Interspecific competition promotes habitat and morphological divergence in a secondary contact zone between two hybridizing songbirds

Interspecific competition is assumed to play an important role in the ecological differentiation of species and speciation. However, empirical evidence for competition's role in speciation remains surprisingly scarce. Here, we studied the role of interspecific competition in the ecological differentiation and speciation of two closely related songbird species, the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (Luscinia luscinia). Both species are insectivorous and ecologically very similar. They hybridize in a secondary contact zone, which is a mosaic of sites where both species co‐occur (syntopy) and sites where only one species is present (allotopy). We analysed fine‐scale habitat data for both species in both syntopic and allotopic sites and looked for associations between habitat use and bill morphology, which have been previously shown to be more divergent in sympatry than in allopatry. We found that the two nightingale species differ in habitat use in allotopic sites, where L. megarhynchos occurred in drier habitats and at slightly higher elevations, but not in syntopic sites. Birds from allotopic sites also showed higher interspecific divergence in relative bill size compared to birds from syntopic sites. Finally, we found an association between bill morphology and elevation. Our results are consistent with the view that interspecific competition in nightingales has resulted in partial habitat segregation in sympatry and that the habitat‐specific food supply has in turn very likely led to bill size divergence. Such ecological divergence may enhance prezygotic as well as extrinsic postzygotic isolation and thus accelerate the completion of the speciation process.     

Oestrous females investigate the unfamiliar male more than the familiar male in both commensal and non-commensal populations of house mice

We studied female preferences for familiar and unfamiliar males. The subjects were laboratory-born house mice: (1) non-commensal Mus musculus domesticus from the eastern part of Syria along the Euphrates River; and (2) commensal M. m. musculus from the Czech Republic. Pair-choice preference tests have revealed that oestrous females of both populations sniffed towards unfamiliar males more than familiar males. In the case of females exhibiting postpartum oestrus, this preference was less pronounced and statistically not significant. Thus, our mice clearly exhibited the behavioural pattern known from commensal populations of polygynous and/or promiscuous M. m. domesticus. We found no inverse tendency to seek proximity to the familiar male that has been previously reported from closely related and presumably monogamous aboriginal mouse Mus spicilegus. We conclude that neither commensal M. m. musculus, nor non-commensal M. m. domesticus, are likely to share a monogamous mating system with mound-building mice.     

Two rhizobial strains, Mesorhizobium loti MAFF303099 and Bradyrhizobium japonicum USDA110, encode haloalkane dehalogenases with novel structures and substrate specificities

Haloalkane dehalogenases are key enzymes for the degradation of halogenated aliphatic pollutants. Two rhizobial strains, Mesorhizobium loti MAFF303099 and Bradyrhizobium japonicum USDA110, have open reading frames (ORFs), mlr5434 and blr1087, respectively, that encode putative haloalkane dehalogenase homologues. The crude extracts of Escherichia coli strains expressing mlr5434 and blr1087 showed the ability to dehalogenate 18 halogenated compounds, indicating that these ORFs indeed encode haloalkane dehalogenases. Therefore, these ORFs were referred to as dmlA (dehalogenase from Mesorhizobium loti) and dbjA (dehalogenase from Bradyrhizobium japonicum), respectively. The principal component analysis of the substrate specificities of various haloalkane dehalogenases clearly showed that DbjA and DmlA constitute a novel substrate specificity class with extraordinarily high activity towards beta-methylated compounds. Comparison of the circular dichroism spectra of DbjA and other dehalogenases strongly suggested that DbjA contains more alpha-helices than the other dehalogenases. The dehalogenase activity of resting cells and Northern blot analyses both revealed that the dmlA and dbjA genes were expressed under normal culture conditions in MAFF303099 and USDA110 strain cells, respectively.     

Macrophage-derived factors increase low density lipoprotein uptake and receptor number in cultured human liver cells.

