Phylogeography of the Chionodraco genus (Perciformes, Channichthydae) in the Southern Ocean

Antarctic fish of the suborder Notothenioidei represent one of the most notable examples of adaptive radiation in the marine environment. The evolutionary relationships between and within the eight families of this suborder have been well established by numerous studies, whereas the microevolutionary processes of notothenioid species remain largely unexplored. In the present paper we investigated the evolutionary relationships between three closely related species of the genus Chionodraco (family Channichthyidae), namely Chionodraco hamatus, Chionodraco rastrospinosus, and Chionodraco myersi by analysing portions of the mitochondrial genome (D-loop and 16S rRNA). The taxonomic status of C. hamatus and C. rastrospinosus as separate species has been questioned because of the limited number of key morphological characters that distinguish these two taxa. Our results, based on the analysis of several specimens belonging to both morphological groups revealed a small genetic differentiation among haplotypes, however, a clear separation between the two nominal species emerged since all individuals of each of the two taxa clustered together in distinct monophyletic groups. C. myersi appeared more distantly related in the phylogenetic analysis. For one species, C. hamatus, sampling was carried out at three different geographic locations in the area of the Ross Sea and Weddell Sea. The results showed that the partition of the genetic variation within this species is not compatible with the hypothesis of panmixia as gene flow between populations was significantly reduced.     

Permanent genetic resources added to Molecular Ecology Resources Database 1 October 2010-30 November 2010

This article documents the addition of 277 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Ascochyta rabiei, Cambarellus chapalanus, Chionodraco hamatus, Coptis omeiensis, Cynoscion nebulosus, Daphnia magna, Gerbillus nigeriae, Isurus oxyrinchus, Lates calcarifer, Metacarcinus magister, Oplegnathus fasciatus, Pachycondyla verenae, Phaethon lepturus, Pimelodus grosskopfii, Rotylenchulus reniformis, Scomberomorus niphonius, Sepia esculenta, Terapon jarbua, Teratosphaeria cryptica and Thunnus obesus. These loci were cross-tested on the following species: Austropotamobius italicus, Cambarellus montezumae, Cambarellus puer, Cambarellus shufeldtii, Cambarellus texanus, Chionodraco myersi, Chionodraco rastrospinosus, Coptis chinensis, Coptis chinensis var. brevisepala, Coptis deltoidea, Coptis teeta, Orconectes virilis, Pacifastacus leniusculus, Pimelodus bochii, Procambarus clarkii, Pseudopimelodus bufonius, Rhamdia quelen, Sepia andreana, Sepiella maindroni, Thunnus alalunga, Thunnus albacares, Thunnus maccoyii, Thunnus orientalis, Thunnus thynnus and Thunnus tonggol.     

Phylogenetic position of the adeleorinid coccidia (Myzozoa, Apicomplexa, Coccidia, Eucoccidiorida, Adeleorina) inferred using 18S rDNA sequences

Investigating the evolutionary relationships of the major groups of Apicomplexa remains an important area of study. Morphological features and host-parasite relationships continue to be important in the systematics of the adeleorinid coccidia (suborder Adeleorina), but the systematics of these parasites have not been well-supported or have been constrained by data that were lacking or difficult to interpret. Previous phylogenetic studies of the Adeleorina have been based on morphological and developmental characters of several well-described species or based on nuclear 18S ribosomal DNA (rDNA) sequences from taxa of limited taxonomic diversity. Twelve new 18S rDNA sequences from adeleorinid coccidia were combined with published sequences to study the molecular phylogeny of taxa within the Adeleorina and to investigate the evolutionary relationships of adeleorinid parasites within the Apicomplexa. Three phylogenetic methods supported strongly that the suborder Adeleorina formed a monophyletic clade within the Apicomplexa. Most widely recognized families within the Adeleorina were hypothesized to be monophyletic in all analyses, although the single Hemolivia species included in the analyses was the sister taxon to a Hepatozoon sp. within a larger clade that contained all other Hepatozoon spp. making the family Hepatozoidae paraphyletic. There was an apparent relationship between the various clades generated by the analyses and the definitive (invertebrate) host parasitized and, to lesser extent, the type of intermediate (vertebrate) host exploited by the adeleorinid parasites. We conclude that additional taxon sampling and use of other genetic markers apart from 18S rDNA will be required to better resolve relationships among these parasites.     

