Investigating the persistence of tick-borne pathogens via the R-0 model

In the epidemiology of infectious diseases, the basic reproduction number, R-0, has a number of important applications, most notably it can be used to predict whether a pathogen is likely to become established, or persist, in a given area. We used the R-0 model to investigate the persistence of 3 tick-borne pathogens; Babesia microti, Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato in an Apodemus sylvaticus-Ixodes ricinus system. The persistence of these pathogens was also determined empirically by screening questing ticks and wood mice by PCR. All 3 pathogens behaved differently in response to changes in the proportion of transmission hosts on which I. ricinus fed, the efficiency of transmission between the host and ticks and the abundance of larval and nymphal ticks found on small mammals. Empirical data supported theoretical predictions of the R-0 model. The transmission pathway employed and the duration of systemic infection were also identified as important factors responsible for establishment or persistence of tick-borne pathogens in a given tick-host system. The current study demonstrates how the R-0 model can be put to practical use to investigate factors affecting tick-borne pathogen persistence, which has important implications for animal and human health worldwide.

Molecular Phylogenies Support Homoplasy of Multiple Morphological Characters Used in the Taxonomy of Heteroscleromorpha (Porifera: Demospongiae)

Sponge classification has long been based mainly on morphocladistic analyses but is now being greatly challenged by more than 12 years of accumulated analyses of molecular data analyses. The current study used phylogenetic hypotheses based on sequence data from 18S rRNA, 28S rRNA, and the CO1 barcoding fragment, combined with morphology to justify the resurrection of the order Axinellida Lévi, 1953. Axinellida occupies a key position in different morphologically derived topologies. The abandonment of Axinellida and the establishment of Halichondrida Vosmaer, 1887 sensu lato to contain Halichondriidae Gray, 1867, Axinellidae Carter, 1875, Bubaridae Topsent, 1894, Heteroxyidae Dendy, 1905, and a new family Dictyonellidae van Soest et al., 1990 was based on the conclusion that an axially condensed skeleton evolved independently in separate lineages in preference to the less parsimonious assumption that asters (star-shaped spicules), acanthostyles (club-shaped spicules with spines), and sigmata (C-shaped spicules) each evolved more than once. Our new molecular trees are congruent and contrast with the earlier, morphologically based, trees. The results show that axially condensed skeletons, asters, acanthostyles, and sigmata are all homoplasious characters. The unrecognized homoplasious nature of these characters explains much of the incongruence between molecular-based and morphology-based phylogenies. We use the molecular trees presented here as a basis for re-interpreting the morphological characters within Heteroscleromorpha. The implications for the classification of Heteroscleromorpha are discussed and a new order Biemnida ord. nov. is erected.

How subtle are the biases that shape the fidelity of the fossil record? A test using marine molluscs

Biases in preservation shape the fossil record, and therefore impact on our reconstructions of past environments and biodiversity. Given the intensive recent research in the general fields of taphonomy and exceptional preservation, surprisingly, fundamental questions remain unanswered about species-level variation in skeletal preservation potential at low taxonomic levels (e.g. between genera from the same family, or between taxa from related families) across myriad groups with multi-element skeletons. Polyplacophoran molluscs (chitons sensu lato) are known from the late Cambrian to Recent, and possess a distinctive articulated scleritome consisting of eight overlapping calcareous valves. The apparent uniformity of living chitons presents an ideal model to test the potential for taphonomic biases at the alpha-taxon level. The vast majority of fossil chitons are preserved as single valves; few exhibit body preservation or even an articulated shell series. An experimental taphonomic programme was conducted using the Recent polyplacophorans Lepidochitona cinerea and Tonicella marmorea (suborder Chitonina) and Acanthochitona crinita (Acanthochitonina). Experiments in a rock tumbler on disarticulated valves found differential resistance to abrasion between taxa; in one experiment 53.8-61.5% of Lepidochitona valves were recovered but 92% of those from Tonicella and 100% of elements from Acanthochitona. Chiton valves and even partly decayed carcasses are more resistant to transportation than their limited fossil record implies. Different species of living chitons have distinctly different preservation potential. This, problematically, does not correlate with obvious differences in gross valve morphology; some, but not all, of the differences correlate with phylogeny. Decay alone is sufficient to exacerbate differences in preservation potential of multi-element skeletons; some, but not all, of the variation that results is due to specimen size and the fidelity of the fossil record will thus vary intra-specifically (e.g. between ontogenetic stages) as well as inter-specifically. 

