Structure and diversity of the Mesozoic wood genus Xenoxylon in Far East Asia: implications for terrestrial palaeoclimates

Although the faunal elements of Far East Asian Mesozoic terrestrial biota have attracted much attention in recent years, their palaeoecology remains poorly known. In particular, features of the palaeoclimate are highly controversial. To address this point we used the Mesozoic fossil wood Xenoxylon , a genus recognized as an indicator of wet temperate biotopes and which is common in the area during the Carnian–Maastrichtian interval. We re-appraised bibliographic data and gathered new data for Xenoxylon in the Mesozoic of Far East Asia. This demonstrated that previous taxonomic approaches to the genus have been so far idiosyncratic. We examined the anatomical diversity of morphogenus Xenoxylon in Far East Asia and compared it to that of samples from Europe. This indicates that in an area centred on north-eastern China, Xenoxylon reached a level of anatomical diversity unmatched elsewhere in the world. We hypothesize that this diversity witnesses the persistence of palaeoecological conditions particularly suitable for Xenoxylon and that a wet temperate climate prevailed over most of the area throughout the Carnian–Maastrichtian interval. It is in this setting that the famous Jehol Biota probably evolved.     

Longevity differs among sexes but is not affected by repeated immune activation in voles (Microtus arvalis)

Investment of resources in immune defences, despite obvious short-term benefits, may be detrimental to long-term maintenance and thus decrease longevity in absence of parasites. In addition, females and males may differ in immune investment and intrinsic longevity because they are subjected to different degrees of sexual competition and extrinsic mortality. In order to test if sex-specific investment in mounting an immune response reduced longevity, we compared the longevity of captive male and female common voles Microtus arvalis regularly challenged with keyhole limpet haemocyanin, an antigen which elicits the production of antibodies, to the longevity of voles injected with the corresponding antigen-free buffer (phosphate-buffered saline). Injections were repeated every 28 days to mimic a chronic infection. The magnitude of immune response did not vary between males and females and did not affect longevity. Overall, females lived longer than males, independently of the immune challenge. Thus, the long-term costs of immunity seem small in voles. The longevity pattern is consistent with the prediction that male-biased predation or parasitism in the wild causes reduced intrinsic lifespan, but this reduction is not mediated by a decrease in male immunity.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 328–333.     

Galápagos' Opuntia (prickly pear) cacti: extensive morphological diversity, low genetic variability

Due to the pronounced morphological variation and geographical distribution of Galápagos' Opuntia cacti, numerous hypotheses have been advanced regarding their radiation, diversification, and classification. The currently accepted classification is based on morphology and recognizes six species and fourteen varieties, but the plasticity of many of the characteristics renders any morphological taxonomy problematic. Our analysis of previously published morphological data agrees only partially with the current classification. We present the first molecular phylogeny of these plants. Multiple DNA sequences indicate little genetic distinction among the currently identified species, despite restricted gene flow and limited long distance dispersal within the archipelago. No clear relationship exists between morphological and genetic differences. These results suggest that both molecular and morphological data should be used in conservation planning.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 451–461.     

Ecologically heterogeneous populations of the invasive ant Wasmannia auropunctata within its native and introduced ranges

Abstract 1. The biology of most invasive species in their native geographical areas remains largely unknown. Such studies are, however, crucial in shedding light on the ecological and evolutionary processes underlying biological invasions. 2. The present study focuses on the little fire ant Wasmannia auropunctata, a species native to Central and South America that has been widely introduced and which has become invasive throughout the tropics. We characterise and compare several ecological traits of native populations in French Guiana with those in one of its introduced ranges, New Caledonia. 3. We found ecologically heterogeneous populations of W. auropunctata coexisting in the species’ native geographical area. First, we found populations restricted to naturally perturbed areas (particularly floodplains) within the primary forest, and absent from the surrounding forest areas. These populations were characterised by low nest and worker densities. Second, we found dominant populations in recent anthropogenic areas (e.g. secondary forest or forest edge along road) characterised by high nest and worker densities, and associated with low ant species richness. The local dominance of W. auropunctata in such areas can be due to the displacement of other species (cause) or the filling‐up of empty habitats unsuitable to other ants (effect). With respect to their demographic features and ant species richness, the populations of native anthropogenic habitats were to a large extent similar to the invasive populations introduced into remote areas. 4. The results point to the need for greater research efforts to better understand the ecological and demographic features of invasive species within their native ranges.     

