Mitochondrial Sequence Variation Research Articles

Continental island effect in Sichuan Basin based on the genetic structure of sparrow

Abstract Islands are ideal settings for the study of evolution, ecology and genetic diversity. The tree sparrow (Passer montanus), which is distributed both inside and outside the Sichuan Basin and is relatively easy to capture, was used as our study species to test whether any genetic differences exist between within and outside of the Sichuan Basin. We analyzed mitochondrial and nuclear gene sequence variations to illustrate the continental island effect within the Sichuan Basin. Overall, fragments from four mtDNA and one nuclear sequence (Cytb + COI + 12S rRNA + Dloop + Myo) were amplified, with the concatenated alignment comprising 3234 bp. The results of Bayesian and maximum parsimony trees indicated two major branches, one of which is composed mainly of populations within the Sichuan Basin, while the other comprised populations distributed in the surrounding mountains. The population in Sichuan Basin was more basal than that in the surrounding mountains. The genetic distance between inner and outer populations was 0.095 and genetic differentiation index (FST) between inner and outer populations was 0.342. This study shows that the overall distribution pattern of tree sparrow populations in the Sichuan Basin and its surrounding mountains is probably the result of a vicariance event due to spatial isolation.

Mitochondrial COI Sequence Variations within and among Geographic Samples of the Hemp Pest Psylliodes attenuata from China.

The hemp flea beetle Psylliodes attenuata (Coleoptera: Chrysomelidae: Psylliodes) is a common pest of Cannabis sativa, including cultivars of both industrial hemp and medicinal marijuana. Both the larval and adult stages of this beetle can cause significant damages to C. sativa, resulting in substantial crop losses. At present, little is known about the populations of this pest, including its genetic diversity. In this study, we obtained 281 P. attenuata samples from nine field sites representing broad industrial hemp productions in China and analyzed their DNA sequences at the mitochondrial COI gene, the insect DNA barcode. Our analyses revealed a total of 48 haplotypes, with 28 being found only in one specimen each while the remaining 20 were shared by two or more specimens each. Of the 20 shared haplotypes, eight were shared among local populations often from far away locations, consistent with recent long-distance dispersals. However, the observed putative long-distance dispersals have not obscured the significant genetic differentiations among the regional populations from northeastern, eastern, central and southwestern China. Interestingly, haplotype network analyses suggest evidence for potential mitochondrial recombination in natural populations of this species. We briefly discuss the implications of our results on its evolution, center of diversity, route of spread, and pest management strategies in hemp fields.

Epinephelus tankahkeei, a new species of grouper (Teleostei, Perciformes, Epinephelidae) from the South China Sea.

A new species of grouper, Epinephelus tankahkeeisp. nov. is described from the South China Sea based on examination of morphological and molecular characteristics. This new species has been treated as, and is similar to, its congener E. chlorostigma. Epinephelus tankahkeeisp. nov. can be distinguished from E. chlorostigma by the following combination of characters: a convex anal fin; closer dark spots on the body; a lack of dark spots on the abdomen, cheek, and pectoral fin; the absence of a clear posterior white margin on the caudal fin. Molecular analyses of the mitochondrial COI sequence variation, genetic distances, and a phylogeny, all highly support E. tankahkeeisp. nov. as a distinct species. A key to E. tankahkeeisp. nov. and its most closely related species is provided.

Genetic variation in morphologically divergent mainland and island populations of Soemmerring’s gazelles (Nanger soemmerringii)

