A hybrid zone between the chromosomal races Łęgucki Młyn and Popielno of the common shrew in north-eastern Poland: preliminary results

A newly discovered hybrid zone between two karyotypic races, ??gucki M?yn (g/r, h/k, i/o, j/l, m/n, p, q) and Popielno (g/r, h/q, i/k, j/l, m/n, o, p), of the common shrewSorex araneus Linnaeus, 1758 has been studied in north-eastern Poland. In the ??gucki M?yn/Popielno hybrid zone the complex heterozygotes form theoretically only short meiotic chain configurations, consisting of four or five elements. In all hybrid populations a high frequency of complex heterozygotes was observed, varying from 0.30 to 0.43 between localities. In the centre of the hybrid zone the frequencies of telocentricsh andk increased. In two individuals of the hybrid populations (Krutyń I and Krutyń II), homozygous telocentric for chromosome armsh, i, k, o andq were observed.     

Distribution of two chromosome races of the common shrew (Sorex araneus L.) in the hybrid zone: may a change of the dispersal mode maintain independent gene frequencies?

Combination of different dispersal modes may itself, without external obstacles, lead to the appearance of subdivided populations and maintain the existence of independent population systems. The common shrew, a mammal convenient for studying different levels of intraspecific differentiation, was the object of the study. Empirical data have been used for simulation taking into account the change of dispersal modes in the population area. The obtained results agree with empirical data on the distribution of races and hybrids in the hybrid zone of chromosome races Moscow and Seliger. Change of the dispersal mode may maintain independent population dynamics and, in the case of chromosome races, prevent the migration of parental individuals into the territory of the other race.     

Distribution of two chromosome races of the common shrew (<Emphasis Type=Italic>Sorex araneus</Emphasis> L.) in the hybrid zone: Can a change of the dispersal mode maintain independent gene frequencies?

Combination of different dispersal modes may itself, without external obstacles, lead to the appearance of subdivided populations and maintain the existence of independent population systems. The common shrew, a mammal convenient for studying different levels of intraspecific differentiation, was the object of the study. Empirical data have been used for simulation taking into account the change of dispersal modes in the population area. The obtained results agree with empirical data on the distribution of races and hybrids in the hybrid zone of chromosome races Moscow and Seliger. Change of the dispersal mode may maintain independent population dynamics and, in the case of chromosome races, prevent the migration of parental individuals into the territory of the other race.     

Beyond the point of no return? A comparison of genetic diversity in captive and wild populations of two nearly extinct species of Goodeid fish reveals that one is inbred in the wild

The relative importance of genetic and non-genetic factors in extinction liability has been extensively debated. Here, we examine the levels of genetic variability at 13 (seven informative) loci in wild and captive populations of two endangered species of Mexican Goodeid fish, Ameca splendens and Zoogoneticus tequila. Allelic diversity was higher in the wild populations, and F(IS) lower. Values of theta (=4Nemu) were estimated using a coalescent approach. These implied that the effective population size of all captive populations of A. splendens were smaller than that of the wild population; qualitatively similar results were obtained using an analytical method based on within-population gene identity disequilibrium. However, the wild population of Z. tequila did not show a significantly greater estimate of theta. We used the Beaumont approach to infer population declines, and found that both species showed clear evidence of a decline in effective population size, although this was stronger and probably occurred over a longer period of time in Z. tequila than in A. splendens. The decline in Z. tequila probably occurred before captive populations were established. We discuss implications for the conservation of critically endangered populations.     

Can we continue to neglect genomic variation in introgression rates when inferring the history of speciation? A case study in a Mytilus hybrid zone

