Egg-size variation in the bluethroat (Luscinia s. svecica): constraints and adaptation

We examined inter- and intra-clutch egg-size variation in the bluethroat (Luscinia s. svecica), an open-nesting passerine breeding in the sub-alpine region in southern Norway. By removing first clutches shortly after egg-laying, we induced laying of a repeat clutch. Females significantly reduced the number of eggs from the first to the second nesting attempt, but increased mean egg size. Females in good condition laid significantly larger eggs than those in poor condition. Consistent with predictions of the brood survival hypothesis, assuming an adaptive investment in last eggs to ensure survival of all eggs in the clutch, we found that the size of the last eggs in first clutches was generally larger than the mean egg size of the clutch, and that the relative size of the last egg increased with clutch size. However, a large last egg reflected a general increase in egg size throughout the laying sequence rather than a specific investment in the last egg only. Egg size was not significantly influenced by sex or paternity (within-pair versus extra-pair) of the embryo. In repeat clutches the last egg was not consistently larger than the mean for the clutch. We conclude that female bluethroats face resource limitations during egg formation early in the season, and that the patterns of increase in egg size with laying order for first clutches, and from first to repeat clutches, can largely be explained by proximate constraints on egg formation.     

A phylogenetic supertree of oscine passerine birds (Aves: Passeri)

Oscine passerine birds make up almost half of all avian diversity. Relationships within the group, and its classification, have long been controversial. Over the last 10 years numerous molecular phylogenies have been published. We compiled source phylogenies from 99 published studies to construct an oscine supertree. We aimed to illustrate weak and strong parts of the phylogeny and set targets for future phylogenetic work and therefore preferred a heuristic approach where we judged the adequacy of taxon sampling and molecular method of each source tree instead of using matrices and automated tree-building programs. We present an estimate of the phylogenetic relationships of 1723 extant and one extinct species of oscine passerine birds (Aves: Passeri) — more than 37% of the total. We included 34/35 (97%) families, 38/39 (97%) subfamilies and 40/43 (93%) tribes. Overall resolution is 83% of a fully bifurcating tree. The basal lineages are all distributed in the Australo-Papuan region, but several more distal lineages dispersed out of this region and radiated in other parts of the world. However, taxa of the Australian region suffer from larger evolutionary gaps and the deep branches of the Sylvioidea and nine South American primaried oscines are still poorly resolved.     

Adrm1, a putative cell adhesion regulating protein, is a novel proteasome-associated factor

We have identified Adrm1 as a novel component of the regulatory ATPase complex of the 26 S proteasome: Adrm1 was precipitated with an antibody to proteasomes and vice versa. Adrm1 co-migrated with proteasomes on gel-filtration chromatography and non-denaturing polyacrylamide gel electrophoresis. Adrm1 has been described as an interferon-gamma-inducible, heavily glycosylated membrane protein of 110 kDa. However, we found Adrm1 in mouse tissues only as a 42 kDa peptide, corresponding to the mass of the non-glycosylated peptide chain, and it could not be induced in HeLa cells with interferon. Adrm1 was present almost exclusively in soluble 26 S proteasomes, albeit a small fraction was membrane-associated, like proteasomes. Adrm1 was found in cells in amounts equimolar with S6a, a 26 S proteasome subunit. HeLa cells contain no pool of free Adrm1 but recombinant Adrm1 could bind to pre-existing 26 S proteasomes in cell extracts. Adrm1 may be distantly related to the yeast proteasome subunit Rpn13, mutants of which are reported to display no obvious phenotype. Accordingly, knock-down of Adrm1 in HeLa cells had no effect on the amount of proteasomes, or on degradation of bulk cell protein, or accumulation of polyubiquitinylated proteins. This indicates that Adrm1 has a specialised role in proteasome function.     

