Tuned protection of aphids by ants against a predatory hoverfly

1. Aphid‐tending ants that feed on honeydew have evolved strategies against aphidophagous insects and tune their aggressive behaviour according to the level of danger for their trophobionts. Here we investigate how Lasius niger Linnaeus (Hymenoptera: Formicidae) ants react to different instars of Episyrphus balteatus De Geer (Diptera: Syrphidae) hoverflies which vary in their voracity and defensive abilities. 2. During pairwise encounters, early syrphid instars (eggs, L1, and L2 larvae) elicited lower aggression scores compared to third larval instars (L3), which was intensively bitten by ants. L3 tried to escape from ants by releasing a sticky and toxic secretion over biting ants that died or underwent severe morbidity. 3. In a standardised system including the host plant, aphid, tending ant, and hoverfly, the ability of ants to protect an Aphis fabae Scopoli (Hemiptera: Aphididae) colony was evaluated. Early E. balteatus instars placed onto the plant elicited no mobilisation of ants, which often removed the hoverfly successfully. Eggs and early instars appeared as the weak links for integrated pest management by hoverfly auxiliaries. 4. In contrast, L3 induced the number of ant patrollers to increase at a local scale without any further recruitment from inside the ant nest. L3 syrphids were quite efficient at gluing ants with defensive secretions and at resisting to removal attempts by ants. 5. While supporting the assumption that ants tune their defensive response to the aphidophagous predator, the present results also showed a lack of efficient protection of their trophobionts from the most voracious late syrphid instar.     

UNIQUE MANIRAPTORAN EGG CLUTCH FROM THE UPPER CRETACEOUS TWO MEDICINE FORMATION OF MONTANA REVEALS THEROPOD NESTING BEHAVIOUR

Abstract: Egg clutches of non‐avian maniraptoran theropods (Dinosauria) are rare, particularly in North America where those of Troodon formosus are the only maniraptoran clutches known. Here we describe a new partial maniraptoran clutch and nesting trace referred to Montanoolithus strongorum oogen. et oosp. nov. (Montanoolithidae oofam. nov.), from the Upper Cretaceous Two Medicine Formation of Montana. Based on a cladistic analysis of reproductive traits, we infer that this clutch belonged either to a caenagnathid or to a dromaeosaurid, which makes it the first clutch known of either taxon. This specimen preserves impressions and eggshell fragments of at least five eggs on a nest structure. The eggs are asymmetrical, paired, and lay radially in a ring configuration on the sloped sides of a bioturbated, flat‐topped sandstone mound. Geology of the locality indicates the female nested in a poorly‐vegetated area of freshly deposited sand, possibly near an active river channel. This clutch reveals that the egg‐layer of Montanoolithus strongorum had a unique suite of reproductive characteristics and nesting behaviours among maniraptorans.     

Curvilinear Three-Dimensional Modeling of Spinal Curves with Dual Kriging

In spinal deformation studies, three-dimensional reconstruction of the spine is frequently represented as a curve in space fitted to the vertebral centroids. Conventional interpolation techniques such as splines, Bezier and the least squares method are limited since they cannot describe precisely the great variety of spinal morphologies. This article presents a more general technique called dual kriging, which includes two mathematical constituents (drift and covariance) to adjust the interpolated functions to spinal deformity better. The cross-validation technique was used to compare the parametric representations of spinal curves with different combinations of drift and covariance functions. Model validation was performed from a series of analytic curves reflecting typical scoliotic spines. Calculation of geometric torsion, a sensitive parameter, was done to evaluate the accuracy of the kriging models. The best model showed an absolute mean difference of 1.2 x 10(-5) (+/- 7.1 x 10(-5) ) mm(-1) between the analytical and estimated geometric torsions compared to 5.25 x 10(-3) (+/- 3.7 x 10(-2) ) mm(-1) for the commonly used least-squares Fourier series method, a significant improvement in spinal torsion evaluation.     