This study focuses on the taxonomic, evolutionary and conservation implications of a striking reduction in body size previously observed in an island population of gazelles by comparing the genetic structure of island and mainland populations. Mitochondrial sequence diversity of the mainland population was found to be comparable to that of other true gazelles of East Africa. We discuss this in the context of the prolonged armed conflict in our study region. In contrast, the gazelles on Dahlak Kebir, one of the over 200 islands and islets of the Dahlak archipelago on the Red Sea, were found to be genetically depauperate. Nucleotide and haplotype diversity estimates were a sixth and a third of that of the mainland population respectively. Using estimates of Tajima’s D statistic, we inferred that the Dahlak population has undergone expansion after a recent bottleneck. A minimum spanning genealogical network of mitochondrial control region sequences produced testable hypotheses on the route and timing of the colonization of Dahlak Kebir by gazelles from the mainland. Our mitochondrial DNA dataset has resolved the taxonomic ambiguity of the island gazelles. Their genetic distinctiveness and, their striking conformity to the Island Rule that was highlighted in a previous study, are discussed from evolutionary and conservation perspectives.

Two new Cnemaspis Strauch, 1887 (Squamata: Gekkonidae) from the Shevaroy massif, Tamil Nadu, India, with a preliminary ND2 phylogeny of Indian Cnemaspis

We present a preliminary ND2 phylogeny of South Asian Cnemaspis, recovering a number of deeply divergent clades within Indian Cnemaspis, endemic to the southern and northern Western Ghats besides the Mysore Plateau and hills of Tamil Nadu. There are a number of unnamed lineages that are >5% divergent on ND2 across the phylogeny, including three from the gracilis clade on an elevation gradient (800-1400 m asl.) around Yercaud in the Shevaroy massif, Salem district, Tamil Nadu. We describe two of these as new species- Cnemaspis shevaroyensis sp. nov. and Cnemaspis thackerayi sp. nov. are both allied to Cnemaspis gracilis and can be diagnosed from all other Indian Cnemaspis by the absence of spine-like scales on flank, heterogeneous dorsal pholidosis, presence of femoral and precloacal pores, tail with enlarged, strongly keeled, conical tubercles forming whorls, a median row of enlarged and smooth sub-caudals. They differ from C. gracilis and each other in body size, the number of tubercles around midbody, the number of tubercles in paravertebral rows, the number of femoral and precloacal pores, the number of poreless scales in-between precloacal pores and between femoral and precloacal pores, and subtle colour pattern differences; besides uncorrected mitochondrial sequence divergence (7.9-16.6 %). We also provide a description of Cnemaspis yercaudensis from its type locality and an additional locality. The discovery of two endemic species and a third unnamed divergent lineage from an isolated massif in peninsular India outside the Western Ghats indicate that many other such understudied hill ranges may harbour high endemic biodiversity.

Mitochondrial sequence variants in patients with schizophrenia.

To investigate whether mitochondrial mutations underly susceptibility to schizophrenia, we sequenced the mtDNAs of two unrelated Swedish patients with schizophrenia and low cytochrome oxidase activity and two maternally related Scottish patients from a family with suspected maternal inheritance of the disease. We found five substitutions in coding regions that have not previously been described as polymorphisms. These new substitutions were studied in 81 schizophrenic patients and five control groups from Sweden and Scotland and found to differ in frequency between populations, emphasizing the importance of using large and well-defined control materials for evaluating the association of mtDNA mutations with disease. The results do not lend strong support to the association of a particular mtDNA substitution with increased risk for schizophrenia. However, the trend towards a higher frequency of substitutions in the patients deserves further attention.

Candidate Gene Selection for Cytoplasmic Male Sterility in Pepper (Capsicum annuum L.) through Whole Mitochondrial Genome Sequencing.

Cytoplasmic male sterility (CMS), which is controlled by mitochondrial genes, is an important trait for commercial hybrid seed production. So far, genes controlling this trait are still not clear in pepper. In this study, complete mitochondrial genomes were sequenced and assembled for the CMS line 138A and its maintainer line 138B. The genome size of 138A is 504,210 bp, which is 8618 bp shorter than that of 138B. Meanwhile, more than 214 and 215 open reading frames longer than 100 amino acids (aas) were identified in 138A and 138B, respectively. Mitochondrial genome structure of 138A was quite different from that of 138B, indicating the existence of recombination and rearrangement events. Based on the mitochondrial genome sequence and structure variations, mitochondrion of 138A and FS4401, a Korean origin CMS line, may have inherited from a common female ancestor, but their CMS traits did originate separately. Candidate gene selection was performed according to the published characteristics of the CMS genes, including the presence SNPs and InDels, located in unique regions, their chimeric structure, co-transcription, and transmembrane domain. A total of 35 ORFs were considered as potential candidate genes and 14 of these were selected, with orf300a and 0rf314a as strong candidates. A new marker, orf300a, was developed which did co-segregate with the CMS trait.