Saccharomyces uvarum, a distinct group within Saccharomyces sensu stricto

A natural subgroup (that we refer to as Saccharomyces uvarum) was identified, within the heterogeneous species Saccharomyces bayanus. The typical electrophoretic karyotype, interfertility of hybrids between strains, distinctive sugar fermentation pattern, and uniform fermentation characteristics in must, indicated that this subgroup was not only highly homogeneous, but also clearly distinguishable from other species within the Saccharomyces sensu stricto group. Investigation of the S. bayanus type strain and other strains that have been classified as S. bayanus, confirmed the apparent lack of homogeneity and, in some cases, supported the hypothesis that they are natural hybrids. Copyright (C) 1999 Federation of European Microbiological Societies.

Shared or unshared parental care in overwintering brent geese (Branta bernicla hrota)

We examine brood size effects on the behaviour of wintering parent and juvenile brent geese (Branta bernicla hrota) to test predictions of shared and unshared parental care models. The behaviour of both parents and offspring appear to be influenced by declining food availability over the winter. Parental vigilance increased with brood size and may be explained by vigilance having functions in addition to antipredator behaviour where the benefits are shared among the brood. There was no increase in parental aggression with brood size and this does not fit the prediction of shared care. Nevertheless, large families are able to monopolize better feeding areas compared with smaller families and large families static feed more but walk feed less than do small families, the former apparently being the preferred mode. The presence of additional young, rather than increasing the amount of parental aggression, seems to enhance the family's competitive ability. Because parents with large broods benefit from enhanced access to resources there is likely to be no additional significant cost in the parental care of larger broods (sensu Trivers 1972).

Cryptic species diversity in a widespread bumble bee complex revealed using mitochondrial DNA RFLPs

Cryptic species diversity is thought to be common within the class Insecta, posing problems for basic ecological and population genetic studies and conservation management. Within the temperate bumble bee (Bombus spp.) fauna, members of the subgenus Bombus sensu stricto are amongst the most abundant and widespread. However, their species diversity is controversial due to the extreme difficulty or inability morphologically to identify the majority of individuals to species. Our character-based phylogenetic analyses of partial CO1 (700 bp) from 39 individuals spread across their sympatric European ranges provided unequivocal support for five taxa (3-22 diagnostic DNA base pair sites per species). Inclusion of 20 Irish specimens to the dataset revealed >= 2.3% sequence divergence between taxa and 200 m) whilst B. cryptarum was relatively more abundant at higher altitudes. Bombus magnus was rarely encountered at urban sites. Both B. lucorum and B. terrestris are nowadays reared commercially for pollination and transported globally. Our RFLP approach to identify native fauna can underpin ecological studies of these important cryptic species as well as the impact of commercial bumble bees on them.

Molecular systematics of Ceramium and Centroceras (Ceramiaceae, Rhodophyta) from Brazil

Morphological investigations identified 11 Ceramium Roth species, of the 18 previously reported from Brazil. Phylogenetic analyses of sequences of the chloroplast-encoded rbcL gene confirmed the presence of seven of these species. Three other species are reported from Brazil for the first time. Ceramium affine Setchell & Gardner and C. filicula Harvey ex Womersley were previously known only from the Pacific Ocean (Mexico and Australia, respectively). A new species, C. fujianum Barros-Barreto et Maggs sp. nov., is described here. Its general habit is similar to that of C. strictum sensu Harvey from Europe but it has one less periaxial cell than C. strictum; its cortical filament arrangement is closest to C. deslongchampsii Chauvin ex Duby, also from Europe, but whorled tetrasporangia partially covered by cortical cells differ strikingly from the naked protruding tetrasporangia of C. deslongchampsii. Ceramium species in which each periaxial cell cuts off transversely only a single basipetal cell formed a robust clade. The genus Ceramium as represented in Brazil is not monophyletic with respect to Centroceras Kutzing and Corallophila Weber-van Bosse; Ceramium nitens, which has axial cells completely covered by rounded cortical cells formed by acropetal and basipetal filaments, did not group with any Ceramium clade but was weakly allied to a species of Corallophila. All three Brazilian Centroceras sequences were attributed to a single species, C. clavulatum.

Fitness costs associated with mounting a social immune response

Social immune systems comprise immune defences mounted by individuals for the benefit of others (sensu Cotter & Kilner 2010a). Just as with other forms of immunity, mounting a social immune response is expected to be costly but so far these fitness costs are unknown. We measured the costs of social immunity in a sub-social burying beetle, a species in which two or more adults defend a carrion breeding resource for their young by smearing the flesh with antibacterial anal exudates. Our experiments on widowed females reveal that a bacterial challenge to the breeding resource upregulates the antibacterial activity of a female's exudates, and this subsequently reduces her lifetime reproductive success. We suggest that the costliness of social immunity is a source of evolutionary conflict between breeding adults on a carcass, and that the phoretic communities that the beetles transport between carrion may assist the beetle by offsetting these costs.

