Seasonal Changes in Microhabitat Use and Niche Overlap between Akodon azarae and Calomys laucha (Rodentia,Muridae) in Agroecosystems of Central Argentina

We examined seasonal changes in microhabitat use by the murid rodents Akodon azarae and Calomys laucha in agroecosystems of the former pampa region of Argentina. In summer, trap data showed that both species had low densities and were almost equally distributed between the mature cropfields and their surrounding weedy borders. Analysis of vegetation at the trap sites revealed no selection for microhabitats at the borders, whereas in the cropfields both species shared preferences for covered microhabitats. In contrast, winter data revealed a sharp habitat segregation, being Calomys numerically dominant in post-harvest cropfields and Akodon more abundant in borders. Moreover, there were clear differences in microhabitat selection at the borders, A. azarae occupying the more covered microhabitats and C. laucha the less covered. Breadth and overlap of niches were calculated using principal component analysis, in order to recognize interspecific competition and its influence on community niche space. Available evidence indicates that the structure of this rodent community is strongly influenced by seasonal changes in habitat stucture and rodent abundance. The socially dominant A. azarae retains the best part of the available niche space, a fact becoming more evident under the harsh winter conditions.     

Geographic pattern of genetic variation in the European globeflower Trollius europaeus L. (Ranunculaceae) inferred from amplified fragment length polymorphism markers

The distribution of genetic variation and the phylogenetic relationships between 18 populations of the arctic-alpine plant Trollius europaeus were analysed in three main regions (Alps, Pyrenees and Fennoscandia) by using dominant AFLP markers. Analysis of molecular variance revealed that most of the genetic variability was found within populations (64%), although variation among regions (17%) and among populations within regions (19%) was highly significant (P < 0.001). Accordingly, the global fixation index FST averaged over loci was high (0.39). The among-population differentiation indicates restricted gene flow, congruent with limited dispersal of specific globeflower's pollinating flies (Chiastocheta spp.). Within-population diversity levels were significantly higher in the Alps (mean Nei's expected heterozygosity HE = 0.229) than in the Pyrenees (HE= 0.197) or in Fennoscandia (HE = 0.158). This finding is congruent with the species-richness of the associated flies, which is maximum in the Alps. We discuss the processes involved in shaping observed patterns of genetic diversity within and among T. europaeus populations. Genetic drift is the major factor acting on the small Pyrenean populations at the southern edge of T. europaeus distribution, while large Fennoscandian populations result probably from a founder effect followed by demographic expansion. The Alpine populations represent moderately fragmented relics of large southern ancestral populations. The patterns of genetic variability observed in the host plant support the hypothesis of sympatric speciation in associated flies, rather than recurrent allopatric speciations.     

Five disulfide bridges stabilize a hevein-type antimicrobial peptide from the bark of spindle tree (Euonymus europaeus L.)

A small 45 amino acid residue antifungal polypeptide was isolated from the bark of spindle tree (Euonymus europaeus L.). Though the primary structure of this so-called E. europaeus chitin-binding protein or Ee-CBP is highly similar to the hevein domain, it distinguishes itself from most previously identified hevein-type antimicrobial peptides (AMP) by the presence of two extra cysteine residues that form an extra disulfide bond. Due to these five disulfide bonds Ee-CBP is a remarkably stable protein. Agar diffusion and microtiterplate assays demonstrated that Ee-CBP is a potent antimicrobial protein. IC₅₀-values as low as 1 μg/ml were observed for the fungus Botrytis cinerea. Comparative assays further demonstrated that Ee-CBP is a stronger inhibitor of fungal growth than Ac-AMP2 from Amaranthus caudatus seeds, which is considered one of the most potent antifungal hevein-type plant proteins.     

Studies on Galalpha3-binding proteins: comparison of the glycosphingolipid binding specificities of Marasmius oreades lectin and Euonymus europaeus lectin

The carbohydrate binding preferences of the Galalpha3Galbeta4 GlcNAc-binding lectins from Marasmius oreades and Euonymus europaeus were examined by binding to glycosphingolipids on thin-layer chromatograms and in microtiter wells. The M. oreades lectin bound to Galalpha3-terminated glycosphingolipids with a preference for type 2 chains. The B6 type 2 glycosphingolipid (Galalpha3[Fucalpha2]Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer) was preferred over the B5 glycosphingolipid (Galalpha3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer), suggesting that the alpha2-linked Fuc is accommodated in the carbohydrate binding site, providing additional interactions. The lectin from E. europaeus had broader binding specificity. The B6 type 2 glycosphingolipid was the best ligand also for this lectin, but binding to the B6 type 1 glycosphingolipid (Galalpha3[Fucalpha2]Galbeta3GlcNAcbeta3Galbeta4Glcbeta1Cer) was also obtained. Furthermore, the H5 type 2 glycosphingolipid (Fucalpha2Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer), devoid of a terminal alpha3-linked Gal, was preferred over the the B5 glycosphingolipid, demonstrating a significant contribution to the binding affinity by the alpha2-linked Fuc. The more tolerant nature of the lectin from E. europaeus was also demonstrated by the binding of this lectin, but not the M. oreades lectin, to the x2 glycosphingolipid (GalNAcbeta3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer) and GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer. The A6 type 2 glycosphingolipid (GalNAcalpha3[Fucalpha2]Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer) and GalNAcalpha3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1-Cer were not recognized by the lectins despite the interaction with B6 type 2 glycosphingolipid and the B5 glycosphingolipid. These observations are explained by the absolute requirement of a free hydroxyl in the 2-position of Galalpha3 and that the E. europaea lectin can accommodate a GlcNAc acetamido moiety close to this position by reorienting the terminal sugar, whereas the M. oreades lectin cannot.     

