Brood sex ratio and male UV ornamentation in blue tits (<Emphasis Type="Italic">Cyanistes caeruleus</Emphasis>): correlational evidence and an experimental test

Sex-allocation theory predicts that females paired to attractive males should bias the brood sex ratio towards male offspring, as these would inherit the attractiveness of their father. We studied sex allocation based on male ornamentation in blue tits. Brood sex ratios varied with male UV coloration in an age-dependent manner. For juvenile males, the proportion of sons increased with increasing UV ornamentation, which is in agreement with previous findings from a Swedish population. However, the relationship between UV ornamentation and brood sex ratio was reversed for adult males, with females paired to less UV-ornamented adult males producing more sons. This pattern fits with the observation that, in our population, less UV-ornamented adult males sire the majority of extra-pair young. To test the causality of the association between brood sex ratio and male coloration, we experimentally manipulated crown colour largely within the natural range. We created two groups of males: one with higher and one with lower UV reflectance, UV(+) and UV(−), respectively. Contrary to our expectations, there was no significant treatment effect. However, in UV(−), but not UV(+) males, the proportion of sons was negatively correlated with male coloration before manipulation. This suggests that the UV(−) treatment caused males that were more UV ornamented to decline more in attractiveness, as shown in a similar experiment in Sweden. However, given that correlational patterns differ between these populations, similarities in experimental results should not be taken as evidence for consistent patterns of adaptive sex allocation in this species.     

Eventual saturation of the climate–carbon cycle feedback studied with a conceptual model

A saturation of climate–carbon cycle feedback was found earlier in the simulations with the IAP RAS climate model of intermediate complexity. Here, this eventual saturation is interpreted by using a conceptual linearised coupled model. It is shown that this saturation is due to weak, logarithmic, dependence of the carbon dioxide radiative forcing on its atmospheric concentration. This eventual saturation leads to the non-monotonic behaviour of climate–carbon cycle parameter f   in time. If the time scale of the atmospheric CO₂${\text{CO}}_2$ build up is _tp$t_{\text{p}}$ then, starting from an initial equilibrium, f   approaches maximum in time ?_tp$?t_{\text{p}}$. Afterwards, climate–carbon cycle parameter decreases and eventually tends to unity. The time scale of the latter decrease is _t1=(1−5)_tp$t_1=(1-5)t_{\text{p}}$. A dependence of _tm$t_{\text{m}}$ and _t1$t_1$ on governing parameters of the conceptual model is studied. It is argued that an eventual saturation of the climate–carbon cycle feedback is expected to occur also in the other integrations of sufficient length with coupled climate–carbon cycle models.     

Earthworm resources of Benghazi, Libya

This study presents the first survey of earthworm species (Oligochaeta) from Benghazi, a Mediterranean coastal city in Libya. A total of three peregrine species were recorded: Allolobophora caliginosa trapezoides, Allolobophora rosea (Family: Lumbricidae), Microscolex dubius (Family: Microscolecidae). Their distribution and density in six habitats (vegetable garden, flower garden, green house, farmland, grassland, plain barren landscape) are discussed in relation to some of the physico-chemical parameters and composition of the soil.     

Insights on plant interaction between dominating species from patterns of plant association: expected covariance of pin-point cover measurements of two species

It has been suggested that in order to infer ecological processes from observed patterns of species abundance we need to investigate the covariance in species abundance. Consequently, an expression for the expected covariance of pin-point cover measurements of two species is developed. By comparing the observed covariance with the expected covariance we get a new type of information on the spatial arrangement of two species. Here the discrepancy between the observed and expected covariance may be thought of as a measure of the spatial configuration of the two species that may indicate underling ecological processes. The method is applied in a case study of Calluna vulgaris and Deschampsia flexuosa on dry heathland sites. The observed covariance of Calluna and Deschampsia at the level of the sites was positively and significantly correlated with the expected covariance. Negative covariance was observed on sites where both Calluna and Deschampsia had a high cover, which is in agreement with the notion that both species form distinct patches. Oppositely, at sites where both species have a low cover, we found that both the expected and observed covariance were positive. The proposed measure for the expected covariance of two species does capture information on the combined spatial configuration of the two species if the species are common. We show how this may be relevant for understanding the underlying ecological processes leading to the observed covariance.     

Chemical mimicry in an incipient leaf-cutting ant social parasite

Some social parasites of insect societies are known to use brute force when usurping a host colony, but most use more subtle forms of chemical cheating either by expressing as few recognition cues as possible to avoid being recognized or by producing similar recognition cues to the host to achieve positive discrimination. The former “chemical insignificance” strategy represents a more general adaptive syndrome than the latter “chemical mimicry” strategy and is expected to be characteristic of early evolutionary stages of social parasitism. We tested this hypothesis by experimentally analyzing the efficiency by which Acromyrmex echinatior leaf-cutting ants recognize intruding workers of the incipient social parasite Acromyrmex insinuator. The results were consistent with the parasite being “chemically insignificant” and not with the “chemical mimicry” hypothesis. Gas chromatography–mass spectrometry analysis of cuticular hydrocarbon profiles showed that social parasite workers produce significantly fewer hydrocarbons overall and that their typical profiles have very low amounts of hydrocarbons in the “normal” C29–C35 range but large quantities of unusually heavy C43–C45 hydrocarbons. This suggests that the C29–C35 hydrocarbons are instrumental in normal host nestmate recognition and that the C43–C45 compounds, all of which are dienes and thus more fluid than the corresponding saturated compounds, may reinforce “chemical insignificance” by blurring any remaining variation in recognition cues.     