Responses of Songbirds to Magpie Reduction in an Urban Habitat

ABSTRACT Bird communities change in response to urbanization, which poses a challenge for conservationists. We examined the consequences of the recent increase in European cities of black-billed magpie (Pica pica), which has become the main bird nest predator in many urban parks, yet its impact remains disputed. We tested predator role in the limitation of postfledging and adult numbers of 10 common songbird species. We conducted before-after, control-treatment experimental magpie removal in the suburbs near Paris, France, during our 3-year study. We also compared the productivity and the relative densities between urban and rural habitats for 14 songbirds. We found that magpies had very limited effect on songbird productivity, even for species sensitive to predation by corvids. In addition, impact of the magpie on population levels of passerines would also be minimized because we found no relationship between productivity of prey and their densities. Thus, the recent colonization of urban parks by magpies should not threaten persistence of local songbird populations. Yet, there was evidence that a small number of non-territorial bird species were attracted to places where magpies were removed. Magpie densities may have modified habitat selection for foraging that might be explained by predator avoidance. But overall, characteristics of urban habitat explain variations of productivity and densities of songbirds better than did magpie predation. In France, conservationists widely use the control of predators, aiming at increasing levels of prey populations. Despite very high densities of magpies in urban parks, we gave evidence that removal of this predator was ineffective to preserve populations of common passerines. This would suggest that the risk induced by the presence of magpies is independent of its density, and conservationists must carefully assess its impact. In the future, we recommend management policies include long-term monitoring of magpie-prey interactions during breeding season to detect potential changes in songbird responses to magpie presence.     

Effects of fertilisation on amino acid mobilisation by a plant‐manipulating insect

1. Phytophagous insects frequently manipulate their host‐plant to improve their immediate environment. This generally implies substantial modifications of host metabolism, and sometimes an alteration of nitrogen allocation within the host‐plant. However, the outcome of plant manipulation on amino acid or protein content can be modulated by environmental factors and host‐plant traits. 2. It was investigated whether the pseudogall induced by the aphid Phloeomyzus passerinii (Signoret) (Aphididae: Phloeomyzinae) in the bark of its host‐plant affects the amino acid content in bark tissues, and whether the strength of the modification is modulated by the fertilisation regime and/or the resistance level of the host‐plant. The development of aphid colonies on a resistant and a susceptible poplar genotype, under three fertilisation regimes, was studied. After the development of colonies, the free and protein‐bound amino acid content of the infested bark were quantified. 3. Fertilisation enhanced poplar growth and increased the free amino acid content of bark tissues. Infestation also triggered accumulations of both free and protein‐bound amino acids in the feeding sites, but in the susceptible genotype only. The increase in amino acid content was more pronounced when fertilisation was low, and fertilisation did not enhance aphid development. 4. In conclusion, infestation by P. passerinii triggers an accumulation of amino acids, but the effect is influenced by both the fertilisation regime and the resistance level of the host‐plant. This suggests that P. passerinii could affect the allocation of nutrients within trees during outbreaks.     

DNA barcoding and morphology reveal three cryptic species of Anania (Lepidoptera: Crambidae: Pyraustinae) in North America,all distinct from their European counterpart

Anania coronata (Hufnagel), a Holarctic species of pyraustine crambid moth, has long been treated as having two geographically separated subspecies – the nominotypical Anania coronata in the Palaearctic Region and Anania coronata tertialis (Guenée) in the Nearctic Region. Maximum likelihood and Bayesian inference analysis of mitochondrial DNA barcodes both recover four well‐supported, reciprocally monophyletic groups within Anania coronata. Qualitative and quantitative analyses of genital structures reveal diagnostic differences that correspond to the four barcode lineages. On the basis of both molecular and morphological evidence, we conclude that Anania coronata is actually a complex of four species. Anania coronata (Hufnagel) is restricted to Europe, whereas three species occur in North America: Anania tertialis (Guenée), Anania plectilis (Grote & Robinson) and Anania tennesseensis sp.n. Yang.     

Testing the regeneration niche hypothesis with Gesneriaceae (tribe Sinningiae) in Brazil: Implications for the conservation of rare species