Mitochondrial genome sequence variation as a useful marker for assessing genetic heterogeneity among Cyclospora cayetanensis isolates and source-tracking

BackgroundCyclospora cayetanensis is an important enteric pathogen, causing diarrhea and food-borne cyclosporiasis outbreaks. For effective outbreak identification and investigation, it is essential to rapidly assess the genetic heterogeneity of C. cayetanensis specimens from cluster cases and identify the likely occurrence of outbreaks.MethodsIn this study, we developed a quantitative PCR (qPCR) targeting the polymorphic link region between copies of the mitochondrial genome of C. cayetanensis, and evaluated the genetic heterogeneity among 36 specimens from six countries using melt curve, gel electrophoresis, and sequence analyses of the qPCR products.ResultsAll specimens were amplified successfully in the qPCR and produced melt peaks with different Tm values in the melt curve analysis. In gel electrophoresis of the qPCR products, the specimens yielded bands of variable sizes. Nine genotypes were identified by DNA sequencing of the qPCR products. Geographical segregation of genotypes was observed among specimens analyzed, which could be useful in geographical source-tracking.ConclusionsThe length and nucleotide sequence variations in the mitochondrial genome marker allow rapid assessment of the genetic heterogeneity among C. cayetanensis specimens by melt curve, gel electrophoresis, or DNA sequence analysis of qPCR products. The sequence data generated could be helpful in the initial source-tracking of the pathogen.

Mitochondrial gene sequence variants in children with severe malaria anaemia with or without lactic acidosis: a case control study

BackgroundEvolutionary pressure by Plasmodium falciparum malaria is known to have favoured a large number of human gene adaptations, but there is surprisingly little investigation of the effect of malaria on human mitochondrial sequence variation. Plasmodium falciparum infection can cause severe malaria anaemia (SMA) with insufficient tissue oxygenation, lactic acidosis and death. Despite equal degrees of severe anaemia, some individuals develop lactic acidosis while others do not. A case–control study design was used to investigate whether differences in host mitochondrial gene sequences were associated with lactic acidosis in SMA. Full mitochondrial sequences were obtained from 36 subjects with SMA complicated by lactic acidosis and 37 subjects with SMA without lactic acidosis. The two groups were matched for age, sex, and degree of anaemia.ResultsCompared with the reference sequence, a median of 60 nucleotide variants per individual (interquartile range 4–91) was found, with an average frequency of 3.97 variants per 1000 nucleotides. The frequency and distribution of non-synonymous DNA variants in genes associated with oxidative phosphorylation were not statistically different between the two groups. Non-synonymous variants predicted to have the most disruptive effect on proteins responsible for oxidative phosphorylation were present at a similar frequency in both groups.ConclusionsLactic acidosis in SMA does not appear to be consistently associated with the high prevalence of any mitochondrial gene variant.