Direct evidence for biased gene diversity estimates from dominant random amplified polymorphic DNA (RAPD) fingerprints

The relevance of using dominant random amplified polymorphic DNA (RAPD) fingerprints for estimating population differentiation was investigated when typically small population sample sizes were used. Haploid sexual tissues were first used to determine genotypes at RAPD loci for 75 eastern white pines ( Pinus strobus L.) representing five populations. Dominant RAPD fingerprints were then inferred from genotypic data for each individual at each locus, and gene diversity estimates from both sources of data were compared. Genotypic information at RAPD loci indicated little or no differentiation among populations, similar to allozyme loci. However, estimates of population differentiation derived from dominant RAPD fingerprints according to various common methods of analysis were generally inflated, especially when all fragments were considered. Simulations showed that an increase in loci sampling and population sample sizes did not significantly alleviate the biases observed.     

New gastropods from East Pacific hydrothermal vents

The following new prosobranch species are described: Cyuthermia (gen.n.) naticoides, Lucunoidc (gen.n.) exquisitus (Neomphalidae); Peltospira Iamellifera, Pachydermia (gen.n.) laevis, Depressigyra (gen. n.) g1obulus. D. plunispira, Solutigyra (gen. n.) reticulata, Lirapex (gen. n.) humata, L. granularis (Peltospiridae); Bathymargarites (gen.n.) symplector (Trochidae) and Provanna mucleani (Littorinoidea). Shells and soft parts of the species are described and figured. One species each of Sinezona (Scissurellidae), Moel1rriopsis (Seguenzoidea) and Phymorrhynchus (Turridae) is recorded from East Pacific hydrothermal vents, but not identified to species. Information about feeding biology and type of larval development is given for most of these species. The systematic position of the new species of Neomphalidae and Peltospiridae is considered uncertain, but further anatomical investigations are in progress. The gastropod fauna of East Pacific sulphide-rich environments is summarized and composition, endemism, age. dispersal, predation, adaptations and feeding biology are discussed.     

Immunocompetent Infants as a Human Reservoir for Pneumocystis jirovecii: Rapid Screening by Non-Invasive Sampling and Real-Time PCR at the Mitochondria1 Large Subunit rRNA Gene

ABSTRACT. We tested a real-time PCR assay targeting the Pneumocystis jirovecii mitochondria1 large subunit rRNA gene on 240 archival nasopharyngeal aspirates from non-immunosuppressed infants. The sensitivity of this assay appeared close to that of a conventional nested-PCR assay targeting the same locus. Because of its one-step procedure, and its sensitivity and rapidity, the real-time PCR assay is particularly suitable for screening individuals parasitized by P. jirovecii within large populations.     

Locomotion in Nebalia bipes: a possible model for Palaeozoic phyllocarid crustaceans

The morphofunctional aspects of locomotion in Recent phyllocarid crustaceans are presented, based on combined video observations of living specimens of the cosmopolitan nektobenthic Nebalia (Leptostraca, Nebaliidae) and scanning electron microscopy of fixed material. N. bipes is infaunal by day, showing a preference for organic-rich black muds and dim light conditions. Under natural conditions, emergence from sediment and nocturnal swimming activities are controlled by a circadian rhythm. The 1st and 2nd antennae perform the major role in digging. The carapace rostral plate acts as a ram diverting particles and preventing inputs of sediment into the carapace. Superficial burrowing may provide camouflaged shelter against predation. Swimming is accomplished by the combined action of the first four pairs of pleopods (backward metachronal flexion during the power stroke) and the well-articulated abdominal shaft (downward flap). Plumose setae present on both the pleopods and furcal rami (governed by low Reynolds numbers) behave like paddles maximizing the resistance to the water. Clusters of cuticular microscales (3-5 μm) and microdenticles are present on the external surface of the carapace and the trunk segments, respectively. Both show a uniform directional arrangement suggesting functional interpretations in relation to locomotion (e.g., to prevent back slippage during digging, to reduce turbulence in the flow layer close to the body, and/or to serve as mechanoreceptors for the detection of variation in water flow). Key features of functional importance in the locomotion of living leptostracans (natatory pleopods, a highly flexible abdomen, setulate or paddle-like furcal rami) are also recognized in Palaeozoic archaeostracan phyllocarids, suggesting that swimming was accomplished by the same pleopodal movements as described for N. bipes. Comparisons with Recent analogues (Nebaliopsis) suggest that phyllocarids with a free swimming life-style existed among the lower Palaeozoic archaeostracans (e.g., Caryocaris; Ordovician). Asymmetrical cuticular ornament in some archaeostracans indicates burrowing habits. Some Palaeozoic phyllocarids may have been occasional (possibly diurnal) mud dwellers comparable to modern nebaliids.