Species boundaries and phylogeography of the "Euscorpius carpathicus complex" (Scorpiones: Euscorpiidae) in Italy

Euscorpius tergestinus (C.L. Koch, 1837), Euscorpius concinnus (C.L. Koch, 1837) and Euscorpius sicanus (C.L. Koch, 1837), three presumed closely related species belonging to the "carpathicus group", occur in the Italian peninsula with a largely parapatric distribution and some zones of range overlap. These areas of sympatry represent interesting opportunities to investigate species boundaries in natural populations. Here we report on a study exploring genetic variation in sympatric populations of the three species from central Tuscany. Additional collecting sites, from different localities across Italy, were also included in the analysis in order to explore the phylogeographic structure of the group. Species boundaries and evolutionary relationships were examined by sequence comparison of mitochondrial 16S rRNA and nuclear ITS-1 rRNA gene fragments. DNA sequence data show no evidence of genetic introgression between different evolutionary lineages from the area of range overlap, suggesting the absence of either past or ongoing inter-specific gene flow. It is therefore probable that reproductive barriers exist, preventing gene pools from amalgamating. Furthermore, our results support the recent morphological distinction of E. tergestinus, as traditionally classified, into two different species: E. tergestinus and E. concinnus. Both mitochondrial and nuclear sequence data clearly indicate that the two taxa represent well-supported and deeply divergent lineages. Euscorpius sicanus seems to represent a monophyletic taxon, but the high genetic variability observed within this taxon calls for future investigation. The present distribution patterns across the Italian peninsula were mainly interpreted as the consequence of climatic oscillations.     

DIET OF WEDDELL SEALS LEPTONYCHOTES WEDDELLII AT VESTKAPP, EASTERN WEDDELL SEA (ANTARCTICA), IN RELATION TO LOCAL FOOD SUPPLY

Thirteen Weddell seals ( Leptonychotes weddellii ) were collected at Vestkapp, eastern Weddell Sea coast, in austral spring 1986. All stomachs contained partially digested food. The mean wet weight of stomach contents was 7.5 kg, 3.3% of the. mean body weight of the collected seals. Twelve fish species and three cephalopod species were identified from 372 left otoliths and 25 lower beaks, representing 58.4% of 679 total prey items obtained. Composition by number of total prey was: Chionodraco myersi (15.8%), Trematomus eulepidotus (10.0%), Pagetopsis maculatus (9.7%), Racovitzia glacialis (9.6%) and Cryodraco antarcticus (4.1%). Otoliths of the seven other fish species and beaks of the three cephalopod species together represented 9.1% of total prey numbers. The pooled wet weights calculated from 13 prey species (regressions for two octopod species were not available) amounted to 43.5 kg food mass and represented 44.7% of the combined food mass in all stomachs. Composition by mass was: C. myersi (44.5%), T. eulepidotus (19.8%), squid Psychroteuthis glacialis (8.5%), P. maculates (7.9%), C. antarcticus (7.1%) and R. glacialis (6.2%). The remaining 7 fish species together represented 5.8% by mass. Temporal variation in food availability was apparent. Midwater fish Pleuragramma antarcticum was the staple food of Weddell seals from the same area during the 1985 summer, whereas it was absent in the samples taken in spring 1986. Estimates of fish biomass from net hauls demonstrate a highly variable availability of pelagic food resources for top predators in the Vestkapp area.     

