Fast and Slow dynamics of Malaria model with relapse

Two mathematical models of malaria with relapse are studied. When the vector population size is constant, complete analyses of the dynamics are conducted. The geometric singular perturbation theory is used to analyze the full dynamics. On the critical manifold, from next generation matrix method, we obtain the basic reproduction number. The global stability of disease-free equilibrium and the uniformly persistence of malaria have also been analyzed. While the vector population size is variable, the basic reproduction number and the stability of disease-free as well as the malaria-infected equilibrium have been obtained in a similar way. Some numerical simulations are also given.     

Analysis of microsatellite DNA from old scale samples of Atlantic salmon Salmo salar: a comparison of genetic composition over 60 years

Microsatellite analysis was applied to scale samples of Atlantic salmon collected up to 60 years ago. Samples from the 1930s, from a now endangered Danish population, were compared with recent samples (1989), to test if the present population consists of descendants from the original one. Allele frequencies had changed over time, but individuals from the two samples caught about 60 years apart clustered together when compared with the closest neighbouring population and another reference population. However, fewer alleles were detected in the recent sample from the endangered population, most likely due to a population bottleneck or sampling artefacts.     

Light filtering function of bud scales in woody plants

Bud scales ofPicea abies (L.) Karst andFagus sylvatica L. selectively transmit the incident spectrum of electromagnetic radiation. It was shown that the scales absorb almost all radiation below 600 nm. Only the red and far-red light which is reduced to 0.01–2% reaches the apical domes. The center of a beech bud receives 0.11% and the center of a spruce bud 0.84% of the incident 300–2,000 nm light.     

Tuberculosis models with fast and slow dynamics: the role of close and casual contacts

Models that incorporate local and individual interactions are introduced in the context of the transmission dynamics of tuberculosis (TB). The multi-level contact structure implicitly assumes that individuals are at risk of infection from close contacts in generalized household (clusters) as well as from casual (random) contacts in the general population. Epidemiological time scales are used to reduce the dimensionality of the model and singular perturbation methods are used to corroborate the results of time-scale approximations. The concept and impact of optimal average cluster or generalized household size on TB dynamics is discussed. We also discuss the potential impact of our results on the spread of TB.     

Importance of scrub–pastureland mosaics for wild-living cats occurrence in a Mediterranean area: implications for the conservation of the wildcat (Felis silvestris)

The European wildcat (Felis silvestris) is a threatened species in Europe. Suitable management of forests has been considered crucial for its conservation in Europe. However, this recommendation may not be general due to the lack of studies that test these hypotheses in the Mediterranean area, where landscapes are very different from those of central-north Europe. In this study, wild-living cat habitat associations were analyzed by means of scat surveys in 78 areas distributed in the four main vegetation types of the Mediterranean area of central Spain, where feral cat populations are probably scarce and restricted. Results show higher occurrences of wild-living cats in landscapes covered by scrub–pastureland mosaics rather than forests. Several applied recommendations are given: (1) to include the scrub–pastureland mosaics as protected habitats for wildcats; (2) to encourage further studies about the importance of this habitat in other areas; (3) to avoid the extensive scrubland removal associated with management practices against fires or infrastructure development; and (4) to promote land management practices that enhance these mosaics, and to use shrub species in the reforestation programmes founded by the European Agricultural Policy.     

Chondrichthyan‐like scales from the Middle Ordovician of Australia

Abstract: Microvertebrate sampling of the Stairway Sandstone (Darriwilian, Middle Ordovician, central Australia) has yielded scales that are chondrichthyan‐like in their overall construction, and Tantalepis gatehousei gen. et sp. nov. is erected here to describe these specimens. Tantalepis gatehousei gen. et sp. nov. is the stratigraphically oldest microsquamous taxon described thus far, and the ‘shark‐like’ appearance of the scales may extend the chondrichthyan lineage back into the Middle Ordovician. The presence of ‘shark‐like’ scales in the fossil record some 50 myr prior to the first articulated chondrichthyan body fossils and 44 myr before the first clearly identifiable chondrichthyan teeth suggests there is a considerable scope for the recovery of articulated specimens with which to document the early history of crown gnathostomes. Traditional hypotheses of phylogenetic relationships among early jawed vertebrates were recently challenged by the proposal of a radically different tree topology. However, the development of a new data set specifically addressing scale‐based characters is required before taxa such as Tantalepis, that are based upon disarticulated remains alone, can be firmly placed within the emerging, revised, evolutionary narrative.     

Hierarchical zooplankton metacommunities: distinguishing between high and limiting dispersal mechanisms

Theoretical development in the field of community ecology needs ground proofing with empirical tests. In addition, these tests need to be continuously updated. Cottenie (2005) linked observed metacommunities to theoretical models based on whether environmental and/or spatial effects in the observed metacommunity significantly explain community structure. However, a species-sorting metacommunity with high dispersal and one with limited dispersal cannot be distinguished in this manner; both produce significant environmental and spatial effects. In the present study, we demonstrate a solution to this problem using a zooplankton rock pool metacommunity in Churchill, Manitoba, sampled in August 2006. We established a hierarchy of metacommunities in the Churchill rock bluff system—a large, across-bluff metacommunity, and small, within-bluff metacommunities. Using this spatial hierarchy, it is possible to determine the zooplankton dispersal capability in the rock bluff system and hence to link the metacommunity to its corresponding model. We found the zooplankton rock bluff system to exhibit limited dispersal, meaning that spatial effects were significant at the across-bluff scale, but depending on the bluff, were significant or insignificant at the within-bluff scale. Environmental effects were significant at both scales. This study demonstrates a novel way to determine dispersal capabilities in species that are cryptic dispersers, and to successfully link observed metacommunities with theoretical models. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: S. I. Dodson