a native relict or a cryptic invader?

The endangered freshwater snail Theodoxus fluviatilis is a widely distributed European member of the gastropod family Neritidae. This taxon was abundantly found in the River Rhine until the end of the 20th century, and was considered to be extinct there since the late 1990s. Since 2006, a new, but morphological different form of T. fluviatilis has been recorded in the Upper Rhine region. Our aim was to identify the source of the recent populations by analysing individuals from five sites throughout the current known distribution along the River Rhine. Therefore, we sequenced the mitochondrial cytochrome c oxidase subunit I (COI) gene, and compared the data with those from individuals collected in the early 1990s and 40 already known haplotypes from a pan-European study. Our results show that all studied recent Rhine individuals harbour only one COI haplotype that corresponds to an already known haplotype described from the River Danube and the Ukraine region near the Black Sea. This suggests that a re-colonisation of the River Rhine by T. fluviatilis from the River Danube is the most likely scenario of the re-establishment of the species. This route of invasion is known for other freshwater taxa that originate from the Ponto-Caspian region. Even though the current Rhine populations belong to T. fluviatilis their invasion may have consequences for the native Central European populations. Therefore, we recommend considering the current Rhine population as ‘cryptic invader’.

미토콘드리아 COI 유전자 서열의 다형성과 반수체형에 근거한 한국산 붉바리(Epinephelus akaara)의 유전적 구조와 계통 유연관계

한국산 붉바리 집단에서 유전적 구조와 계통 유연관계를 mtDNA COI 유전자 서열의 다형성을 이용하여 조사하였다. COI 유전자 서열을 결정하였고 기존에 보고된 서열들과 비교하였다. 본 연구를 통해 결정된 COI 서열들은 기존에 보고된 EF607565에 대하여 99.1-99.8%의 동일성을 나타내었다. 전체 20가지의 haplotype들이 발견되었고, 한국산 붉바리 집단은 19가지의 haplotype을 나타내었다. 이들 중 Hap_03과 Hap_08은 각각 제주도와 중국-특이적인 COI 서열들을 보였다. 반면, Hap_07은 한국에서 채집된 시료들과 홍콩과 대만에서 보고된 기록 등 여러 COI 서열들을 포함하였다. COI haplotype들의 다형성에 근거한 계통 유전학적 분석을 통해 작성된 NJ tree는 Epinephelus 속 내에서 단계통적인 분지양상을 나타내었고, 이는 붉바리 집단들이 공통의 모계 선조에서 진화한 것임을 나타내었다. 또한 중국해에서 보고된 COI 서열만을 포함하였던 Hap_08은 NJ tree의 중앙부에서 위치하였고, Hap_07의 서열들과도 근연의 관계임을 보여주었다. 이 결과는 중국산 붉바리 역시 동아시아의 다른 집단들과 모계적으로 연관되어있음을 보여주었다. 결과적으로, 동아시아 붉바리 집단들은 모계적으로 연관되어있을 뿐만 아니라 공통의 진화 역사를 공유하고 있으며 여전히 동아시아 해류(Kuroshio 해류)에 의해 영향을 받는 집단이라고 할 수 있다. 본 연구는 붉바리의 유전적 구조와 계통 유연관계를 이해하는 데 도움을 줄 수 있으며, 인공증식과 산업화에 관련된 연구에 있어 중요한 역할을 담당할 것으로 기대된다. The genetic structure and phylogenetic relationship were investigated in Korean red spotted grouper populations using the nucleotide sequence polymorphisms of the mitochondrial DNA (mtDNA) cytochrome c oxidase subunit I (COI) gene. The COI gene was sequenced showed 99.1-99.8% identity with the EF607565 sequence previously reported. A total of twenty haplotypes were found, and the Korean population showed nineteen haplotypes. Among those, Hap_03 and Hap_08 showed Jeju-do and China-specific COI sequences, respectively. However, Hap_07 had twelve COI sequences from South Korea and records from Hong Kong and Taiwan. Neighbor-joining (NJ) trees constructed from the phylogenetic analyses based on the polymorphisms of the COI haplotypes showed a monophyletic branching pattern within the genus Epinephelus. This indicated that the red spotted grouper populations had evolved from common maternal ancestors. In addition, the Hap_08, which had the COI sequence recorded only from China Sea, was found in the middle of the NJ tree nearby Hap_07 and showed a close relationship with Hap_07. This indicates that Chinese red spotted grouper is also maternally related to other populations in East Asia. Consequently, East Asian red spotted grouper populations are maternally related, as well as sharing the same evolutionary history, and are still affected by the East Asian ocean current (Kuroshio). These findings help to explain the genetic structure and phylogenetic relationship of red spotted grouper and also contribute to research on artificial breeding and industrialization.