Identification and localization of α- and β-spectrins in oocytes of three Antarctic teleosts: Trematomus bernacchii, Trematomus newnesi (Nototheniidae) and Chionodraco hamatus (Channichthyidae)

The presence and localization of α- and β-spectrins and of the spectrin cross-linking protein actin were investigated, in previtellogenic oocytes of three species of Antarctic teleosts: the two red-blooded nototheniids, Trematomus bernacchii and Trematomus newnesi , and the channichthyid, the ice fish Chionodraco hamatus . Analyses by western blotting indicated that these species had an unusual abundance of spectrin isoforms and that they were characterized by rather low molecular masses. The immunocytochemistry in situ demonstrated that α- and β-spectrins showed a variable pattern of localization that clearly depended on both the species considered and the stage of oocyte differentiation. In particular, the two Trematomus spp. showed a distribution of spectrins absolutely comparable and rather different from that of C. hamatus . The evidences collected confirmed that channichthyids have isolated early from the group of red-blooded species and suggest that in notothenioids significant changes might have occurred in spectrin genes and in their protein products.     

A CHLOROPLAST-DNA PHYLOGENY OF THE WILD PERENNIAL RELATIVES OF SOYBEAN (GLYCINE SUBGENUS GLYCINE): CONGRUENCE WITH MORPHOLOGICAL AND CROSSING GROUPS

Hypotheses of evolutionary relationships among the Australian wild perennial relatives of soybean (Glycine subgenus Glycine) are based largely on patterns of meiotic pairing in intra- and interspecific experimental hybrids. This evidence has indicated a number of genome groupings within the subgenus but has not resolved most phylogenetic relationships. Restriction-endonuclease site variation of chloroplast DNA (cpDNA) within the perennial subgenus is reported here, representing a sampling of approximately 3% of the approximately 150-kilobase plastome. Seven hundred twenty-one unique restriction sites were compared within Glycine using 29 restriction endonucleases; 157 sites varied within the genus. Distance and parsimony methods using these data yielded congruent results, recognizing the existence of three major groups within subgenus Glycine: the species-rich and geographically diverse A clade consisting of G. canescens and related taxa; the B clade, which includes the stoloniferous species; and the C group, containing two species with distinctive curved pods. These results are in general agreement with hypotheses based on genome analysis; inconsistencies involve the inclusion of genetically divergent taxa such as G. falcata in well-supported plastome clades comprised of otherwise interfertile species. Such findings are not unexpected if crossing barriers are considered to be unique features of such anomalous species, paralleling their often numerous morphological and cpDNA autapomorphies. Consideration of cpDNA divergence within the three major clades of subgenus Glycine indicates that the rate of plastome evolution is uncoupled from rates of morphological or ecological diversification.     

Molecular phylogenetics at the population/species interface in cave spiders of the southern Appalachians (Araneae:Nesticidae:Nesticus)

This paper focuses on the relationship between population genetic structure and speciation mechanisms in a monophyletic species group of Appalachian cave spiders (Nesticus). Using mtDNA sequence data gathered from 256 individuals, I analyzed patterns of genetic variation within and between populations for three pairs of closely related sister species. Each sister-pair comparison involves taxa with differing distributional and ecological attributes; if these ecological attributes are reflected in basic demographic differences, then speciation might proceed differently across these sister taxa comparisons. Both frequency-based and gene tree analyses reveal that the genetic structure of the Nesticus species studied is characterized by similar and essentially complete population subdivision, regardless of differences in general ecology. These findings contrast with results of prior genetic studies of cave-dwelling arthropods that have typically revealed variation in population structure corresponding to differences in general ecology. Species fragmentation through both extrinsic and intrinsic evolutionary forces has resulted in discrete, perhaps independent, populations within morphologically defined species. Large sequence divergence values observed between populations suggest that this independence may extend well into the past. These patterns of mtDNA genealogical structure and divergence imply that species as morphological lineages are currently more inclusive than basal evolutionary or phylogenetic units, a suggestion that has important implications for the study of speciation mechanisms.      