The use of molecular data to reconstruct the history of divergence and gene flow between populations of closely related taxa represents a challenging problem. It has been proposed that the long‐standing debate about the geography of speciation can be resolved by comparing the likelihoods of a model of isolation with migration and a model of secondary contact. However, data are commonly only fit to a model of isolation with migration and rarely tested against the secondary contact alternative. Furthermore, most demographic inference methods have neglected variation in introgression rates and assume that the gene flow parameter (Nm) is similar among loci. Here, we show that neglecting this source of variation can give misleading results. We analysed DNA sequences sampled from populations of the marine mussels, Mytilus edulis and M. galloprovincialis, across a well‐studied mosaic hybrid zone in Europe and evaluated various scenarios of speciation, with or without variation in introgression rates, using an Approximate Bayesian Computation (ABC) approach. Models with heterogeneous gene flow across loci always outperformed models assuming equal migration rates irrespective of the history of gene flow being considered. By incorporating this heterogeneity, the best‐supported scenario was a long period of allopatric isolation during the first three‐quarters of the time since divergence followed by secondary contact and introgression during the last quarter. By contrast, constraining migration to be homogeneous failed to discriminate among any of the different models of gene flow tested. Our simulations thus provide statistical support for the secondary contact scenario in the European Mytilus hybrid zone that the standard coalescent approach failed to confirm. Our results demonstrate that genomic variation in introgression rates can have profound impacts on the biological conclusions drawn from inference methods and needs to be incorporated in future studies.     

Adventitious roots as a source of information in reconstructing the activity of modern aeolian processes in the temperate climate zone: A case study from the Kozłów sandy area (SW Poland)

This paper presents a spatial-temporal reconstruction of inland dune movements at an anthropogenic active sandy area known as the Kozłów Desert, SW Poland. This unique sandy area, with assemblages of aeolian forms typical of “true” deserts, is an inactive military training ground (decommissioned in 1992) where military activity led to the initiation of geomorphic processes. The reconstruction was carried out based on the growth reaction characteristics of Scots pine (Pinus sylvestris L.) and downy birch (Betula pubescens L.) trees. 14 increment cores were collected from 12 trees and analysed with standard dendrochronological techniques. Samples of adventitious roots from all the trees examined were collected and prepared to extend the analyses and check their usefulness in dating modern geomorphic processes. The adventitious roots of pine and birch were found to react differently to burial, in terms of both reaction time and the shape of the root system. Growth-ring widths and wood anatomy were indicative of sudden or multi-stage sand movement, thus confirming the usefulness of adventitious roots as an additional source of information about aeolian process activity. More broadly, the study shows that the dynamics of landforming processes can be assessed more accurately and reliably by using such a combination of methods, comparing data from roots to data from tree trunks.     

A case of Kearns–Sayre syndrome with two novel deletions (9.768 and 7.253 kb) of the mtDNA associated with the common deletion in blood leukocytes,buccal mucosa and hair follicles

Kearns–Sayre syndrome is a mitochondrial disorder characterized by the emergence before the age of 20 years of progressive external ophthalmoplegia, pigmentary retinopathy, with other heterogeneous clinical manifestations. Generally, mitochondrial DNA deletions were associated with KSS but the size and position of these deletions differ among patients. This study reported a Tunisian patient with typical features of KSS. Long-range PCR amplification of the mtDNA in different tissues from this patient showed multiple mitochondrial deletions: two novel 9.768 and 7.253 kb deletions spanning respectively nucleotides 6124–15,893 and 8572–15,826 associated with the common 4.977 kb deletion.     

A 119Sn M?ssbauer spectroscopic study on the interaction of dimethyltin (IV) derivatives with rat hemoglobin, and of related model systems in aqueous solution

