Bulk carbon, oxygen, and hydrogen stable isotope composition of recent resins from amber-producing Hymenaea

Resins of Hymenaea, an angiosperm tree genus known to be a copious resin producer and a major source of amber since the Oligo-Miocene, were collected from a wide range of tropical environments from Latin America and Africa, and analyzed for their carbon, hydrogen, and oxygen stable isotope composition. The average value for ¹³C in the resins was found to be –27.0±1.3, which is very similar to the values reported for resins in other studies. ¹⁸ values for the Hymenaea resins averaged +11.2±1.6, or about 20 more depleted than normal plant cellulose. D values of the resins ranged from –196 to –319, with an average of –243±30. Rough estimates suggest a fractionation of –200 to –210 between the resins and the environmental water. This value is similar to the –200 value observed for the fractionation between other plant lipids and environmental water. The present study suggests that the stable isotope composition of fossil resins (amber) has the potential to provide information on ancient environmental waters.     

Is dauer pheromone of<Emphasis Type="Italic"> Caenorhabditis elegans</Emphasis> really a pheromone?

Animals respond to signals and cues in their environment. The difference between a signal (e.g. a pheromone) and a cue (e.g. a waste product) is that the information content of a signal is subject to natural selection, whereas that of a cue is not. The model free-living nematode Caenorhabditis elegans forms an alternative developmental morph (the dauer larva) in response to a so-called dauer pheromone, produced by all worms. We suggest that the production of dauer pheromone has no fitness advantage for an individual worm and therefore we propose that dauer pheromone is not a signal, but a cue. Thus, it should not be called a pheromone.     

Individual protein balance strongly influences δ<Superscript>15</Superscript>N and δ<Superscript>13</Superscript>C values in Nile tilapia,<Emphasis Type="Italic"> Oreochromis niloticus</Emphasis>

Although stable isotope ratios in animals have often been used as indicators of the trophic level and for the back-calculation of diets, few experiments have been done under standardized laboratory conditions to investigate factors influencing ¹⁵N and ¹³C values. An experiment using Nile tilapia [Oreochromis niloticus (L.)] was therefore carried out to test the effect of different dietary protein contents (35.4, 42.3, and 50.9%) on ¹⁵N and ¹³C values of the whole tilapia. The fish were fed the isoenergetic and isolipidic semi-synthetic diets at a relatively low level. ¹⁵N and ¹³C values of the lipid-free body did not differ between the fish fed the diets with different protein contents, but the trophic shift for N and C isotopes decreased with increasing protein accretion in the individual fish, for N from 6.5 to 4 and for C in the lipid-free body from 4 to 2.5. This is the first study showing the strong influence of the individual protein balance to the degree to which the isotopic signature of dietary protein was modified in tissue protein of fish. The extrapolation of the trophic level or the reconstruction of the diet of an animal from stable isotope ratios without knowledge of the individual physiological condition and the feeding rate may lead to erroneous results.     

Does exaggerated morphology preclude plasticity to cuckoldry in the midshipman fish (<Emphasis Type="Italic">Porichthys notatus</Emphasis>)?

In species with more than one male reproductive morph, there typically exists a larger morph with exaggerated secondary sexual characters, and a smaller morph with reduced secondary sexual characters. These exaggerated and reduced morphologies are commonly thought to represent specializations to alternative behavioral reproductive tactics—large body size and exaggerated secondary sexual characters should both facilitate territoriality, courtship, and pair-spawning; while small body size and reduced secondary sexual characters should facilitate sneaky cuckoldry. Given this postulated relationship between morphology and behavior, we examined the relationship between the morphology of exaggerated males and cuckoldry. In a field and aquarium study of the midshipman fish, a fish with both exaggerated and reduced morphs, we demonstrated cuckoldry in some males of the exaggerated morph. Since the reduced morphology is thought to be an adaptation towards sneaky cuckoldry, we predicted that, of males with the exaggerated morph, less-exaggerated (smaller) males would be better able to gain proximity to the spawning pair during cuckoldry. In contrast to that prediction, access to the spawning pair during cuckoldry increased with the body size of the cuckolding exaggerated-morph males. This may be related to our observation that exaggerated males often cuckolded aggressively. Thus the exaggerated morphology need not preclude adaptive plasticity to cuckoldry, and may even aid it.     

