Phylogeny of hagfish based on the mitochondrial 16S rRNA gene

The phylogenetic relationships among the species belonging to the family Myxinidae are still debatable. The mitochondrial DNA sequences from the large ribosomal RNA gene may be of great value for systematic and phylogenetic studies within families. Partial sequences of the 16S rRNA gene were obtained for comparisons among the following hagfish species, Paramyxine nelsoni, Paramyxine sheni, Paramyxine taiwanae, Paramyxine yangi, Paramyxine cheni, Eptatretus burgeri, Eptatretus stouii, Eptatretus cirrhatus, Myxine glutinosa, Myxine formosana, Myxine circifrons, Myxine sp1, and Myxine sp2. The boundary of four Paramyxine species (P. sheni, P. taiwanae, P. nelsoni, and P. yangi) from 16S rRNA sequences is ambiguous, however, they are valid based on our unpublished isozyme data as well as the gill aperture arrangement pattern. Both NJ and MP trees constructed from the present molecular data indicate that the genus Paramyxine is diphyletic and Eptatretus paraphyletic. The complexity of Eptatretus and Paramyxine in the clade would not be solved until the farther departed P. cheni is included to form a new clade under the genus Eptatretus. The other clade of Myxininae contains but single genus Myxine.     

Review of the Australian hagfishes with description of two new species of Eptatretus (Myxinidae)

This paper revises and updates taxonomic and distributional information about hagfishes (Myxinidae) from Australia. It covers five species of the genus Eptatretus: Eptatretus cirrhatus known from eastern Australia and also distributed around New Zealand, Eptatretus longipinnis endemic to South Australia, Eptatretus strahani originally described from the Philippines and reported here as a new record from Western Australia and two new species described herein as Eptatretus alastairi and Eptatretus gomoni, both from Western Australia. Eptatretus alastairi is distinguished from all congeners by the unique combination of the following characters: six pairs of gill pouches; three‐cusp multicusps on the anterior and posterior rows of cusps; anterior unicusps 9–12; posterior unicusps 8–11; total cusps 48–56; prebranchial pores 13–16; branchial pores 5–6; trunk pores 50–55; tail pores 11–13; total pores 83–88; two bilaterally symmetrical nasal‐sinus papillae in the dorsal surface of the nasal sinus. Eptatretus gomoni is distinguished from all congeners by the unique combination of the following characters: eight pairs of gill pouches; three‐cusp multicusps on the anterior and two‐cusp multicusps on the posterior row of cusps; anterior unicusps 10–11; posterior unicusps 9–10; total cusps 50; prebranchial pores 12–13; branchial pores 7–8; trunk pores 57–58; tail pores 14–15; total pores 91–93; no nasal‐sinus papillae. An identification key for the Australian species of Eptatretus is also provided.     

Review and phylogeny of the New Zealand hagfishes (Myxiniformes: Myxinidae), with a description of three new species

Hagfishes from New Zealand are reviewed and a phylogeny proposed using morphological and genetic data (DNA sequences of cytochrome c oxidase subunit I gene, COI, and the small subunit RNA, 16S). E ptatretus cryptus sp. nov. was previously confused with Eptatretus cirrhatus (Forster in Bloch & Schneider, 1801) because of their similar morphology, and is found from the Three Kings Islands to Stewart Island and in the eastern part of the Chatham Rise (at depths of 96–922 m). E ptatretus poicilus sp. nov. is endemic to the Three Kings Islands, where it is common and associated with soft sediment and deep‐sea coral‐sponge habitats (114–842 m). N eomyxine caesiovitta sp. nov. is a slender hagfish found along the east coast of the North Island south to the Chatham Rise (430–1083 m). A neotype is erected for E. cirrhatus (type locality: Breaksea Sound, Fiordland), occurring widely in New Zealand coastal, shelf, and slope waters (1–922 m), but not at the Three Kings Islands. Eptatetrus goliath Mincarone & Stewart, 2006, Neomyxine biniplicata (Richardson & Jowett, 1951), and Nemamyxine elongata Richardson, 1958 are further described using additional material. Rubicundus eos (Fernholm, 1991) is still only known from the holotype (type locality: Challenger Plateau). Genetic results showed that the New Zealand Eptatretus species form a monophyletic group within the subfamily Eptatretinae, indicating likely speciation from a single common ancestor within the area. E ptatretus poicilus sp. nov. is the sister species of E. cirrhatus, and E . cryptus sp. nov. is closely associated with the clade formed by these two species. Eptatretus goliath is most closely associated with Eptatretus minor Fernholm & Hubbs, 1981 (Gulf of Mexico), these two species basally diverging within New Zealand hagfishes. The endemic genus Neomyxine forms a well‐supported monophyletic group of as yet uncertain position within the phylogenetic tree. A key to the New Zealand hagfishes, fresh colour photographs, distribution maps, and in situ video recordings are presented. © 2015 The Linnean Society of London     

