CONFIDENCE ELLIPSES APPLIED TO THE COMPARISON OF SENSORY PROFILES

Our experiment involved seven panels and six chocolates – five dark chocolates and one milk chocolate. The aim of the study was to compare the sensory profiles of the chocolates. A natural question to ask is “Did the panelists detect any differences among the five dark chocolates or did they systematically contrast them with the milk chocolate?” The scatter plot of the chocolates obtained by principal component analysis was useless to answer that question, because of the proximity of the points. To overcome that, we used confidence ellipses calculated using bootstrap. The originality of the study lies in the fact that we applied those ellipses to hierarchical multiple factor analysis (HMFA): among the seven panels, six were composed of trained professionals and the last one was composed of untrained students, and through that method, we managed to compare the two types of panels and balance the role of each trained panel. HMFA provides in a single scatter plot a representation of the six chocolates for each panel, the trained panels and all the panels. Confidence ellipses around each chocolate show that the combined panels – the six trained panels and also the untrained panel – differentiate the five dark chocolates. They also show how much larger the untrained panel's variability is than that of the trained panels, and how comparable are the trained panels' variability to each other.     

Developing a realistic sexual network model of chlamydia transmission in Britain

Background  

A national chlamydia screening programme is currently being rolled out in the UK and other countries. However, much of the epidemiology remains poorly understood. In this paper we present a stochastic, individual based, dynamic sexual network model of chlamydia transmission and its parameterisation. Mathematical models provide a theoretical framework for understanding the key epidemiological features of chlamydia: sexual behaviour, health care seeking and transmission dynamics.     

Mechanisms driving the specificity of a myrmecophyte–ant association

In the understory of pristine Guianese forests, the myrmecophyte Hirtella physophora almost exclusively shelters colonies of the plant-ant Allomerus decemarticulatus in its leaf pouches. We experimentally tested three non-mutually exclusive hypotheses concerning phenomena that can determine the species specificity of this association throughout the foundation stage of the colonies: (1) interspecific competition results in the overwhelming presence of A. decemarticulatus queens or incipient colonies; (2) exclusion filters prevent other ant species from entering the leaf pouches; and (3) host-recognition influences the choice of founding queens, especially A. decemarticulatus . Neither interspecific competition, nor the purported exclusion filters that we examined play a major role in maintaining the specificity of this association. Unexpectedly, the plant trichomes lining the domatia appear to serve as construction material during claustral foundation rather than as a filter. Finally, A. decemarticulatus queens are able to identify their host plant from a distance through chemical and/or visual cues, which is rarely demonstrated in studies on obligatory ant–plant associations. We discuss the possibility that this specific host-recognition ability could participate in shaping a compartmentalized plant-ant community where direct competition between ant symbionts is limited.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 90–97.     

Isolation and cross‐familial amplification of 41 microsatellites for the brook charr (Salvelinus fontinalis)

The brook charr (Salvelinus fontinalis; Osteichthyes: Salmonidae) is a phenotypically diverse fish species inhabiting much of North America. But relatively few genetic diagnostic resources are available for this fish species. We isolated 41 microsatellites from S. fontinalis polymorphic in one or more species of salmonid fish. Thirty‐seven were polymorphic in brook charr, 15 in the congener Arctic charr (Salvelinus alpinus) and 14 in the lake charr (Salvelinus namaycush). Polymorphism was also relatively high in Oncorhynchus, where 21 loci were polymorphic in rainbow trout (Oncorhynchus mykiss) and 16 in cutthroat trout (Oncorhynchus clarkii) but only seven and four microsatellite loci were polymorphic in the more distantly related lake whitefish (Coregonus clupeaformis) and Atlantic salmon (Salmo salar), respectively. One duplicated locus (Sfo228Lav) was polymorphic at both duplicates in S. fontinalis.     