A butterfly’s chemical key to various ant forts: intersection-odour or aggregate-odour multi-host mimicry?

Deception is a crucial yet incompletely understood strategy of social parasites. In central Europe, the Mountain Alcon Blue, Maculinea rebeli, a highly endangered butterfly, parasitises several Myrmica ant species. Caterpillars gain access to host nests probably by faking the ants odour. We analysed gas chromatography–mass spectrometry data of body surface hydrocarbons of pre-adoption and hibernated larvae of Maculinea rebeli and of their host species Myrmica sabuleti and M. schencki. Data were ordinated by different methods, based on similarities in the relative quantities of compounds between chromatograms. The two Myrmica species exhibit species-specific profiles. The Maculinea rebeli pre-adoption larva has a complex profile that simultaneously contains species-specific substances of the two investigated host species. This evidence leads to the interpretation that, in central Europe, Maculinea rebeli is predisposed for multi-host use by the chemical signature of its pre-adoption larva. The Maculinea rebeli larva clearly does not rely on an intersection-odour of compounds common to all host ant species, but synthesises an aggregate-odour containing specific compounds of each of the investigated hosts. We term this previously unknown chemical strategy aggregate-odour multi-host mimicry.B.C. Schlick-Steiner and F.M. Steiner contributed equally to this work.     

Recycling plant wax constituents for chemical defense: hemi-biosynthesis of triterpene saponins from β-amyrin in a leaf beetle

Several species of Doryphorina leaf beetles from Central- and South America produce oleanane triterpene glycosides in their defensive glands. The presence of pentacyclic triterpenes in insects is intriguing since they lack the key enzymes necessary to synthesize these compounds. Since -amyrin is a common constituent of leaf waxes, we hypothesized that these leaf beetles use this compound as a precursor to their oleanane glycosides. To test this hypothesis we first confirmed the presence of -amyrin in Ipomoea batatas, the food plant of Platyphora kollari. Next, adults of P. kollari were fed for 10 days with I. batatas leaf disks painted with a solution of [2,2,3-²H₃]-amyrin ([2,2,3-²H₃]-1). The secretion from their defensive glands was collected and analyzed by HPLC-ESIMS. The results demonstrated that the secretion of beetles fed with an amount of [2,2,3-²H₃]-amyrin corresponding to the quantity of unlabeled (natural) -amyrin present in the leaf disks contained on average 5.1% of [2,2,3-²H₃]-3-O--d-glucopyranosyl-(1-->4)--d-glucuronopyranosyl-hederagenin ([2,2,3-²H₃]-2), whereas the secretions of beetles fed with 10 times this amount of [2,2,3-²H₃]-amyrin contained on average 23.9% of [2,2,3-²H₃]-2. In both series of experiments, the percentage of labeled versus unlabeled triterpene glycoside in the secretion was positively correlated with the amount of deuterated -amyrin ingested. These results demonstrate for the first time that some leaf beetles are able to metabolize a widespread triterpenic constituent of leaf wax into more complex glycosides that are stored in their defensive glands.     

Movements and corridors of African elephants in relation to protected areas

Understanding how mammals satisfy their need for space in fragmenting ecosystems is crucial for ecosystem conservation. Using state-of-the-art global positioning system (GPS) technology we tracked 11 focal African elephants (Loxodonta africana) in Kenya at 3-hourly fix intervals and collected between 34 and 406 days per individual. Our recordings gave a high spatio-temporal resolution compared to previous studies and allowed novel insights into range use. The actual ranges of the tracked elephants are smaller than usually represented. Moreover, the ranges in our sample were complex and not confined to officially designated protected areas, except where fenced. All the unfenced elephants in our sample had distinct home sectors linked by travel corridors. Within each home sector the elephants concentrated in favourite core zones. Such core zones tended to lie in protected areas whereas corridors typically crossed unprotected range. Elephants moved significantly faster along corridors than elsewhere in their range, which suggests awareness of danger outside the protected area. We conclude that understanding the complex use of an animals range is crucial for conservation planning aiming to balance animal interests with those of human beings that co-habit in their range.The revised version was published online in April 2005 with correction to figure 1a and b.     