Secondary buds in Scots pine trees infested with <Emphasis Type="Italic">Gremmeniella abietina</Emphasis>

In winter 2000–2001, there was a serious outbreak of Gremmeniella abietina Morelet in southeastern Norway. During the outbreak, we noted that injured Scots pine trees (Pinus sylvestris L.) developed secondary buds in response to the fungus attack, and we decided to study the relationship between injury, appearance of secondary buds and recovery of the trees thereafter. For this purpose, 143 trees from 10 to 50 years of age were chosen and grouped into crown density classes. Injury was assessed in detail, and buds were counted before bud burst in the spring of 2002. In addition, a subset of 15 trees was followed through the summer of 2002 to assess recovery. All injured trees developed secondary buds, with a clear overweight of dormant winter buds in proportion to interfoliar buds. Healthy control trees did not develop secondary buds at all. The secondary buds appeared predominantly on the injured parts of the tree; interfoliar buds in particular developed just beneath the damaged tissue. Most of the secondary buds died during the winter of 2001–2002, mainly because the fungus continued to spread after the first outbreak. Many of the remaining buds developed shoots with abnormal growth during the summer. Secondary buds may help trees to recover from Gremmeniella attacks, but this strategy may fail when the fungus continues to grow and injure the newly formed buds and shoots.     

Avian Clock gene polymorphism: evidence for a latitudinal cline in allele frequencies

In comparison with most animal behaviours, circadian rhythms have a well-characterized molecular genetic basis. Detailed studies of circadian clock genes in 'model' organisms provide a foundation for interpreting the functional and evolutionary significance of polymorphic circadian clock genes found within free-living animal populations. Here, we describe allelic variation in a region of the avian Clock orthologue which encodes a functionally significant polyglutamine repeat (ClkpolyQcds), within free-living populations of two passerine birds, the migratory bluethroat (Luscinia svecica) and the predominantly nonmigratory blue tit (Cyanistes caeruleus). Multiple ClkpolyQcds alleles were found within populations of both species (bluethroat: 12 populations, 7 alleles; blue tit: 14 populations, 9 alleles). Some populations of both species were differentiated at the ClkpolyQcds locus as measured by F(ST) and R(ST) values. Among the blue tit, but not bluethroat populations, we found evidence of latitudinal clines in (i) mean ClkpolyQcds repeat length, and (ii) the proportions of three ClkpolyQcds genotype groupings. Parallel analyses of microsatellite allele frequencies, which are considered to reflect selectively neutral processes, indicate that interpopulation allele frequency variation at the ClkpolyQcds and microsatellite loci does not reflect the same underlying demographic processes. The possibility that the observed interpopulation ClkpolyQcds allele frequency variation is, at least in part, maintained by selection for microevolutionary adaptation to photoperiodic parameters correlated with latitude warrants further study.     

Helicobacter pylori infection and gastroesophageal reflux in a population-based study (The HUNT Study)

BACKGROUND AND AIM: It has been suggested that Helicobacter pylori infection may prevent gastroesophageal reflux, possibly through gastric atrophy. Since, however, previous results are contradictory and no population-based studies are available, the relationship between H. pylori and reflux remains uncertain. The aim of this study was to investigate this relationship in a population-based, nested, case-control study. METHODS: From a cohort of 65,363 individuals, representing 71.2% of the adult population in the Norwegian county of Nord-Trondelag, we randomly selected 472 persons with recurrent reflux symptoms (cases) and 472 without such symptoms (controls). Occurrence of H. pylori and its virulence factor cagA was determined serologically, using an immunoblot assay. Gastric atrophy was assessed through serum levels of pepsinogen I. Odds ratios (OR) with 95% confidence intervals (CI), adjusted for potential confounding factors, represented relative risks. RESULTS: H. pylori infection was not associated with a decreased risk of reflux symptoms (OR 1.1, 95% CI 0.8-1.6), irrespective of positive cagA status (OR 1.1, 95% CI 0.8-1.5). Gastric atrophy reduced the risk of reflux symptoms (OR 0.2, 95% CI 0.0-0.6). Infection with H. pylori entailed a ninefold increase in the risk of gastric atrophy compared to non-infection (OR 8.9, 95% CI 2.0-39.9). CONCLUSIONS: H. pylori infection, irrespective of cagA status, did not affect the occurrence of reflux symptoms in this population-based setting. Infected individuals are at increased risk of gastric atrophy, which in turn reduces reflux symptoms, but due to the low frequency of gastric atrophy among infected individuals overall, there was no association with reflux symptoms on a population level.