Mitochondrial genomics in the cancer cell line encyclopedia and a scoring method to effectively pair cell lines for cytoplasmic hybridization

Mitochondrial sequence variants have been associated with many human diseases, including cancer. A well-established experimental strategy to assess the impact of mitochondrial sequence variants is to generate cytoplasmic hybrids (cybrids). Cybridization facilitates the study of mitochondrial DNA (mtDNA) mutations under a controlled nuclear genetic background. However, in generating cybrids, it is important to select most suitable mtDNA donor and recipient cells so that any change in recipient's cellular phenotype may be attributed to the introduction, through the donor, of mutations in the gene of interest. Here we catalog mitochondrial sequence variants, gene expression, and haplogroups across 937 publicly available cancer cell lines curated by the Cancer Cell Line Encyclopedia (CCLE). We then present DoReMi (Donor, Recipient Mitochondrial DNA matching) as a method to score candidate donor and recipient cell lines based on their mtDNA mutational profiles, including their heteroplasmy levels. DoReMi will allow researchers to design successful cybrid experiments for querying the role of mutations in their mitochondrial-encoded gene of interest. Researchers may also apply DoReMi to study their own cell lines. DoReMi and the other resources provided by this study help optimize cybridization experiments. This software is available for use at http://mendel.gene.cwru.edu/laframboiselab/software.php.

High mitochondrial sequence divergence in synanthropic flea species (Insecta: Siphonaptera) from Europe and the Mediterranean

BackgroundAdult fleas are haematophagous ectoparasites of warm-blooded vertebrates, particularly mammals. Among them, the cat flea (Ctenocephalides felis) and the human flea (Pulex irritans) have high veterinary-medical significance, owing to their cosmopolitan distribution and role in the transmission of important vector-borne pathogens. While the taxonomy of Ct. felis has been investigated on a morphological basis during the past decades, its molecular-phylogenetic analyses have been only recently conducted. This study expands the knowledge on Ct. felis from hitherto less studied geographical regions, and includes representatives from additional flea families, less investigated with molecular approaches.MethodsFleas were collected in four countries of the Mediterranean Basin (Croatia, Italy, Malta and Israel), as well as in Hungary, from domestic and wild carnivores, rodents and humans. The DNA extracts of representative fleas (n = 148), belonging to ten species of eight genera, were used for PCR amplification of part of their cytochrome c oxidase subunits 1, 2 (cox1, cox2) and 18S rRNA genes, followed by sequencing and phylogenetic analyses.ResultsThe majority (65.6%) of Ct. felis felis cox2 sequences showed 99.4–100% similarity to each other (haplogroup A), whereas those from Malta and Israel had 98.1–98.7% sequence similarity (haplogroup B), and a third sequence from Israel (haplotype C) had as low as 96.3% sequence similarity in comparison with a reference sequence from group “A”. Except for the shape of the head, no consistent morphological differences (e.g. in chaetotaxy) were found between haplogroups “A” and “C”. Haplotypes of Ct. canis were genetically more homogenous, with 99.6–100% sequence similarity to each other. However, when P. irritans collected from humans was compared to those from three species of wild carnivores, these only had 96.6% cox2 similarity. The mouse flea, Leptopsylla segnis and the northern rat flea, Nosopsyllus fasciatus were both shown to have haplotypes with low intraspecific cox2 similarities (96.2 and 94.4%, respectively). Taken together, differences between mitochondrial lineages within four flea species exceeded that observed between two Chaetopsylla spp. (which had 97.3% cox2 similarity). The topologies of cox1 and cox2 phylogenetic trees were in line with relevant sequence comparisons. Conversely, 18S rRNA gene analyses only resolved differences above the species level.ConclusionsCtenocephalides felis felis, P. irritans, L. segnis and N. fasciatus were shown to have such a high level of mitochondrial gene heterogeneity, that the uniformity of these flea taxa should be reconsidered. Although the present results are limited (especially in the case of L. segnis and N. fasciatus), there appears to be no geographical or host restriction, which could explain the divergence of these genetic lineages.