Mating behavior of a flower-visiting longhorn beetle Zorion guttigerum (Westwood) (Coleoptera: Cerambycidae: Cerambycinae)

Long-range sex pheromones have been demonstrated for several cerambycid beetle species. Our field study on the mating behavior of Zorion guttigerum, on the basis of its temporal and spatial distributions on mating and feeding sites (flowers), and longevity, however, suggests that such pheromones are not used by this species. Plant characteristics rather than long-range sex pheromones may play an important role in bringing both sexes together. Adult activities on flowers occur exclusively during the day with two peaks, one around midday and the other in the late afternoon. Overall operational sex ratio is male-biased (1 :1.5 ) but it becomes very highly male-biased (1 :9 ) when mating and feeding activities decrease to the minimum in mid-afternoon, suggesting that females leave flowers to oviposit during that period of time. For cerambycid species whose females oviposit alone, and in which mating and oviposition occur on different plants or different plant parts, the operational sex ratio appears to vary significantly over time on the mating sites. The number and duration of pair-bondings also vary over time for Z. guttigerum. Fewer and shorter pair-bondings in the morning may suggest a strong sexual selection process. After 2 h of selection, both sexes tend to engage in longer pair-bondings and mate more times before females leave the mating sites in mid-afternoon. Details of the mating behavior are described here.     

Carbon Offset Potentials of Four Alternative Forest Management Strategies in Canada: A Simulation Study

Using an Integrated TerrestrialEcosystem C-budget model (InTEC), we simulated thecarbon (C) offset potentials of four alternativeforest management strategies in Canada: afforestation,reforestation, nitrogen (N) fertilization, andsubstitution of fossil fuel with wood, under differentclimatic and disturbance scenarios. C offset potentialis defined as additional C uptake by forest ecosystemsor reduced fossil C emissions when a strategy isimplemented to the theoretical maximum possibleextent. The simulations provided the followingestimated gains from management: (1) Afforesting allthe estimated 7.2 Mha of marginal agricultural landand urban areas in 1999 would create an average Coffset potential of 8 Tg C y^-1 during 1999–2100,at a cost of 3.4 Tg fossil C emission in 1999. (2)Prompt reforestation of all forest lands disturbed inthe previous year during 1999–2100 would produce anaverage C offset potential of 57 Tg C y^-1 forthis period, at a cost of 1.33 Tg C y^-1. (3)Application of N fertilization (at the low rate of 5kg N ha^-1 y^-1) to the 125 Mha ofsemi-mature forest during 1999–2100 would create anaverage C offset of 58 Tg C y^-1 for this period,at a cost of 0.24 Tg C y^-1. (4) Increasingforest harvesting by 20% above current average ratesduring 1999–2100, and using the extra wood products tosubstitute for fossil energy would reduce averageemissions by 11 Tg C y^-1, at a cost of 0.54 TgC y^-1. If implemented to the maximum extent, thecombined C offset potential of all four strategieswould be 2–7 times the GHG emission reductionsprojected for the National Action Plan for ClimateChange (NAPCC) initiatives during 2000–2020, and anorder of magnitude larger than the projected increasein C uptake by Canada's agricultural soils due toimproved agricultural practices during 2000–2010.     

The dinosaurian origin of feathers: perspectives from dolphin (Cetacea) collagen fibers

