Neue Aspekte zur zugzeitlichen Frugivorie der Gartengrasmücke (Sylvia borin)

Zusammenfassung Freilandbeobachtungen und frühere Laboruntersuchungen (Berthold 1976) führten bisher zu einer widersprüchlichen Bewertung der zugzeitlichen Frugivorie bei der Gartengrasmücke. Deshalb wurden das Wahlverhalten gegenüber verschiedenen Beeren und Früchten in deren natürlichem Gehänge in einer Voliere geprüft sowie die Auswirkung unterschiedlich frugivorer Ernährung auf Körpermasse und tägliche Nahrungsaufnahme unter kontrollierten Laborbedingungen untersucht. Zwischen dem Präferenzverhalten gegenüber bestimmten Beeren und Früchten und deren Profitabilität bzw. Nährstoffgehalt bestand kein eindeutiger Zusammenhang. Demnach ist die Wahl zwischen verschiedenen Vegetabilien nicht einfach abhängig von ihrer Größe oder dem Nährstoffgehalt. Erhebliche Unterschiede zwischen den getesteten Beeren und Früchten zeigten sich bei der täglichen Aufnahmerate und den Auswirkungen auf die Körpermasse. Während bestimmte Beeren nur als Zusatzfutter zu einem immer, wenn auch geringfügig notwendigen, animalischen Standardfutter verabreicht werden konnten, waren die Gartengrasmücken mit Schwarzem Holunder und Feige auch bei ausschließlicher Gabe nicht nur in der Lage, ihre Körpermasse zu halten, sondern konnten dabei sogar normale Fettdeposition vollziehen. Offensichtlich sind bestimmte Vegetabilien für die Gartengrasmücke wesentlich bedeutsamer als bisher angenommen. Die Ergebnisse stimmen somit mit Beobachtungen aus dem Freiland überein. Die beobachteten qualitativen Unterschiede zwischen den Früchten und deren Wirkung auf die Körpermasse der Versuchsvögel ließen sich nicht allein mit dem Nährstoffgehalt der Beeren erklären. Vermutlich spielen die spezifische Qualität der Nährstoffe (z. B. Fettsäurezusammensetzung) und möglicherweise auch sekundäre Pflanzenstoffe eine wichtige Rolle.

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The significance of seasonal frugivory in migratory Garden WarblersSylvia borin

Summary In contrast to field observation, exhibiting an important role of seasonal frugivory,Berthold (1976) concluded that fruits are only a supplementary food, and he rejected the hypothesis that songbirds shift to a fruit diet during migration in order to render or to accelerate fat deposition.We investigated the preference of Garden Warblers upon various berries and pulpy fruits in an outdoor aviary. Furthermore, the effects of frugivory on body mass and food intake is measured in caged specimens under controlled laboratory conditions.In almost all feeding trials a significant selection between the two alternative fruit diets are obvious. However, no clearcut relationship between profitability or nutritive content of the various fruits and food choice is evident.In the experiments under controlled laboratory conditions the effects of varying extends of frugivory on body mass and food intake of captive Garden Warblers reveal a considerable difference between various berries and fruits. In some berries, the birds were not able to compensate for a reduction of the standard animal food by increasing frugivory. With Black Elder berries or figs, however, they did not only compensate for to maintain body mass rather they were able to gain mass during migratory fat deposition, even kept on an exclusive fruit diet.These results clearly exhibit a significant role of fruit diets in migrating Garden Warblers, with particular regards to Black Elder berries and figs, respectively.The observed differences between the various fruit diets do not correspond to the crude nutritive content of the pulp. Presumably, the specific quality of nutrients (for instance, fatty acid composition) or even secondary plant compounds have to be considered.The experimental results agree with field observations, indicating the importance of frugivory for the Garden Warbler, and they contradict Berthold's suggestion that fruits are only a least important supplementary food to an always necessary animal food.

