Separating historic events from recurrent processes in cryptic species: phylogeography of mud snails (Hydrobia spp.)

The present study combines methods that were designed to infer intraspecific relationships (e.g. nested-clade analysis (NCA), mismatch distributions and maximum likelihood gene flow analysis) to analyse historic events and recurrent processes in the cryptic mud snail species Hydrobia acuta and H. glyca. Specifically, we test the proposed allopatry of cryptic species and whether the peculiar range-subdivision of the putative subspecies H. a. acuta and H. a. neglecta is a result of long-distance dispersal or continuous range expansion. The NCA indicates a past fragmentation of the two H. acuta subspecies as well as past fragmentations within H. glyca. Gene-flow analyses show extensive gene flow in an E-W direction (towards the Atlantic) in the Mediterranean H. a. acuta, generally low gene flow in a W-E direction in the Atlantic H. a. neglecta and complex gene-flow pattern in a N-S but also in a S-N direction (against the Gulf Stream) in H. glyca. Based on these data and supportive ecological and oceanographical data, we hypothesize that the separation of the two H. acuta subspecies was not caused by long-distance dispersal but by a range shift and/or range expansion of the closely related competitor H. glyca as a result of an interglacial warming with a subsequent range shift in H. acuta. Moreover, our data do not show evidence for a long-term, stable sympatry of Hydrobia species, supporting the concept of allopatric relationships within cryptic radiations. NCA and gene-flow analyses indicate that the only sympatric population found in our study is the result of a recent dispersal event from the nearby Mediterranean. It is assumed that allopatric relationships in ephemeral Hydrobia populations constitute an evolutionary advantage relative to competition, recruitment and re-establishment of habitats. Mechanisms that could be of relevance for maintaining allopatry are discussed.

Effects of climate-driven temperature changes on the diversity of freshwater macroinvertebrates

Increasing temperatures due to climate change were found to influence abundance and timing of species in numerous ways. Whereas many studies have investigated climate-induced effects on the phenology and abundance of single species, less is known about climate-driven shifts in the diversity and composition of entire communities. Analyses of long-term data sets provide the potential to reveal such relationships. We analysed time series of entire communities of macrozoobenthos in lakes and streams in Northern Europe. There were no direct linear effects of temperature and climate indices (North Atlantic Oscillation index) on species composition and diversity, but using multivariate statistics we were able to show that trends in average temperature have already had profound impacts on species composition in lakes. These significant temperature signals on species composition were evident even though we analysed comparatively short time periods of 10-15 years. Future climate shifts may thus induce strong variance in community composition.

Phenotypic evolution and hidden speciation in Candidula unifasciata ssp. (Helicellinae, Gastropoda) inferred by 16S variation and quantitative shell traits

In an effort to link quantitative morphometric information with molecular data on the population level, we have analysed 19 populations of the conchologically variable land snail Candidula unifasciata from across the species range for variation in quantitative shell traits and at the mitochondrial 16S ribosomal (r)DNA locus. In genetic analysis, including 21 additional populations, we observed two fundamental haplotype clades with an average pairwise sequence divergence of 0.209 +/- 0.009 between clades compared to 0.017 +/- 0.012 within clades, suggesting the presence of two different evolutionary lineages. Integrating additional shell material from the Senckenberg Malacological Collection, a highly significant discriminant analysis on the morphological shell traits with fundamental haplotype clades as grouping variable suggested that the less frequent haplotype corresponds to the described subspecies C. u. rugosiuscula, which we propose to regard as a distinct species. Both taxa were highly subdivided genetically (FST = 0.648 and 0.777 P < 0.001). This was contrasted by the partition of morphological variance, where only 29.6% and 21.9% of the variance were distributed among populations, respectively. In C. unifasciata, no significant association between population pairwise FST estimates and corresponding morphological fixation indices could be detected, indicating independent evolution of the two character sets. Partial least square analysis of environmental factors against shell trait variables in C. u. unifasciata revealed significant correlations between environmental factors and certain quantitative shell traits, whose potential adaptational values are discussed.

The complete mitochondrial genome of Radix balthica (Pulmonata, Basommatophora), obtained by low coverage shot gun next generation sequencing

A 454-FLX low-coverage sequencing approach was used to assemble the mitochondrial genome of Radix balthica. The mtDNA sequence is 13,993 nt long and contains 37 genes (13 protein coding genes, two rRNAs and 22 tRNAs). Four genes, the 12S RNA and seven tRNAs are transcribed in reverse order. The sequence is AT rich (71.3%), similar to other basommatophoran species. Comparison with the most closely related mt genomes available (Biomphalaria glabrata and Biomphalaria tenagophila) revealed identical gene orders except for five tRNAs. Next generation sequencing proved to be a fast and easy method for sequencing an entire mitochondrial genome.

A voyage to Terra Australis: human-mediated dispersal of cats

BACKGROUND

Cats have been transported as human commensals worldwide giving rise to many feral populations. In Australia, feral cats have caused decline and extinction of native mammals, but their time of introduction and origin is unclear. Here, we investigate hypotheses of cat arrival pre- or post-European settlement, and the potential for admixture between cats of different invasion events. We analyse the genetic structure and diversity of feral cats from six locations on mainland Australia, seven Australian islands and samples from Southeast Asia and Europe using microsatellite and mitochondrial DNA data.