Relationships among species inCarex sect.Phyllostachys (Cyperaceae) based on allozyme divergence

Allozyme variation was examined inCarex sect.Phyllostachys (Cyperaceae) to provide insight into phylogenetic relationships hypothesized in an earlier study and to determine the degree of genetic differentiation within and between taxa. Genetic identity values are concordant with the morphological differences found between species. The lowest values are found between species with the greatest morphological dissimilarity. Conversely, the highest values are associated with species pairs distinguished by relatively few morphological differences. Conspecific populations possess high genetic identities, although interpopulation differentiation has characterized the evolutionary history of some species. Geographic patterning is also evident within species, with geographically proximate populations often having the highest identity values. Phylogenetic trees produced using different cladistic methods were poorly supported and varied in their depiction of relationships among species. One cladogram produced using presence/absence allelic data is more or less congruent with a topology recovered from an earlier analysis utilizing molecular and morphological data. The wide- and narrow-scaled clades are maintained as are the sister species pairsC. backii/C. saximontana, C. basiantha/C. superata, andC. jamesii/C. juniperorum. Contrary to the finding of our previous study, however,C. willdenowii is aligned withC. jamesii/C. juniperorum.     

Phylogeny and a revised classification of the Monogenoidea Bychowsky, 1937 (Platyhelminthes)

A hypothesis (CI=57.3%) on the evolutionary relationships of families comprising the class Monogenoidea is proposed based on 141 character states in 47 homologous series and employing phylogenetic systematics. Based on the analysis, three subclasses, the Polyonchoinea, Polystomatoinea and Oligonchoinea, are recognised. The analysis supports independent origins of the Montchadskyellidae within the Polyonchoinea and of the Neodactylodiscidae and Amphibdellatidae within the order Dactylogyridea (Polyonchoinea); the suborder Montchadskyellinea is raised to ordinal status and new suborders Neodactylodiscinea and Amphibdellatinea are proposed to reflect these origins. The Gyrodactylidea (Polyonchoinea) is supported by three synapomorphies and comprises the Gyrodactylidae, Anoplodiscidae, Tetraonchoididae and Bothitrematidae. The analysis supports recognition of the Polystomatoinea comprising Polystomatidae and Sphyranuridae. Evolutionary relationships within the Oligonchoinea indicate independent origins of three ordinal taxa, the Chimaericolidea (monotypic), Diclybothriidea (including Diclybothriidae and Hexabothriidae) and Mazocraeidea (with five suborders). The suborder Mazocraeinea comprises the Plectanocotylidae, Mazocraeidae and Mazoplectidae, and is characterised by two synapomorphies. The suborder Gastrocotylinea, characterised by presence of accessory sclerites in the haptoral sucker, is divided into two infraorders, the monotypic Anthocotylina infraorder novum and Gastrocotylina. Two superfamilies of the Gastrocotylina are recognised, the Protomicrocotyloidea and Gastrocotyloidea; the Pseudodiclidophoridae is considered incertae sedis within the Gastrocotylina. The suborder Discocotylinea comprises the Discocotylidae, Octomacridae and Diplozoidae and is supported by four synapomorphies. The monotypic Hexostomatinea suborder novum is proposed to reflect an independent origin of the Hexostomatidae within the Mazocraeidea. The terminal suborder Microcotylinea comprises four superfamilies, the Microcotyloidea, Allopyragraphoroidea, Diclidophoroidea and Pyragraphoroidea. The analysis supports incorporation of the Pterinotrematidae in the Pyragraphoroidea and rejection of the monotypic order Pterinotrematidea. The following taxa are also rejected for reasons of paraphyly and/or polyphyly: Articulonchoinea, Bothriocotylea, Eucotylea, Monoaxonematidea, Tetraonchidea, Gotocotyloidea, Anchorophoridae and Macrovalvitrematidae. The Sundanonchidae, Iagotrematidae and Microbothriidae were not included in the analysis because of lack of pertinent information regarding character states.     

