Chilling outweighs photoperiod in preventing precocious spring development

It is well known that increased spring temperatures cause earlier onset dates of leaf unfolding and flowering. However, a temperature increase in winter may be associated with delayed development when species' chilling requirements are not fulfilled. Furthermore, photosensitivity is supposed to interfere with temperature triggers. To date, neither the relative importance nor possible interactions of these three factors have been elucidated. In this study, we present a multispecies climate chamber experiment to test the effects of chilling and photoperiod on the spring phenology of 36 woody species. Several hypotheses regarding their variation with species traits (successional strategy, floristic status, climate of their native range) were tested. Long photoperiods advanced budburst for one‐third of the studied species, but magnitudes of these effects were generally minor. In contrast to prior hypotheses, photosensitive responses were not restricted to climax or oceanic species. Increased chilling length advanced budburst for almost all species; its effect greatly exceeding that of photoperiod. Moreover, we suggest that photosensitivity and chilling effects have to be rigorously disentangled, as the response to photoperiod was restricted to individuals that had not been fully chilled. The results indicate that temperature requirements and successional strategy are linked, with climax species having higher chilling and forcing requirements than pioneer species. Temperature requirements of invasive species closely matched those of native species, suggesting that high phenological concordance is a prerequisite for successful establishment. Lack of chilling not only led to a considerable delay in budburst but also caused substantial changes in the chronological order of species' budburst. The results reveal that increased winter temperatures might impact forest ecosystems more than formerly assumed. Species with lower chilling requirements, such as pioneer or invasive species, might profit from warming winters, if late spring frost events would in parallel occur earlier.     

Intraspecific nestmate recognition in two parabiotic ant species: acquired recognition cues and low inter-colony discrimination

Parabiotic ants—ants that share their nest with another ant species—need to tolerate not only conspecific nestmates, but also nestmates of a foreign species. The parabiotic ants Camponotus rufifemur and Crematogaster modiglianii display high interspecific tolerance, which exceeds their respective partner colony and extends to alien colonies of the partner species. The tolerance appears to be related to unusual cuticular substances in both species. Both species possess hydrocarbons of unusually high chain lengths. In addition, Cr. modiglianii carries high quantities of hereto unknown compounds on its cuticle. These unusual features of the cuticular profiles may affect nestmate recognition within both respective species as well. In the present study, we therefore examined inter-colony discrimination within the two parabiotic species in relation to chemical differentiation. Cr. modiglianii was highly aggressive against workers from alien conspecific colonies in experimental confrontations. In spite of high inter-colony variation in the unknown compounds, however, Cr. modiglianii failed to differentiate between intracolonial and allocolonial unknown compounds. Instead, the cuticular hydrocarbons functioned as recognition cues despite low variation across colonies. Moreover, inter-colony aggression within Cr. modiglianii was significantly influenced by the presence of two methylbranched alkenes acquired from its Ca. rufifemur partner. Ca. rufifemur occurs in two varieties (‘red’ and ‘black’) with almost no overlap in their cuticular hydrocarbons. Workers of this species showed low aggression against conspecifics from foreign colonies of the same variety, but attacked workers from the respective other variety. The low inter-colony discrimination within a variety may be related to low chemical differentiation between the colonies. Ca. rufifemur majors elicited significantly more inter-colony aggression than medium-sized workers. This may be explained by the density of recognition cues: majors carried significantly higher quantities of cuticular hydrocarbons per body surface.     

How biologists conceptualize genes: an empirical study

Philosophers and historians of biology have argued that genes are conceptualized differently in different fields of biology and that these differences influence both the conduct of research and the interpretation of research by audiences outside the field in which the research was conducted. In this paper we report the results of a questionnaire study of how genes are conceptualized by biological scientists at the University of Sydney, Australia. The results provide tentative support for some hypotheses about conceptual differences between different fields of biological research.     

The automatic pilot of honeybees

Using scanning harmonic radar, we make visible for the first time the complete trajectories of "goal-vector" flights in honeybees. We demonstrate that bees captured at an established feeding station, and released elsewhere, nevertheless embark on the previously learned vector flight that would have taken them directly home from the station, had they not been artificially displaced. Almost all of the bees maintained accurate compensation for lateral wind drift, and many completed the full length of the vector flight before starting to search for their hive. Our results showed that bees tend to disregard landscape cues during these vector flights, at least initially, and rely on the "optic flow" of the ground beneath them, and their sun compass, to judge both direction and distance.     

Calreticulin mRNA and protein are localized to protein bodies in storage maize callus cells

Maize callus cells possess numerous protein bodies which develop as sub-compartments of the endoplasmic reticulum. We localized maize calreticulin mRNAs and protein in maize callus cells using in situ hybridization and immunocytochemistry. Calreticulin mRNAs were selectively targeted to the endoplasmic reticulum (ER) subdomains surrounding protein bodies. Profilin mRNAs, used as a positive control for in situ hybridization experiments, showed distinct and rather diffuse localization pattern. Using both, immunofluorescence and immunogold electron microscopy localization techniques, calreticulin was found to be enriched around and within protein bodies in maize callus storage cells. As a positive control for reticuloplasmins, HDEL antibody revealed labelling of protein bodies and of the nuclear envelope. The identity of protein bodies was confirmed by specific binding of an α zein antibody. These data suggest that calreticulin mRNA is targeted towards protein body forming subdomains of the ER, and that calreticulin is localized and enriched in these protein bodies. The possibility that calreticulin plays an important role in zein retention within the ER and/or its assembly and packaging into protein bodies during protein body biogenesis in maize callus is discussed.     