Two new species of the Ophisops microlepis (Squamata: Lacertidae) complex from northwestern India with a key to Indian Ophisops

ABSTRACTWe describe two new species of the lacertid genus Ophisops based on a series of 19 specimens from semi-arid habitats in the states of Gujarat and Rajasthan in northwestern India, provide a description of Ophisops microlepis sensu stricto, and a key to Indian Ophisops. Ophisops pushkarensis sp. nov. and Ophisops kutchensis sp. nov. are allied to Ophisops microlepis and can be diagnosed from all other Indian Ophisops by the fusion of the lower and upper eyelids, their large body size (snout to vent length > 50 mm), and ≥ 50 scales around midbody. They differ from O. microlepis and each other in the number of scales around midbody, the number of dorsal scales, subtle colour pattern differences, as well as uncorrected mitochondrial sequence divergence (6–9%). These are some of the only known endemic reptiles in these semi-arid landscapes and indicate that many other such habitats may harbour endemic biodiversity.www.zoobank.org/urn:lsid:zoobank.org:pub:3CD04F6F-D699-4100-A462-9BDD4B36FEE2

Population genetic structure and molecular diversity of Leucinodes orbonalis based on mitochondrial COI gene sequences

Leucinodes orbonalis is a destructive pest found throughout eggplant cultivating fields of Tamil Nadu, India. The genetic diversity and its population structure were investigated in this pest using mitochondrial cytochrome c oxidase subunit I (COI) gene sequences from 20 populations of L. orbonalis collected from various agro-climatic conditions. The study indicated almost no genetic diversity among various populations. The COI nucleotide sequence based haplotype analysis also revealed no significant genetic variation among various populations. However, haplotype network analysis with three clades was nearly matching with the structure of phylogenetic analysis that showed geographical separations induced distribution of some genetic variation. The PCA and nMDS Shephard’s plot analyses were also illustrated that the populations sampled were nearly matched with phylogenetic tree and haplotype network. This study on phylogeographical structure using the mitochondrial COI sequence diversity of L. orbonalis therefore suggested presence of few genetically distinct populations due to some specific habitat requirements.

<b>Mitochondrial D-loop sequence variation among Central Javanese Duck in Indonesia

This study was realized to determine the genetic variation of Central Javanese duck based on the D-Loop mtDNA gene. D-loop gene was amplified using PCR technique by specific primer and sequenced using dideoxy termination method with ABI automatic sequencer. ClustalW from MEGA-6.06 software program was employed for multiple alignments of nucleotide sequences. Nucleotide sequences of D-loop gene of mtDMA from the Central Javanese duck were aligned together with other Anas isolates from Genbank using ClustalW of MEGA-6.06 program. The estimation of genetic distance and phylogenetic tree construction were analyzed by Neighbor-Joining method, whereas the calculation of distance matrix was performed using Kimura 2-parameter. Multiple alignments obtained were 720 nucleotides at position 56 to 779 at the 5 'end. The results of the polymorphism analysis on D-loop sequences produced 23 haplotypes. However, this haplotype information does not represent the relationship among the geographical origins of duck with the certain duck species name. Moreover, a total number of 32 variable sites were identified. Insertions were detected in four sequences (126, 155, 771 and 779 nucleotide number). In the phylogenetic analysis, it is safe to conclude that the Central Javanese duck is closely related to Anas platyrhynchos and Anas zonorynchos .

Genetic isolation in an endemic African habitat specialist.

The Chestnut‐banded Plover Charadrius pallidus is a Near‐Threatened shorebird species endemic to mainland Africa. We examined levels of genetic differentiation between its two morphologically and geographically distinct subspecies, C. p. pallidus in southern Africa (population size 11 000–16 000) and C. p. venustus in eastern Africa (population size 6500). In contrast to other plover species that maintain genetic connectivity over thousands of kilometres across continental Africa, we found profound genetic differences between remote sampling sites. Phylogenetic network analysis based on four nuclear and two mitochondrial gene regions, and population genetic structure analyses based on 11 microsatellite loci, indicated strong genetic divergence, with 2.36% mitochondrial sequence divergence between individuals sampled in Namibia (southern Africa) and those of Kenya and Tanzania (eastern Africa). This distinction between southern and eastern African populations was also supported by highly distinct genetic clusters based on microsatellite markers (global FST = 0.309, GST′ = 0.510, D = 0.182). Behavioural factors that may promote genetic differentiation in this species include habitat specialization, monogamous mating behaviour and sedentariness. Reliance on an extremely small number of saline lakes for breeding and limited dispersal between populations are likely to promote reproductive and genetic isolation between eastern and southern Africa. We suggest that the two Chestnut‐banded Plover subspecies may warrant elevation to full species status. To assess this distinction fully, additional sample collection will be needed, with analysis of genetic and phenotypic traits from across the species’ entire breeding range.