The Iberian Peninsula: ancient history of a hot spot of mite harvestmen (Arachnida: Opiliones: Cyphophthalmi: Sironidae) diversity

The Iberian Peninsula represents a hot spot of cyphophthalmid (mite harvestman) disparity, with four of the eight genera currently recognized in the family Sironidae represented in the region – a generic diversity and morphological disparity not found in any other region of the World so far. From these, two genera (Iberosiro and Odontosiro) are monotypic, and are restricted to the western side of the peninsula. Parasiro is restricted to the north‐east region, from the Catalonian Coastal Ranges and both sides of the Eastern Pyrenees, in areas where the annual rainfall surpasses 1000 mm, and mostly restricted to areas with Paleozoic and Variscan rocks, with other species of the genus extending to Corsica, Sardinia, and the Italian Peninsula. A second species of the genus Paramiopsalis, Paramiopsalis eduardoi sp. nov. from Fragas do Eume, is described here along with a re‐diagnosis of the genus. Paramiopsalis species, together with Odontosiro, inhabit the north‐west corner of the Iberian Peninsula, an area with some of the highest recorded annual rainfall, and with Paleozoic rocks from the Iberian Massif or Variscan granitoid rocks. A phylogenetic analysis of the members of the family Sironidae using four molecular markers, despite not including all of the Iberian genera, clearly shows the non‐monophyly of the Iberian Cyphophthalmi, indicating that the Iberian Peninsula is home to multiple ancient lineages of mite harvestmen. The two Paramiopsalis species form a sister clade to the Balkan genus Cyphophthalmus, whereas Parasiro constitutes the first lineage of the sironids represented.     

Mites as biological tags of their hosts

Movements and spatial distribution of host populations are expected to shape the genetic structure of their parasite populations. Comparing the genetic patterns of both interacting species may improve our understanding of their evolutionary history. Moreover, genetic analyses of parasites with horizontal transmission may serve as indicators of historical events or current demographic processes that are not apparent in the genetic signature of their hosts. Here, we compared mitochondrial variation in populations of the ectoparasitic mite Spinturnix myoti with the genetic pattern of its host, the Maghrebian bat Myotis punicus in North Africa and in the islands of Corsica and Sardinia. Mite mitochondrial differentiation among populations was correlated with both host mitochondrial and nuclear differentiation, suggesting spatial co‐differentiation of the lineages of the two interacting species. Therefore our results suggest that parasite dispersal is exclusively mediated by host movements, with open water between landmasses as a main barrier for host and parasite dispersal. Surprisingly the unique presence of a continental European mite lineage in Corsica was inconsistent with host phylogeographical history and strongly suggests the former presence of European mouse‐eared bats on this island. Parasites may thus act as biological tags to reveal the presence of their now locally extinct host.     

The taste of polycose in hamsters

Hamsters show a preference for Polycose, a mixture of starch-derived glucose polymers, that is as strong as their preference for sucrose. However, in the hamster, taste aversions to Polycose may be less easily acquired than taste aversions to sucrose and the qualitative aspects of Polycose are unknown in this species. In order to examine the taste of Polycose in the hamster, we utilized a taste-aversion protocol with two conditioning trials. Animals were trained to avoid one of three different conditioning stimuli: 50 mM sucrose, 100 mM Polycose and a mixture of 50 mM sucrose with 100 mM Polycose. Control animals were conditioned with deionized water. After the second conditioning trial, generalization testing began for the three conditioning stimuli plus 3 mM citric acid, 300 mM KCI and 30 mM NaCl. The results showed that aversions to Polycose, sucrose or the Polycose/sucrose mixture cross- generalized, demonstrating that Polycose and sucrose share a common taste percept in the hamster. None of the aversions generalized to NaCl, citric acid or KCI. In addition, comparisons among the patterns of taste generalizations indicated that the tastes of Polycose and sucrose also had distinct qualitative components. Finally, although the taste of 100 mM Polycose was more salient than the taste of 50 mM sucrose, the taste of sucrose could still be detected in a mixture with Polycose.      

Molecular phylogeny of the genus Tibicina (Hemiptera, Cicadidae): rapid radiation and acoustic behaviour

To estimate the potential contribution of ethological and ecological parameters to the mechanisms of species formation and species isolation in the Palearctic cicada genus Tibicina , we constructed a molecular phylogenetic hypothesis of extant Tibicina species. Seven mitochondrial genes and a fragment of a nuclear gene were sequenced (3046 bp). Mitochondrial genes included 547 informative sites but the nuclear gene was too conserved to be included in the analysis. The tree was characterized by a basal polytomy indicating that Tibicina species arose rapidly. Such rapid radiation might explain the low divergence in the acoustic communication observed between species. Parameters describing habitat selection and acoustic communication were mapped onto the tree. A shift in habitat selection accompanied by acoustic changes might have contributed to one speciation event. The stochastic distribution of the same acoustic characters on the other branches of the tree implies, however, that the subtle acoustic differences between species could be the result of previous speciation events and independent evolutionary histories, rather than having contributed themselves in the speciation and isolation processes.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 611–626.