Johann-Wolfgang Wägele

Molecular species identification of Central European ground beetles (Coleoptera: Carabidae) using nuclear rDNA expansion segments and DNA barcodes

BackgroundThe identification of vast numbers of unknown organisms using DNA sequences becomes more and more important in ecological and biodiversity studies. In this context, a fragment of the mitochondrial cytochrome c oxidase I (COI) gene has been proposed as standard DNA barcoding marker for the identification of organisms. Limitations of the COI barcoding approach can arise from its single-locus identification system, the effect of introgression events, incomplete lineage sorting, numts, heteroplasmy and maternal inheritance of intracellular endosymbionts. Consequently, the analysis of a supplementary nuclear marker system could be advantageous.ResultsWe tested the effectiveness of the COI barcoding region and of three nuclear ribosomal expansion segments in discriminating ground beetles of Central Europe, a diverse and well-studied invertebrate taxon. As nuclear markers we determined the 18S rDNA: V4, 18S rDNA: V7 and 28S rDNA: D3 expansion segments for 344 specimens of 75 species. Seventy-three species (97%) of the analysed species could be accurately identified using COI, while the combined approach of all three nuclear markers provided resolution among 71 (95%) of the studied Carabidae.ConclusionOur results confirm that the analysed nuclear ribosomal expansion segments in combination constitute a valuable and efficient supplement for classical DNA barcoding to avoid potential pitfalls when only mitochondrial data are being used. We also demonstrate the high potential of COI barcodes for the identification of even closely related carabid species.

Multiple origins of deep-sea Asellota (Crustacea: Isopoda) from shallow waters revealed by molecular data

The Asellota are a highly variable group of Isopoda with many species in freshwater and marine shallow-water environments. However, in the deep sea, they show their most impressive radiation with a broad range of astonishing morphological adaptations and bizarre body forms. Nevertheless, the evolution and phylogeny of the deep-sea Asellota are poorly known because of difficulties in scoring morphological characters. In this study, the molecular phylogeny of the Asellota is evaluated for 15 marine shallow-water species and 101 deep-sea species, using complete 18S and partial 28S rDNA gene sequences. Our molecular data support the monophyly of most deep-sea families and give evidence for a multiple colonization of the deep sea by at least four major lineages of asellote isopods. According to our molecular data, one of these lineages indicates an impressive radiation in the deep sea. Furthermore, the present study rejects the monophyly of the family Janiridae, a group of plesiomorphic shallow-water Asellota, and several shallow-water and deep-sea genera (Acanthaspidia, Ianthopsis, Haploniscus, Echinozone, Eurycope, Munnopsurus and Syneurycope).

On the reproductive biology of Ceratoserolis trilobitoides (crustacea: isopoda): Latitudinal variation of fecundity and embryonic development

SummaryThe embryonic development of Ceratoserolis trilobitoides (Crustacea: Isopoda) is described. It is estimated that breeding lasts nearly 2 years. In comparison with non-polar isopods 3 causes for the retardation of embryonic development are discussed: genetically fixed adaptations to the polar environment, the physiological effect of temperature and the effect of egg size. The latter seems to be of minor importance. Intraspecific variations of fecundity are found in populations from the Weddell Sea, the largest eggs occur in the coldest region. The distribution of physiological races corresponds to the distribution of morphotypes.

Description of the postembryonal stages of the Antarctic fish parasiteGnathia calva Vanhöffen (Crustacea: Isopoda) and synonymy withHeterognathia Amar & Roman

SummaryThe postembryonal stages ofGnathia calva Vanhöffen 1914 (Crustacea: Isopoda: Gnathiidea) are described. The setation of antennae, pereopods and tail fan does not change much during development from the first praniza to the adult animals, while mouthparts, pleopods and habitus show the typical gnathiid sexual dimorphism. For the first time an immature male is described. It is identical with the stage on which the genusHeterognathia Amar and Roman was erected; the latter is therefore considered to be a junior synonym ofGnathia Leach.G. calva is very frequent in the benthos of the upper 500 m of the Weddell Sea. It had formerly often been overlooked because it lives in sponges.

Polymorphism and distribution of Ceratoserolis trilobitoides (Eights, 1833) (Crustacea, Isopoda) in the Weddell Sea and synonymy with C. cornuta (Studer, 1879)

SummaryA rich collection of Ceratoserolis trilobitoides from the Antarctic Peninsula and the western and southern Weddell Sea is evaluated to describe the polymorphism and variations of the pigmentation. The species is very variable, though local populations show a relatively homogenous morphology. Transitional forms connect different morphotypes. Presumably the relative immobility of these animals, together with low fecundity and geographical or hydrographical barriers are responsible for the evolution of local races. C. cornuta and the “colour-spcies” of Cals (1977) are synonymized with C. trilobitoides.