The Olfactory System in the Pacific Hagfishes Eptatretus stoutii,Eptatretus deani,and Myxine circifrons

In front of the olfactory organ in the northeastern Pacific hagfishes Eptatretus stoutii, E. deani, and Myxine circifrons there is a valve that may function to direct water in between the olfactory laminae. In Myxine circifrons the well developed valve is supposed to act alone, whereas the smaller valve in the two species of Eptatretus studied is supposed to act together with the horizontal extensions of the median olfactory lamina. No significant differences were found between the investigated species by ultrastructural examination. In the olfactory epithelium the supporting cells are provided with microvilli and generally contain a great amount of light secretory granules. Both ciliated olfactory receptor cells and microvillous olfactory receptor cells are present. The cilia show a 9 + 0 arrangement of the microtubules with a tendency for a dislocation of one pair of the microtubules toward the center of the cilium. These remarkable features of the olfactory receptor cells, not yet seen in other vertebrates, appear to be a character common to the myxinoid cyclostomes.     

Genetic relationships among species of hagfish revealed by protein electrophoresis

Hagfish species of the genera Myxine, Eptatretus and Paramyxine were analysed for genetic variation by allozyme electrophoresis and isoelectric focusing of general proteins. Large genetic differences were observed between samples of supposed conspecifics of Myxine circifrons from off the Californian coast, and also within one sample of Paramyxine sp. from Sagami Bay, Japan. The results are convincing evidence of the existence of additional sympatric species in these two areas. In general, the highest genetic identities were found between species within the subfamilies Myxininae and Eptatretinae. Within Eptatretinae, the Japanese species Eptatretus burgeri was genetically more similar to Japanese species of Paramyxine than to American species of Eptatretus . Thus, our data indicate that the generic status of Paramyxine should be reconsidered.     

The Different Vascular Patterns of Slime Glands in the Hagfishes,Myxine glutinosa Linnaeus and Eptatretus stouti Lockington A Scanning Electron Microscope Study of Vascular Corrosion Casts*

The vascular patterns of the epidermally derived slime glands of the Atlantic hagfish, Myxine glutinosa, and of the Pacific hagfish, Eptatretus stouti, have been studied by scanning electron microscopy of vascular corrosion casts. In Myxine a simple two-dimensional vascular network sheaths the slime glands, while in Eptatretus there is also a great number of capillary loops of different lengths arising from the sheathing network and extending into the interior of the glands. These basic differences in slime glands vascular patterns are thought to reflect substantially different physiological behaviour of the slime glands in Myxine and Eptatretus.     

Morphological analysis of the hagfish heart. II. The venous pole and the pericardium