     

A new H-2.1-PositiveD region allele,D dx,controlling two molecules,H-2Ddx and H-2Ldx

The inbred strains GRS/A and LIS/A carry the haplotypeH-2 ^dx , which had earlier been shown to have theK ^d ,I ^f ,S ^f , andG ^f alleles and a previously unknownD region allele,D ^dx . We show here that theD ^dx allele determines a new private specificity, H-2.63, is H-2.28 negative, and determines at least one public specificity of the H-2.1 family. It is thus a second example (afterD ^k ) of a H-2.1-positive H-2.28-negativeD region allele. Capping experiments show that the D^dx product comprises two molecules: H-2D^dx bearing the private specificity H-2.63, and H-2L^dx, which is H-2.63-negative but reacts with sera against the H-2.1 family of specificities. SDS gel electrophoresis of detergent-solubilized immunoprecipitated D^dx products shows that the H-2L^dx antigen has a molecular weight of approximately 45,000 daltons and is associated with a smaller polypeptide (mol. wt. 12,000).     

Complex genetic effect of B10.D2 (M504) (H-2dm1) mutation

Serological and capping experiments show that the strain B10.D2 (M504) carrying the mutant haplotypeH-2 ^dm1 has two molecules in the products of theD region: H-2D^dm1 and H-2L^dm1 which are detectable by anti-H-2.4 and by anti-H-2.28 sera, respectively. Both these molecules differ serologically from the H-2D^d and H-2L^d molecules of the original (nonmutant) strain B10.D2. A third molecule, different from H-2D and H-2L, was detected inH-2 ^d ,H-2 ^dm2 but not inH-2 ^dm1 products.     

A diploid form ofPhragmites communis,as a possible result of cytogenetical response to ecological stress

Phragmites communis Trin., a highly polymorphous and widely spread species has been described by several authors by the series of polyploidy ranging from triploid to octoploid forms (2n=36 to 96). The original spontaneous diploid form was not known. The present communication describes the experimental transplantation of a dwarf saline form into freshwater substrate conditions, including a new and extremely changed habitus of a sterile plant, the chromosome number of which has been determined as 2n=24.     

Daughter cells as an important factor in determining the physiological state of yeast populations

Cells of Candida utilis grown in a single-stage chemostat at D = 0.05, 0.1, 0.25, and 0.35 hr^?l were separated into a fraction of scar-bearing mother cells and a fraction of scar-free daughter cells. The scar-free cells were transferred into small batch cultures where the length of the maturation phase, changes in length and width of cells, specific growth rate, and specific rate of RNA and protein synthesis were examined for 5 hr. The daughter cells grown at D = 0.05 hr^?1 were very small at the moment of separation from the mother cells (about one-third of the mother cell). Their maturation phase (in a batch culture), at the beginning of which they attain the specific growth rate approaching the μ_max of the strain used, lasts for 3 hr. On the other hand, daughter cells grown at D = 0.35 hr^?1 are almost the same size as the mother cells at the moment of separation. After transfer to a batch culture they begin to bud almost immediately. Similarly, in their other morphological and physiological parameters they differ strikingly from immature daughter cells which are formed at low specific growth rates. The importance of these differences from the point of view of mathematical modeling of growth processes is discussed.     

Secondary dispersal mechanisms of winged seeds: a review

Winged seeds, or samaras, are believed to promote the long‐distance dispersal and invasive potential of wind‐dispersed trees, but the full dispersive potential of these seeds has not been well characterised. Previous research on the ecology of winged seeds has largely focussed on the initial abscission and primary dispersal of the samara, despite it being known that the primary wind dispersal of samaras is often over short distances, with only rare escapes to longer distance dispersal. Secondary dispersal, or the movement of the seeds from the initial dispersal area to the site of germination, has been largely ignored despite offering a likely important mechanism for the dispersal of samaras to microhabitats suitable for establishment. Herein, we synthesise what is known on the predation and secondary dispersal of winged seeds by multiple dispersive vectors, highlighting gaps in knowledge and offering suggestions for future research. Both hydrochory and zoochory offer the chance for samaroid seeds to disperse over longer distances than anemochory alone, but the effects of the wing structure on these dispersal mechanisms have not been well characterised. Furthermore, although some studies have investigated secondary dispersal in samaroid species, such studies are scarce and only rarely track seeds from source to seedling. Future research must be directed to studying the secondary dispersal of samaras by various vectors, in order to elucidate fully the invasive and colonisation potential of samaroid trees.