Evolution in the deep sea: a combined analysis of the earliest diverging living chitons (Mollusca : Polyplacophora : Lepidopleurida)

Lepidopleurida is the earliest diverged group of living polyplacophoran molluscs. They are found predominantly in the deep sea, including sunken wood, cold seeps, other abyssal habitats, and a few species are found in shallow water. The group is morphologically identified by anatomical features of their gills, sensory aesthetes, and gametes. Their shell features closely resemble the oldest fossils that can be identified as modern polyplacophorans. We present the first molecular phylogenetic study of this group, and also the first combined phylogenetic analysis for any chiton, including three gene regions and 69 morphological characters. The results show that Lepidopleurida is unambiguously monophyletic, and the nine genera fall into five distinct clades, which partly support the current view of polyplacophoran taxonomy. The genus Hanleyella Sirenko, 1973 is included in the family Protochitonidae, and Ferreiraellidae constitutes another distinct clade. The large cosmopolitan genus Leptochiton Gray, 1847 is not monophyletic; Leptochiton and Leptochitonidae sensu stricto are restricted to North Atlantic and Mediterranean taxa. Leptochitonidae s. str. is sister to Protochitonidae. The results also suggest two separate clades independently inhabiting sunken wood substrates in the south-west Pacific. Antarctic and other chemosynthetic-dwelling species may be derived from wood-living species. Substantial taxonomic revision remains to be done to resolve lepidopleuran classification, but the phylogeny presented here is a dramatic step forward in clarifying the relationships within this interesting group.

Ceramium Roth (Ceramiales, Rhodophyta) from Venice lagoon (Adriatic Sea, Italy): Comparative studies of Mediterranean and Atlantic taxa

The cosmopolitan genus Ceramium (Ceramiaceae, Rhodophyta) is a large and systematically complex group. The taxonomy of this genus remains in a chaotic state due to the high degree of morphological variation. Culture studies, suggesting a strong influence of environment on phenotype, and the use of molecular tools have recently questioned the validity of morphological features used in species recognition. Here we compare three Ceramium taxa from Venice lagoon with samples from northwest Europe using the plastid ribulose-1,5-bisphosphate carboxylase/oxygenase gene (rbcL) and the rbcL-rbcS intergenic spacer combined with morphological observations. A strongly banded species, previously identified as member of a poorly understood and misnamed group, the Ceramium diaphanum complex sensu Feldmann-Mazoyer, is probably conspecific with British samples of Ceramium diaphanum sensu Harvey, for which no valid name has been identified up to now. We show that Ceramium polyceras (Kutzing) Zanardini is a valid name for this species. A fully corticated Ceramium species morphologically resembling C. secundatum differs at the species level from Atlantic C. secundatum; a valid name for this entity is Ceramium derbesii Solier ex Kutzing, described from Mediterranean France. A third species characterized by cortical spines, previously listed as Ceramium ciliation var. robustum (J. Agardh) Mazoyer, is shown to be Ceramium nudiusculum (Kutzing) Rabenhorst, originally described from Venice.

Growth, dye degradation and ligninolytic activity studies on Zimbabwean white rot fungi

White rot fungi were collected from Chirinda and Chimanimani hardwood forests in Zimbabwe and studied with respect to growth temperature optima and dye decolorization. Temperature optima were found to vary (between 25-37 degreesC) amongst the isolates. The isolates were screened for their ability to degrade the polymeric dyes; blue dextran and Poly R478 and the triphenylmethane dyes; cresol red, crystal violet and bromophenol blue. Semi-quantitative determination of the hydrolytic enzyme activities possessed by the white rot fungi was determined using the API ZYM system. Lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase activities in the fungi were also determined. No LiP was detected in any of the isolates but all isolates showed manganese peroxidase and laccase activities. Time related decolorization studies and optimum pH determinations for Poly R478 degradation by the isolates were carried out in liquid cultures. The most significant rates of Poly R478 decolorization in liquid cultures were found with the following isolates: Trametes cingulata, Trametes versicolor, Trametes pocas, DSPM95 (a species to be identified), Datronia concentrica and Pyenoporus sanguineus. (C) 2001 Elsevier Science Inc. All rights reserved.