The morphological characteristics of the venous pole and pericardium of the heart were examined in three hagfish species, Myxine glutinosa, Eptatretus stoutii, and Eptatretus cirrhatus. In these species, the atrioventricular (AV) canal is long, funnel‐shaped and contains small amounts of myocardium. The AV valve is formed by two pocket‐like leaflets that lack a papillary system. The atrial wall is formed by interconnected muscle trabeculae and a well‐defined collagenous system. The sinus venosus (SV) shows a collagenous wall and is connected to the left side of the atrium. An abrupt collagen‐muscle boundary marks the SV‐atrium transition. It is hypothesized that the SV is not homologous to that of other vertebrates which could have important implications for understanding heart evolution. In M. glutinosa and E. stoutii, the pericardium is a closed bag that hangs from the tissues dorsal to the heart and encloses both the heart and the ventral aorta. In contrast, the pericardium is continuous with the loose periaortic tissue in E. cirrhatus. In all three species, the pericardium ends at the level of the SV excluding most of the atrium from the pericardial cavity. In M. glutinosa and E. stoutii, connective bridges extend between the base of the aorta and the ventricular wall. In E. cirrhatus, the connections between the periaortic tissue and the ventricle may carry blood vessels that reach the ventricular base. A further difference specific to E. cirrhatus is that the adipose tissue associated with the pericardium contains thyroid follicles. J. Morphol. 277:853–865, 2016. © 2016 Wiley Periodicals, Inc.     

Morphological analysis of the hagfish heart. I. The ventricle,the arterial connection and the ventral aorta

We have studied the heart in three species of hagfish: Myxine glutinosa, Eptatretus stoutii, and Eptatretus cirrhatus and report about the morphology of the ventricle, the arterial connection and the ventral aorta. On the whole, the hagfish heart lacks outflow tract components, the ventricle and atrium adopt a dorso‐caudal rather than a ventro‐dorsal relationship, and the sinus venosus opens into the left side of the atrium. This may indicate a “defective” cardiac looping during embryogenesis. The ventral aorta is elongated in M. glutinosa and E. stoutii but sac‐like in E. cirrhatus. The ventricles are entirely trabeculated. The myocytes show a low myofibrillar content and junctional complexes formed by fascia adherens and desmosomes. Gap junctions could not be demonstrated. Myocardial cells in M. glutinosa contain numerous lipid droplets. These droplets are less numerous in E. stoutii and practically absent in E. cirrhatus, suggesting different metabolic requirements. Other cell types present in the ventricle are chromaffin cells and granular leukocytes that contain rod‐shaped granules. The ventricle‐aorta connection is guarded by a bicuspid valve with left and right, pocket‐like leaflets. The leaflets extend from the cranial end of the ventricle into the aorta but the junction is asymmetrical. This junction contains a ganglion‐like structure in E. cirrhatus. The ventral aorta shows endothelial, media, and adventitial layers. The media contains smooth muscle cells surrounded by dense bands formed by tightly‐packed extracellular filaments. In addition, a short number of elastic fibers are observed in M. glutinosa and E. stoutii. Cellular and extracellular elements are more loosely organized in the aorta of E. cirrhatus. The collagenous adventitia contains ganglion‐like cells in the three species. In the absence of nerves, chromaffin and ganglion‐like cells may control the activity of the myocardium and that of the aortic smooth muscle cells, respectively. J. Morphol. 277:326–340, 2016. © 2015 Wiley Periodicals, Inc.     

Redescription of the hagfishes (Myxinidae: Eptatretus) from southern Africa

The hagfishes of the genus Eptatretus (Myxinidae) from southern Africa are known from three poorly studied species: Eptatretus hexatrema, a common species from Namibia and South Africa; Eptatretus profundus, known only from the holotype collected off Cape Point (South Africa); and Eptatretus octatrema, known from two syntypes from the Agulhas Bank (South Africa). Taxonomic, morphological and distributional information about these three species are reviewed and updated based on the examination of additional specimens collected in South African waters. Eptatretus hexatrema differs from all congeners by having six pairs (rarely seven) of gill apertures arranged in a straight line, 3/2 multicusp pattern of teeth, total cusps 44–49, trunk pores 53–60, total pores 93–107, preventral length 45.1–57.4% TL, tail length 11.6–14.3% TL, tail depth 5.7–8.1% TL, and two bilaterally symmetrical nasal-sinus papillae. Eptatretus octatrema differs from all congeners by having usually eight (some specimens with seven) pairs of gill apertures arranged in a straight line, 3/2 multicusp pattern of teeth, 42–46 total cusps, 22–26 prebranchial pores, 63–68 trunk pores, 104–117 total pores, and two bilaterally symmetrical nasal-sinus papillae. Eptatretus profundus differs from all congeners by having five pairs of gill apertures arranged in a straight line, 3/2 multicusp pattern of teeth, total cusps 42–46, prebranchial pores 12–15, branchial pores 4–5, trunk pores 48–52, tail pores 15–17, total pores 81–86, and body depth at PCD 7.0–9.7% TL. An identification key for the hagfishes from southern Africa is provided and the conservation status of E. octatrema, a species considered to be Critically Endangered, is discussed in light of the new findings.     