The early origin of birds is a hotly disputed debate and may be broadly framed as a conflict between paleontologists and ornithologists. The paleontological emphasis has shifted from Archaeopteryx and its origins to recent finds of Cretaceous birds and feathered dinosaurs from China. The identification of alleged feathers has, however, relied principally on the visual image. Some workers have interpreted these integumentary structures as collagen fibers. To test the latter hypothesis, using light microscopy, collagen from the hypodermis (blubber) and subdermal connective tissue sheath was examined from a dolphin that had been buried for a year as part of an experiment. Within the blubber, toward the central thicker parts of the material, the collagen fibers had compacted and the three-dimensional latticework of normal blubber had more or less collapsed. Chromatographic analysis of the blubber revealed pronounced oxidation of the unsaturated lipids, probably accounting for the collapse of the latticework. Fibers normally bound together in bundles became separated into individual fibers or smaller bundles by degradation of the glue-like substance binding them together. These degraded collagen fibers show, in many instances, feather-like patterns, strikingly reminiscent of many of those identified as either protofeathers or modern feathers in dromaeosaurid dinosaurs. The findings throw serious doubt on the virtually complete reliance on visual image by supporters of the feathered dinosaur thesis and emphasize the need for more rigorous methods of identification using modern feathers as a frame of reference. Since collagen is the main fiber type found in most supporting tissues, the results have wide implications regarding the degradation and fossilization of vertebrate integument, such as that of the ichthyosaurs, dinosaurs and birds.     

Simple rules for measuring changes in ecosystem carbon in forestry-offset projects

There is growing interest in the useof forestry-offset projects to mitigate increasingconcentrations of carbon dioxide in the atmosphere. If forestry-offset projects are to be employed broadlyand successfully there need to be accounting rulesthat are easy to operationalize and effective inpreventing cheating. Since carbon is both tangibleand predictable in where it occurs it is feasible todevelop simple accounting rules. Such rules must beconservative with respect to the amount of carboncredited.If accounting practices based on the following simplerules are employed, costs will be kept low andprojects will credit only carbon that is physicallypresent:Changes in living aboveground biomass must always be measured in forestry –offset projects.Belowground living biomass can be estimated from aboveground living biomass in forestry-offset projects. Generalized root/shoot ratios can be used as long as conservative ratios are applied.Not all changes in soil carbon stocks need to be measured, only those for which there is a possibility the stock is declining.The necromass pool need not be measured except when there has been a recent disturbance (interval varies with ecosystem). To insure that inaccurate techniques do not lead to overestimating of carbon stock changes, imprecise estimates of the carbon content of an ecosystem compartment should be discounted.There should be no required level of accuracy associated with estimates of carbon stock changes in forestry-offset projects, but the creditable carbon should be discounted proportional to the uncertainty.     

Fünfte Runde im Leibniz-Programm der Deutschen Forschungsgemeinschaft

Naturwissenschaften Aktuell

Anregungen zu einer strategisch agierenden Forschungspolitik vor der AGF-Jahrestagung     

A cost of alarm pheromone production in cotton aphids, Aphis gossypii

The sesquiterpene, (E)--farnesene, is used by many aphid species as an alarm pheromone to warn related individuals of predation. Disturbed cotton aphids, Aphis gossypii Glover, released (E)--farnesene into the air as detected by solid phase microextraction and gas chromatography mass spectrometry (GC–MS). Solvent extracts of cotton aphids of various life stages and weights also were analyzed by GC–MS for sums of ions 69 and 93, which discriminated (E)--farnesene from coeluting compounds. Aphids of all life stages and sizes reared on cotton plants in both an environmental chamber and glasshouse contained (E)--farnesene in amounts ranging from 0.1 to 1.5 ng per individual. The quantities of (E)--farnesene in aphids increased in relation to increasing body weight, and variation in individual weights explained about 82% of the variation in alarm pheromone. However, the concentrations (ng/mg fresh weight) declined exponentially with increasing body weight. These findings indicate that aphid nymphs try to compensate for their smaller size by producing relatively more pheromone per weight than adults but still cannot approach an evolutionary optimal load, as assumed in adults with the greatest total amounts. This suggests that young aphids need to balance costs of growth and maturation with costs of producing the alarm pheromone.     