Recent evidence suggests the possibility that macrophages can influence lipoprotein metabolism. Therefore we investigated the ability of cultured macrophages to alter low density lipoprotein (LDL) uptake in a human liver cell line (HepG2). Conditioned media from phlogogenic-induced mouse peritoneal macrophages or from a human macrophage cell line stimulated with endotoxin increased HepG2 LDL uptake by as much as 60-70%. The increase was due, in part, to a significant macrophage-induced 40% increase in the number of LDL receptors per cell. Although macrophage conditioned media inhibited HepG2 cholesterol synthesis, the LDL receptor up-regulation did not appear to be due to the effects on cholesterol synthesis. The LDL receptor stimulatory activity was sensitive to proteolysis and heat. Its molecular mass was approximately 20 kDa based on gel filtration. Several macrophage secretory proteins were tested in HepG2 cultures for LDL uptake stimulation. Of these, oncostatin M (approximately 18 kDa by gel filtration) gave the strongest response. The rank order for LDL uptake stimulation was oncostatin M much greater than interleukin 6 = interleukin 1 = transforming growth factor-beta 1. A neutralizing antibody directed against oncostatin M inhibited the ability of conditioned media to up-regulate LDL receptors by 85%. Thus, our results indicate that macrophages can secrete several proteins that up-regulate LDL receptors in HepG2 cells and that most of the up-regulatory activity in macrophage conditioned media appears to be due to oncostatin M.     

Different growth response of five co-existing stoloniferous plant species to inoculation with native arbuscular mycorrhizal fungi

Five species of stoloniferous plants originating from the same field site (Galeobdolon montanum, Glechoma hederacea, Potentilla anserina, Ranunculus repens and Trifolium repens) were studied with respect to their interaction with arbuscular mycorrhizal (AM) fungi. More specifically, the question was addressed whether mycorrhizal growth response of host plant species could be related to their vegetative mobility. The roots of all the species examined were colonised with AM fungi in the field, with the percentage of colonisation varying among species from approximately 40% to 90%. In a subsequent pot experiment, plants of all the species were either left non-inoculated or were inoculated with a mixture of three native AM fungi isolated from the site of plant origin (Glomus mosseae, G. intraradices and G. microaggregatum). AM fungi increased phosphorus uptake in all the plant species; however, plant growth response to inoculation varied widely from negative to positive. In addition to the biomass response, AM inoculation led to a change in clonal growth traits such as stolon number and length or ramet number in some species. Possible causes of the observed differences in mycorrhizal growth response of various stoloniferous plants are discussed.     

Isoflavones in the Rutaceae family: twenty selected representatives of the genera Citrus, Fortunella, Poncirus, Ruta and Severinia

Enzyme-linked immunosorbent assays in combination with semi-preparative high-performance liquid chromatography (HPLC) and analytical HPLC with mass spectroscopy in the selective ion monitoring mode were used for the determination of selected isoflavones, daidzein, genistein, biochanin A and their homologues, in 20 representatives of the Rutaceae family. Species belonging to five genera were studied, namely Citrus, Fortunella, Poncirus, Ruta and Severinia. The enzyme immunoassays used were based on polyclonal antibodies raised against isoflavonoid conjugates with bovine serum albumin (BSA), namely biochanin A-7-BSA, daidzein-7-BSA, daidzein-4'-BSA, genistein-7-BSA and genistein-4'-BSA. Aglycones as well as glycosides were detected, and methoxyisoflavones appeared to be more abundant than hydoxyisoflavones. The content of individual isoflavonoids ranged from 0 to 2.6 mg/kg (dry weight); the sum of all measured substances reached up to 5.9 mg.     

Male ornamentation and within-pair paternity are not associated with male provisioning rates in scarlet rosefinches Carpodacus erythrinus

As proposed by the ‘good parent model’ for evolution of secondary male ornamentation, secondary ornaments may signal male provisioning rates and, therefore, direct benefit to females. On the other hand, male parental care intensity can potentially be affected by the occurrence of extra-pair offspring in its nest. According to ‘parental investment theory’, males that lose paternity in their nests should reduce their parental care. In this study, we analyse potential relationships between intensity of parental care, male ornamentation, the occurrence of extra-pair paternity and male extra-pair fertilisation success in the scarlet rosefinch Carpodacus erythrinus. Our results based on 50 observed nests indicate no effect of paternity loss on the rate of food provisioning to nestlings in scarlet rosefinches. Simultaneously, we found no evidence for an association between male ornamentation and male provisioning rates. The only male trait associated with provisioning was the ability to sire extra-pair offspring. Our data indicate that direct selection against female promiscuity is weak or absent in rosefinches.     

Single Nucleotide Variants in KIF14 Gene May Have Prognostic Value in Breast Cancer

Molecular Diagnosis & Therapy - Human kinesin 14 (KIF14) is one of the 70 prognostic marker genes (so-called Amsterdam profile) previously identified by the microarray of breast carcinomas, and...