RESULTS

Our results based on phylogeographic model selection are consistent with a European origin of cats in Australia. We find genetic distinctiveness of Australian mainland samples compared with Dirk Hartog Island, Flinders Island, Tasman Island and Cocos (Keeling) Island samples, and genetic similarities between some of the island populations. Historical records suggest that introduction of cats to these islands occurred at the time of European exploration and/or in connection with the pearling, whaling and sealing trades early in the 19th century. On-going influx of domestic cats into the feral cat population is apparently causing the Australian mainland populations to be genetically differentiated from those island populations, which likely are remnants of the historically introduced cat genotypes.

CONCLUSION

A mainly European origin of feral cats in Australia, with possible secondary introductions from Asia following the initial establishment of cats in Australia is reasonable. The islands surrounding Australia may represent founding populations and are of particular interest. The results of the study provide an important timeframe for the impact of feral cats on native species in Australia.

Highly polymorphic microsatellite markers for Radix balthica (Linnaeus 1758)

We present data for eight polymorphic microsatellite markers isolated from a microsatellite-enriched DNA library for the freshwater snail Radix balthica. Three of them were specific for R. balthica while five also amplified polymorphic products in two congeneric species. Test application on populations from all over the species range has shown that these loci are highly informative for analysing population structure and estimating migration rates. Observed deviations from Hardy-Weinberg equilibrium are attributed to a mixed mating system.

Northern blot analysis of simple repetitive sequence transcription in plants

The presence of simple repetitive sequence motifs in RNA from various plant species was probed by Northern blot analysis. Hybridization of total, poly(A)(+)- and poly(A)(-)-RNA with microsatellite-complementary oligonucleotide probes revealed distinct bands with most but not all probe/species combinations, demonstrating the presence of di-, tri- and tetranucleotide repeat motifs in plant transcripts. Only trinucleotide repeat-derived hybridization signals were found to be enriched in the poly(A)(+)-fraction. The quality of Northern blot signals proved to be highly dependent on hybridization stringency. Thus, under the stringency conditions usually applied for oligonucleotide hybridization, some probes [(GT)8, (CAC)5, (TCC)5, and (CCTA)4] cross-hybridized to bands corresponding in size to 18S and/or 26S rRNA. Cross-hybridization to rRNA was significantly reduced at higher stringencies. These results stress the importance of carefully adjusting the hybridization conditions in Northern blot analysis of simple sequence transcripts.

Synthesis of precursors of C4 and C5 cumulenones

Bicyclo[2.2.l]hept-5-en-2-one was condensed with 2,2-dimethyl-1,3-dioxan-4,6-dione in the presence of titanium tetrachloride/pyridine to yield 5-(bicyclo[2.2.1]hept-5'-en-2'-ylidene)-2,2-dimethyl-1,3- dioxan-4,6-dione (6a) which on pyrolysis at 520-560�/0.01 mm gave acetone, carbon dioxide, cyclopentadiene and butatrienone. In the same way 5-(7'-oxabicyclo[2.2.1]hept-5'-en-2'-ylidene)-2,2- dimethyl-1,3-dioxan-4,6-dione (6b) was prepared from 7-oxabicyclo[2.2.1]hept-5-en-2-one and on pyrolysis at 570�/0.01 mm it gave acetone, carbon dioxide, furan and butatrienone. Alkylation of 2-trimethylsiloxybicyclo[2.2.1]hepta-2,5 with phenylthiomethyl chloride with titanium tetrachloride as catalyst followed by condensation with 2,2-dimethyl-1,3-dioxan-4,6-dione gave an endo/exo mixture of 5-(3'-phenylthiomethylbicyclo[2.2.1]hept-5'-en-2'-ylidene)-2,2-dimethy 1-1,3-dioxan- 4,6-dione. The structure of the endo isomer was established by X-ray crystallography. Oxidation of the phenylthiomethyl compound with m-chloroperbenzoic acid yielded the sulfoxide which was converted by boiling in carbon tetrachloride into 5-(3'-methylenebicyclo[2.2.l]hept-5'-en-2'-ylidene)- 2,2-dimethyl-1,3-dioxan-4,6-dione (8). Preliminary studies on the fragmentation of compound (8) have shown that at 450�/0.01 mm it is converted into acetone, carbon dioxide and products showing ketene absorption at 2140 cm-1. The formation of pentatetraenone has not been established with certainty. The 3'-phenylsulfonylmethyl, phenylselenyl and methyl derivatives of (6a) are also described.

Dynamic microsatellites in transcribed regions of gastropod mitochondrial 16S rDNA

Length variations of repetitive sequences in different AT-rich loop-coding regions of mitochondrial 16S rDNA in two gastropod species were discovered during intraspecific haplotype surveys. Examination of the discrete length variation of the basic repeat unit in a phylogenetic framework led to the conclusion of a microsatellite-like mutational dynamic. The observations suggest that the presence of a repetitive sequence structure alone is sufficient to trigger this dynamic.

[The value of acetylsalicylic acid for the prevention of postoperative thromboembolic complications]

All studies on the value of acetylsalicylic acid for the prevention of postoperative thromboembolic complications have been evaluated. Controlled, prospective and randomized studies have been analyzed only where the incidence of postoperative deep vein thrombosis or pulmonary emboli was proven by objective diagnostic methods such as the fibrinogen test, phlebography or autopsy. In 6 studies there is no significant reduction in the incidence of deep vein thrombosis in general surgical and orthopedic patients after acetylsalicylic acid prevention. One study, though it has definite methodological defects, does suggest a significant reduction in the number of postoperative fatal pulmonary emboli in 120 patients with fractures of the upper end of the femur. On the basis of all these data, the prevention of postoperative thromboembolic complications by means of acetylsalicylic acid cannot be recommended.