Panbiogeographical analysis of distribution patterns in hagfishes (Craniata: Myxinidae)

Aim To analyse the worldwide distribution patterns of hagfishes using panbiogeographical track analysis, and to attempt to correlate these patterns with the tectonic history of the ocean basins. Location Atlantic and Pacific oceans. Method The distributions of 47 out of 70 species of hagfish (in the genera Eptatretus, Myxine, Nemamyxine, Neomyxine, and Paramyxine) were studied by the panbiogeographical method of track analysis. The analysis was performed using distributional data obtained from the collections included in the Ocean Biogeographic Information System (OBIS, http://www.iobis.org ) and FishBase ( http://www.fishbase.org ), with additional records from the literature. Individual tracks were obtained for each species by plotting localities and connecting them by minimum‐spanning trees. Generalized tracks were determined from the spatial overlap between individual tracks. Results Six generalized tracks were found: in the Gulf of Mexico, Caribbean Sea, South‐eastern Atlantic, Western Pacific, North‐eastern Pacific and South‐eastern Pacific. Main conclusions The distribution patterns of myxinids are marked by a high degree of endemism and vicariance, and are correlated with the tectonic features involved in many of the events that led to the development of oceanic basins. The main massing of the group is around the Pacific Basin. In the Atlantic Ocean, the distribution of Myxine glutinosa seems to correspond to a classic trans‐oceanic track and vicariance resulting from the opening of the Atlantic Ocean during the Cretaceous. In the Pacific Ocean, the distribution of the Eptatretus and Paramyxine species is clearly associated with the margins of the Pacific tectonic plate. The generalized tracks of hagfishes are shared by several other groups of marine organisms, including many from shallow tropical waters, implying a common history for this marine biota. Overall, vicariance is a major feature of hagfish distribution, suggesting vicariant differentiation of widespread ancestors as a result of sea‐floor spreading between continents in connection with ocean formation.     

Variability in the Presence of Elastic Fibre-like Structures in the Ventral Aorta of Agnathans (Hagfishes and Lampreys)

This paper investigates whether elastic fibre-like structures are present in the ventral aorta of hagfishes and lampreys. Fibres, which are morphologically similar to the elastic fibres of gnathostomatous (jawed) vertebrates, are shown to be present in the ventral aorta of the hagfish Paramyxine atami, and also, but to a lesser extent, the dorsal aorta of this species and the ventral aorta of another hagfish, Eptatretus stouti.The ‘elastic’ tissue formed irregular sheet-like aggregates, comprising well-defined amorphous material surrounded by tubular microfibrils, whose diameters ranged from 10 to 15 nm. While this tissue was most abundant in the same region of the aortae as that occupied by the elastica interna in the blood vessels of gnathostomes, it was also found deeper in the wall of these blood vessels. Although tubular microfibrils were found in the ventral aorta of the hagfish Myxine glutinosaand the lamprey Geotria australis, these were never associated with well–defined, amorphous material. This parallels the results of previous studies on Myxine glutinosaand another species of lamprey, Petromyzon marinus.Thus, the elastic fibre–like tissues found in the ventral aortae of P. atamiand E. stoutiprovide the first examples of such structures in this region in agnathan vertebrates.     

Eptatretus eos: A new species of hagfish (Myxinidae) from the Tasman Sea

A new species of hagfish (Myxinidae),Eptatretus eos, is described on the basis of one specimen from the Tasman Sea, west of New Zealand. This five-gilled, deep-sea species differs from previously described hagfish in having the unpaired nostril prolonged into a tube-like snout and in being uniformly pink.     