Reproducibility of Retinol Binding Protein 4 and Omentin-1 Measurements over a Four Months Period: A Reliability Study in a Cohort of 207 Apparently Healthy Participants

The reliability of single time point measurements of the novel adipokines retinol-binding protein 4 and omentin-1 in the blood has not been evaluated in large samples yet. The present study aimed to assess the amount of biological variation of these two adipokines within individuals. The study sample comprised 207 participants (124 women and 83 men) from Potsdam (Germany) and surrounding areas, with an average age of 56.5 years (SD 4.2). Blood samples were collected from each participant twice, approximately four months apart. Using enzyme linked immunosorbent assays, the concentrations of retinol-binding protein 4 and omentin-1 were determined in EDTA plasma. As indicators of reliability, intraclass correlation coefficients (ICCs) were calculated from the repeated biomarker measurements. The ICCs for repeated retinol-binding protein 4 and omentin-1 measurements were 0.77 (95% CI 0.71, 0.82) and 0.83 (95% CI 0.78, 0.87), respectively, indicating for both adipokines excellent reliability. ICCs were stable across strata according to sex, age, BMI, and blood pressure. Thus, for epidemiological studies it seems reasonable to rely on concentrations of retinol-binding protein 4 and omentin-1 in samples from a single time point if repeated measurements are not available.     

Temporal and dietary niche is context-dependent in tropical ants

1. Niche traits (those that describe a species' niche) are not constant within a species, and the importance of intraspecific variation is increasingly appreciated. However, little is known about the extent of niche variability across species. This study investigated variation in dietary and temporal niches of ant species in two tropical rainforests. 2. Ants were collected from baits reflecting seven different natural resources and from pitfalls at 128 grid points. Sampling was done separately for day and night. Co-occurrence analyses were used to estimate the monopolisation capacity of each species. 3. It was expected that species would show similar dietary and temporal preferences across sites. Therefore, species with high or low niche variability between grid points (within a site) should show similar tendencies when comparing sites. It was predicted that between sites, intraspecific variability should be lower than interspecific variability, and that numerically dominant species should have higher monopolisation rates and lower intraspecific niche variability than less common ones. 4. These results showed that niche traits such as temporal activity and realised food niche shifted drastically between conspecifics of different sites. Even the most common species showed different food or temporal preferences between sites. In general, species with the highest monopolisation rates displayed lower niche variability. 5. This study also demonstrates that niche characterisation via combined continuous rather than categorical values permits a quantification of a species' niche variability. Categorising niche traits without considering context dependency may be misleading if one tries to assess niche width and a species' ability to cope with environmental change.     

Climate-Induced Changes in Grapevine Yield and Must Sugar Content in Franconia (Germany) between 1805 and 2010

When attempting to estimate the impacts of future climate change it is important to reflect on information gathered during the past. Understanding historical trends may also aid in the assessment of likely future agricultural and horticultural changes. The timing of agricultural activities, such as grape harvest dates, is known to be influenced by climate and weather. However, fewer studies have been carried out on grapevine yield and quality. In this paper an analysis is undertaken of long-term data from the period 1805–2010 on grapevine yield (hl/ha) and must sugar content (°Oe) and their relation to temperature. Monthly mean temperatures were obtained for the same time period. Multiple regression was used to relate the viticulture variables to temperature, and long-term trends were calculated. Overall, the observed trends over time are compatible with results from other long term studies. The findings confirm a relationship between yield, must sugar content and temperature data; increased temperatures were associated with higher yields and higher must sugar content. However, the potential increase in yield is currently limited by legislation, while must sugar content is likely to further increase with rising temperatures.     

Cotton Rat (Sigmodon hispidus) Signaling Lymphocyte Activation Molecule (CD150) Is an Entry Receptor for Measles Virus

Cotton rats (Sigmodon hispidus) replicate measles virus (MV) after intranasal infection in the respiratory tract and lymphoid tissue. We have cloned the cotton rat signaling lymphocytic activation molecule (CD150, SLAM) in order to investigate its role as a potential receptor for MV. Cotton rat CD150 displays 58% and 78% amino acid homology with human and mouse CD150, respectively. By staining with a newly generated cotton rat CD150 specific monoclonal antibody expression of CD150 was confirmed in cotton rat lymphoid cells and in tissues with a pattern of expression similar to mouse and humans. Previously, binding of MV hemagglutinin has been shown to be dependent on amino acids 60, 61 and 63 in the V region of CD150. The human molecule contains isoleucine, histidine and valine at these positions and binds to MV-H whereas the mouse molecule contains valine, arginine and leucine and does not function as a receptor for MV. In the cotton rat molecule, amino acids 61 and 63 are identical with the mouse molecule and amino acid 60 with the human molecule. After transfection with cotton rat CD150 HEK 293 T cells became susceptible to infection with single cycle VSV pseudotype virus expressing wild type MV glycoproteins and with a MV wildtype virus. After infection, cells expressing cotton rat CD150 replicated virus to lower levels than cells expressing the human molecule and formed smaller plaques. These data might explain why the cotton rat is a semipermissive model for measles virus infection.