The modern theory of biological evolution: an expanded synthesis

In 1858, two naturalists, Charles Darwin and Alfred Russel Wallace, independently proposed natural selection as the basic mechanism responsible for the origin of new phenotypic variants and, ultimately, new species. A large body of evidence for this hypothesis was published in Darwins Origin of Species one year later, the appearance of which provoked other leading scientists like August Weismann to adopt and amplify Darwins perspective. Weismanns neo-Darwinian theory of evolution was further elaborated, most notably in a series of books by Theodosius Dobzhansky, Ernst Mayr, Julian Huxley and others. In this article we first summarize the history of life on Earth and provide recent evidence demonstrating that Darwins dilemma (the apparent missing Precambrian record of life) has been resolved. Next, the historical development and structure of the modern synthesis is described within the context of the following topics: paleobiology and rates of evolution, mass extinctions and species selection, macroevolution and punctuated equilibrium, sexual reproduction and recombination, sexual selection and altruism, endosymbiosis and eukaryotic cell evolution, evolutionary developmental biology, phenotypic plasticity, epigenetic inheritance and molecular evolution, experimental bacterial evolution, and computer simulations (in silico evolution of digital organisms). In addition, we discuss the expansion of the modern synthesis, embracing all branches of scientific disciplines. It is concluded that the basic tenets of the synthetic theory have survived, but in modified form. These sub-theories require continued elaboration, particularly in light of molecular biology, to answer open-ended questions concerning the mechanisms of evolution in all five kingdoms of life.Dedicated to Prof. Dr. Dr. hc mult. Ernst Mayr on the occasion of his 100th birthdayThis revised version was published online in March 2004, with corrections to the caption of Figure 6.     

Latest precambrian (Cadomian) zircon ages, Nd isotopic systematics and P-T evolution of granitoid orthogneisses of the Erzgebirge, Saxony and Czech Republic

Single zircons from two orthogneiss complexes, the Grey Gneiss and Red Gneiss, the lowermost tectonic units in the Erzgebirge, were dated. The grey Freiberg Gneiss is of igneous origin and has a ²⁰⁷Pb/²⁰⁶Pb emplacement age of 550±7 Ma. A quartz monzonite from Lauenstein contains idiomorphic zircons with a mean ²⁰⁷Pb/²⁰⁶Pb age of 555±7 Ma as well as xenocrysts ranging in age between 850 and 1910 Ma. Red gneisses from the central Erzgebirge contain complex zircon populations, including numerous xenocrysts up to 2464 Ma in age. The youngest, idiomorphic, zircons in all samples yielded uniform ²⁰⁷Pb/²⁰⁶Pb ages between 550±9 and 554±10 Ma. Nd isotopic data support the interpretation of crustal anatexis for the origin of both units. _Nd(t) values for the grey gneisses are –7.5 and –6.0 respectively, (mean crustal residence ages of 1.7–1.8 Ga). The red gneisses have a wider range in _Nd(t) values from –7.7 to –2.8 (T _DM ages of 1.4–1.8 Ga). The zircon ages document a distinct late Proterozoic phase of granitoid magmatism, similar in age to granitoids in the Lusatian block farther north-east. However, Palaeozoic deformation as well as medium pressure metamorphism ( 8 kbar/600–650° C) are identical in both gneiss units and distinguish these rocks from the Lusatian granitoids. The grey and red gneisses were overthrust by units with abundant high-pressure relicts and a contrasting P-T evolution. Zircon xenocryst and Nd model ages in the range 1000–1700 Ma are similar to those in granitoid rocks of Lusatia and the West-Sudetes, and document a pre-Cadomian basement in parts of east-central Europe that, chronologically, has similarities with the Sveconorwegian domain in the Baltic Shield.     

Rapid modification in the olfactory signal of ants following a change in reproductive status

In insect societies, the presence and condition of egg-layers can be assessed with pheromones. Exocrine secretions are expected to vary in time in order to give up-to-date information on an individuals reproductive physiology. In the queenless monogynous ant Streblognathus peetersi, we allowed a previously infertile high-ranking worker to accede to the alpha rank, thus triggering the onset of her oogenesis (15 replicates). We then studied her interactions with an established egg-layer from the same colony after different durations, ranging from 20 h to several days. Even though her eggs are only ready to be laid after 30 days, the new alpha was recognised within 1–2 days. Detection occurred at a distance of a few millimetres, suggesting the involvement of a pheromone with low volatility, such as cuticular hydrocarbons. When the new alpha had differentiated for >48 h, she was attacked by the established egg-layer. In all cases, low-ranking workers eventually immobilised one of the two alphas: the new alpha was the target if she had differentiated only recently, suggesting that police workers select the dominant worker with the less fertile odour. Using the behaviour of ants as our measure, we demonstrate that a dominants olfactory signal changes rapidly with a modification in her social status, and it occurs well before the onset of egg-laying.     