Exploring phylogenetic informativeness and nuclear copies of mitochondrial DNA (numts) in three commonly used mitochondrial genes: mitochondrial phylogeny of peppermint,cleaner, and semi‐terrestrial shrimps (Caridea: Lysmata,Exhippolysmata, and Merguia)

Of paramount importance to studies that profit from molecular trees is the accuracy and robustness of the reconstructed phylogenies. Causes of systematic error that can mislead phylogenetic methods include nuclear copies of mitochondrial DNA (numts) and low phylogenetic informativeness (PI). Herein, numts and PI were explored in three mitochondrial genes commonly used for phylogenetic reconstruction: 16S, 12S, and cytochrome c oxidase I (COI). Shrimps from the genera Lysmata, Exhippolysmata, and Merguia were used as a model system. The existence of: (1) multiple bands on gels of COI and 12S polymerase chain reaction (PCR) products from various species; (2) double peaks, background noise, and ambiguity in sequence chromatograms of COI and 12S PCR products that produced a single clear band in other species; and (3) indels, stop codons, and considerable composition bias in COI‐like cloned sequences of one problematic species (Lysmata seticaudata), was interpreted as evidence of pervasive non‐functional nuclear copies of mitochondrial DNA (numts) of the targeted COI (and probably 12S) mtDNA fragment. The information content of the three mtDNA markers studied was investigated using PI profiling, spectral analysis, and neighbour‐nets. Marker‐specific PI profiles suggested that the COI marker has the highest information content and greatest power for resolving both shallow and deep nodes in trees depicting the phylogenetic relationship among the species studied. Nonetheless, spectral analysis of splits and neighbour‐nets suggested that the 16S and 12S markers were equally or even more powerful than the COI marker for resolving nodes at all phylogenetic levels. Altogether, these analyses suggest that all three mtDNA markers are equally useful for resolving phylogenetic relationships in the shrimps studied, and that PI profiling is not necessarily useful to estimate overall gene utility. A ‘total‐evidence’ phylogenetic analysis that included 34 species and used a concatenated data set of 1403 characters (from reliable 16S, 12S and COI sequences), demonstrated that the genus Lysmata is paraphyletic, and that the monophyletic clade comprising species of Lysmata and Exhippolysmata can be divided into four well‐supported subclades (Neotropical, Cleaner, Cosmopolitan, and Morphovariable). © 2013 The Linnean Society of London     

A molecular phylogeny of the checkered beetles and a description of Epiclininae a new subfamily (Coleoptera: Cleroidea: Cleridae)

We provide the first molecular phylogeny of the clerid lineage (Coleoptera: Cleridae, Thanerocleridae) within the superfamily Cleroidea to examine the two most recently proposed hypotheses of higher level classification. Phylogenetic relationships of checkered beetles were inferred from approximately ～5000 nt of both nuclear and mitochondrial rDNA (28S, 16S and 12S) and the mitochondrial protein‐coding gene COI. A worldwide sample of ～70 genera representing almost a quarter of generic diversity of the clerid lineage was included and phylogenies were reconstructed using Bayesian and Maximum Likelihood approaches. Results support the monophyly of many proposed subfamilies but were not entirely congruent with either current classification system. The subfamilial relationships within the Cleridae are resolved with support for three main lineages. Tillinae are supported as the sister group to all other subfamilies within the Cleridae, whereas Thaneroclerinae, Korynetinae and a new subfamily formally described here, Epiclininae subf.n ., form a sister group to Clerinae + Hydnocerinae.     

Follicles in the Endocrine Pancreas of Some Myxinoid Species

A light microscopic study of the endocrine pancreas in some myxinoids has revealed a striking difference in the occurrence of follicles. Islet tissue follicles are regularly occurring and also abundant in Myxine glutinosa, but are sparse or absent in Eptatretus burgeri and Eptatretus stouti. Whether this is caused by a decreased need for insulin in Myxine glutinosa is discussed but remains an open question.     