In the context of a study of the molecular basis of the antileukemia (murine) activity of diorganotin (IV) compounds, the interaction with rat hemoglobin (selected as a model protein) of the representative terms dimethyltin dichloride, dimethyltin glycylglycinate (Me2SnGlyGly), and dimethyltin L-cysteinate (Me2Sn-Cys) has been investigated by 119Sn M?ssbauer spectroscopy. In order to possibly determine the reaction pathway, aqueous model systems in Hepes buffer at pH 7.4 were also considered. The structural characteristics of reactants and products were advanced on the basis of semiempirical calculations of M?ssbauer nuclear quadrupole splitting parameters, delta E, by the point-charge model approach. In aqueous Hepes at pH 7.4, evidence was obtained for the formation of the five-coordinated species, trigonal bipyramidal type (tbp), Me2Sn(OH)2.Hepes(II), Me2Sn(OH)(GlyGly).Hepes(III), and Me2Sn(OH)Cys(IV) (see Fig. 1). Equatorial groups or atoms would be the Me radicals, as well as OH, N(peptide), and S(thiol), respectively. Hepes would coordinate to tin in axial position through the tertiary amino nitrogen, while cysteine would behave as a bidentate chelating agent, with an axially located amino group. Species (II), (III), and (IV) react with cysteine in aqueous Hepes at pH 7.4, yielding Me2Sn(OH)Cys(IV), as well as Me2SnCys2(V), where tin would be embedded into a tbp structure due to one cysteine probably chelating (equatorial S thiol and axial amino nitrogen), and one monodentate through S thiol. Species (II), (III), and (IV) react analogously with rat hemoglobin, primarily through the S thiol of a cysteine side chain, yielding pellets where the environment of tin could be tetrahedral, such as in Me2Sn(OH)(S thiol), (VI), and tetrahedral (IX) or tbp (V) in Me2Sn(Cys)(S thiol), where Cys would act either as chelating or monodentate. Further reaction of (VI) and (IX) could involve imidazole nitrogen atoms, N het, of histidine side chains, forming tetrahedral Me2Sn(S thiol)(N het), (VIII), or tbp Me2Sn(OH)(S thiol)(N het), (VII), and Me2Sn(Cys)(S thiol)(N het), (V) (see Figs. 1 and 5).     

A comparison of reproduction, growth and acute toxicity in two populations of Tubifex tubifex (Müller,1774) from the North American Great Lakes and Northern Spain

Reproduction in Tubifex tubifex is being used as part of a suite of indicators of sediment toxicity in Canada and Spain, and reproduction of T. tubifex is being considered as a component of sediment objectives for environmental regulation and clean-up in the Canadian Great Lakes. The data being used to set these reproductive targets have been developed from a single culture of T. tubifex from Lake Erie. The plasticity of this particular species is well known and before it can be adopted widely as a test organism it is necessary to determine whether a single culture source should be used or if cultures derived from different populations respond similarly. A series of experiments with two cultures, one from Lake Erie the second from a small mountain stream in Northern Spain have shown that the Spanish worms appear to produce fewer cocoons per adult (mean 8.6 S.D. 1.0) than those from Lake Erie (mean 10.4 S.D. 0.3) at 22.5 °C, a standard test temperature. The number of young produced per adult by the Spanish culture is also lower (mean 19.0 S.D. 4.6) than the L. Erie population (mean 30.6 S.D. 2.3), however, the Spanish population has higher reproductions rates at a lower temperature. The Spanish worms also have lower and more variable growth rates than the Canadian population. There also appear to be slight differences in the sensitivities to toxicants, with the Canadian worms having higher LC50s for copper, chromium and cadmium. While there are differences in the responses in the two cultures these are not considered to be sufficient to invalidate the use of either population in a standard bioassay protocol as long as appropriate calibration and validation are undertaken.     

Filling of eco-climatological niches in a polyploid complex – A case study in the plant genus Leucanthemum Mill. (Compositae,Anthemideae) from the Iberian Peninsula

In order to assess the effects of polyploidisation on distribution patterns of species in a polyploid complex, we compared potential and actual distribution ranges of representatives from the genus Leucanthemum Mill. (Compositae, Anthemideae), which occur on the Iberian Peninsula with 20 taxa spanning ploidy levels between 2n = 2x = 18 and 2n = 22x = 198. Actual distribution ranges of taxa were derived from geo-referenced herbarium specimens by defining buffer circles around the collection localities to account for geographical uncertainties and haphazardness of specimen collecting. Eco-climatologically potential ranges were modelled with the maximum entropy method (Maxent) based on the actual distributions. By comparison of sizes of realised and eco-climatologically potential areas for each taxon we computed taxon-specific overlap indices that express the filling of eco-climatological niches. The correlation between overlap indices and ploidy levels was tested by Spearman's rank correlation coefficient. We observed a significant negative correlation between ploidy level and sizes of realised distribution ranges and no significant correlation of ploidy level and sizes of potential ranges. Finally, we found that diploid and low-ploidy taxa are filling their potential eco-climatological distribution ranges more exhaustively than highly polyploid taxa. Assuming that ascending polyploidisation is the prevailing mode compared to descending polyploidisation, our results demonstrate that the distribution patterns of members of the Leucanthemum polyploid complex on the Iberian Peninsula are mainly influenced by the age of taxa and not by ecological advantages or disadvantages connected with polyploidy.     