The breeding biology of introduced hedgehogs (Erinaceus europaeus) on a Scottish Island: lessons for population control and bird conservation

The breeding biology of a recently (1974) introduced hedgehog Erinaceus europaeus population was studied on a large Scottish island. These hedgehogs have caused serious declines in internationally important ground-nesting shorebirds, and population control is now being attempted. Sexual behaviour commenced in late April, a few days after the main emergence from hibernation. It peaked in mid-May and again in late June/early July, and ceased by mid-August. Females were promiscuous and were estimated to have sexual encounters (although not necessarily matings) with at least five males during the main mating period. Two-thirds of females attempted to breed for the first time in their second calendar year (i.e. as sub-adults), and the rest in their third calendar year (i.e. as adults). At least 96% ( n =27) of adult females attempted to breed in the early part of the season (litters born in June). The vast majority (81%, n =26) bred again in the later part of the season (litters born after mid-July). Breeding success (≥1 young emerged) was relatively high. For adults, 63% ( n =24) of early-season and 86% ( n =18) of late-season attempts were successful. For sub-adult females the figure was 62% ( n =9). The annual mean productivity per female was estimated at 4.04 young for adults and 0.85 young for sub-adults. The implications of these results for the effectiveness, timing and welfare aspects of hedgehog control programmes are discussed.     

Habitat use of nightjar (Caprimulgus europaeus) in an Austrian pine forest

The Steinfeld in Lower Austria supports a population of European Nightjar (Caprimulgus europaeus) which was extensively studied during 1997 and 1998. The study area encompassed a pine forest of 20 km². The population densities of 1.05 and 1.25 territories/km², respectively, lies within the range found in central European populations. Annual monitoring until 2001 has shown the population to be stable. To gain an insight into habitat use of the species, various habitat-related parameters were measured inside and outside the territories, namely structure of trees, density of trees, structure of undergrowth vegetation and structure of clearings. Discriminant analysis was applied to assess the factors responsible for habitat choice of the Nightjar population. The findings showed that the Nightjars territories were frequently centered on a large clearing with an area of at least 0.7 ha. Clearings less than 50 m wide were not colonized. The requirement for a minimum width of a clearing in addition to a minimum area probably relates to better hunting conditions. Nightjars prefer trees where the lower edge of the crown is on average 4.38 m higher than at control points so that males can churr from dead branches immediately below the canopy. Such trees were found on the edge of clearings in the forest, and the edge of a clearing thus had a pronounced effect on the quality of a territory. In contrast to reports in the literature, neither the proportion of bare patches of ground nor the average height of undergrowth vegetation was found to be decisive for territory selection.     

Homozygosity at a class II MHC locus depresses female reproductive ability in European brown hares

The link between adaptive genetic variation, individual fitness and wildlife population dynamics is fundamental to the study of ecology and evolutionary biology. In this study, a Bayesian modelling approach was employed to examine whether individual variability at two major histocompatibility complex (MHC) class II loci (DQA and DRB) and eight neutral microsatellite loci explained variation in female reproductive success for wild populations of European brown hare (Lepus europaeus). We examined two aspects of reproduction: the ability to reproduce (sterility) and the number of offspring produced (fecundity). Samples were collected from eastern Austria, experiencing a sub‐continental climatic regime, and from Belgium with a more Atlantic‐influenced climate. As expected, reproductive success (both sterility and fecundity) was significantly influenced by age regardless of sampling locality. For Belgium, there was also a significant effect of DQA heterozygosity in determining whether females were able to reproduce (95% highest posterior density interval of the regression parameter [−3.64, −0.52]), but no corresponding effect was found for Austria. In neither region was reproduction significantly associated with heterozygosity at the DRB locus. DQA heterozygotes from both regions also showed a clear tendency, but not significantly so, to produce a larger number of offspring. Predictive simulations showed that, in Belgium, sub‐populations of homozygotes will have higher rates of sterile individuals and lower average offspring numbers than heterozygotes. No similar effect is predicted for Austria. The mechanism for the spatial MHC effect is likely to be connected to mate choice for increased heterozygosity or to the linkage of certain MHC alleles with lethal recessives at other loci.     

Genetic variation in flowering phenology and avoidance of seed predation in native populations of Ulex europaeus

The genetic variation in flowering phenology may be an important component of a species’ capacity to colonize new environments. In native populations of the invasive species Ulex europaeus, flowering phenology has been shown to be bimodal and related to seed predation. The aim of the present study was to determine if this bimodality has a genetic basis, and to investigate whether the polymorphism in flowering phenology is genetically linked to seed predation, pod production and growth patterns. We set up an experiment raising maternal families in a common garden. Based on mixed analyses of variance and correlations among maternal family means, we found genetic differences between the two main flowering types and confirmed that they reduced seed predation in two different ways: escape in time or predator satiation. We suggest that this polymorphism in strategy may facilitate maintain high genetic diversity for flowering phenology and related life‐history traits in native populations of this species, hence providing high evolutionary potential for these traits in invaded areas.