Population genetics and recent colonization history of the invasive drosophilid Zaprionus indianus in Mexico and Central America

Zaprionus indianus, also known as the African fig fly, is an invasive pest of a variety of commercial and native fruit. The species was first reported in Brazil in 1999, but has established itself in much of the New World within the last 10–15 years. We used nucleotide sequences from a segment of the mitochondrial cytochrome c oxidase subunit I (COI) gene to examine haplotype relationships, population structure, and infer the colonization history of Z. indianus in Mexico and Panama. Construction of a haplotype network showed that six COI haplotypes, obtained from flies collected at six localities in Mexico and one in Panama, clustered into three distinct clades. Clade composition was generally consistent in flies from Panama to northwestern Mexico, and analysis of molecular variance indicated no significant structure among populations. Three of the six haplotypes from Mexico and Panama were identical to previously reported haplotypes from Brazil. None of the six haplotypes, however, were shared with previously reported haplotypes from potential source populations in the Old World. The results of our genetic analysis suggest that the invasion of Z. indianus into Central America and Mexico most probably includes a northward migration of individuals from Brazil, with the possibility of at least one additional introduction of Z. indianus to the New World. Additional sequence data from potential source populations in the Old World will be required to confidently determine the number of introductions of Z. indianus into the New World, and to identify the geographic source.

DNA barcode assessment of Gracilaria salicornia (Gracilariaceae, Rhodophyta) from Southeast Asia.

BackgroundDNA barcoding is becoming a widely applied tool for the quick and accurate identification of species. The evolution of the mitochondrial cytochrome c oxidase subunit I (COI) gene is sufficiently rapid to allow discrimination between closely related species and biogeographic subgroups within species. Gracilaria salicornia was originally described as being from Manila, the Philippines, and is distributed throughout Asia and the Indian Ocean. To more accurately define this species and its genetic diversity owing to the confusion of identification historically, DNA barcoding using the 5’ end of the COI gene of the mitochondrial genome was applied to specimens collected from the Philippines, Malaysia, Thailand, China, and Japan, and they were compared to other gracilarian species.ResultsWithin species, the COI marker yielded two clusters with nucleotide divergences of 0.0–1.3%. This divergence is slightly higher than the typical intraspecific variation for red algae. A total of eight COI haplotypes were found for G. salicornia, comprising the following groups: H1–H3 from the Philippines; H4 from Okinawa in Japan; H5–H7 from Malaysia, Thailand, and China; and H8 from Thailand.ConclusionAlthough this work concentrated on a limited geographical region of a widespread taxon, the data shows intraspecific molecular divergences in G. salicornia and provides further evidence that DNA barcodes are useful tools for identifying species boundaries and examining biogeographical haplotypes for the genus Gracilaria.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-54-27) contains supplementary material, which is available to authorized users.

Genetic diversity in the parthenogenetic reproducing tardigrade Echiniscus testudo (Heterotardigrada: Echiniscoidea)