Secondary structure of Aβ(1–16) complexes with zinc: A study in the gas phase using deuterium/hydrogen exchange and ultra-high-resolution mass spectrometry

Complexes of peptide fragment 1–16 of beta-amyloid with transition metals play an important role in the development of a broad class of neurodegenerative diseases, which determines the interest in investigating the structures of these complexes. In this work, we have applied the method of the deuterium/hydrogen exchange in combination with ultra-high-resolution mass spectrometry to study conformational changes in (1–16) beta-amyloid peptide induced by binding of zinc(II) atoms. The efficiency of the deuterium/hydrogen exchange depended on the number of zinc atoms bound to the peptide and on the temperature of the ionization source region. Deuterium/hydrogen exchange reactions have been performed directly in the ionization source. The number of exchanges decreased considerably with an increasing numbers of zinc atoms. The relationship has been described with a damped exponential curve, which indicated that the binding of zinc atoms altered the conformation of the peptide ion by making it less open, which limits the access to inner areas of the molecule.     

A new species of Paracreptotrema (Digenea,Plagiorchiformes, Allocreadiidae) infecting two species of poeciliids in Río Malila of the Río Pánuco basin,Hidalgo, México,with a key to the species of the genus

Paracreptotrema rosenthali sp. n. was discovered in the intestine of Xiphophorus malinche and Pseudoxiphophorus jonesii, collected from the headwaters of Río Malila, tributary of Río Conzintla, in the Río Pánuco basin, Hidalgo, México, during 2008–2009. The new species differs from the five known species of Paracreptotrema Choudhury, Pérez-Ponce de León, Brooks & Daverdin, 2006 by having vitelline follicles that extend from a level anterior to the pharynx to mid-testes, the seminal vesicle which is more extensively folded, and a wider cirrus sac. The new species resembles Paracreptotrema heterandriae in the length of its ceca, which surpasses the posterior margin of the ovary but do not reach the testes. A key to the species of Paracreptotrema is provided.     

A 13C-nuclear magnetic resonance study of polysaccharide gels. Molecular architecture in the gels consisting of fungal,branched (1 → 3)-β-d-glucans (lentinan and schizophyllan) as manifested by conformational changes induced by sodium hydroxide

To gain further insight into the architecture of the gel network of some branched (1 → 3)-β-d-glucans, a ¹³C-n.m.r. study of sodium hydroxide-induced, conformational change was performed. The branched d-glucans examined were lentinan from Lentinusedodes, a lower-molecular-weight fraction thereof, and schizophyllan from Scilizophyllum commune; these (1 → 3)-β-d-glucans have two branches for every five d-glucopyranosyl residues (lentinan), or one for every three or four (schizophyllan) at 0-6. In contrast to the gel oflinear (1 → 3)-β-d-glucan (curdlan), all of the ¹³C signals due to the β-d-(1 → 3)-linked d-glucosyl residues were completely suppressed in the gel state. As the peak intensity and line width of the ¹³C-resonance peaks for the gel state are strongly influenced by the degree of cross-linking, such a complete loss of the peak areas can be explained in terms of a higher degree of cross-linking than that of the linear d-glucans. As demonstrated previously, the cross-links involve physical association of the helical segments, such as the double- or triple-stranded helices. These helix forms were found to be converted, at 0.2M sodium hydroxide, into the random-coil form (gel-to-sol transition), which gives rise to full peak-areas, because of complete breaking of the physical cross-links. Also, in contrast to the linear d-glucan, such helix-coil transition of the branched d-glucans proceeded in a noncooperative way: the peak intensity and line width gradually changed with the concentration of sodium hydroxide. This behavior is best interpreted in terms of distribution of the various degrees of cross-linking. Some loose cross-links are readily broken in the lower range of concentration of alkali (0.09M), and others are resistant until complete conversion into the random coil occurs (0.2M). This result is consistent with the view that the primary structure of the branched (1 → 3)-β-d-glucans is hi-highly branched, as in a tree-like structure.