Solid-phase microextraction-based cuticular hydrocarbon profiling for intraspecific delimitation in Acyrthosiphon pisum.

Insect cuticular hydrocarbons (CHCs) play critical roles in reducing water loss and chemical communication. Species-specific CHC profiles have been used increasingly as an excellent character for species classification. However, considerably less is known about their potential for population delimitation within species. The aims of this study were to develop a solid-phase microextraction (SPME)-based CHC collection method and to investigate whether CHC profiles could serve as potential chemotaxonomic tools for intraspecific delimitation in Acyrthosiphon pisum. Optimization of fibers for SPME sampling revealed that 7 μm polydimethylsiloxane (PDMS) demonstrated the most efficient adsorption of CHCs among five different tested fibers. SPME sampling showed good reproducibility with repeated collections of CHCs from a single aphid. Validation of SPME was performed by comparing CHC profiles with those from conventional hexane extractions. The two methods showed no qualitative differences in CHCs, although SPME appeared to extract relatively fewer short-chained CHCs. While CHC profiles of a given population differed among developmental stages, wing dimorphism types, and host plants, wingless adult aphids showed very low variance in relative proportions of individual CHC components. Reproducibility of CHC profiles was explored further to classify wingless adult morphs of A. pisum from five different geographic regions that showed no variation in mitochondrial COI gene sequences. Our results demonstrate that CHC profiles are useful in intraspecific delimitation in the field of insect chemotaxonomy.

Molecular phylogenetics of western deer mice (Peromyscus): Taxonomic and biogeographic implications

Abstract The deer mouse species group centers around Peromyscus maniculatus and contains four peripherally distributed species. In order to address phylogenetic, taxonomic, and biogeographic questions concerning the westernmost deer mice, we analyzed mitochondrial sequence variation for 174 specimens from California to Washington and compared these to relevant reference specimens. These analyses confirm the genetic distinction of a clade of physiographically bounded deer mouse populations from Southern and Baja California and the close affinity of this clade to the endangered and island-endemic Peromyscus sejugis. In accordance with the phylogenetic species concept and taxonomic priority, we recommend that all populations currently recognized as Peromyscus maniculatus coolidgei (Baja California) and those of Peromyscus maniculatus gambelii from south of the San Francisco Bay and west of the Sierra Nevada mountains be recognized as Peromyscus gambelii. Despite its low level of mitochondrial sequence diverg...

Historical demography and genetic differentiation of the giant freshwater prawn Macrobrachium rosenbergii in Bangladesh based on mitochondrial and ddRAD sequence variation.

Macrobrachium rosenbergii, the giant freshwater prawn, is an important source of high quality protein and occurs naturally in rivers as well as commercial farms in South and South‐East Asia, including Bangladesh. This study investigated the genetic variation and population structure of M. rosenbergii sampled from four rivers in Bangladesh (sample size ranged from 19 to 20), assessing sequence variation, both in the mitochondrial cytochrome oxidase subunit 1 (CO1) gene and in 106 single nucleotide polymorphisms (SNPs) sampled randomly from the genome with double digest RAD sequencing (ddRADseq). The mitochondrial variation presented a shallow genealogy with high haplotype diversity (h = 0.95), reflecting an expansion in population size for the last ~82 kyr. Based on the CO1 variation the current effective population size (N e) was 9.7 × 106 (CI: 1.33 × 106 – 35.84 × 106) individuals. A significant population differentiation was observed with the mitochondrial CO1 sequence variation and based on the ddRADseq variation, which could be traced to the divergence of the population in the Naf River in the South‐East border with Myanmar from the other populations. A differentiation in mtDNA haplotype frequencies was also observed between the Biskhali River and the Karnaphuli Rivers in eastern Bangladesh. This study demonstrated the use of high‐throughput genotyping based on the ddRADseq method to reveal population structure at a small geographical scale for an important freshwater prawn. The information from this study can be utilized for management and conservation of this species in Bangladesh.

