Effect of local spatial plant distribution and conspecific density on bumble bee foraging behaviour

1. Size variations in pollinator populations may modify competitive interactions among foragers. Competition among pollinators has been shown to lead to one of two contrasting behaviours: either specialisation to the most profitable plant species or generalisation to several species. When foraging, pollinators are also confronted with heterogeneity in the spatial distribution of plant resources. Because variations in both the forager density and plant spatial distribution can affect pollinator behaviour, focus was on the interactive effect of these two factors. 2. Bumble bee (Bombus terrestris L.) individuals were trained on a focal species (Lotus corniculatus L.) and experimentally tested whether variations in the forager density (two or six bumble bees foraging together), plant community spatial distribution (two plant species: L. corniculatus and Medicago sativa, which were either patchily or randomly distributed), and their interaction modified bumble bee foraging behaviour. 3. It was shown that when confronted with a high forager density, bumble bees focused their visits towards the most familiar species, especially when foraging under a random plant distribution. These modifications affected the fruiting of the focal plant species, with a significantly lower reproductive success under low density/patchy conditions. 4. This study demonstrates that the foraging decisions of bumble bees are influenced by variations in both the conspecific density and plant spatial distribution. Given the increasing impact of human activities on plant‐pollinator communities, this raises the question of the potential implications of these results for plant communities in natural conditions when confronted with variations in the pollinator density and spatial distribution of plants.     

Notochordal Catecholamines in Exogastrulated Xenopus Embryos

The notochord of anuran amphibian embryos, treated according to the procedure of Falk et al. (1962) in early stages, exhibits the characteristic formaldehyde-induced fluorescence of catecholamines. Neurectodermal derivatives, such as the neural tube and neural crests are known to synthesize catecholamines in more advanced stages. For determination of the influence of these neurectodermal derivatives on the formation of catecholamines in the notochord, exogastrulation experiments were performed on Xenopus laevis embryos. In exogastrulated embryos, the differentiation of neural derivatives was inhibited. Treatment of such exogastrulae with formaldehyde vapours shows that, in the absence of the neural tube and neural crests, the notochord developed similar fluorescence to that observed in normal embryos. Thus, these neurectodermal derivatives do not seem to be required for the formation of notochordal catecholamines.     

Linking territory quality and reproductive success in the Red-billed Chough Pyrrhocorax pyrrochorax: implications for conservation management of an endangered population

As changes in land use have been identified as the main factor explaining the decline in Red-billed Chough Pyrrhocorax pyrrochorax populations across western Europe, a study was carried out in Ouessant (western France) in order to assess the relationship between territory quality and reproductive success. As such an approach could be hindered by the fact that the birds' reproductive performance could be influenced by their breeding experience, we analysed both inter- and intranest-site variation in fledging success. Territory quality was quantified, combining habitat selection, territory size, the amount of feeding area and distance between nest and feeding area. Feeding habitats selected positively by Red-billed Choughs were characterized by a mean sward height of less than 5 cm. Foraging area was on average 21 557 m². Feeding areas (i.e. feeding habitat within foraging area) close to the nest were used preferentially. Fledging success appeared to be influenced neither by the total area of feeding sites in a Chough territory, nor by the mean feeding flight distance. However, fledging success adjusted to nest-site and year appeared to be influenced by feeding area close to the nest: one additional fledgling was expected for each additional 10 000 m² of feeding habitat within 300 m of the nest. These first results allowed us to consider recommending landscape management measures to ensure a favourable conservation status of local Chough populations.     

Phylogeny of ensign scale insects (Hemiptera: Coccoidea: Ortheziidae) based on the morphology of Recent and fossil females

The Ortheziidae (ensign scale insects) is a morphologically well‐defined family. The morphology and occurrence in the fossil record suggests a probable early origin of the family in scale insect evolution. The present phylogenetic analysis – based on 69 morphological characters of female ortheziids, using 39 exemplar Recent species – provides the first analytical assessment of relationships among living genera of the family, as well as the relationships of eight fossil species, based on complete, well‐preserved specimens in amber. Monophyly of the subfamilies Newsteadiinae, Ortheziinae and Ortheziolinae is supported, but Nipponortheziinae is found to be paraphyletic by inclusion of the Ortheziolinae. Thus, the subfamily Ortheziolinae is reduced in rank to tribe Ortheziolini stat.n. , which now includes Matileortheziola Kozár & Foldi, Ortheziolacoccus Kozár, Ortheziolamameti Kozár and Ortheziola?ulc. Consequently, the tribes Matileortheziolini, Ortheziolacoccini and Ortheziolamametini are synonymized ( syn.n. ) here under Ortheziolini. Five new species and one new genus of fossil ensign scales are described from three amber deposits: Burmorthezia gen.n. with type species Burmorthezia kotejai sp.n. and also B. insolita sp.n ., both in mid‐Cretaceous Burmese amber (98 Ma) and Arctorthezia baltica sp.n. in Eocene Baltic amber (c. 43 Ma) based on second‐instar nymphs; Mixorthezia kozari sp.n . and M. dominicana sp.n . in Miocene Dominican amber (c. 17 Ma) based on adult females. Fossil placements are unambiguous, with Burmorthezia forming a stem to crown‐group (Recent and Tertiary) Ortheziidae. A summary of described fossil ortheziids is provided.     