Allozyme Variation and Genetic Relationships among Species of Cimicifuga (Ranunculaceae) from Korea

Allozyme investigation of the five Cimicifuga taxa in Korea was conducted to assess genetic and clonal diversity within populations and genetic divergence among populations and taxa. Levels of allozyme variation maintained in Korean Cimicifuga taxa were comparable to those for most herbaceous perennials. In general, samples excluding copies of the same multilocus genotype maintained higher levels of genetic diversity than the total samples within populations. Copies of homozygous genotypes at several loci resulting from clonal spread lead to decreased levels of genetic diversity within populations, indicating that clonal reproduction found in Cimicifuga affects population genetic structure. In general, more widely distributed species such as C. dahurica and C. japonica harbored higher levels of allozyme diversity than the other taxa examined. Although two varieties of C. heracleifolia are geographically and reproductively isolated, the genetic and clonal structure of var. bifida seems to resemble var. heracleifolia, indicating that the two varieties may have had a similar evolutionary history. However, the allozyme data strongly indicate that the two morphological types (Groups I and II) of C. simplex should be treated as separate species.     

Relationships and position of the taxa of the subfamily Xiphisterinae in the system of the suborder Zoarcoidei (Perciformes)

Analysis of the nucleotide sequences of mitochondrial and nuclear DNA genes was used to examine the relationships and position of the subfamily Xiphisterinae in the system of the suborder Zoarcoidei. This study showed the genetic heterogeneity of Xiphisterinae and the propriety of its division into two subfamilies: Xiphisterinae with the genera Xiphister and Phytichthys and Cebidichthyinae with the genera Cebidichthys, Dictyosoma, Esselenichthys, and Nivchia. The genetic differences between the two subfamilies were not less, but in some cases even greater than the differences between families within the suborder; therefore, they should be raised to the rank of a family, Xiphisteridae and Cebidichthyidae, and classified not within the superfamily Stichaeoidae but rather as independent taxa of the suborder Zoarcoidei.     

Phylogenetic relationships in the orchid genus Serapias L. based on noncoding regions of the chloroplast genome

A molecular phylogenetic analysis was performed on 14 species of the Mediterranean unrewarding orchid genus Serapias using sequences of four noncoding regions of chloroplast DNA. This study has led to a new interpretation of the evolutionary relationships in this genus. The well-defined phylogenetic tree supports a division of taxa into two main clades, each including two minor groups. The molecular relationships found in this study differ from those defined by traditional systematic morphological assessments. By comparing the variation in sequence to variations in floral traits, we propose that the split in the two main lineages reflects an early differentiation of flower size, perhaps due to the shift from allo- to self-pollination. Conversely, the relationships within each minor group do not reflect floral size variation; therefore, we presume that this diversification resulted from genetic drift, local selection forces, and multiple, independent transitions towards self-pollination and polyploidy.     

Structural features that govern enzymatic activity in carbonic anhydrase from a low-temperature adapted fish, Chionodraco hamatus

The carbonic anhydrase (CA) family of zinc metalloenzymes includes many known isozymes that have different subcellular distributions. The study described here focuses on identification of the structural features that define low-temperature adaptation in a Chionodraco hamatus protein, both for the reaction center, at an atomic level, and for the tertiary structure of the protein. To this aim, an x-ray absorption near-edge spectroscopy/Minuit x-ray absorption near-edge spectroscopy analysis of the reaction center was undertaken for both a structurally characterized human CAII and CA of C. hamatus. Higher structural levels were analyzed by sequence comparison and homology modeling. To establish whether the structural insights acquired in fish CAs are general, theoretical models were generated by homology modeling for three temperate-climate-adapted fish CAs. The measured structural differences between the two proteins are discussed in terms of the differences in the electrostatic potential between human CAII and CA of C. hamatus. We conclude that modulation of the interaction between the catalytic water molecule and the zinc ion could depend on the effect of the electrostatic potential distribution.     

Genetic diversity of Echinacea species based upon amplified fragment length polymorphism markers.