Going deep: common murres dive into frigid water for aggregated,persistent and slow-moving capelin

Owing to the necessity of delivering food to offspring at colonies, breeding seabirds are highly constrained in their foraging options. To minimize constraints imposed by central-place foraging and to optimize foraging behavior, many species exhibit flexible foraging tactics. Here we document the behavioral flexibility of pursuit-diving common murres Uria aalge when foraging on female capelin Mallotus villosus in the northwest Atlantic. Quite unexpectedly, being visual foragers, we found that common murres dived throughout the day and night. Twenty-one percent of recorded dives (n = 272 of 1,308 dives) were deep (≥50 m; maximum depth = 152 m, maximum duration = 212 s), bringing murres into sub-0°C water in the Cold Intermediate Layer (CIL; 40–180 m) of the Labrador Current. Deep dives occurred almost exclusively during the day when murres would have encountered spatially predictable aggregations of capelin between 100 and 150 m in the water column. Temperatures within the CIL shaped trophic interactions and involved trade-offs for both predators and prey. Sub-0°C temperatures limit a fish’s ability to escape from endothermic predators by reducing burst/escape speeds and also lengthening the time needed to recover from burst-type activity. Thus, while deep diving may be energetically costly, it likely increases certainty of prey capture. Decreased murre foraging efficiency at night (indicated by an increase in the number of dives per bout) reflects both lower light conditions and changing prey behavior, as capelin migrate to warmer surface waters at night where their potential to escape from avian predators could increase.     

Movement and memory: different cognitive strategies are used to search for resources with different natural distributions

Recent attempts to integrate function and mechanism have resulted in an appreciation of the relevance of forager psychology to understanding the functional aspects of foraging behaviour. Conversely, an acknowledgement of the functional diversity of learning mechanisms has led to greater understanding of the adaptive nature of cognition. In this paper, we present data from three experiments suggesting that noisy miner birds use different cognitive strategies when searching for foods with different distributions. When searching for nectar, an immobile, readily depleted resource, birds spontaneously attend to fine-scale spatial information and use a spatial memory-based strategy that is efficient in a novel context and largely resistant to disruptions to movement. When searching for invertebrates, a mobile, clumped and cryptic resource, birds employ a strategy whose efficiency increases with increased task familiarity, is vulnerable to disruptions to their movement and may rely more on memory for movement rules than memory for location information. Previous reports of adapted cognition have reported performance differences between species (for example, better spatial cognitive performance in storing versus non-storing birds). Ours is the first study to demonstrate that differences in cognitive strategy (as opposed to just enhanced performance) occur within a single species in different foraging contexts. As well as providing an example of how specially adapted cognitive mechanisms might work, our data further emphasise the importance of jointly considering functional and mechanistic aspects to fully understand the adaptive complexities of behaviour.     

Spatial–temporal variability of epibenthic assemblages on subtidal biogenic reefs in the northern Adriatic Sea

Spatial distribution and temporal variation of epibenthic assemblages of coralligenous biogenic rocky outcrops occurring in the northern Adriatic Sea (45°04′–45°24′N; 12°23′–12°43′E) were investigated by photographic sampling from 2003 to 2006 at 12 randomly selected sites. The dominant reef-forming organisms were the encrusting calcareous algae (Lithophyllum stictaeforme, Lithothamnion minervae and Peyssonnelia polymorpha), while the main bioeroders were boring sponges (Cliona viridis, C. celata, C. thoosina, C. rhodensis, Piona vastifica) and the bivalve Gastrochaena dubia. Composition of the assemblages varied thorough years and among sites. Spatial heterogeneity, at local and regional scale, prevailed over temporal variation. This variability was related both to the geo-morphological features of the outcrops and to environmental variables. Sites clearly differed in the percent cover of reef builder and bioeroder species while only limited temporal variation within site was found. Some taxa revealed complex intra-site temporal trends. These results provide valuable information on the diversity and variability of epibenthic assemblages of the northern Adriatic coralligenous reefs, essential for the management and conservation of these unique biogenic habitats.     

Storage and depletion of lipid components in the pyloric caeca and ovaries of the seastarAsterias rubens during its annual reproductive cycle

Detailed information is presented on the changes in lipid-class profiles (polar lipids, total neutral lipids, free sterols, steryl esters, triacylglycerols, neutral ether lipids and free fatty acids), which are manifest during the annual reproductive cycle of the seastarAsterias rubens for both the storage organs (pyloric caeca) and utilizing organs (ovaries). The ovaries appear to accumulate all individual lipid components proportional to progression of vitellogenesis. Pyloric caeca, in contrast, show variable lipid-class levels, probably due to more complex processes in these organs, operating simultaneously: digestion of food, accumulation of storage lipids, mobilization of stored lipids and their release. The results are discussed in terms of current knowledge on the role of lipids in echinoderm reproduction.