The germination requirements of sexually reproducing plants are regulated by environmental factors such as temperature. Those factors acting at the germination phase are part of the regeneration niche, which is fundamental in the processes that contribute to habitat suitability and geographic distribution. We tested the hypothesis that rarity is associated with regeneration niche in three species of plants in the family Gesneriaceae (tribe Sinningieae), Sinningia rupicola (Mart.) Wiehler, Paliavana sericiflora Benth and Sinningia allagophylla (Mart.) Wiehler, which vary in their distribution and habitat specificity but share a small zone of sympatry in rocky fields south of Belo Horizonte in Minas Gerais, Brazil. The regeneration niche was tested using a seed germination experiment under controlled light conditions at seven fixed temperatures (10–40°C at 5°C intervals). Each of the three species germinated differently at the various temperatures. The species with the smallest geographic range, S. rupicola, also had the most restricted germination: germination peaked at 15°C when relatively few seeds germinated (45%), and even fewer germinated at other temperatures. The regeneration niche was wider in P. sericiflora and wider still in S. allagophylla, with germination greater than 90% between 15–25°C and greater than 80% between 15–30°C, respectively. Our germination results provide qualified support for the hypothesis of correlation of the regeneration niche with geographic distribution of related plant taxa, with important conservation implications for rare and endangered species.     

Carotenoid limitation and allocation priorities in asynchronous raptor nestlings

The evolution and maintenance of conspicuous animal traits and communication signals have long fascinated biologists. Many yellow–red conspicuous traits are coloured by carotenoid pigments, and in some species they are displayed at a very young age. In nestling birds, the functions and proximate mechanisms of carotenoid‐pigmented traits are probably different and not as well known as those of adults. Here we investigated how Montagu's harrier (Circus pygargus) nestlings within structured families used a limited resource, carotenoid pigments, and whether they used these for increasing coloration (deposition in integuments) or for mounting a response to a phytohaemagglutinin (PHA) challenge, which measures pro‐inflammatory potential and aspects of cellular immune responsiveness. We manipulated carotenoid availability, using dietary carotenoid supplementations, and show that when supplemented, nestlings primarily allocated supplemental carotenoids to increase their coloration, irrespective of their sex, but depending of their position within the brood. Responses to PHA challenge were condition‐dependent, but depending on carotenoid availability. Moreover, how nestlings allocated carotenoids depended on their rank within the brood, which in turn influenced their level of carotenoid limitation (first‐hatched nestlings being less constrained than later‐hatched nestlings). We discuss why nestlings would use supplemental carotenoids for increasing bare parts coloration rather than for responding to a PHA challenge, and the potential benefits for doing so in a parent–offspring communication context. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 13–24.     

Low levels of ribosomal RNA partly account for the very high photosynthetic phosphorus‐use efficiency of Proteaceae species

Proteaceae species in south‐western Australia occur on phosphorus‐ (P) impoverished soils. Their leaves contain very low P levels, but have relatively high rates of photosynthesis. We measured ribosomal RNA (rRNA) abundance, soluble protein, activities of several enzymes and glucose 6‐phosphate (Glc6P) levels in expanding and mature leaves of six Proteaceae species in their natural habitat. The results were compared with those for Arabidopsis thaliana. Compared with A. thaliana, immature leaves of Proteaceae species contained very low levels of rRNA, especially plastidic rRNA. Proteaceae species showed slow development of the photosynthetic apparatus (‘delayed greening’), with young leaves having very low levels of chlorophyll and Calvin–Benson cycle enzymes. In mature leaves, soluble protein and Calvin–Benson cycle enzyme activities were low, but Glc6P levels were similar to those in A. thaliana. We propose that low ribosome abundance contributes to the high P efficiency of these Proteaceae species in three ways: (1) less P is invested in ribosomes; (2) the rate of growth and, hence, demand for P is low; and (3) the especially low plastidic ribosome abundance in young leaves delays formation of the photosynthetic machinery, spreading investment of P in rRNA. Although Calvin–Benson cycle enzyme activities are low, Glc6P levels are maintained, allowing their effective use.     

Involvement of the hyperglycemic neurohormone family in the control of reproduction in decapod crustaceans

Summary

In the last few years, (bio)chemical and molecular biological studies have shown that several members of the hyperglycemic hormone family are present in different molecular forms. In vivo and in vitro bioassays revealed that some of these isoforms also play a role in the control of reproduction in decapod crustaceans. This communication gives a review of the cytological aspects of the eyestalk X-organ sinus gland complex, responsible for the synthesis, storage and release of these neuropeptides, and the molecular and functional aspects of those members involved in the control of reproduction. Finally, the role of the hyperglycemic hormone family in the regulation of reproduction in the female lobster is described as an example of the (possible) interactions of the members of the hyperglycemic hormone family with other (neuro)endocrine factors in the reproductive process of crustaceans.