Microstructure and mineralogy of the outer calcareous layer in the lower jaws of Cretaceous Tetragonitoidea and Desmoceratoidea (Ammonoidea)

Tanabe, K., Landman, N.H. & Kruta, I. 2011: Microstructure and mineralogy of the outer calcareous layer in the lower jaws of Cretaceous Tetragonitoidea and Desmoceratoidea (Ammonoidea). Lethaia, Vol. 45, pp. 191–199. Based on the differences in their relative size, overall shape, structure and the degree of development of an outer calcified covering, lower jaws of the Ammonoidea have been classified into four morphotypes: normal, anaptychus, aptychus and rhynchaptychus types. However, detailed microstructural and mineralogical comparison of these morphotypes has not yet been addressed. This article documents the results of SEM and XRD observations of the lower jaws of three Late Cretaceous ammonoid species belonging to the Tetragonitoidea (Anagaudryceras limatum) and Desmoceratoidea (Pachydiscus kamishakensis and Damesites aff. sugata), based on excellent material preserved in situ within the body chamber, and retaining an aragonitic shell wall. The lower jaws of the three species are assigned to an intermediate form between anaptychus and aptychus types for the first two species and the rhynchaptychus type for the third species. Their black, presumably originally chitinous outer lamella is wholly covered with a calcareous layer. The calcareous layer is composed of aragonite in D. aff. sugata and A. limatum, and calcite in P. kamishakensis. The microstructure of the outer calcareous layer differs among the three species, i.e. granular in A. limatum, spherulitic prismatic in D. sugata, and prismatic in P. kamishakensis, all of which can be distinguished from the lamellar and spongy structure of the outer‐paired calcitic plates of the typical aptychus‐type lower jaws in some Jurassic and Cretaceous Ammonitina and Ancyloceratina. Our study suggests that most Jurassic and Cretaceous ammonoids possessed an outer calcareous layer in their lower jaws, although its mineralogy, microstructure and relative thickness vary among different taxa. □Ammonoidea, Cretaceous, Desmoceratoidea, lower jaw, microstructure, Tetragonitoidea.     

Does competition with wind‐pollinated species alter Echium plantagineum's attractiveness to a common pollinator Bombus terrestris?

1. In insect‐pollinated plants, pollinator attraction is influenced by flowers (e.g. number, size) and their associated rewards (e.g. pollen, nectar). These traits can depend on plant interactions. Indeed, below‐ground competition between plants can lead to a decrease in flower or reward production in insect‐pollinated species. 2. Wind‐pollinated plants, in particular, which are almost never studied in plant–pollinator networks, can alter insect‐pollinated plants' attractiveness through competition for nutrients. The response of pollinators to such changes has never been investigated. 3. A pot experiment was carried out in which an insect‐pollinated species, Echium plantagineum, was grown in binary mixture with three wind‐pollinated species selected to exert a panel of competitive interactions. Below‐ground competition was controlled using dividers limiting interspecific root competition. Floral traits of E. plantagineum (i.e. flower production, floral display size, flower size and nectar production) were measured. For each species mixture, the visits (i.e. first visit, number of visits, 10‐min sequences) of Bombus terrestris individuals released in a flight cage containing two pots were followed, one with and one without below‐ground competition. 4. Below‐ground competition significantly affected nectar's sucrose concentration but did not influence flower and nectar production. Likewise, pollinator visits were not influenced by below‐ground competition. Competitor identity significantly influenced flower and reward production of E. plantagineum, with a decrease in the presence of the most competitive wind‐pollinated species. A tendency for faster flower visitation events was also detected in the presence of the least competitive competitor. This study raises new questions regarding the influence of wind‐pollinated plants on plant–pollinator interactions.     

Spatio-temporal population genetic structure of the parasitic mite Spinturnix bechsteini is shaped by its own demography and the social system of its bat host

Information about the population genetic structures of parasites is important for an understanding of parasite transmission pathways and ultimately the co-evolution with their hosts. If parasites cannot disperse independently of their hosts, a parasite's population structure will depend upon the host's spatial distribution. Geographical barriers affecting host dispersal can therefore lead to structured parasite populations. However, how the host's social system affects the genetic structure of parasite populations is largely unknown. We used mitochondrial DNA (mtDNA) to describe the spatio-temporal population structure of a contact-transmitted parasitic wing mite ( Spinturnix bechsteini ) and compared it to that of its social host, the Bechstein's bat ( Myotis bechsteinii ). We observed no genetic differentiation between mites living on different bats within a colony. This suggests that mites can move freely among bats of the same colony. As expected in case of restricted inter-colony dispersal, we observed a strong genetic differentiation of mites among demographically isolated bat colonies. In contrast, we found a strong genetic turnover between years when we investigated the temporal variation of mite haplotypes within colonies. This can be explained with mite dispersal occuring between colonies and bottlenecks of mite populations within colonies. The observed absence of isolation by distance could be the result from genetic drift and/or from mites dispersing even between remote bat colonies, whose members may meet at mating sites in autumn or in hibernacula in winter. Our data show that the population structure of this parasitic wing mite is influenced by its own demography and the peculiar social system of its bat host.