The taxonomy of Echinacea is based on morphological characters and has varied depending on the monographer. The genus consists of either nine species and four varieties or four species and eight varieties. We have used amplified fragment length polymorphisms (AFLP) to assess genetic diversity and phenetic relationships among nine species and three varieties of Echinacea (sensu McGregor). A total of 1086 fragments, of which approximately 90% were polymorphic among Echinacea taxa, were generated from six primer combinations. Nei and Li's genetic distance coefficient and the neighbor-joining algorithm were employed to construct a phenetic tree. Genetic distance results indicate that all Echinacea species are closely related, and the average pairwise distance between populations was approximately three times the intrapopulation distances. The topology of the neighbor-joining tree strongly supports two major clades, one containing Echinacea purpurea, Echinacea sanguinea, and Echinacea simulata and the other containing the remainder of the Echinacea taxa (sensu McGregor). The species composition within the clades differs between our AFLP data and the morphometric treatment offered by Binns and colleagues. We also discuss the suitability of AFLP in determining phylogenetic relationships.     

Systematics of Nothofagus (Nothofagaceae) based on rDNA spacer sequences (ITS): taxonomic congruence with morphology and plastid sequences

Phylogenetic relationships were examined within the southern beech family Nothofagaceae using 22 species representing the four currently recognized subgenera and related outgroups. Nuclear ribosomal DNA sequences encoding the 5.8s rRNA and two flanking internal transcribed spacers (ITS) provided 95 phylogenetically informative nucleotide sites from a single alignment of ~588 bases per species. Parsimony analysis of this variation produced two equally parsimonious trees supporting four monophyletic groups, which correspond to groups designated by pollen type. These topologies were compared to trees from reanalyses of previously reported rbcL sequences and a modified morphological data set. Results from parsimony analysis of the three data sets were highly congruent, with topological differences restricted to the placement of a few terminal taxa. Combined analysis of molecular and morphological data produced six equally parsimonious trees. The consensus of these trees suggests two basal clades within Nothofagus. Within the larger of the two clades, tropical Nothofagus (subgenus Brassospora) of New Guinea and New Caledonia are strongly supported as sister to cool-temperate species of South America (subgenus Nothofagus). Most of the morphological apomorphies of the cupule, fruit, and pollen of Nothofagus are distributed within this larger clade. An area cladogram based on the consensus of combined data supports three trans-Antarctic relationships, two within pollen groups and one between pollen groups. Fossil data support continuous ancestral distributions for all four pollen groups prior to continental drift; therefore, vicariance adequately explains two of these disjunctions. Extinction of trans-Antarctic sister taxa within formerly widespread pollen groups explains the third disjunction; this results in a biogeographic pattern indicative of phylogenetic relationship not vicariance. For the biogeographically informative vicariant clades, area relationships based on total evidence support the recently advanced hypothesis that New Zealand and Australia share a unique common ancestry. Contrary to previous thought, the distribution of extant Nothofagus is informative on the area relationships of the Southern Hemisphere, once precise phylogenetic relationships are placed in the context of fossil data.     

Deciphering primate phylogeny from macromolecular specificities

A problem in deciphering primate phylogeny, morphological convergence between different evolutionary lines, can be overcome by species comparisons of proteins, macromolecules with specificities closely linked to the genetic code in DNA. Various chemical, electrophoretic, and immunological data on serum and tissue proteins in primates are reviewed with respect to their phylogenetic significance. Much of this data deals with protein specificities in the Hominoidea and depicts a particularly close genetic relationship between man and the African apes. Hominoidea, Cercopithecoidea, Ceboidea, and Lorisoidea are characterized by their proteins as monophyletic or natural taxa, even though the conventional subdivisions within several of these superfamilies are not in complete accord with the protein analyses. The protein evidence supports the conventional grouping of Cercopithecoidea with Hominoidea in the infraorder Catarrhini and the grouping of Catarrhini and Platyrrhini (Ceboidea) in the suborder Anthropoidea. Lemuroidea and Lorisoidea appear to be closer to one another than to either Tupaioidea or Anthropoidea and closer to the Anthropoidea than to the Tupaioidea. Comparisons of primate DNA's by Hoyer and coworkers are demonstrating genetic affinities among primates which agree with those deduced from the comparison of protein specificities. Species differences and similarities in the relative amounts of different protein macromolecules reflect the grade relationships of primates, but, unlike the comparisons of amino-acid sequences or antigenic specificities, are not reliable indicators of phyletic affinities. Data on the ratios of M(uscle) to H(eart) type lactate dehydrogenase in a series of primate brains provides a biochemical example of the concept that there are “lower” (primitive) and “higher” (advanced) grades of evolutionary development among the extant primates.     