Highly repetitive DNA sequences that are restricted to the germ line in the hagfish Eptatretus cirrhatus: a mosaic of eliminated elements

The New Zealand hagfish, Eptatretus cirrhatus, is known to eliminate parts of its chromosomes during embryogenesis from presumptive somatic cells. Electrophoresis of germ line and somatic DNAs of this species, after treatment with the restriction endonucleases DraI and EcoRI, revealed three fragments of DNA that were restricted to the germ line. DNA filter hybridization experiments demonstrated that these fragments were present almost exclusively in the germ line DNA of E. cirrhatus and that they were highly and tandemly repeated. Thus, these DNA fragments appeared to be eliminated during embryogenesis. Moreover, one fragment (a DraI fragment) cross-hybridized with the germ line DNA from other species of hagfish, namely, Eptatretus okinoseanus and Paramyxine atami. Molecular cloning and sequence analysis revealed that the DraI fragment was composed mainly of closely related sequences of 85 bp in length and that this sequence was about 75% homologous to the sequence of EEEo2 (eliminated element of E. okinoseanus 2) which is a germ line-restricted and highly repetitive sequence that was isolated previously from E. okinoseanus. The other two fragments were composed of three families of closely related sequences that were 172 bp long (designated EEEc1), 61 bp long (EEEc2) and 54 bp long (EEEc3). Fluorescence in situ hybridization experiments revealed that each eliminated element was distributed on several chromosomes that are limited to germ cells. EEEo2 was dispersed on 12 C-band-positive chromosomes. EEEc1 and EEEc3 were dispersed on all C-band-positive and several C-band-negative chromosomes. By contrast, EEEc2 was located to terminal regions of several C-band-negative chromosomes. These results suggest that the eliminated chromosomes in hagfish are mosaics of highly repeated, germ line-restricted families of DNA sequences. Received: ██; in revised form: 25 October 1997 / Accepted: ██     

Phylogenetic analyses of the isonychiid mayflies (Ephemeroptera: Isonychiidae) in the northeast palearctic region

We investigated the molecular phylogeny of isonychiid mayflies inhabiting the East Palearctic region, Isonychia (Isonychia) japonica, Isonychia (Isonychia) ignota, Isonychia (Isonychia) ussurica and Isonychia (Prinoides) shima. We discuss their genetic structures, phylogeny and phylogeography. We collected a total of 100 specimens of isonychiid mayfly species from 47 localities of the Northeast Palearctic region (the Japanese archipelago, the Korean peninsula, the Russian Far East and Mongolia). We analyzed the DNA sequences at the mtDNA COI and 16S rRNA regions, and the nuDNA Histone H3 region. As a result of our genetic analyses of the four Northeast Palearctic isonychiid mayflies, their monophyly at the species level was supported by both the mtDNA (COI and 16S rRNA regions) and the nuDNA (Histone H3 region). In addition, it also became clear that significantly large genetic differentiation exists at the inter‐species level; thus, the relationship of “shima + (japonica + (ignota + ussurica))” is supported. Among the four isonychiid mayflies of the Northeast Palearctic area, I. (P.) shima was shown to be a basal‐most linage within the included species     

Phylogeny,phylogeography, and systematics of the American pea crab genus Calyptraeotheres Campos, 1990, inferred from molecular markers

We used mitochondrial cytochrome oxidase I (COI) and the large ribosomal subunit (16S) genes to establish evolutionary relationships amongst species of Calyptraeotheres, evaluate their usefulness as DNA‐barcoding genes, and assess molecular diversity at the population level within Calyptraeotheres garthi. Bayesian, maximum likelihood, and maximum parsimony phylogenies confirmed the monophyly of Calyptraeotheres, showing that the ancestor of C. garthi, Calyptraeotheres hernandezi, and Calyptraeotheres granti radiated after the formation of the Panamanian isthmus. This finding contradicts the austral/tropical hypothesis previously proposed based on morphological data. The COI and 16S distance matrices supported separation of species as well as the genera, and corroborated that DNA barcoding is a useful tool and complements the classical taxonomy in Pinnotheridae. Phylogenetic and genetic distance analyses suggested that C. hernandezi is a junior synonym of C. garthi. Finally, C. garthi did not show a population structure across its distribution range, and showed a pattern consistent with a recent population expansion event that began 230–300 Kya. © 2013 The Linnean Society of London     