Little is known about the genetic structure of microscopic animals from mosses and lichens. A few studies have investigated the geographic variation in tardigrades from mosses, but so far no study has investigated the intra-population or local clonal lineage variation. Echiniscus testudo (Echiniscoidea: Echiniscidae) belongs to a large cosmopolitan genus of terrestrial tardigrades comprising more than 150 species. It is a common tardigrade in mosses in the temperate part of the Northern hemisphere, and is highly tolerant of desiccation and freezing. In a previous study, we reported a maximum of 1.28% sequence variation (uncorrected p-distance) in cytochrome c oxidase subunit I (COI) haplotypes between clonal lineages covering a large geographical area. However, in this previous study we used pooled specimens to constitute a sample, and the genetic diversity from single specimens within a locality therefore remains unknown. Accordingly, the present study investigates the COI sequence variation and haplotype diversity between single specimens of E. testudo collected at three Danish localities, separated by 80 m and 186 km. A total of 10 COI haplotypes were found in the present study (Et2, Et3, Et9, Et12-Et18); only three of these were previously reported (Et2, Et3 and Et9). The uncorrected COI sequence diversity ranged between 0-2.07%, with haplotype Et18 having the highest genetic difference. The second most variable haplotypes (Et14, Et15, and Et17) all showed a maximum diversity of 1.19% compared to the other haplotypes. No general pattern of haplotype distribution was evident. Our data suggest that E. testudo has dispersed across the Baltic sea as haplotypes Et3, Et13 and Et14 are present at all three localities. The most likely dispersal mode is passive wind dispersal in the cryptobiotic tun stage. The current study emphasises that numerous sequences from single specimens are needed to describe the genetic diversity within single moss cushions.

Mitochondrial Haplotypes Indicate Parapatric-like Phylogeographic Structure in Blue-Spotted Maskray (Neotrygon kuhlii) from the Coral Triangle Region

Phylogeographic structure was investigated in the blue-spotted maskray, Neotrygon kuhlii, focusing on the Coral Triangle region. We used as genetic marker a 519-bp fragment of the cytochrome c-oxidase subunit I (COI) gene, sequenced in a total of 147 individuals from 26 sampling locations. The parsimony network of COI haplotypes was split into seven distinct clades within the Coral Triangle region. Different clades had exclusive but contiguous geographic distributions, indicating parapatric-like phylogeographic structure. Strong genetic differences were also inferred between local populations within a clade, where reciprocal monophyly between geographically adjacent samples was observed on several instances. Nearly 25% of the total molecular variance could be ascribed to differences between geographic samples within a clade, whereas interclade variation accounted for >65% of the total variance. The strong phylogeographic structure observed within a clade can be explained by either sedentarity or female philopatry. We interpret the parapatric distribution of clades as the joint result of 1) expansion from refuge populations at times of low sea level, and 2) possible enhanced competition between individuals from different clades, or assortative mating, or hybrid zones, along lines of secondary contact. The parapatric-like structure uncovered in the present study parallels regional differences at nuclear marker loci, thus pointing to incipient speciation within Coral Triangle N. kuhlii.

Genetic Connectivity between North and South Mid-Atlantic Ridge Chemosynthetic Bivalves and Their Symbionts

Transform faults are geological structures that interrupt the continuity of mid-ocean ridges and can act as dispersal barriers for hydrothermal vent organisms. In the equatorial Atlantic Ocean, it has been hypothesized that long transform faults impede gene flow between the northern and the southern Mid-Atlantic Ridge (MAR) and disconnect a northern from a southern biogeographic province. To test if there is a barrier effect in the equatorial Atlantic, we examined phylogenetic relationships of chemosynthetic bivalves and their bacterial symbionts from the recently discovered southern MAR hydrothermal vents at 5°S and 9°S. We examined Bathymodiolus spp. mussels and Abyssogena southwardae clams using the mitochondrial cytochrome c oxidase subunit I (COI) gene as a phylogenetic marker for the hosts and the bacterial 16S rRNA gene as a marker for the symbionts. Bathymodiolus spp. from the two southern sites were genetically divergent from the northern MAR species B. azoricus and B. puteoserpentis but all four host lineages form a monophyletic group indicating that they radiated after divergence from their northern Atlantic sister group, the B. boomerang species complex. This suggests dispersal of Bathymodiolus species from north to south across the equatorial belt. 16S rRNA genealogies of chemoautotrophic and methanotrophic symbionts of Bathymodiolus spp. were inconsistent and did not match the host COI genealogy indicating disconnected biogeography patterns. The vesicomyid clam Abyssogena southwardae from 5°S shared an identical COI haplotype with A. southwardae from the Logatchev vent field on the northern MAR and their symbionts shared identical 16S phylotypes, suggesting gene flow across the Equator. Our results indicate genetic connectivity between the northern and southern MAR and suggest that a strict dispersal barrier does not exist.