Growth in captivity and aspects of reproductive biology of the Antarctic fish parasite Aega antarctica (Crustacea, Isopoda)

SummarySpecimens of the fish parasite Aega antarctica caught in the Weddell Sea and off the South Shetlands and South Orkneys were kept in aquaria for more than 2 years. These isopods were fed with plaice (Pleuronectes platessa) from the North Sea. Growth in captivity was very slow. For the first growth phase before reaching sexual maturity of females the value K = 0.12 was calculated for the Bertalanffy growth constant. Mature males are markedly smaller than breeding females (average lengths: 16.0 and 22.5 mm). An age of more than 5 years was calculated for an average-sized male, females spawn at an age of more than 10 years. No evidence for protandric hermaphroditism could be found.

Phylogenetic analysis of the mitochondrial genes LSU rRNA and COI suggests early adaptive differentiation of anal teeth in chrysidine cuckoo wasps (Hymenoptera: Chrysididae)

Cuckoo wasps are a morphologically diverse group of Hymenoptera with parasitoid or cleptoparasitic life histories. In the present paper, we explore the phylogenetic signal in fragments of the mitochondrial genes LSU rRNA and COI to resolve the groups phylogeny. We analyzed sequence data of 33 species representing the taxa Cleptinae, Elampini, Parnopini, and Chrysidini. Most of the currently recognized relationships of major cuckoo wasp lineages are supported by the molecular data. A key difference concerns the phylogenetic position of the Euchroeus (=Brugmoia) group within the tribe Chrysidini. It seems likely that an erroneous interpretation of morphological characters has led to inappropriate rooting of that tribe. We suggest that species of the Euchroeus group be interpreted as forming the stem group of the Chrysidini and that the remaining genera of that tribe be united in a subordinated taxon. Our results imply that the evolution of anal dentition, of significance for breaking into sealed host nests otherwise not accessible to cuckoo wasps, already happened at the base of the Chrysidini and that an even number of anal teeth arose prior to an odd number.

Searching factors causing implausible non-monophyly: ssu rDNA phylogeny of Isopoda Asellota (Crustacea: Peracarida) and faster evolution in marine than in freshwater habitats.

This contribution addresses two questions: which alignment patterns are causing non-monophyly of the Asellota and what is the phylogenetic history of this group? The Asellota are small benthic crustaceans occurring in most aquatic habitats. In view of the complex morphological apomorphies known for this group, monophyly of the Asellota has never been questioned. Using ssu rDNA sequences of outgroups and of 16 asellote species from fresh water, littoral marine habitats and from deep-sea localities, the early divergence between the lineages in fresh water and in the ocean, and the monophyly of the deep-sea taxon Munnopsidae are confirmed. Relative substitution rates of freshwater species are much lower than in other isopod species, rates being highest in some littoral marine genera (Carpias and Jaera). Furthermore, more sequence sites are variable in marine than in freshwater species, the latter conserve outgroup character states. Monophyly is recovered with parsimony methods, but not with distance and maximum likelihood analyses, which tear apart the marine from the freshwater species. The information content of alignments was studied with spectra of supporting positions. The scarcity of signal (=apomorphic nucleotides) supporting monophyly of the Asellota is attributed to a short stem-line of this group or to erosion of signal in fast evolving marine species. Parametric boostrapping in combination with spectra indicates that a tree model cannot explain the data and that monophyly of the Asellota should not be rejected even though many topologies do not recover this taxon.

Protognathia n. gen. bathypelagica (Schultz, 1977) rediscovered in the Weddell Sea: A missing link between the Gnathiidae and the Cirolanidae (Crustacea, Isopoda)

SummaryA new genus (Protognathia) and family (Protognathiidae) are described for Cirolana bathypelagica Schultz, 1977. The morphology of this unique species proves that the Gnathiidae are closely related to the Cirolanidae. The characters of P. bathypelagica are intermediate between the carnivorous cirolanids and the highly specialized gnathiid fish parasites.

Redescriptions of Cymodocella tubicauda Pfeffer 1887 and Exosphaeroma gigas (Leach 1818) (Crustacea, Isopoda, Sphaeromatidae)

Detailed redescriptions of the poorly known isopods Cymodocella tubicauda Pfeffer 1887 and Exosphaeroma gigas (Leach 1818) are presented in order to allow easier identification of these two species. Similarities to and differences from other species of the genus are discussed.