Mastrus ridibundus parasitoids eavesdrop on cocoon-spinning codling moth, Cydia pomonella, larvae

Cocoon-spinning larvae of the codling moth, Cydia pomonella L. (Lepidoptera: Olethreutidae) employ a pheromone that attracts or arrests conspecifics seeking pupation sites. Such intraspecific communication signals are important cues for illicit receivers such as parasitoids to exploit. We tested the hypothesis that the prepupal C. pomonella parasitoid Mastrus ridibundus Gravenhorst (Hymenoptera: Ichneumonidae) exploits the larval aggregation pheromone to locate host prepupae. In laboratory olfactometer experiments, female M. ridibundus were attracted to 3-day-old cocoons containing C. pomonella larvae or prepupae. Older cocoons containing C. pomonella pupae, or larvae and prepupae excised from cocoons, were not attractive. In gas chromatographic-electroantennographic detection (GC-EAD) analyses of bioactive Porapak Q extract of cocoon-derived airborne semiochemicals, ten compounds elicited responses from female M. ridibundus antennae. Comparative GC-mass spectrometry of authentic standards and cocoon-volatiles determined that these compounds were 3-carene, myrcene, heptanal, octanal, nonanal, decanal, (E)-2-octenal, (E)-2-nonenal, sulcatone, and geranylacetone. A synthetic 11-component blend consisting of these ten EAD-active compounds plus EAD-inactive (+)-limonene (the most abundant cocoon-derived volatile) was as effective as Porapak Q cocoon extract in attracting both female M. ridibundus and C. pomonella larvae seeking pupation sites. Only three components could be deleted from the 11-component blend without diminishing its attractiveness to M. ridibundus, which underlines the complexity of information received and processed during foraging for hosts. Mastrus ridibundus obviously eavesdrop on the pheromonal communication signals of C. pomonella larvae that reliably indicate host presence.

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Zum Gedenken an Prof. Dr. Dr. h.c. Adolf Butenandt

Ansprache vor dem Wissenschaftlichen Rat der Max-Planck-Gesellschaft am 8.2.1995. Adolf Butenandt war Ehrenprasident der MPG und von 1960 bis 1983 Mitglied des Beirats der Naturwissenschaften.     

Bei „Gebildeten“ ist die Ablehnung der Gentechnik besonders ausgeprägt

Naturwissenschaften Aktuell

Bei Gebildeten ist die Ablehnung der Gentechnik besonders ausgeprägt     

The eyes of oilbirds (<Emphasis Type="Italic">Steatornis caripensis</Emphasis>): pushing at the limits of sensitivity

An extreme example of a low light-level lifestyle among flying birds is provided by the oilbird, Steatornis caripensis (Steatornithidae, Caprimulgiformes). Oilbirds breed and roost in caves, often at sufficient depth that no daylight can penetrate, and forage for fruits at night. Using standard microscopy techniques we investigated the retinal structure of oilbird eyes and used an ophthalmoscopic reflex technique to determine the parameters of these birds visual fields. The retina is dominated by small rod receptors (diameter 1.3±0.2 m; length 18.6±0.6 m) arranged in a banked structure that is unique among terrestrial vertebrates. This arrangement achieves a photoreceptor density that is the highest so far recorded (1,000,000 rods mm^–2) in any vertebrate eye. Cone photoreceptors are, however, present in low numbers. The eye is relatively small (axial length 16.1±0.2 mm) with a maximum pupil diameter of 9.0±0.0 mm, achieving a light-gathering capacity that is the highest recorded in a bird (f-number 1.07). The binocular field has a maximum width of 38° and extends vertically through 100° with the bill projecting towards the lower periphery; a topography that suggests that vision is not used to control bill position. We propose that oilbird eyes are at one end of the continuum that juxtaposes the conflicting fundamental visual capacities of sensitivity and resolution. Thus, while oilbird visual sensitivity may be close to a maximum, visual resolution must be low. This explains why these birds employ other sensory cues, including olfaction and echolocation, in the control of their behaviour in low-light-level environments.