Mitochondrial DNA Mutations in Grade II and III Glioma Cell Lines Are Associated with Significant Mitochondrial Dysfunction and Higher Oxidative Stress.

The role of mitochondria in tumorigenesis has regained much attention as it could dysregulate cellular energetics, oxidative stress and apoptosis. However, the role of mitochondria in different grade gliomasis still unknown. This study aimed to identify mitochondrial DNA (mtDNA) sequence variations that could possibly affect the mitochondrial functions and also the oxidative stress status. Three different grades of human glioma cell lines and a normal human astrocyte cell line were cultured in-vitro and tested for oxidative stress biomarkers. Relative oxidative stress level, mitochondria activity, and mitochondrial mass were determined by live cell imaging with confocal laser scanning microscope using CM-H2DCFDA, MitoTracker Green, and MitoTracker Orange stains. The entire mitochondrial genome was sequenced using the AffymetrixGeneChip Human Mitochondrial Resequencing Array 2.0. The mitochondrial sequence variations were subjected to phylogenetic haplogroup assessment and pathogenicity of the mutations were predicted using pMUT and PolyPhen2. The Grade II astrocytoma cells showed increased oxidative stress wherea high level of 8-OHdG and oxidative stress indicator were observed. Simultaneously, Grade II and III glioma cells showed relatively poor mitochondria functions and increased number of mutations in the coding region of the mtDNA which could be due to high levels of oxidative stress in these cells. These non-synonymous mtDNA sequence variations were predicted to be pathogenic and could possibly lead to protein dysfunction, leading to oxidative phosphorylation (OXPHOS) impairment, mitochondria dysfunction and could create a vicious cycle of oxidative stress. The Grade IV cells had no missense mutation but preserved intact mitochondria and excellent antioxidant defense mechanisms thus ensuring better survival. In conclusion, Grade II and III glioma cells demonstrated coding region mtDNA mutations, leading to mitochondrial dysfunction and higher oxidative stress.

RAD sequencing reveals genomewide divergence between independent invasions of the European green crab (Carcinus maenas) in the Northwest Atlantic.

Genomic studies of invasive species can reveal both invasive pathways and functional differences underpinning patterns of colonization success. The European green crab (Carcinus maenas) was initially introduced to eastern North America nearly 200 years ago where it expanded northwards to eastern Nova Scotia. A subsequent invasion to Nova Scotia from a northern European source allowed further range expansion, providing a unique opportunity to study the invasion genomics of a species with multiple invasions. Here, we use restriction‐site‐associated DNA sequencing‐derived SNPs to explore fine‐scale genomewide differentiation between these two invasions. We identified 9137 loci from green crab sampled from 11 locations along eastern North America and compared spatial variation to mitochondrial COI sequence variation used previously to characterize these invasions. Overall spatial divergence among invasions was high (pairwise FST ~0.001 to 0.15) and spread across many loci, with a mean FST ~0.052 and 52% of loci examined characterized by FST values >0.05. The majority of the most divergent loci (i.e., outliers, ~1.2%) displayed latitudinal clines in allele frequency highlighting extensive genomic divergence among the invasions. Discriminant analysis of principal components (both neutral and outlier loci) clearly resolved the two invasions spatially and was highly correlated with mitochondrial divergence. Our results reveal extensive cryptic intraspecific genomic diversity associated with differing patterns of colonization success and demonstrates clear utility for genomic approaches to delineating the distribution and colonization success of aquatic invasive species.