Biogeography of Iberian freshwater fishes revisited: the roles of historical versus contemporary constraints

Aim The question of how much of the shared geographical distribution of biota is due to environmental vs. historical constraints remains unanswered. The aim of this paper is to disentangle the contribution of historical vs. contemporary factors to the distribution of freshwater fish species. In addition, it illustrates how quantifying the contribution of each type of factor improves the classification of biogeographical provinces. Location Iberian Peninsula, south‐western Europe (c. 581,000 km²). Methods We used the most comprehensive data on native fish distributions for the Iberian Peninsula, compiled from Portuguese and Spanish sources on a 20‐km grid‐cell resolution. Overall, 58 species were analysed after being categorized into three groups according to their ability to disperse through saltwater: (1) species strictly intolerant of saltwater (primary species); (2) species partially tolerant of saltwater, making limited incursions into saltwaters (secondary species); and (3) saltwater‐tolerant species that migrate back and forth from sea to freshwaters or have invaded freshwaters recently (peripheral species). Distance‐based multivariate analyses were used to test the role of historical (basin formation) vs. contemporary environmental (climate) conditions in explaining current patterns of native fish assemblage composition. Cluster analyses were performed to explore species co‐occurrence patterns and redefine biogeographical provinces based on the distributions of fishes. Results River basin boundaries were better at segregating species composition for all species groups than contemporary climate variables. This historical signal was especially evident for primary and secondary freshwater fishes. Eleven biogeographical provinces were delineated. Basins flowing to the Atlantic Ocean north of the Tagus Basin and those flowing to the Mediterranean Sea north of the Mijares Basin were the most dissimilar group. Primary and secondary freshwater species had higher province fidelity than peripheral species. Main conclusions The results support the hypothesis that historical factors exert greater constraints on native freshwater fish assemblages in the Iberian Peninsula than do current environmental factors. After examining patterns of assemblage variation across space, as evidenced by the biogeographical provinces, we discuss the likely dispersal and speciation events that underlie these patterns.     

Vicariance patterns in the Mediterranean Sea: east–west cleavage and low dispersal in the endemic seagrass Posidonia oceanica

Aim The seagrass, Posidonia oceanica is a clonal angiosperm endemic to the Mediterranean Sea. Previous studies have suggested that clonal growth is far greater than sexual recruitment and thus leads to low clonal diversity within meadows. However, recently developed microsatellite markers indicate that there are many different genotypes, and therefore many distinct clones present. The low resolution of markers used in the past limited our ability to estimate clonality and assess the individual level. New high‐resolution dinucleotide microsatellites now allow genetically distinct individuals to be identified, enabling more reliable estimation of population genetic parameters across the Mediterranean Basin. We investigated the biogeography and dispersal of P. oceanica at various spatial scales in order to assess the influence of different evolutionary factors shaping the distribution of genetic diversity in this species. Location The Mediterranean. Methods We used seven hypervariable microsatellite markers, in addition to the five previously existing markers, to describe the spatial distribution of genetic variability in 34 meadows spread throughout the Mediterranean, on the basis of an average of 35.6 (± 6.3) ramets sampled. Results At the scale of the Mediterranean Sea as a whole, a strong east–west cleavage was detected (amova) . These results are in line with those obtained using previous markers. The new results showed the presence of a putative secondary contact zone at the Siculo‐Tunisian Strait, which exhibited high allelic richness and shared alleles absent from the eastern and western basins. F statistics (pairwise θ ranges between 0.09 and 0.71) revealed high genetic structure between meadows, both at a small scale (about 2 to 200 km) and at a medium scale within the eastern and western basins, independent of geographical distance. At the intrameadow scale, significant spatial autocorrelation in six out of 15 locations revealed that dispersal can be restricted to the scale of a few metres. Main conclusions A stochastic pattern of effective migration due to low population size, turnover and seed survival is the most likely explanation for this pattern of highly restricted gene flow, despite the importance of an a priori seed dispersal potential. The east–west cleavage probably represents the outline of vicariance caused by the last Pleistocene ice age and maintained to this day by low gene flow. These results emphasize the diversity of evolutionary processes shaping the genetic structure at different spatial scales.     

Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Ultrastructural study of inflammatory bowel disease.

Ultrastructural changes that occurred in chronic active ulcerative colitis and Crohn's disease were investigated and compared to normal as well as to higher grades of dysplasia in adenomas and carcinomas. A greater number of immature absorptive cells, undifferentiated and intermediate cells were seen as compared to normal. One case of Crohn's and two cases of chronic ulcerative colitis including one with coexisting carcinoma showed increased number of vesicles and electron-dense bodies (EDB) in the absorptive cells and increased heterogeneity of mucin droplets in goblet cells and presence of atypical secretory cells (ASC). Higher grades of dysplasia characterised by large numbers of atypical secretory cells were not seen in the present series and provide no relationship between the atypical ultrastructural features and increased risk of malignancy. However, the number of cases investigated is too small and a large series is required to clarify the significance of observations such as increased number of electron-dense bodies and vesicles in the apical cytoplasm and presence of atypical secretory cells.     

Update on proliferation-associated antibodies applicable to formalin-fixed paraffin-embedded tissue and their clinical applications

Summary This review provides an update on proliferation-associated antibodies applicable to immunohistochemical techniques in formalin-fixed paraffin-embedded tissue. New insights into proliferating cell nuclear antigen (PCNA) and antibodies to PCNA are presented. The characterization of the protein recognized by the Ki-67 antibody has enabled production of a new range of antibodies (monoclonal and polyclonal) which have immunostaining profiles similar to those of the original antibody. A new proliferation-associated antibody, KiS1, is described. The clinical applications of antibodies to PCNA in human material are summarized, and the limitations of these studies are discussed.     

Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata

Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice.     

Pentoxifylline

Pentoxifylline (PTX), a tri-substituted purine and xanthine derivative, has been used for several years to improve microcirculation because of its hemorheological properties. PTX has also antifibrotic and anti-inflammatory effects. We studied the reaction of PTX with the hydroxyl radical and superoxide anion. Hydroxyl radical was generated by a mixture of ascorbic acid, H₂O₂ and Fe (III)-EDTA. We evaluated the iron-dependent degradation of deoxyribose, mediated by hydroxyl radical, in the presence of different concentrations of PTX (from 0.05 to 3 mM), measuring the degradation products of deoxyribose that react with 2-thiobarbituric acid (TBA). The reaction of PTX with hydroxyl radical occurred with a rate constant of (1.1±0.2)×10¹⁰ M ⁻¹/s. These results support the properties of PTX as a hydroxyl radical scavenger. Some authors verified that PTX decreases the release of superoxide anion from activated neutrophils. We studied the effect of PTX as a scavenger of superoxide generated in vitro by a hypoxanthine-xanthine oxidase system. PTX was not a superoxide anion scavenger in this system.