Phylogeography of the cold‐water barnacle Chthamalus challengeri in the north‐western Pacific: effect of past population expansion and contemporary gene flow

Aim Phylogeographical patterns of marine organisms in the north‐western Pacific are shaped by the interaction of past sea‐level fluctuations during glacial maxima and present‐day gene flow. This study examines whether observed population differentiation in the barnacle Chthamalus challengeri, which is endemic to the north‐western Pacific, can be explained by the interactions between historical glacial events and patterns of contemporary gene flow. Location Eleven locations in the north‐western Pacific. Methods Partial sequences of mitochondrial cytochrome c oxidase subunit I (COI), 12S, 16S and nuclear internal transcribed spacer 1 (ITS1) were obtained from 312 individuals. Parsimony haplotype networks and analysis of molecular variance (AMOVA) were used to determine whether the observed genetic structure corresponds to marine provinces (Kuroshio Current and China Sea Coastal Provinces), zoogeographical zones (oriental and Japan warm‐temperate zones) and/or potential refugial areas (Sea of Japan and East China Sea) in the north‐western Pacific. Neutrality tests, mismatch distribution analysis and Bayesian skyline plots were used to infer the demographic history of C. challengeri. Results In total, 312, 117, 182 and 250 sequences were obtained for COI, 12S, 16S and ITS1, respectively. A panmictic population was revealed, which did not conform to the ‘isolation by distance’ model. None of the a priori population groupings based on marine provinces, zoogeographical zones or potential refugial areas was associated with observed genetic patterns. Significant negative values from neutrality tests and the unimodal mismatch distribution and expansion patterns in Bayesian skyline plots for the COI and 16S data sets indicate a population expansion in the mid‐Pleistocene (c. 200 ka). Information from the fossil record suggests that there has been a northward range shift of this species from the East China Sea or the Palaeo‐Pacific coast of Japan to the Sea of Japan since the mid‐Pleistocene. Main conclusions Chthamalus challengeri has experienced a population expansion and range shift since the mid‐Pleistocene. The observed lack of population differentiation can be explained by this past population expansion and present‐day wide‐scale larval dispersal (owing to the long planktonic larval duration) across marine provinces, which have led to the successful establishment of the species in different zoogeographical zones and habitats.     

Molecular systematics of Scaphirhynchinae: an assessment of North American and Central Asian Freshwater Sturgeon Species

The sturgeon subfamily Scaphirhynchinae contains two genera of obligate freshwater sturgeon: Scaphirhynchus and Pseudoscaphirhynchus, from North America and Central Asia, respectively. Both genera contain morphologically variable species. A novel data set containing multiple individuals representing four diagnosable morphological variants for two species of Pseudoscaphirhynchus, P. hermanni and P. kaufmanni, was generated. These data were used to test taxonomic hypotheses of monophyly for the subfamily Scaphirhynchinae, monophyly of both Scaphirhynchus and Pseudoscaphirhynchus, monophyly of P. hermanni and P. kaufmanni, and monophyly of the recognized morphological variants. Monophyly of the subfamily Scaphirhynchinae is consistently rejected by all phylogenetic reconstruction methodologies with the molecular character set while monophyly of both river sturgeon genera is robustly supported. The molecular data set also rejects hypotheses of monophyly for sampled species of Pseudoscaphirhynchus as well as monophyly for the recognized intraspecific morphological variants. Interestingly both Scaphirhynchus and Pseudoscaphirhynchus demonstrate the same general pattern in reconstructed topologies; a lack of phylogenetic structure in the clade with respect to recognized diversity. Despite rejection of monophyly for the subfamily Scaphirhynchinae with molecular data, reconstructed hypotheses from morphological character sets consistently support monophyly for this subfamily. Disparities among the data sets, as well as reasons for rejection of monophyly for Scaphirhynchinae and species of Scaphirhynchus and Pseudoscaphirhynchus with molecular characters are examined and a decreased rate of molecular evolution is found to be most consistent with the data.