Genetic differences within and between species of deep-sea crabs (chaceon) from the North Atlantic Ocean

The deep-sea red crab Chaceon quinquedens is a commercially important crustacean on the Atlantic continental shelf and slope of North America. To assess genetic subdivision in C. quinquedens, we examined the nucleotide sequence of the mitochondrial 16S rDNA gene and the internal transcribed spacers (ITS) of the nuclear ribosomal repeat in samples from southern New England and the Gulf of Mexico. We compared those data to sequences from two congeners, a sympatric species from the Florida coast, C. fenneri, and an allopatric eastern Atlantic species, C. affinis. The 16S rDNA data consisted of 379 aligned nucleotides obtained from 37 individuals. The greatest genetic difference among geographical groups or nominal species was between C. quinquedens from southern New England and C. quinquedens from the Gulf of Mexico. Haplotypes from these two groups had a minimum of 10 differences. All 11 C. fenneri samples matched the most common haplotype found in C. quinquedens from the Gulf of Mexico, and this haplotype was not detected in C. quinquedens from southern New England. The three haplotypes of C. affinis were unique to that recognized species, but those haplotypes differed only slightly from those of C. fenneri and C. quinquedens from the Gulf of Mexico. Based on 16S rDNA and ITS data, genetic differences between C. quinquedens from southern New England and the Gulf of Mexico are large enough to conclude that these are different fishery stocks. Our results also indicate that the designation of morphological species within the commercially important genus Chaceon is not congruent with evolutionary history. The genetic similarity of C. affinis from the eastern Atlantic and C. quinquedens from the Gulf of Mexico suggests these trans-Atlantic taxa share a more recent common history than the two populations of "C. quinquedens" that we examined.     

New molecular data for tardigrade phylogeny, with the erection of Paramacrobiotus gen. nov.

Up to few years ago, the phylogenies of tardigrade taxa have been investigated using morphological data, but relationships within and between many taxa are still unresolved. Our aim has been to verify those relationships adding molecular analysis to morphological analysis, using nearly complete 18S ribosomal DNA gene sequences (five new) of 19 species, as well as cytochrome oxidase subunit 1 (COI) mitochondrial DNA gene sequences (15 new) from 20 species, from a total of seven families. The 18S rDNA tree was calculated by minimum evolution, maximum parsimony (MP) and maximum likelihood (ML) analyses. DNA sequences coding for COI were translated to amino acid sequences and a tree was also calculated by neighbour-joining, MP and ML analyses. For both trees (18S rDNA and COI) posterior probabilities were calculated by MrBayes. Prominent findings are as follows: the molecular data on Echiniscidae (Heterotardigrada) are in line with the phylogenetic relationships identifiable by morphological analysis. Among Eutardigrada, orders Apochela and Parachela are confirmed as sister groups. Ramazzottius (Hypsibiidae) results more related to Macrobiotidae than to the genera here considered of Hypsibiidae. Macrobiotidae and Macrobiotus result not monophyletic and confirm morphological data on the presence of at least two large groups within Macrobiotus. Using 18S rDNA and COI mtDNA genes, a new phylogenetic line has been identified within Macrobiotus , corresponding to the ' richtersi-areolatus group'. Moreover, cryptic species have been identified within the Macrobiotus ' richtersi group' and within Richtersius . Some evolutionary lines of tardigrades are confirmed, but others suggest taxonomic revision. In particular, the new genus Paramacrobiotus gen. n. has been identified, corresponding to the phylogenetic line represented by the ' richtersi-areolatus group'.